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fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.2.11.4 Number of PDU Sessions per network slice availability check and update procedure | This clause applies to Non-Hierarchical NSAC and centralized NSAC architectures. The difference between the two architectures for the various steps, where applicable, is described at the end of the clause.
The number of PDU Sessions per network slice availability check and update procedure is to update (i.e. increase or decrease) the number of PDU Sessions established on S-NSSAI which is subject to NSAC. The SMF is configured with the information indicating which network slice is subject to NSAC.
NOTE 1: EAC mode is not applicable for Number of PDU Sessions per network slice availability check and update procedure.
Figure 4.2.11.4-1: Number of PDU Sessions per network slice availability check and update procedure
1. If the SMF is not aware of which NSACF to communicate, the SMF performs NSACF discovery as described in clause 6.3.22 of TS 23.501 [2] and in clause 5.2.7.3.2. The SMF anchoring the PDU session triggers the Number of PDU Sessions per network slice availability check and update procedure for the network slices that are subject to NSAC at the beginning of a PDU Session Establishment procedure (clause 4.3.2.2.1 and clause 4.3.2.2.2) only for new PDU Sessions to be established and as a last step of successful PDU Session Release procedure (clause 4.3.4.2 and clause 4.3.4.3).
NOTE 2: SMFs handling PDU sessions associated with UE Request Type "Existing PDU Session" for intra access handover purposes do not interact with the NSACF.
2. The SMF anchoring the PDU session sends Nnsacf_NSAC_NumOfPDUsUpdate_Request message to the NSACF. The SMF includes in the message the UE-ID, the PDU session ID, S-NSSAI for which the number of PDU Sessions per network slice update is required, Access Type and the update flag. The update flag may include one of the following values:
- 'increase' which indicates that the number of PDUs established on the S-NSSAI is to be increased when the procedure is triggered at the beginning of PDU Session Establishment procedure or when a new user plane leg is to be established for an MA PDU Session;
- 'decrease' which indicates that the number of PDU Sessions on the S-NSSAI is to be decreased when the procedure is triggered at the end of PDU Sessions Release procedure or when an existing user plane leg is to be released for an MA PDU Session. In the case of a PDU Session Establishment failure, the anchor SMF triggers another request to the NSACF with the update flag parameter equal to decrease in order to re-adjust back the PDU Session counter in the NSACF; or
- 'update' which indicates that for existing PDU Session the Access Type is to be replaced with a new Access Type during inter access mobility.
NOTE 3: For SSC mode 3 PDU session, the SMF of the new PDU Session invokes the NSACF to increase the number of PDU Session and adds the new PDU session ID in the NSACF. When the old PDU session is released the SMF of the old PDU session invokes the NSACF to decrease the number of PDU Session and remove the old PDU session ID in the NSACF.
NOTE 4: An SMF anchoring an IPv6 Multi-homed PDU session does not invoke NSACF for an S-NSSAI subject to NSAC when the PDU session replaces an existing anchor according to clause 4.3.5.3.
3. The NSACF updates the current number of PDU Sessions established on the S-NSSAI, i.e. increase or decrease the number of PDU Sessions per network slice based on the information provided by the anchor SMF in the update flag parameter.
If the update flag parameter from the SMF anchoring the PDU session indicates increase value and the maximum number of PDU Sessions established on the S-NSSAI has already been reached, then the NSACF returns a result parameter indicating that the maximum number of PDU Sessions per network slice has been reached. If the maximum number of PDU Sessions established on the S-NSSAI has not been reached, the NSACF checks the UE ID. If the UE ID is located, the NSACF, stores the PDU Session ID and the Access Type and increases the number of PDU Sessions for that S-NSSAI. If the NSACF did not locate the UE ID, it creates an entry for the UE ID, stores the PDU Session ID and Access Type and increases the number of PDU Sessions for that S-NSSAI.
If the update flag parameter from the SMF anchoring the PDU session indicates decrease value, the current number of PDU Sessions per S-NSSAI, the NSACF locates the UE ID and decreases the number of PDU Sessions for that S-NSSAI and removes the related PDU Session ID entry. If the UE ID has no more PDU sessions, after the decrease, the NSACF removes the UE ID entry.
If the update flag parameter from the SMF anchoring the PDU session indicates update value, the NSACF locates the existing entry with UE ID and PDU Session ID and replaces the Access Type in the existing entry.
The NSACF takes the Access Type parameter into account for increasing and decreasing the number of PDU Sessions per S-NSSAI as described in clause 5.15.11.2 of TS 23.501 [2]. For MA PDU Session, if the SMF received information that the UE is registered over both accesses, the SMF provides multiple Access Types to the NSACF. If the NSACF receives a request containing multiple Access Types, the NSACF provides a Result indication for each Access Type.
4. The NSACF acknowledges the update to the anchor SMF with Nnsacf_NSAC_NumOfPDUsUpdate_Response message including a Result indication. If the NSACF returns a Result indication including 'maximum number of PDU Sessions per S-NSSAI reached', the SMF rejects the PDU Session establishment request with reject cause set to 'maximum number of PDU Sessions per S-NSSAI reached' and optionally a back-off timer and the Access Type.
For MA PDU Session Establishment, the NSACF may accept the MA PDU Session and may provide to the SMF a Result indicating 'maximum number of PDU Sessions per S-NSSAI reached' or 'maximum number of PDU Sessions per S-NSSAI not reached' associated with an Access Type. If the NSACF indicates a failure that is associated with the Access Type over which the UE sent the MA PDU Session Establishment Request, the SMF sends to the UE a PDU Session Establishment Reject with a Result indication including 'maximum number of PDU Sessions per S-NSSAI reached' ,optionally a back-off timer and the Access Type. When the SMF rejects the MA PDU Session, the SMF sets the Access Type parameter as follows:
- If the UE is registered via both accesses and:
- If the NSACF indicates failure for both accesses, the Access Type indicates both accesses;
- If the NSACF indicates failure for the access over which the MA PDU Session Establishment Request is received, the Access Type indicates the access over which the MA PDU Session Request is received.
NOTE 5: If the UE is registered in both accesses and the NSACF indicates failure for the access different from the access over which the MA PDU Session Establishment Request is received, the SMF accepts the MA PDU Session Request and does not provide back-off timer to the UE.
- If the UE is registered via a single access, the Access Type indicates the access over which the MA PDU Session Request is received.
- For MA PDU Session Release over single Access Type, the NSACF locates the existing entry with PDU Session ID and if founds the entry with both Access Type then it removes only the received Access Type entry while keeping the PDU Session ID.
For a centralized architecture the following differences apply:
- In step 2, the SMF additionally includes the NSAC service area the SMF belongs to, if available, as an additional parameter in the Nnsacf_NSAC_NumOfPDUsUpdate_Request.
- In step 3, based on operator configuration, the NSACF performs the validation against the maximum number of PDU Sessions established on the S-NSSAI per NSAC service area, if applicable and available, or maximum number of PDU Sessions established on the S-NSSAI in the entire PLMN. Additionally the NSACF stores the NSAC service area of SMF if available.
4.2.11.4a Hierarchical NSACF-based Number of PDU Sessions per network slice availability check and update procedure
Figure 4.2.11.4a-1: Hierarchical NSAC-based number of PDU Sessions per network slice availability check and update procedure
For an S-NSSAI subject to counting of the number of PDU sessions, if hierarchical NSACF architecture is deployed in the network the enforcement of maximum number of PDU Session established for an S-NSSAI is performed as follow:
1-2. Same as for steps 1-2 defined in clause 4.2.11.4.
3. The NSACF performs NSAC for the indicated S-NSSAI.
If the PDU session ID entry update at the NSACF is possible, e.g. create a new entry associated with the received NSAC request for increase case, the same action as for step 3 defined in clause 4.2.11.4 is executed. Steps 4-8 are skipped.
If the PDU session ID entry at the NSACF is not possible, i.e. by admitting the PDU session the local maximum PDU session number is exceeded, the NSACF delegates the request to the Primary NSACF for an updated local maximum PDU sessions from the Primary NSACF.
4. If the Primary NSACF has not been discovered before, the NSACF discovers and selects the Primary NSACF, which manages the global NSAC service area as for clause 6.3.22 of TS 23.501 [2].
5. The NSACF invokes Nnsacf_NSAC_NumOfPDUsUpdate request to the Primary NSACF. The request message includes the S-NSSAI.
6. The Primary NSACF checks the global maximum PDU session number and determines whether to accept or reject the request to update local maximum PDU session number from NSACF.
NOTE: When NSACF sends a delegation request to the Primary NSACF, the Primary NSACF either increases local maximum number at NSACF or rejects the NSAC request.
7. The Primary NSACF returns the Nnsacf_NSAC_NumOfPDUsUpdate response. The response includes a new allocated local maximum PDU sessions number or an indication to reject the request to update local maximum PDU session number.
8. If the primary NSACF provides an updated local maximum number, the NSACF replaces the local maximum PDU session number with the received local maximum PDU sessions number value. The same action is executed as for step 3 in clause 4.2.11.4 based on the updated configured value.
9. Same as for step 4 of clause 4.2.11.4. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.2.11.5 Network Slice Admission Control Support for Roaming | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.2.11.5.1 Network Slice Admission Control Support for Roaming by VPLMN | This clause describes the case of VPLMN NSAC admission mode.
For NSAC for roaming UEs, a maximum number of allowed UEs per mapped S-NSSAI in HPLMN and/or a maximum number of allowed PDU Sessions in LBO mode per mapped S-NSSAI in HPLMN is allocated to the VPLMN for each S-NSSAI in HPLMN and stored in one NSCAF in the VPLMN responsible for NSAC for the S-NSSAI in the HPLMN, subject to NSAC.
Enforcement for the maximum number of UEs registered with a network slice is done in the VPLMN by the NSACF in the VPLMN as per the description in Figure 4.2.11.2-1 with the following differences:
- Step 2, in the Nnsacf_NSAC_NumOfUEsUpdate_Request service operation where the AMF provides both the S-NSSAI in VPLMN and the corresponding mapped S-NSSAI in HPLMN to the NSACF in the VPLMN.
- Step 3, the NSACF in the VPLMN performs NSAC for both the S-NSSAI in VPLMN and the corresponding mapped S-NSSAI in HPLMN based on the SLA between VPLMN and HPLMN.
For LBO PDU sessions, enforcement for the maximum number of PDU Sessions established for an S-NSSAI is performed in the VPLMN by the NSACF in the VPLMN as per the description in Figure 4.2.11.4-1 with the following differences:
- Step 2, in the Nnsacf_NSAC_NumOfPDUsUpdate_Request service operation where the V-SMF provides both the S-NSSAI in VPLMN and the corresponding mapped S-NSSAI in HPLMN to the NSACF in the VPLMN.
- Step 3, the NSACF in the VPLMN performs NSAC for both the S-NSSAI in VPLMN and the corresponding mapped S-NSSAI in HPLMN based on the SLA between VPLMN and HPLMN.
An NSACF at VPLMN can optionally fetch the maximum number of registered UEs to be enforced and the maximum number of LBO PDU sessions to be enforced rather than have them pre-configured. In this case, the following is performed:
- For a centralized NSAC architecture in the VPLMN, the NSACF, being a centralized NSACF, issues the Nnsacf_NSAC_QuotaUpdate Request to fetch from the HPLMN centralized NSACF or primary NSACF the maximum number of registered UEs and the maximum number of LBO PDU sessions to be enforced.
- For a hierarchical NSAC architecture in the VPLMN, the NSACF issues the Nnsacf_NSAC_NumOfUEsUpdate_Request or Nnsacf_NSAC_NumOfPDUsUpdate_Request to the VPLMN primary NSACF for NSAC for the maximum number of registered UEs, or NSAC for the maximum number of LBO PDU sessions. The VPLMN primary NSACF in turn issues the Nnsacf_NSAC_QuotaUpdate Request, to fetch from the HPLMN centralized NSACF or primary NSACF the maximum number of registered UEs, or the maximum number of LBO PDU sessions to be admitted; this information in turn may be distributed to the VPLMN NSACF.
The NSACF in VPLMN discovers the primary or central NSACF in HPLMN as defined in clause 6.3.22 of TS 23.501 [2], or optionally be configured with the needed information. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.2.11.5.2 Network Slice Admission Control Support for Roaming by HPLMN | 4.2.11.5.2.1 General
For maximum number of UEs in roaming case, there are two types of NSAC admission modes requiring interaction with HPLMN for inbound roamers; VPLMN with HPLMN assistance NSAC admission mode or HPLMN NSAC admission mode.
For PDU sessions in the home-routed roaming case, the SMF in HPLMN performs NSAC for the S-NSSAI(s) subject to NSAC.
For LBO PDU sessions, there are two types of NSAC admission mode requiring interaction with HPLMN for LBO PDU sessions; VPLMN with HPLMN assistance NSAC admission mode or HPLMN NSAC admission mode.
4.2.11.5.2.2 VPLMN with HPLMN assistance NSAC admission mode
For inbound roamers, depending on the NSAC architecture deployed in the VPLMN, enforcement for the maximum number of registered UEs with an S-NSSAI is done in the VPLMN by an NSACF in the VPLMN per the procedure described in clause 4.2.11.2 or 4.2.11.2a with the following differences:
- The AMF verifies the applicable NSAC admission mode for the inbound roamer based on the subscription data from UDM.
- When the AMF invokes the Nnsacf_NSAC_NumOfUEsUpdate_Request service operation with the NSACF in the VPLMN, the AMF provides in the Request the additional NSAC admission mode parameter, i.e. VPLMN with HPLMN assistance NSAC admission mode.
- If the maximum number of UEs is not available or the maximum number of UEs has been reached at the Primary (or Central) NSACF of the VPLMN and the type of NSAC admission mode is VPLMN with HPLMN assistance NSAC admission mode, the following is performed:
- The Primary (or Central) NSACF in the VPLMN invokes Nnsacf_NSAC_NumOfUEsUpdate_Request to the Primary (or central) NSACF in the HPLMN for NSAC delegation and to receive an initial or a new allocated maximum number of UEs for the mapped S-NSSAI in HPLMN for inbound roamers. The request includes mapped S-NSSAI in HPLMN, PLMN ID and NSAC admission mode.
- The Primary (or central) NSACF in HPLMN provides Nnsacf_NSAC_NumOfUEsUpdate_Response message to the Primary (or Central) NSACF of VPLMN. The response message includes mapped S-NSSAI in HPLMN, the new allocated maximum number of UEs for the mapped S-NSSAI in HPLMN for inbound roamers. Alternatively, the Primary (or central) NSACF rejects the request for the NSAC delegation.
- The Primary (or central) NSACF in VPLMN updates the previous stored maximum number of UEs based on the new received allocated maximum UEs number.
- At any time, the Primary (or central) NSACF in HPLMN may trigger Nnsacf_NSAC_LocalNumberUpdate Request message to the Primary (or central) NSAC in VPLMN to provide an updated maximum number of registered UEs for the mapped S-NSSAI in HPLMN for inbound roamers. Based on the updated maximum UEs number of the S-NSSAI, where applicable, the Primary NSACF in VPLMN may further perform distribution of local maximum UEs number to the NSACFs it interacts with. For more detail refer to clause 4.2.11.6.
The complete procedure of the VPLMN with HPLMN assistance NSAC admission mode for number of registered UEs is described in clause 4.2.11.5.2.3.
For LBO PDU sessions, depending on the NSAC architecture deployed in the VPLMN, enforcement for the maximum number of LBO PDU sessions established for an S-NSSAI is performed by the NSACF in the VPLMN per the procedure described in clause 4.2.11.4 or 4.2.11.4a with the following differences:
- The SMF verifies the applicable NSAC admission mode for the S-NSSAI PDU session associated with the inbound roamer based on the subscription data from UDM.
- When the SMF invokes the Nnsacf_NSAC_NumOfPDUsUpdate_Request service operation to the NSACF in the VPLMN, the SMF provides in the Request the additional NSAC admission mode parameter, i.e. VPLMN with HPLMN assistance NSAC admission mode.
- If the maximum number of PDU Session is not available or the maximum number of PDU Sessions has been reached at the Primary (or Central) NSACF of the VPLMN and the type of NSAC admission mode is VPLMN with HPLMN assistance NSAC admission mode, the following is performed:
- The Primary (or Central) NSACF in the VPLMN invokes Nnsacf_NSAC_NumOfPDUsUpdate_Request to the Primary (or central) NSACF in the HPLMN for the NSAC delegation and to receive an initial or a new allocated maximum number of LBO PDU Sessions for the mapped S-NSSAI in HPLMN for inbound roamers. The request includes mapped S-NSSAI in HPLMN, PLMN ID and NSAC admission mode.
- The Primary (or central) NSACF in HPLMN provides the Nnsacf_NSAC_NumOfPDUsUpdate_Response message to the Primary NSACF of VPLMN. The response message includes mapped S-NSSAI in HPLMN, the allocated maximum number of LBO PDU Sessions for the mapped S-NSSAI in HPLMN for inbound roamers. Alternatively, the Primary (or central) NSACF rejects the request for the NSAC delegation.
- The Primary (or central) NSACF in VPLMN updates the previous stored maximum number of PDU Sessions based on the new received allocated maximum number of LBO PDU Sessions.
- At any time, the Primary (or central) NSACF in HPLMN may trigger Nnsacf_NSAC_LocalNumberUpdate Request message to the Primary (or central) NSAC in VPLMN to provide an updated new allocated maximum number of LBO PDU Sessions for the mapped S-NSSAI in HPLMN for the roaming UEs. Based on the updated maximum number of LBO PDU Sessions number of the S-NSSAI, where applicable, the Primary NSACF in VPLMN may further perform distribution of local maximum PDU Sessions number to the NSACFs it contacts. For more detail refer to clause 4.2.11.6.
The complete procedure for the VPLMN with HPLMN assistance NSAC Admission mode for number of registered UEs and number of LBO PDU Sessions is described in Clause 4.2.11.5.2.4.
NSACF nodes to be contacted in all the above are either configured or discovered.
4.2.11.5.2.3 VPLMN with HPLMN assistance NSAC Admission mode for number of Registered UEs
Figure 4.2.11.5.2.3-1: HPLMN Delegated NSAC admission for UE number Procedure
The procedure of NSAC for maximum number of UEs for a roaming UE registration is performed as follows:
1. Same as step 1 defined in clause 4.2.11.2. For the inbound roaming UE, the AMF checks the NSAC admission mode of the registered S-NSSAI based on the subscription data from UDM.
If the Hierarchical NSAC architecture is deployed in the VPLMN, steps 2a-3a are executed and step 2b is skipped.
2a. The AMF invokes Nnsacf_NSAC_NumOfUEsUpdate request to the NSACF in VPLMN same as step 2 of clause 4.2.11.2a with the additional parameter NSAC admission mode, i.e. VPLMN with HPLMN assistance NSAC admission mode.
3a. Same procedure of steps 3-5 in clause 4.2.11.2a is executed.
If the centralized NSAC architecture is deployed in the VPLMN, step 2b is executed and steps 2a-3a are skipped.
2b. The AMF invokes Nnsacf_NSAC_NumOfUEsUpdate request to the central NSACF in VPLMN same as step 2 of clause 4.2.11.2 with the additional parameter NSAC admission mode, i.e. VPLMN with HPLMN assistance NSAC admission mode.
4. If there is no allocated maximum number of UEs from HPLMN or the allocated maximum number of registered UEs has been reached and the type of NSAC admission mode is VPLMN with HPLMN assistance NSAC admission mode, the Primary (or central) NSACF in VPLMN interacts with HPLMN. In this case, steps 5-7 are executed. Otherwise, steps 5-7 are skipped.
The Primary (or central) NSACF in VPLMN discovers the Primary (or central) NSACF in HPLMN.
NOTE 1: The Primary (or central) NSACF in HPLMN can be configured or be discovered via NRF.
5. The Primary (or central) NSACF in the VPLMN invokes Nnsacf_NSAC_NumOfUEsUpdate Request to the Primary (or central) NSACF in the HPLMN for NSAC delegation and to receive an initial or an updated maximum number of registered UEs for the mapped S-NSSAI in HPLMN for the inbound roamers. The request includes mapped S-NSSAI in HPLMN, PLMN ID and NSAC admission mode.
6. The Primary (or central) NSACF in HPLMN invokes Nnsacf_NSAC_NumOfUEsUpdate Response message to the Primary (or central) NSACF of VPLMN. The response message includes mapped S-NSSAI in HPLMN, the allocated maximum number of registered UEs for the mapped S-NSSAI in HPLMN for inbound roamers. Alternatively, the Primary (or central) NSACF in HPLMN rejects the request for the NSAC delegation.
7. The Primary (or central) NSACF in VPLMN updates the previous stored maximum number of UE based on the received allocated maximum number of UEs.
If the Hierarchical NSAC architecture is deployed in the VPLMN, steps 8a-9a are executed and steps 8b-9b are skipped.
8a. This step is executed only if the NSACF in VPLMN has interacted with Primary NSACF in VPLMN at step 3a before. The NSACF with the assistance of Primary NSACF in VPLMN perform NSAC according to the steps 6-8 in clause 4.2.11.2a.
9a. Based on the response from Primary NSACF in VPLMN, the NSACF in VPLMN returns the response (i.e. acceptance or rejection) message to the AMF. The AMF provides the corresponding response to the inbound roaming UE.
If the centralized NSAC architecture is deployed in the VPLMN, steps 8b-9b are executed and steps 8a-9a are skipped.
8b. Same as the step 3 in clause 4.2.11.2 with the replacement of NSACF with Central NSACF.
9b. The Central NSACF in VPLMN returns the response (i.e. acceptance or rejection) message to the AMF. The AMF provides the corresponding response to the inbound roaming UE.
4.2.11.5.2.4 VPLMN with HPLMN assistance NSAC Admission mode for number of LBO PDU Sessions
Figure 4.2.11.5.2.4-1: HPLMN Delegated NSAC admission for PDU Session number procedure
The NSAC procedure for maximum number of LBO PDU Sessions for inbound roamers, is performed as follow:
1. Same as steps 1 defined in clause 4.2.11.4. For the inbound roaming UE, the SMF checks the NSAC admission mode of the S-NSSAI for the LBO PDU session based on the subscription data from UDM.
If the Hierarchical NSAC architecture is deployed in the VPLMN, steps 2a-3a are executed and step 2b is skipped.
2a. The SMF invokes Nnsacf_NSAC_NumOfsPDUsUpdate request to the NSACF in VPLMN same as step 2 of clause 4.2.11.4 with the additional parameter NSAC admission mode, i.e. VPLMN with HPLMN assistance NSAC admission mode.
3a. Same procedure of steps 3-5 in clause 4.2.11.4a is executed.
If the centralized NSAC architecture is deployed in the VPLMN, step 2b is executed and steps 2a-3a are skipped.
2b. The SMF invokes Nnsacf_NSAC_NumOfsPDUsUpdate request to the central NSACF in VPLMN same as step 2 of clause 4.2.11.4 with the additional parameter NSAC admission mode, i.e. VPLMN with HPLMN assistance NSAC admission mode.
4-7. The same procedure as step 4-7 of Figure 4.2.11.5.2.3-1 is applied with the difference that the maximum number of registered UE parameter is replaced with the maximum number of LBO PDU Sessions number. Nnsacf_NSAC_NumOfUEsUpdate service operation is replaced with Nnsacf_NSAC_NumOfPDUsUpdate service operation.
If the Hierarchical NSAC architecture is deployed in the VPLMN, steps 8a-9a are executed and steps 8b are skipped.
8a. This step is executed only if the NSACF in VPLMN has interacted with Primary NSACF in VPLMN at step 3a before. The NSACF with the assistance of Primary NSACF in VPLMN performs NSAC according to the steps 6-8 in clause 4.2.11.4a.
9a. Based on the response from Primary NSACF in VPLMN, the NSACF in VPLMN returns the response (i.e. acceptance or rejection) message to the SMF. The SMF provides the corresponding response to the inbound roaming UE.
If the centralized NSAC architecture is deployed in the VPLMN, steps 8b-9b are executed and steps 8a-9a are skipped.
8b. Same as the step 3 in clause 4.2.11.4 with the replacement of NSACF with Central NSACF.
9b. The Central NSACF in VPLMN returns the response (i.e. acceptance or rejection) message to the SMF. The SMF provides the corresponding response to the inbound roaming UE.
4.2.11.5.2.5 HPLMN NSAC Admission
Monitoring and enforcement for the maximum number of UEs registered with a network slice monitoring is done by the NSACF in the HPLMN per the procedure described in clause 4.2.11.2 with the following differences:
- Step 1, the AMF verifies the applicable NSAC admission mode for the registered S-NSSAI for the UE based on the subscription data from UDM. The S-NSSAI is the mapped S-NSSAI in HPLMN.
- Step 2, in the Nnsacf_NSAC_NumOfUEsUpdate_Request service operation the V-AMF provides both the S-NSSAI in VPLMN and the corresponding mapped S-NSSAI in HPLMN to the NSACF in the HPLMN.
- Step 3, the NSCAF in the HPLMN performs NSAC for the corresponding mapped S-NSSAI in HPLMN.
Enforcement of the maximum number of LBO PDU Sessions established for an S-NSSAI is performed by the NSACF in the HPLMN as per the procedure described in clause 4.2.11.4 with the following differences:
- Step 1, the SMF verifies the applicable NSAC admission mode for the S-NSSAI used for the established PDU session based on the subscription data from UDM. The S-NSSAI is the mapped S-NSSAI in HPLMN.
- Step 2, in the Nnsacf_NSAC_NumOfPDUsUpdate_Request service operation the V-SMF provides both the S-NSSAI in VPLMN and the corresponding mapped S-NSSAI in HPLMN to the NSACF in the VPLMN.
- Step 3, the NSACF in the HPLMN performs NSAC for the corresponding mapped S-NSSAI in HPLMN.
NSACF nodes to be contacted in all the above are either configured or discovered as defined in clause 6.3.22 of TS 23.501 [2]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.2.11.6 Update of local maximum number in Hierarchical NSAC Architecture | Figure 4.2.11.6-1: Update of local maximum number in hierarchical NSAC architecture
At any time the Primary NSACF may update the allocated local Maximum number of UE and/or PDU sessions configured at the NSACFs as follow:
1. The Primary NSACF decides to update the local maximum number of UE or PDU session values at the NSACF(s), i.e. the configured value at NSACF(s) based on the current registered UE/PDU session number at NSACFs and based on operator policy.
2. The Primary NSACF invokes Nnsacf_NSAC_LocalNumberUpdate Request to the NSACF(s). The message includes the new configured value of local Maximum number of UE or PDU sessions.
NOTE: The new configured value(s) of local maximum number given by the Primary NSACF can be lower than the existing local maximum number configured at the NSACF(s).
3. The NSACF replaces the local maximum number with the received new local maximum number value.
4. The NSACF returns the Nnsacf_NSAC_LocalNumberUpdate Response to the Primary NSACF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3 Session Management procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.1 General | Clause 4.3 defines the Session Management related procedures. It refers to clause 4.4 for the N4 interactions.
As defined in clause 5.6.3 of TS 23.501 [2], considering the case of Home Routed PDU Session, the NAS SM information processing by SMF considers following kind of NAS SM information:
- Information that both the V-SMF and H-SMF process: indication of the nature of the NAS SM signalling (e.g. PDU Session Establishment Request), PDU Session Type, Session-AMBR, UE addressing information (allocated IPv4 address, interface identifier).
- Information that is not visible to the V-SMF, only processed by the H-SMF: SSC mode, Protocol Configuration Options, SM PDU DN Request Container, QoS Rule(s) and QoS Flow level QoS parameters if any for the QoS Flow(s) associated with the QoS rule(s).
NOTE 1: "Information that is not visible to the V-SMF" refers to information that the V-SMF is to relay between the UE and the H-SMF (and that it can store in CDR) but that the V-SMF is not assumed to process otherwise.
The NAS SM information processing split between V-SMF and H-SMF is transparent to the UE.
Both V-SMF and H-SMF process information interpreted by the AMF as the PDU Session ID, the DNN, the S-NSSAI (with values for the Serving PLMN and HPLMN processed by the V-SMF and with a value for the HPLMN processed by the H-SMF).
In the case of Home Routed PDU Session the H-SMF provides also the V-SMF with the IPv6 Prefix allocated to the PDU Session.
NOTE 2: IPv6 Prefix allocated to the PDU Session is provided to allow the V-SMF fulfilling regulatory requirements for data storage in the visited country.
In non roaming and LBO cases the SMF processes all NAS SM information.
In HR roaming scenarios, in order to support SM features only requiring support from the H-SMF without impacting the V-SMF, as specified in detail in TS 29.502 [36]:
- The V-SMF transfers NAS SM information, which is not visible to the V-SMF, in a container towards the H-SMF;
- The V-SMF transfers NAS SM information which it does not comprehend (unknown IEs or IEs with an unknown value not set to "reserved" according to the release to which the V-SMF complies), in a different container towards the H-SMF;
- The H-SMF transfers NAS SM information which the V-SMF does not need to interpret, in one container towards the V-SMF;
- The V-SMF appends unknown NAS SM information received in the N16 container at the end of the NAS SM message it sends to the UE.
AMF and SMFs may subscribe at the NWDAF for Signalling Storm Analytics to obtain information related to signalling storms caused by UE or NF signalling as specified in TS 23.288 [50] and may decide to take mitigations actions as described in the present clause 5.19 of TS 23.501 [2], based on the received analytics information. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.2 PDU Session Establishment | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.2.1 General | A PDU Session establishment may correspond to:
- a UE initiated PDU Session Establishment procedure.
- a UE initiated PDU Session handover between 3GPP and non-3GPP.
- a UE initiated PDU Session handover from EPS to 5GS.
- a Network triggered PDU Session Establishment procedure. In this case the network sends the device trigger message to application(s) on the UE side. The payload included in Device Trigger Request message contains information on which application on the UE side is expected to trigger the PDU Session establishment request. Based on that information, the application(s) on the UE side trigger the PDU Session Establishment procedure. For more detail refer to clause 4.13.2.
If the UE is simultaneously registered to a non-3GPP access via a N3IWF/TNGF/W-AGF located in a PLMN different from the PLMN of the 3GPP access, the functional entities in the following procedures are located in the PLMN of the access used to exchange NAS with the UE for the PDU Session.
As specified in clause 5.6.1 of TS 23.501 [2], a PDU Session may be associated either (a) with a single access type at a given time, i.e. either 3GPP access or non-3GPP access, or (b) simultaneously with multiple access types, i.e. one 3GPP access and one non-3GPP access. A PDU Session associated with multiple access types is referred to as Multi Access-PDU (MA PDU) Session and it may be requested by ATSSS-capable UEs.
The following clause 4.3.2.2 specifies the procedures for establishing PDU Sessions associated with a single access type at a given time. The particular procedures associated with MA PDU Sessions are specified as part of the ATSSS procedures in clause 4.22.
For the BH PDU sessions establishment by a MWAB-UE specified in clause 5.49.1 of TS 23.501 [2], the existing S-NSSAI/DNN control mechanism for PDU session, based on subscription data and policies related to S-NSSAI/DNN, is applied for the MWAB-UE during the PDU session establishment. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.2.2 UE Requested PDU Session Establishment | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.2.2.1 Non-roaming and Roaming with Local Breakout | Clause 4.3.2.2.1 specifies PDU Session establishment in the non-roaming and roaming with local breakout cases. The procedure is used to:
- Establish a new PDU Session;
- Handover a PDN Connection in EPS to PDU Session in 5GS without N26 interface;
- Switching an existing PDU Session between non-3GPP access and 3GPP access. The specific system behaviour in this case is further defined in clauses 4.9.2 and 4.9.3; or
- Request a PDU Session for Emergency services.
In the case of roaming, the AMF determines if a PDU Session is to be established in LBO or Home Routing. In the case of LBO, the procedure is as in the case of non-roaming with the difference that the AMF, the SMF, the UPF and the PCF are located in the visited network. PDU Sessions for Emergency services are never established in Home Routed mode. If Control Plane CIoT 5GS Optimisation is enabled for the PDU session with LBO, the NEF is not used as the anchor of this PDU Session.
NOTE 1: UE provides both the S-NSSAIs of the Home PLMN and Visited PLMN to the network as described in clause 5.15.5.3 of TS 23.501 [2].
Figure 4.3.2.2.1-1: UE-requested PDU Session Establishment for non-roaming and roaming with local breakout
The procedure assumes that the UE has already registered on the AMF thus unless the UE is Emergency Registered the AMF has already retrieved the user subscription data from the UDM.
1. From UE to AMF: NAS Message (S-NSSAI(s), [Alternative S-NSSAI], UE Requested DNN, PDU Session ID, Request type, Old PDU Session ID, N1 SM container (PDU Session Establishment Request, [Port Management Information Container])).
In order to establish a new PDU Session, the UE generates a new PDU Session ID.
The UE initiates the UE Requested PDU Session Establishment procedure by the transmission of a NAS message containing a PDU Session Establishment Request within the N1 SM container. The PDU Session Establishment Request includes a PDU session ID, Requested PDU Session Type, a Requested SSC mode, 5GSM Capability, PCO, SM PDU DN Request Container, [Number Of Packet Filters], [Header Compression Configuration], UE Integrity Protection Maximum Data Rate, [Always-on PDU Session Requested], [RSN], [URSP rule enforcement reports] and [PDU Session Pair ID].
The Request Type indicates "Initial request" if the PDU Session Establishment is a request to establish a new PDU Session and indicates "Existing PDU Session" if the request refers to an existing PDU Session switching between 3GPP access and non-3GPP access or to a PDU Session handover from an existing PDN connection in EPC. If the request refers to an existing PDN connection in EPC, the S-NSSAI is set as described in clause 5.15.7.2 of TS 23.501 [2]
When Emergency service is required and an Emergency PDU Session is not already established, a UE shall initiate the UE Requested PDU Session Establishment procedure with a Request Type indicating "Emergency Request".
The Request Type indicates "Emergency Request" if the PDU Session Establishment is a request to establish a PDU Session for Emergency services. The Request Type indicates "Existing Emergency PDU Session" if the request refers to an existing PDU Session for Emergency services switching between 3GPP access and non-3GPP access or to a PDU Session handover from an existing PDN connection for Emergency services in EPC.
The 5GSM Core Network Capability is provided by the UE and handled by SMF as defined in clause 5.4.4b of TS 23.501 [2].
The Number Of Packet Filters indicates the number of supported packet filters for signalled QoS rules for the PDU Session that is being established. The number of packet filters indicated by the UE is valid for the lifetime of the PDU Session. For presence condition, see TS 24.501 [25].
The UE Integrity Protection Maximum Data Rate indicates the maximum data rate up to which the UE can support UP integrity protection. The UE shall provide the UE Integrity Protection Data Rate capability independently of the Access Type over which the UE sends the PDU Session Establishment Request.
If the use of header compression for Control Plane CIoT 5GS optimisation was negotiated successfully between the UE and the network in the previous registration procedure, the UE shall include the Header Compression Configuration, unless "Unstructured" PDU Session Type is indicated. The Header Compression Configuration includes the information necessary for the header compression channel setup. Optionally, the Header Compression Configuration may include additional header compression context parameters.
The NAS message sent by the UE is encapsulated by the AN in a N2 message towards the AMF that should include User location information and Access Type Information.
The PDU Session Establishment Request message may contain SM PDU DN Request Container containing information for the PDU Session authorization by the external DN.
The UE includes the S-NSSAI from the Allowed NSSAI of the current access type or Partially Allowed NSSAI. If the UE is provided with the mapping of an S-NSSAI that is replaced by an Alternative S-NSSAI, the UE shall provide both the Alternative S-NSSAI and the S-NSSAI that is replaced by it. If the Mapping of Allowed NSSAI or Mapping Of Partially Allowed NSSAI was provided to the UE, the UE shall provide both the S-NSSAI of the VPLMN from the Allowed NSSAI or Partially Allowed NSSAI and the corresponding S-NSSAI of the HPLMN from the Mapping Of Allowed NSSAI or Mapping Of Partially Allowed NSSAI. If the UE is provided with the mapping of the VPLMN S-NSSAI to a VPLMN Alternative S-NSSAI, the UE provides both the VPLMN Alternative S-NSSAI and the VPLMN S-NSSAI in the PDU Session Establishment message. If the UE is provided with the mapping of the HPLMN S-NSSAI to a HPLMN Alternative S-NSSAI, the UE provides both the HPLMN Alternative S-NSSAI and the HPLMN S-NSSAI in the PDU Session Establishment message. The AMF verifies whether the Alternative S-NSSAI and the S-NSSAI provided in the PDU Session Establishment Request message is valid based on the UE context as described in clause 5.15.19 of TS 23.501 [2].
If the procedure is triggered for SSC mode 3 operation, the UE shall also include the Old PDU Session ID which indicates the PDU Session ID of the on-going PDU Session to be released, in NAS message. The Old PDU Session ID is included only in this case.
The AMF receives from the AN the NAS SM message (built in step 1) together with User Location Information (e.g. Cell Id in the case of the NG-RAN).
The UE shall not trigger a PDU Session establishment for a PDU Session corresponding to a LADN when the UE is outside the area of availability of the LADN.
The UE shall not trigger a PDU Session establishment for a PDU Session associated to an S-NSSAI if the S-NSSAI is not valid as per the S-NSSAI location availability information.
If the UE is establishing a PDU session for IMS and the UE is configured to discover the P-CSCF address during connectivity establishment, the UE shall include an indicator that it requests a P‑CSCF IP address(es) within the SM container.
The PS Data Off status is included in the PCO in the PDU Session Establishment Request message.
The UE capability to support Reliable Data Service is included in the PCO in the PDU Session Establishment Request message.
If the UE has indicated that it supports transfer of Port Management Information Containers as per UE 5GSM Core Network Capability and if the PDU session type is Ethernet, then the UE shall include the MAC address of the DS-TT Ethernet port used for this Ethernet PDU session. If the UE is aware of the UE-DS-TT Residence Time, then the UE shall additionally include the UE-DS-TT Residence Time.
If the UE requests to establish always-on PDU session, the UE includes an Always-on PDU Session Requested indication in the PDU Session Establishment Request message.
As described in TS 23.548 [74], a UE that hosts EEC(s) may indicate in the PCO that it supports the ability to receive ECS address(es) via NAS and to transfer the ECS Address(es) to the EEC(s).
A UE that hosts the EDC functionality shall indicate in the PCO its capability to support the EDC functionality (see clause 5.2.1 of TS 23.548 [74]).
The UE may also include PDU Session Pair ID and/or RSN in PDU Session Establishment Request message as described in clause 5.33.2.1 of TS 23.501 [2].
A UE that supports EAS re-discovery as described in clause 6.2.3.3 of TS 23.548 [74], may indicate so in the PCO.
Port Management Information Container may be received from DS-TT and includes port management capabilities, i.e. information indicating which standardized and deployment-specific port management information is supported by DS-TT as defined in clause 5.28.3 of TS 23.501 [2].
If UE supports to report URSP rule enforcement to network and the URSP rule that triggered this PDU Session Establishment Request included the Indication for reporting URSP rule enforcement, the UE may provide URSP rule enforcement report as described in clause 6.6.2.4 of TS 23.503 [20].
2. For NR satellite access, the AMF may decide to verify the UE location as described in clause 5.4.11.4 of TS 23.501 [2].
The AMF determines that the message corresponds to a request for a new PDU Session based on that Request Type indicates "initial request" and that the PDU Session ID is not used for any existing PDU Session of the UE. If the NAS message does not contain an S-NSSAI, the AMF determines an S-NSSAI of the Serving PLMN for the requested PDU Session from the current Allowed NSSAI for the UE. If there is only one S-NSSAI in the Allowed NSSAI, this S-NSSAI shall be used. If there is more than one S-NSSAI in the Allowed NSSAI, the S-NSSAI selected is either according to the UE subscription, if the subscription contains only one default S-NSSAI and the corresponding mapped HPLMN S-NSSAI of the Serving PLMN is included in the Allowed NSSAI, or based on operator policy (e.g. also ensures any UE Requested DNN is allowed for the selected S-NSSAI)). When the NAS Message does not contain a DNN, the AMF determines the DNN for the requested PDU Session by selecting the default DNN for the S-NSSAI (irrespective of whether the S-NSSAI is included in the NAS message or determined by the AMF) if the default DNN is present in the UE's Subscription Information (or for the corresponding S-NSSAI of the HPLMN, in the case of LBO); otherwise the serving AMF selects a locally configured DNN for this S-NSSAI of the Serving PLMN. If the AMF cannot select an SMF (e.g. the UE requested DNN is not supported by the network, or the UE requested DNN is not in the Subscribed DNN List for the S-NSSAI (or its mapped value for the HPLMN in the case of LBO) and wildcard DNN is not included in the Subscribed DNN list), the AMF shall, based on operator policies received from PCF, either reject the NAS Message containing PDU Session Establishment Request from the UE with an appropriate cause or request PCF to replace the UE requested DNN by a selected DNN. If the DNN requested by the UE is present in the UE subscription information but indicated for replacement in the operator policies received from PCF, the AMF shall request the PCF to perform a DNN replacement to a selected DNN. AMF requests DNN replacement as specified in clause 4.16.2.1.1. If the DNN requested by the UE is present in the UE subscription information but not supported by the network and not indicated for replacement in the operator policies received from PCF, the AMF shall reject the NAS Message containing PDU Session Establishment Request from the UE with an appropriate cause value.
The AMF selects an SMF as described in clause 6.3.2 of TS 23.501 [2] and clause 4.3.2.2.3. If the Request Type indicates "Initial request" or the request is due to handover from EPS or from non-3GPP access serving by a different AMF, the AMF stores an association of the S-NSSAI(s), the DNN, the PDU Session ID, the SMF ID as well as the Access Type of the PDU Session. If the AMF determines to replace the S-NSSAI received from the UE with the Alternative S-NSSAI or the AMF receives the Alternative S-NSSAI and the S-NSSAI is by the UE, the AMF selects the SMF based on the Alternative S-NSSAI.
During registration procedures, the AMF determines the use of the Control Plane CIoT 5GS Optimisation or User Plane CIoT 5GS Optimisation based on UEs indications in the 5G Preferred Network Behaviour, the serving operator policies and the network support of CIoT 5GS optimisations. The AMF selects an SMF that supports Control Plane CIoT 5GS optimisation or User Plane CIoT 5GS Optimisation as described in clause 6.3.2 of TS 23.501 [2].
If the Request Type is "initial request" and if the Old PDU Session ID indicating the existing PDU Session is also contained in the message, the AMF selects an SMF as described in clause 4.3.5.2 and stores an association of the new PDU Session ID, the S-NSSAI(s), the selected SMF ID as well as Access Type of the PDU Session.
If the Request Type indicates "Existing PDU Session", the AMF selects the SMF based on SMF-ID received from UDM. The case where the Request Type indicates "Existing PDU Session" and either the AMF does not recognize the PDU Session ID or the subscription context that the AMF received from UDM during the Registration or Subscription Profile Update Notification procedure does not contain an SMF ID corresponding to the PDU Session ID constitutes an error case. The AMF updates the Access Type stored for the PDU Session.
If the Request Type indicates "Existing PDU Session" referring to an existing PDU Session moved between 3GPP access and non-3GPP access, then if the Serving PLMN S-NSSAI of the PDU Session is present in the Allowed NSSAI of the target access type or Partially Allowed NSSAI, the PDU Session Establishment procedure can be performed in the following cases:
- the SMF ID corresponding to the PDU Session ID and the AMF belong to the same PLMN;
- the SMF ID corresponding to the PDU Session ID belongs to the HPLMN;
Otherwise the AMF shall reject the PDU Session Establishment Request with an appropriate reject cause.
NOTE 2: The SMF ID includes the PLMN ID that the SMF belongs to.
The AMF shall reject a request coming from an Emergency Registered UE and the Request Type indicates neither "Emergency Request" nor "Existing Emergency PDU Session". When the Request Type indicates "Emergency Request", the AMF is not expecting any S-NSSAI and DNN value provided by the UE and uses locally configured values instead. The AMF stores the Access Type of the PDU Session.
If the Request Type indicates "Emergency Request" or "Existing Emergency PDU Session", the AMF selects the SMF as described in clause 5.16.4 of TS 23.501 [2].
If the AMF is running a slice deregistration inactivity timer for the S-NSSAI of the PDU Session and the timer is associated with the Access Type over which the PDU Session Establishment Request was received, the AMF stops the timer.
3. From AMF to SMF: Either Nsmf_PDUSession_CreateSMContext Request (SUPI, selected DNN, UE requested DNN, S-NSSAI(s), [Alternative S-NSSAI], [Slice Area Restriction indication], PDU Session ID, AMF ID, Request Type, [PCF ID, Same PCF Selection Indication], Priority Access, [Small Data Rate Control Status], N1 SM container (PDU Session Establishment Request), User location information, Access Type, RAT Type, PEI, GPSI, UE presence in LADN service area, Subscription For PDU Session Status Notification, DNN Selection Mode, Trace Requirements, Control Plane CIoT 5GS Optimisation indication, Control Plane Only indicator, Satellite backhaul category, Satellite ID, [PVS FQDN(s) and/or PVS IP address(es), Onboarding Indication], Disaster Roaming service indication) or Nsmf_PDUSession_UpdateSMContext Request (SUPI, DNN, S-NSSAI(s), SM Context ID, AMF ID, Request Type, N1 SM container (PDU Session Establishment Request), User location information, Access Type, RAT type, PEI, Serving Network (PLMN ID, or PLMN ID and NID, see clause 5.18 of TS 23.501 [2]), Satellite backhaul category, Satellite ID), [PCF binding information, Request for notification of SM Policy Association establishment and termination].
NOTE 3: Satellite ID was named GEO Satellite ID in earlier Releases of this specification.
If the AMF does not have an association with an SMF for the PDU Session ID provided by the UE (e.g. when Request Type indicates "initial request"), the AMF invokes the Nsmf_PDUSession_CreateSMContext Request, but if the AMF already has an association with an SMF for the PDU Session ID provided by the UE (e.g. when Request Type indicates "existing PDU Session"), the AMF invokes the Nsmf_PDUSession_UpdateSMContext Request.
The AMF sends the S-NSSAI of the Serving PLMN from the Allowed NSSAI or Partially Allowed NSSAI to the SMF. If the AMF determined to replace the S-NSSAI received from the UE with an Alternative S-NSSAI and the AMF selected the SMF based on the Alternative S-NSSAI in step 2, the AMF sends both the S-NSSAI value of the Alternative S-NSSAI and the S-NSSAI value of the S-NSSAI received from the UE to the SMF. If the Alternative S-NSSAI and the S-NSSAI is provided by the UE and the AMF selected the SMF based on the Alternative S-NSSAI in step 2, the AMF sends both the S-NSSAI value of the Alternative S-NSSAI and the S-NSSAI value of the S-NSSAI received from the UE to the SMF. For roaming scenario in local breakout (LBO), the AMF also sends the corresponding S-NSSAI of the HPLMN from the Mapping Of Allowed NSSAI or Mapping Of Partially Allowed NSSAI to the SMF. If the AMF determines to replace the HPLMN S-NSSAI received from the UE with the HPLMN Alternative S-NSSAI or the AMF receives the HPLMN Alternative S-NSSAI and the HPLMN S-NSSAI provided by the UE, the AMF sends both HPLMN S-NSSAI and HPLMN Alternative S-NSSAI to the SMF.
When the AMF determines that the S-NSSAI is subject to area restriction, i.e. the S-NSSAI is configured with an NS-AoS, or the S-NSSAI is present in the Partially Allowed NSSAI, the AMF sends Slice Area Restriction indication to SMF indicating that the PDU Session is subject to area restriction for the S-NSSAI. If the S-NSSAI is replaced with the Alternative S-NSSAI, the AMF checks the area restriction only for the Replaced S-NSSAI.
The AMF ID is the UE's GUAMI which uniquely identifies the AMF serving the UE. The AMF forwards the PDU Session ID together with the N1 SM container containing the PDU Session Establishment Request received from the UE. The GPSI shall be included if available at AMF.
The AMF determines Access Type and RAT Type, see clause 4.2.2.2.1.
The AMF provides the PEI instead of the SUPI when the UE in limited service state has registered for Emergency services (i.e. Emergency Registered) without providing a SUPI. The PEI is defined in clause 5.9.3 of TS 23.501 [2]. If the UE in limited service state has registered for Emergency services (i.e. Emergency Registered) with a SUPI but has not been authenticated the AMF indicates that the SUPI has not been authenticated. The SMF determines that the UE has not been authenticated when it does not receive a SUPI for the UE or when the AMF indicates that the SUPI has not been authenticated.
If the AMF determines that the selected DNN corresponds to an LADN then the AMF provides the "UE presence in LADN service area" that indicates if the UE is IN or OUT of the LADN service area. If the AMF enforces the LADN Service Area per LADN DNN and S-NSSAI, then the AMF also provides an indication that "the PDU Session is subject to LADN per LADN DNN and S-NSSAI".
If the Old PDU Session ID is included in step 1 and if the SMF is not to be reallocated, the AMF also includes Old PDU Session ID in the Nsmf_PDUSession_CreateSMContext Request.
DNN Selection Mode is determined by the AMF. It indicates whether an explicitly subscribed DNN has been provided by the UE in its PDU Session Establishment Request.
The SMF may use DNN Selection Mode when deciding whether to accept or reject the UE request.
When the Establishment cause received as part of AN parameters during the Registration procedure or Service Request procedure is associated with priority services (e.g. MPS, MCX), or when the AMF determines the UE has priority subscription (e.g. MPS, MCX) in the UDM, the AMF includes a Message Priority header to indicate priority information. The SMF uses the Message Priority header to determine if the UE request is subject to exemption from NAS level congestion control. Other NFs relay the priority information by including the Message Priority header in service-based interfaces, as specified in TS 29.500 [17].
In the local breakout case, if the SMF (in the VPLMN) is not able to process some part of the N1 SM information that Home Routed Roaming is required and the SMF responds to the AMF that it is not the right SMF to handle the N1 SM message by invoking Nsmf_PDUSession_CreateSMContext Response service operation. The SMF includes a proper N11 cause code triggering the AMF to proceed with home routed case. The procedure starts again at step 2 of clause 4.3.2.2.2.
In the non-roaming case, for PDU Session with Request Type "initial request", the AMF checks if the PCF Selection Assistance info from the UDM indicates that the same PCF is required for the requested DNN and S-NSSAI and if required, the AMF includes in Nsmf_PDUSession_CreateSMContext Request both the Same PCF Selection Indication and the PCF ID selected by the AMF, this PCF ID identifies the H-PCF,
If PCF Selection Assistance info is not received from the UDM, the AMF may include a PCF ID in the Nsmf_PDUSession_CreateSMContext Request based on operator policies. This PCF ID identifies the H-PCF in the non-roaming case and the V-PCF in the local breakout roaming case.
The AMF includes Trace Requirements if Trace Requirements have been received in subscription data.
If the AMF decides to use the Control Plane CIoT 5GS Optimisation or User Plane CIoT 5GS Optimisation as specified in step 2 or to only use Control Plane CIoT 5GS Optimisation for the PDU session as described in clause 5.31.4 of TS 23.501 [2], the AMF sends the Control Plane CIoT 5GS Optimisation indication or Control Plane Only indicator to the SMF.
If the AMF determines that the RAT type is NB-IoT and the number of PDU Sessions with user plane resources activated for the UE has reached the maximum number of supported user plane resources (0, 1 or 2) based on whether the UE supports UP data transfer and the UE's 5GMM Core Network Capability as described in clause 5.31.19 of TS 23.501 [2], the AMF may either reject the PDU Session Establishment Request or continue with the PDU Session establishment and include the Control Plane CIoT 5GS Optimisation indication or Control Plane Only indicator to the SMF.
The AMF includes the latest Small Data Rate Control Status if it has stored it for the PDU Session.
If the RAT type was included in the message, then the SMF stores the RAT type in SM Context.
If the UE supports CE mode B and use of CE mode B is not restricted according to the Enhanced Coverage Restriction information in the UE context in the AMF, then the AMF shall include the extended NAS-SM timer indication. Based on the extended NAS-SM timer indication, the SMF shall use the extended NAS-SM timer setting for the UE as specified in TS 24.501 [25].
If the identity of an NWDAF is available to the AMF, the AMF informs the SMF of the NWDAF ID(s) used for UE related Analytics and corresponding Analytics ID(s).
If the AMF, based on configuration, is aware that the UE is accessing over a gNB using satellite backhaul as defined in clause 5.43.4 of TS 23.501 [2], the AMF determines the type of satellite backhaul category and includes Satellite backhaul category to the SMF.
If the AMF, based on configuration, is aware that the UE is accessing over a gNB using GEO satellite backhaul, the AMF may, based on configuration, include the GEO satellite ID as described in clause 5.43.2 of TS 23.501 [2].
If the AMF is aware that the UE access is over a gNB onboard a satellite, the AMF includes the UE's serving satellite ID.
The AMF may provide the Disaster Roaming service indication as specified in TS 23.501 [2].
4. If Session Management Subscription data for corresponding SUPI, DNN and S-NSSAI of the HPLMN is not available, then SMF retrieves the Session Management Subscription data using Nudm_SDM_Get (SUPI, Session Management Subscription data, selected DNN, S-NSSAI of the HPLMN, Serving PLMN ID, [NID]) and subscribes to be notified when this subscription data is modified using Nudm_SDM_Subscribe (SUPI, Session Management Subscription data, selected DNN, S-NSSAI of the HPLMN, Serving PLMN ID, [NID]). The UDM may get this information from UDR by Nudr_DM_Query (SUPI, Subscription Data, Session Management Subscription data, selected DNN, S-NSSAI of the HPLMN, Serving PLMN ID, [NID]) and may subscribe to notifications from UDR for the same data by Nudr_DM_subscribe. If a S-NSSAI is subject to network slice usage control and the S-NSSAI is dedicated to a single AF, for a PDU Session for non-roaming subscribers, the UDM may provide a Slice Usage Policy information including whether a network slice is on demand and a PDU Session inactivity timer value as described in clause 5.15.15 of TS 23.501 [2]. If the SMF received Alternative S-NSSAI (for the HPLMN in roaming case) in step 3, the SMF retrieves subscription data as specified in clause 5.15.19 of TS 23.501 [2].
The SMF may use DNN Selection Mode when deciding whether to retrieve the Session Management Subscription data e.g. if the (selected DNN, S-NSSAI of the HPLMN) is not explicitly subscribed, the SMF may use local configuration instead of Session Management Subscription data.
If the Request Type in step 3 indicates "Existing PDU Session" or "Existing Emergency PDU Session" the SMF determines that the request is due to switching between 3GPP access and non-3GPP access or due to handover from EPS. The SMF identifies the existing PDU Session based on the PDU Session ID. In such a case, the SMF does not create a new SM context but instead updates the existing SM context and provides the representation of the updated SM context to the AMF in the response.
If the Request Type is "Initial request" and if the Old PDU Session ID is included in Nsmf_PDUSession_CreateSMContext Request, the SMF identifies the existing PDU Session to be released based on the Old PDU Session ID.
The Subscription data includes the Allowed PDU Session Type(s), Allowed SSC mode(s), default 5QI and ARP, subscribed Session-AMBR, SMF-Associated external parameters.
IP Index or Static IP address/prefix may be included in the subscription data if the UE has subscribed to it.
The SMF checks the validity of the UE request: it checks:
- Whether the UE request is compliant with the user subscription and with local policies;
- (If the selected DNN corresponds to an LADN), whether the UE is located within the LADN service area based on the "UE presence in LADN service area" indication from the AMF. If the AMF does not provide the "UE presence in LADN service area" indication and the SMF determines that the selected DNN corresponds to a LADN, then the SMF considers that the UE is OUT of the LADN service area.
The SMF determines whether the PDU Session requires redundancy and the SMF determines the RSN as described in clause 5.33.2.1 of TS 23.501 [2]. If the SMF determines that redundant handling is not allowed or not possible for the given PDU Session, the SMF shall either reject the establishment of the PDU Session or accept the establishment of a PDU session without redundancy handling based on local policy.
If the UE request is considered as not valid, the SMF decides to not accept to establish the PDU Session.
NOTE 4: The SMF can, instead of the Nudm_SDM_Get service operation, use the Nudm_SDM_Subscribe service operation with an Immediate Report Indication that triggers the UDM to immediately return the subscribed data if the corresponding feature is supported by both the SMF and the UDM.
For a Disaster Roaming service, the UDM provides the Session Management Subscription data to the SMF based on the local policy and/or the local configuration as specified in clause 5.40.4 of TS 23.501 [2].
For an S-NSSAI subject to NSAC and if LBO applies, the SMF in supporting VPLMN stores the applicable NSAC admission mode.
5. From SMF to AMF: Either Nsmf_PDUSession_CreateSMContext Response (Cause, SM Context ID or N1 SM container (PDU Session Reject (Cause))) or an Nsmf_PDUSession_UpdateSMContext Response depending on the request received in step 3.
If the SMF received Nsmf_PDUSession_CreateSMContext Request in step 3 and the SMF is able to process the PDU Session establishment request, the SMF creates an SM context and responds to the AMF by providing an SM Context ID.
If the UP Security Policy for the PDU Session is determined to have Integrity Protection set to "Required", the SMF may, based on local configuration, decide whether to accept or reject the PDU Session request based on the UE Integrity Protection Maximum Data Rate.
NOTE 5: The SMF can e.g. be configured to reject a PDU Session if the UE Integrity Protection Maximum Data Rate has a very low value, if the services provided by the DN would require higher bitrates.
When the SMF decides to not accept to establish a PDU Session, the SMF rejects the UE request via NAS SM signalling including a relevant SM rejection cause by responding to the AMF with Nsmf_PDUSession_CreateSMContext Response. The SMF also indicates to the AMF that the PDU Session ID is to be considered as released, the SMF proceeds to step 20 and the PDU Session Establishment procedure is stopped.
6. Optional Secondary authentication/authorization.
If the Request Type in step 3 indicates "Existing PDU Session", the SMF does not perform secondary authentication/authorization.
If the Request Type received in step 3 indicates "Emergency Request" or "Existing Emergency PDU Session", the SMF shall not perform secondary authentication\authorization.
If the SMF needs to perform secondary authentication/authorization during the establishment of the PDU Session by a DN-AAA Server as described in clause 5.6.6 of TS 23.501 [2], the SMF triggers the PDU Session establishment authentication/authorization as described in clause 4.3.2.3.
7a. If dynamic PCC is to be used for the PDU Session, the SMF performs PCF selection as described in clause 6.3.7.1 of TS 23.501 [2]. If the Request Type indicates "Existing PDU Session" or "Existing Emergency PDU Session", the SMF shall use the PCF already selected for the PDU Session.
Otherwise, the SMF may apply local policy.
7b. The SMF may perform an SM Policy Association Establishment procedure as defined in clause 4.16.4 to establish an SM Policy Association with the PCF and get the default PCC Rules for the PDU Session. The SMF shall include the 3GPP Data Off status if received in step 1. If the UE provided support for (S)RTP Multiplexed Media Identification Information in IP Packet Filters in the 5GSM Core Network Capability received in step 3, the SMF shall provide such UE capability information to the PCF as described in clause 5.37.11 in TS 23.501 [2]. The GPSI, PVS FQDN(s) and/or PVS IP address(es) and the Onboarding Indication shall be included if available at SMF in the case of ON-SNPN. The SMF shall include both the S-NSSAI and the Alternative S-NSSAI, if received in step 3. If the Request Type in step 3 indicates "Existing PDU Session", the SMF provides information on the Policy Control Request Trigger condition(s) that have been met by an SMF initiated SM Policy Association Modification procedure as defined in clause 4.16.5.1. The PCF may provide policy information defined in clause 5.2.5.4 (and in TS 23.503 [20]) to SMF.
The PCF for the UE subscribes to notifications of event "UE reporting Connection Capabilities from associated URSP rule" as defined in clause 6.1.3.18 in TS 23.503 [20], using Npcf_PolicyAuthorization_Subscribe (EventId set to "UE reporting Connection Capabilities from associated URSP rule", EventFilter set to at least "list of Connection Capabilities") to the PCF for the PDU Session. The PCF for session may notify the PCF for UE about the URSP rule enforcement together with the PDU session parameters that this application associated with by Npcf_PolicyAuthorization_Notify.
During the SM Policy Association Establishment procedure, if the PCF detects the request relates to SM Policy Association enabling integration with TSN or TSC or Deterministic Networking (as defined in TS 23.501 [2] clause 5.28) based on local configuration (e.g. for a certain requested DNN/S-NSSAI for which Time Sensitive Networking, Time Sensitive Communications, Time Synchronization and/or Deterministic Networking is applicable), the PCF may provide policy control request trigger for 5GS Bridge/Router Information as defined in clause 6.1.3.5 of TS 23.503 [20].
The PCF, based on the Emergency DNN, sets the ARP of the PCC rules to a value that is reserved for Emergency services as described in TS 23.503 [20].
NOTE 6: The purpose of step 7 is to receive PCC rules before selecting UPF. If PCC rules are not needed as input for UPF selection, step 7 can be performed after step 8.
- During the SM Policy Association Establishment procedure for PDU Sessions for non-roaming UEs, if a S-NSSAI is subject to network slice usage control, the PCF may provide a Slice Usage Policy information including whether a network slice is on demand and a PDU Session inactivity timer value as described in clause 5.15.15 of TS 23.501 [2].
8. If the Request Type in step 3 indicates "Initial request", the SMF selects an SSC mode for the PDU Session as described in clause 5.6.9.3 of TS 23.501 [2]. The SMF also selects one or more UPFs as needed as described in clause 6.3.3 of TS 23.501 [2]. In the case of PDU Session Type IPv4 or IPv6 or IPv4v6, the SMF allocates an IP address/prefix for the PDU Session (unless configured otherwise) as described in clause 5.8.2 of TS 23.501 [2]. In the case of PDU Session Type IPv6 or IPv4v6, the SMF also allocates an interface identifier to the UE for the UE to build its link-local address. For Unstructured PDU Session Type the SMF may allocate an IPv6 prefix for the PDU Session and N6 point-to-point tunnelling (based on UDP/IPv6) as described in clause 5.6.10.3 of TS 23.501 [2]. For Ethernet PDU Session Type, neither a MAC nor an IP address is allocated by the SMF to the UE for this PDU Session.
If the AMF indicated Control Plane CIoT 5GS Optimisation in step 3 for this PDU session, then,
1) For Unstructured PDU Session Type, the SMF checks whether UE's subscription include a "NEF Identity for NIDD" for the DNN/S-NSSAI combination. When the "NEF Identity for NIDD" is present in the UE's subscription data, the SMF will select the NEF identified for the S-NSSAI and selected DNN in the "NEF Identity for NIDD" as the anchor of this PDU Session. Otherwise, the SMF will select a UPF as the anchor of this PDU Session.
2) For other PDU Session Types, the SMF will perform UPF selection to select a UPF as the anchor of this PDU Session.
If the Request Type in Step 3 is "Existing PDU Session", the SMF maintains the same IP address/prefix that has already been allocated to the UE in the source network.
If the Request Type in step 3 indicates "Existing PDU Session" referring to an existing PDU Session moved between 3GPP access and non-3GPP access the SMF maintains the SSC mode of the PDU Session, the current PDU Session Anchor and IP address.
NOTE 7: The SMF may decide to trigger e.g. new intermediate UPF insertion or allocation of a new UPF as described in step 5 in clause 4.2.3.2.
If the Request Type indicates "Emergency Request", the SMF selects the UPF as described in clause 5.16.4 of TS 23.501 [2] and selects SSC mode 1.
SMF may select a UPF (e.g. based on requested DNN/S-NSSAI) that supports NW-TT functionality.
SMF may select a PSA UPF that supports PDU Set identification and marking for a QoS flow with PDU Set based handling capability.
If a PCC Rule indicates that Media over QUIC (MoQ) is requested by setting Protocol Description as Media over QUIC Transport SMF may select a PSA UPF that supports MoQ relay functionality e.g. using NRF for this selection.
9. SMF may perform an SMF initiated SM Policy Association Modification procedure as defined in clause 4.16.5.1 to provide information on the Policy Control Request Trigger condition(s) that have been met. If Request Type is "initial request" and dynamic PCC is deployed and PDU Session Type is IPv4 or IPv6 or IPv4v6, SMF notifies the PCF (if the Policy Control Request Trigger condition is met) with the allocated UE IP address/prefix(es).
NOTE 8: If an IP address/prefix has been allocated before step 7 (e.g. subscribed static IP address/prefix in UDM/UDR) or the step 7 is performed after step 8, the IP address/prefix can be provided to PCF in step 7 and the IP address/prefix notification in this step can be skipped.
If the PCF has subscribed to Policy Control Request Trigger for "UE reporting Connection Capabilities from associated URSP rule" and if SMF received the URSP rule enforcement report (i.e. connection capabilities information) from the UE at step 1, then the SMF may include the URSP rule enforcement report as described in clause 6.1.3.5 of TS 23.503 [20] and clause 6.6.2.4 of TS 23.503 [20].
The PCF may provide updated policies to the SMF. The PCF may provide policy information defined in clause 5.2.5.4 (and in TS 23.503 [20]) to SMF.
The PCF may make policy control decisions based on the awareness of URSP rule enforcement, as described in clause 6.1.1.5 in TS 23.503 [20].
10. If Request Type indicates "initial request", the SMF initiates an N4 Session Establishment procedure with the selected UPF(s), otherwise it initiates an N4 Session Modification procedure with the selected UPF(s):
10a. The SMF sends an N4 Session Establishment/Modification Request to the UPF and provides Packet detection, enforcement and reporting rules to be installed on the UPF for this PDU Session. If the SMF is configured to request IP address allocation from UPF as described in clause 5.8.2 of TS 23.501 [2] then the SMF indicates to the UPF to perform the IP address/prefix allocation and includes the information required for the UPF to perform the allocation. If the selective User Plane deactivation is required for this PDU Session, the SMF determines the inactivity timer and provides it to the UPF. For a PDU Session for non-roaming subscribers, if the S-NSSAI of the PDU Session is subject to network slice usage control, the SMF obtains the PDU Session inactivity timer value for the PDU Session as described in step 4 or step 7 or uses preconfigured value and configures the UPF to run the PDU Session inactivity timer. The SMF provides Trace Requirements to the UPF if it has received Trace Requirements. If the Reliable Data Service is enabled for the PDU Session by the SMF as specified in TS 23.501 [2], the RDS Configuration information is provided to the UPF in this step. The SMF provides Small Data Rate Control parameters to the UPF for the PDU Session, if required. The SMF provides the Small Data Rate Control Status to the UPF, if received from the AMF. If the Serving PLMN intends to enforce Serving PLMN Rate Control (see clause 5.31.14.2 of TS 23.501 [2]) for this PDU session then the SMF shall provide Serving PLMN Rate Control parameters to UPF for limiting the rate of downlink control plane data packets.
For a PDU Session of type Ethernet or IP, if the trigger for 5GS Bridge/Router information is armed in step 7b, the SMF, based on local configuration (e.g. for a certain requested DNN/S-NSSAI for which Time Sensitive Networking, Time Sensitive Communications, Time Synchronization and/or Deterministic Networking is applicable), includes a bridge information indication or a router information indication to request the UPF to provide a port number.
If SMF decides to perform redundant transmission for one or more QoS Flows of the PDU session as described in clause 5.33.1.2 of TS 23.501 [2], two CN Tunnel Info are requested by the SMF from the UPF. The SMF also indicates the UPF to eliminate the duplicated packet for the QoS Flow in uplink direction. The SMF indicates the UPF that one CN Tunnel Info is used as the redundancy tunnel of the PDU session described in clause 5.33.2.2 of TS 23.501 [2].
If SMF decides to insert two I-UPFs between the PSA UPF and the NG-RAN for redundant transmission as described in clause 5.33.1.2 of TS 23.501 [2], the SMF requests the corresponding CN Tunnel Info and provides them to the I-UPFs and PSA UPF respectively. The SMF also indicates the PSA UPF to eliminate the duplicated packet for the QoS Flow in uplink direction. The SMF indicates the PSA UPF that one CN Tunnel Info is used as the redundancy tunnel of the PDU session described in clause 5.33.2.2 of TS 23.501 [2].
NOTE 9: The method to perform elimination and reordering on RAN/UPF based on the packets received from the two GTP-U tunnels is up to RAN/UPF implementation. The two GTP-U tunnels are terminated at the same RAN node and UPF.
If Control Plane CIoT 5GS Optimisation is enabled for this PDU session and the SMF selects the NEF as the anchor of this PDU Session in step 8, the SMF performs SMF-NEF Connection Establishment Procedure as described in clause 4.25.2.
If interworking with TSN deployed in the transport network is supported (see clause 4.4.8 of TS 23.501 [2]) and the UPF supports CN-TL, the SMF includes a TL-Container with a get-request to the N4 Session Establishment/Modification request that is sent to the UPF, as described in clause 5.28a.2 of TS 23.501 [2].
If SMF decides to enable ECN marking for L4S by PSA UPF, a QoS Flow level ECN marking for L4S indicator shall be sent by SMF to PSA UPF over N4 as described in clause 5.37.3.3 of TS 23.501 [2].
If selected PSA UPF supports Nupf_EventExposure service, the SMF should include DNN and S-NSSAI in the N4 Session Establishment procedure.
If the Protocol Description in the PCC Rule indicates Media over QUIC (MoQ) and the PSA UPF supports the MoQ relay functionality, then the SMF indicates the UPF to return the MoQ relay address via the N4 session management request procedures as described in clause 5.37.9.2 of TS 23.501 [2].
NOTE 10: If SMF does not provide DNN and S-NSSAI to UPF it could result in rejections for the Nupf_EventExposure_Subscribe service operations, unless UPF is configured with a DNN and S-NSSAI for a specific IP address range.
10b. The UPF acknowledges by sending an N4 Session Establishment/Modification Response.
If the SMF indicates in step 10a that IP address/prefix allocation is to be performed by the UPF then this response contains the requested IP address/prefix. The requested CN Tunnel Info is provided to SMF in this step. If SMF indicated the UPF to perform packet duplication and elimination for the QoS Flow in step 10a, two CN Tunnel Info are allocated by the UPF and provided to the SMF. If SMF decides to insert two I-UPFs between the PSA UPF and the NG-RAN for redundant transmission as described in clause 5.33.1.2 of TS 23.501 [2], CN Tunnel Info of two I-UPFs and the UPF (PSA) are allocated by the UPFs and provided to the SMF. The UPF indicates the SMF that one CN Tunnel Info is used as the redundancy tunnel of the PDU session as described in clause 5.33.2.2 of TS 23.501 [2].
If SMF requested UPF to provide a port number then UPF includes the port number and user-plane Node ID in the response according to TS 23.501 [2]. To support integration with IEEE TSN, the user-plane node ID is Bridge ID. To support integration with IETF DetNet, the user-plane node ID can be Router ID. Besides the network instance, the SMF may also provide DNN/S-NSSAI for the UPF to respond with user-plane Node ID based on pre-configuration information.
If multiple UPFs are selected for the PDU Session, the SMF initiate N4 Session Establishment/Modification procedure with each UPF of the PDU Session in this step.
NOTE 11: If the PCF has subscribed to the UE IP address change Policy Control Trigger (as specified in clause 6.1.3.5 of TS 23.503 [20]) then the SMF notifies the PCF about the IP address/prefix allocated by the UPF. This is not shown in figure 4.3.2.2.1-1.
If interworking with TSN deployed in the transport network is supported and the UPF supports CN-TL and received a TL-Container with a get-request from the SMF/CUC in step 10a (see clause 4.4.8 of TS 23.501 [2]), the UPF/CN-TL includes a TL-Container with a get-response in the N4 Session Establishment/Modification response, as described in clause 5.28a.2 of TS 23.501 [2]. The SMF/CUC stores the information provided in the get-response.
If the SMF indicates in step 10a the UPF to provide the MoQ relay address, then the UPF returns the MoQ relay address via the N4 Session Establishment/Modification Response as described in clause 5.37.9.2 of TS 23.501 [2].
11. SMF to AMF: Namf_Communication_N1N2MessageTransfer (PDU Session ID, N2 SM information (PDU Session ID, QFI(s), QoS Profile(s), CN Tunnel Info, S-NSSAI from the Allowed NSSAI or Partially Allowed NSSAI, Session-AMBR, PDU Session Type, User Plane Security Enforcement information, UE Integrity Protection Maximum Data Rate, RSN, PDU Session Pair ID, TL-Container), N1 SM container (PDU Session Establishment Accept ([QoS Rule(s) and associated UL Protocol Description(s) (if available), QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s)], selected SSC mode, S-NSSAI(s), UE Requested DNN, allocated IPv4 address, interface identifier, Session-AMBR, selected PDU Session Type, [Reflective QoS Timer] (if available), [P-CSCF address(es)], [Control Plane Only indicator], [Header Compression Configuration], [Always-on PDU Session Granted], [Small Data Rate Control parameters], [Small Data Rate Control Status], [Serving PLMN Rate Control], [PVS FQDN(s) and/or PVS IP address(es)], [Non-3GPP QoS Assistance Information Container]))). If multiple UPFs are used for the PDU Session, the CN Tunnel Info contains tunnel information related with the UPFs that terminate N3.
The SMF may provide the SMF derived CN assisted RAN parameters tuning to the AMF by invoking Nsmf_PDUSession_SMContextStatusNotify (SMF derived CN assisted RAN parameters tuning) service. The AMF stores the SMF derived CN assisted RAN parameters tuning in the associated PDU Session context for this UE.
The N2 SM information carries information that the AMF shall forward to the (R)AN which includes:
- The CN Tunnel Info corresponds to the Core Network address(es) of the N3 tunnel corresponding to the PDU Session. If two CN Tunnel Info are included for the PDU session for redundant transmission, the SMF also indicates the NG-RAN that one of the CN Tunnel Info used as the redundancy tunnel of the PDU session as described in clause 5.33.2.2 of TS 23.501 [2].
- One or multiple QoS profiles and the corresponding QFIs can be provided to the (R)AN. This is further described in clause 5.7 of TS 23.501 [2]. The SMF may indicate for each QoS Flow whether redundant transmission shall be performed by a corresponding redundant transmission indicator.
- The PDU Session ID may be used by AN signalling with the UE to indicate to the UE the association between (R)AN resources and a PDU Session for the UE.
- A PDU Session is associated to an S-NSSAI of the HPLMN and if applicable, to an S-NSSAI of the VPLMN and a DNN. The S-NSSAI provided to the (R)AN, is the S-NSSAI with the value for the Serving PLMN (i.e. the HPLMN S-NSSAI or, in LBO roaming case, the VPLMN S-NSSAI). When Alternative S-NSSAI is received from AMF in step 3, the S-NSSAI provided to the (R)AN is the Alternative S-NSSAI.
- User Plane Security Enforcement information is determined by the SMF as described in clause 5.10.3 of TS 23.501 [2].
- If the User Plane Security Enforcement information indicates that Integrity Protection is "Preferred" or "Required", the SMF also includes the UE Integrity Protection Maximum Data Rate as received in the PDU Session Establishment Request.
- The use of the RSN parameter and the PDU Session Pair ID by NG-RAN are described in clause 5.33.2.1 of TS 23.501 [2].
- For each QoS Flow, the SMF may at most request one of the following to the NG-RAN:
- ECN marking for L4S at NG-RAN in the case of ECN marking for L4S in RAN as described in clause 5.37.3 of TS 23.501 [2]; or
- Congestion information monitoring as described in clauses 5.45.3 and 5.37.4 of TS 23.501 [2]; or
- provide information for ECN marking for L4S at UPF in the case of ECN marking for L4S by PSA UPF as described in clause 5.37.3 of TS 23.501 [2].
- In the case of non-3GPP access, where the 5G-AN corresponds to an N3IWF or TNGF:
- For each QoS Flow, the SMF may request the following to the N3IWF or TNGF:
- ECN marking for L4S at N3IWF or TNGF in the case of ECN marking for L4S in non-3GPP access as described in clause 5.37.3 of TS 23.501 [2].
- TL-Container as described in clause 5.28a.2 of TS 23.501 [2]. If interworking with TSN deployed in the transport network is supported and the NG-RAN supports AN-TL (see clause 4.4.8 of TS 23.501 [2]), the SMF includes a TL-Container with a get-request to the N2 SM information, as described in clause 5.28a.2 of TS 23.501 [2].
The N1 SM container contains the PDU Session Establishment Accept that the AMF shall provide to the UE. If the UE requested P-CSCF discovery then the message shall also include the P-CSCF IP address(es) as determined by the SMF and as described in clause 5.16.3.4 of TS 23.501 [2]. The PDU Session Establishment Accept includes S-NSSAI from the Allowed NSSAI or Partially Allowed NSSAI. The S-NSSAI value of the Alternative S-NSSAI is included in the PDU session Establishment Accept if the SMF has received the Alternative S-NSSAI from the AMF. For LBO roaming scenario, the PDU Session Establishment Accept includes the S-NSSAI from the Allowed NSSAI or Partially Allowed NSSAI for the VPLMN and also it includes the corresponding S-NSSAI of the HPLMN from the Mapping Of Allowed NSSAI or Mapping Of Partially Allowed NSSAI that SMF received in step 3. If the SMF has received the VPLMN Alternative S-NSSAI from the AMF, the PDU Session Establishment Accept includes the VPLMN Alternative S-NSSAI. If the SMF has received the HPLMN Alternative S-NSSAI from the AMF, the PDU Session Establishment Accept includes the HPLMN Alternative S-NSSAI. If the PCF, based on the local configuration, provides the PCC rules with Protocol Descriptions for UL in step 7b or step 9, the SMF may additionally provide the Protocol Description for UL with the associated QoS rule as described in clause 5.37.5.1 of TS 23.501 [2].
If the PDU Session being established was requested to be an always-on PDU Session, the SMF shall indicate whether the request is accepted by including an Always-on PDU Session Granted indication in the PDU Session Establishment Accept message. If the PDU Session being established was not requested to be an always-on PDU Session but the SMF determines that the PDU Session needs to be established as an always-on PDU Session, the SMF shall include an Always-on PDU Session Granted indication in the PDU Session Establishment Accept message indicating that the PDU session is an always-on PDU Session.
If Control Plane CIoT 5GS Optimisation is enabled for this PDU session, the N2 SM information is not included in this step. If Control Plane CIoT 5GS optimisation is enabled for this PDU session and the UE has sent the Header Compression Configuration in the PDU Session Establishment Request and the SMF supports the header compression parameters, the SMF shall include the Header Compression Configuration in the PDU Session Establishment Accept message. If the UE has included Header Compression context parameters in Header Compression Configuration in the PDU Session Establishment Request, the SMF shall establish the header compression context and may acknowledge the Header Compression context parameters. If the header compression context is not established during the PDU Session Establishment procedure, before using the compressed format for sending the data, the UE and the SMF need to establish the header compression context based on the Header Compression Configuration. If the SMF has received the Control Plane Only Indicator in step 3, the SMF shall include the Control Plane Only Indicator in the PDU Session Establishment Accept message. The SMF shall indicate the use of Control Plane only on its CDR. If the Small Data Rate Control is configured in the SMF, the SMF shall also include Small Data Rate Control parameters and the Small Data Rate Control Status (if received from the AMF) in the PDU Session Establishment Accept message as described in clause 5.31.14.3 of TS 23.501 [2]. If the Serving PLMN intends to enforce Serving PLMN Rate Control (see clause 5.31.14.2 of TS 23.501 [2]) for this PDU session then the SMF shall include the Serving PLMN Rate Control parameters in the PDU Session Establishment Accept message. The UE shall store and use Serving PLMN Rate Control parameters as the maximum allowed limit of uplink control plane user data.
If the UE indicates the support of RDS in the PCO in the PDU Session Establishment Request and RDS is enabled for the PDU Session, the SMF shall inform the UE that RDS is enabled in the PCO in the PDU Session Establishment Accept (see clause 5.31.6 of TS 23.501 [2]).
If the NIDD parameters (e.g. maximum packet size) were received from NEF during the SMF-NEF Connection Establishment procedure in step 10, the SMF shall inform the UE of the NIDD parameters in the PCO in the PDU Session Establishment Accept (see clause 5.31.5 of TS 23.501 [2]).
If the UE indicated in the PCO that it supports the ability to receive ECS address(es) via NAS, the SMF may provide the ECS Address Configuration Information (as described in clause 6.5.2 of TS 23.548 [74]) to the UE in the PCO. The SMF may derive the ECS Address Configuration Information based on local configuration and/or UE subscription information. In non-roaming scenarios, the SMF may also derive the ECS Address Configuration Information based on the UE's location.
If the UE indicated in the PCO that it supports the EDC functionality, the SMF may indicate to the UE either that the use of the EDC functionality is allowed for the PDU Session or that the use of the EDC functionality is required for the PDU Session (see clause 5.2.1 of TS 23.548 [74]).
Multiple QoS Rules, QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with those QoS rule(s) and QoS Profiles may be included in the PDU Session Establishment Accept within the N1 SM and in the N2 SM information.
The Namf_Communication_N1N2MessageTransfer contains the PDU Session ID allowing the AMF to know which access towards the UE to use.
If the PDU session establishment failed anywhere between step 5 and step 11, then the Namf_Communication_N1N2MessageTransfer request shall include the N1 SM container with a PDU Session Establishment Reject message (see clause 8.3.3 of TS 24.501 [25]) and shall not include any N2 SM container. The (R)AN sends the NAS message containing the PDU Session Establishment Reject to the UE. In this case, steps 12-17 are skipped.
Based on the S-NSSAI and DNN for PIN, the SMF may provide the UE with per QoS-flow Non-3GPP QoS Assistance Information in the N1 SM container as specified in clause 5.44.3.3 of TS 23.501 [2].
12. AMF to (R)AN: N2 PDU Session Request (N2 SM information, NAS message (PDU Session ID, N1 SM container (PDU Session Establishment Accept)), [CN assisted RAN parameters tuning]). If the N2 SM information is not included in the step 11, an N2 Downlink NAS Transport message is used instead.
The AMF sends the NAS message containing PDU Session ID and PDU Session Establishment Accept targeted to the UE and the N2 SM information received from the SMF within the N2 PDU Session Request to the (R)AN.
If the SMF derived CN assisted RAN parameters tuning are stored for the activated PDU Session(s), the AMF may derive updated CN assisted RAN parameters tuning and provide them the (R)AN.
13. (R)AN to UE: The (R)AN may issue AN specific signalling exchange with the UE that is related with the information received from SMF. For example, in the case of a NG-RAN, an RRC Connection Reconfiguration may take place with the UE establishing the necessary NG-RAN resources related to the QoS Rules for the PDU Session request received in step 12.
(R)AN also allocates (R)AN Tunnel Info for the PDU Session. In the case of Dual Connectivity, the Master RAN node may assign some (zero or more) QFIs to be setup to a Master RAN node and others to the Secondary RAN node. The AN Tunnel Info includes a tunnel endpoint for each involved (R)AN node and the QFIs assigned to each tunnel endpoint. A QFI can be assigned to either the Master RAN node or the Secondary RAN node and not to both.
If the (R)AN receives two CN Tunnel Info for a PDU session in step 12 for redundant transmission, (R)AN also allocates two AN Tunnel Info correspondingly and indicate to SMF one of the AN Tunnel Info is used as the redundancy tunnel of the PDU session as described in clause 5.33.2.2 of TS 23.501 [2].
(R)AN forwards the NAS message (PDU Session ID, N1 SM container (PDU Session Establishment Accept)) provided in step 12 to the UE. (R)AN shall only provide the NAS message to the UE if the AN specific signalling exchange with the UE includes the (R)AN resource additions associated to the received N2 command.
If MICO mode is active and the NAS message Request Type in step 1 indicated "Emergency Request", then the UE and the AMF shall locally deactivate MICO mode.
If the N2 SM information is not included in the step 11, then the following steps 14 to 16b and step 17 are omitted.
If the UE is running a slice deregistration inactivity timer for the S-NSSAI of the established PDU Session and the timer is associated with the Access Type over which the PDU Session Establishment Request was received, the UE stops the timer as described in clause 5.15.15 of TS 23.501 [2].
14. (R)AN to AMF: N2 PDU Session Response (PDU Session ID, Cause, N2 SM information (PDU Session ID, AN Tunnel Info, List of accepted/rejected QFI(s), User Plane Enforcement Policy Notification, TL-Container, established QoS Flows status (active/not active) (for one of the following: congestion information monitoring, ECN marking for L4S at PSA UPF, ECN marking for L4S at NG-RAN, ECN marking for L4S at N3IWF or TNGF), PDU Set Based Handling Support Indication)).
The AN Tunnel Info corresponds to the Access Network address of the N3 tunnel corresponding to the PDU Session.
The (R)AN may reject the addition or modification of a QoS Flow, e.g. due to handling of the UE-Slice-MBR as described in clause 5.7.1.10 of TS 23.501 [2]. If the (R)AN rejects QFI(s) the SMF is responsible of updating the QoS rules and QoS Flow level QoS parameters associated to the rejected QoS Flow(s) in the UE accordingly.
The NG-RAN rejects the establishment of UP resources for the PDU Session when it cannot fulfil User Plane Security Enforcement information with a value of Required. The NG-RAN notifies the SMF when it cannot fulfil a User Plane Security Enforcement with a value of Preferred.
If the NG-RAN cannot establish redundant user plane for the PDU Session as indicated by the RSN parameter and PDU Session Pair ID, the NG-RAN takes the decision on whether to reject the establishment of RAN resources for the PDU Session based on local policies as described in TS 23.501 [2].
If interworking with TSN deployed in the transport network is supported and the NG-RAN supports AN-TL and received a TL-Container with a get-request from the SMF/CUC in step 12 (see clause 4.4.8 of TS 23.501 [2]), the NG-RAN/AN-TL includes a TL-Container with a get-response to the N2 SM information, as described in clause 5.28a.2 of TS 23.501 [2].
5G-AN includes the PDU Set Based Handling Support Indication in N2 SM information as defined in clause 5.37.5.3 of TS 23.501 [2].
15. AMF to SMF: Nsmf_PDUSession_UpdateSMContext Request (SM Context ID, N2 SM information, Request Type).
The AMF forwards the N2 SM information received from (R)AN to the SMF.
If the list of rejected QFI(s) is included in N2 SM information, the SMF shall release the rejected QFI(s) associated QoS profiles.
If the N2 SM information indicates failure of user plane resource setup, the SMF shall reject the PDU session establishment by including a N1 SM container with a PDU Session Establishment Reject message (see clause 8.3.3 of TS 24.501 [25]) in the Nsmf_PDUSession_UpdateSMContext Response in step 17. Step 16 is skipped in this case and instead the SMF releases the N4 Session with UPF.
If the User Plane Enforcement Policy Notification in the N2 SM information indicates that no user plane resources could be established and the User Plane Enforcement Policy indicated "required" as described in clause 5.10.3 of TS 23.501 [2], the SMF shall reject the PDU session establishment by including a N1 SM container with a PDU Session Establishment Reject message (see clause 8.3.3 of TS 24.501 [25]) in the Nsmf_PDUSession_UpdateSMContext Response in step 17. Step 16 is skipped in this case.
If the N2 SM information includes a TL-Container with a get-response as described in clause 5.28a.2 of TS 23.501 [2], the SMF/CUC stores the information provided in the get-response.
16a. The SMF initiates an N4 Session Modification procedure with the UPF. The SMF provides AN Tunnel Info to the UPF as well as the corresponding forwarding rules.
If SMF decides to perform redundant transmission for one or more QoS Flows of the PDU, the SMF also indicates the UPF to perform packet duplication for the QoS Flow(s) in downlink direction by forwarding rules.
In the case of redundant transmission with two I-UPFs for one or more QoS Flows of the PDU, the SMF provides AN Tunnel Info to two I-UPFs and also indicates the UPF (PSA) to perform packet duplication for the QoS Flow(s) in downlink direction by forwarding rules. The SMF also provides the UL Tunnel Info of the UPF (PSA) to the two I-UPFs and the DL Tunnel Info of the two I-UPFs to the UPF (PSA).
If the N2 SM information includes the PDU Set Based Handling Support Indication, SMF configures PSA UPF to perform PDU Set information marking for the QoS flow as defined in clause 5.37.5.3 of TS 23.501 [2].
NOTE 12: If the PDU Session Establishment Request was due to mobility between 3GPP and non-3GPP access or mobility from EPC, the downlink data path is switched towards the target access in this step.
16b. The UPF provides an N4 Session Modification Response to the SMF.
If multiple UPFs are used in the PDU Session, the UPF in step 16 refers to the UPF terminating N3.
After this step, the UPF delivers any down-link packets to the UE that may have been buffered for this PDU Session.
16c. If Request Type in step 3 indicates neither "Emergency Request" nor "Existing Emergency PDU Session" and if the SMF has not yet registered for this PDU Session, then the SMF registers with the UDM using Nudm_UECM_Registration (SUPI, DNN, S-NSSAI of HPLMN, PDU Session ID, SMF Identity, Serving Node PLMN ID, [NID], PCF ID) for a given PDU Session. As a result, the UDM stores following information: SUPI, SMF identity and the associated DNN, S-NSSAI of HPLMN, PDU Session ID, PCF ID and Serving Network (PLMN ID, [NID], see clause 5.18 of TS 23.501 [2]). The UDM may further store this information in UDR by Nudr_DM_Update (SUPI, Subscription Data, UE context in SMF data). If the UDM has existing applicable event exposure subscriptions for events detected in SMF for this UE or any of the groups this UE belongs to (possibly retrieved from UDR), UDM invokes the Nsmf_EventExposure_Subscribe service for creating the event exposure subscriptions. If the SMF received Alternative S-NSSAI in step 3, the S-NSSAI provided to the UDM is the replaced S-NSSAI.
If the Request Type received in step 3 indicates "Emergency Request":
- For an authenticated non-roaming UE, based on operator configuration (e.g. related with whether the operator uses a fixed SMF for Emergency calls, etc.), the SMF may register in the UDM using Nudm_UECM_Registration (SUPI, PDU Session ID, SMF identity, Indication of Emergency Services) for a given PDU Session that is applicable for emergency services. As a result, the UDM shall store the applicable PDU Session for Emergency services.
- For an unauthenticated UE or a roaming UE, the SMF shall not register in the UDM for a given PDU Session.
17. SMF to AMF: Nsmf_PDUSession_UpdateSMContext Response (Cause).
The SMF may subscribe to the UE mobility event notification from the AMF (e.g. location reporting, UE moving into or out of Area Of Interest), after this step by invoking Namf_EventExposure_Subscribe service operation as specified in clause 5.2.2.3.2. For LADN, the SMF subscribes to the UE moving into or out of LADN service area event notification by providing the LADN DNN as an indicator for the Area Of Interest (see clause 5.6.5 and 5.6.11 of TS 23.501 [2]).
If SMF receives the indication in step 3 that "the PDU Session is subject to LADN per LADN DNN and S-NSSAI", the SMF subscribes to the UE moving into or out of LADN service area event notification by providing the LADN DNN and S-NSSAI as an indicator for the Area Of Interest.
If SMF receives the indication in step 3 that the PDU Session is subject to area restriction for the S-NSSAI, the SMF subscribe to "UE mobility event notification" event for reporting UE presence in Area of Interest by providing the S-NSSAI as an indicator for the Area Of Interest (see clauses 5.6.11 and 5.3.4.4 of TS 23.501 [2]).
After this step, the AMF forwards relevant events subscribed by the SMF.
For those scenarios where the PCFs serving the AMF and the SMF are different, the SMF informs the AMF of the NWDAF ID(s) used for UE related Analytics and corresponding Analytics ID(s).
18. [Conditional] SMF to AMF: Nsmf_PDUSession_SMContextStatusNotify (Release)
If during the procedure, any time after step 5, the PDU Session establishment is not successful, the SMF informs the AMF by invoking Nsmf_PDUSession_SMContextStatusNotify (Release). The SMF also releases any N4 session(s) created, any PDU Session address if allocated (e.g. IP address) and releases the association with PCF, if any. In this case, step 19 is skipped.
For a PDU Session for non-roaming subscribers, if the S-NSSAI of the PDU Session is subject to network slice usage control and there is no other PDU Session using the S-NSSAI over the same Access Type, the AMF starts the slice deregistration inactivity timer for the S-NSSAI over this Access Type as described in clause 5.15.15.3 of TS 23.501 [2].
19. SMF to UE: In the case of PDU Session Type IPv6 or IPv4v6, the SMF generates an IPv6 Router Advertisement and sends it to the UE. If Control Plane CIoT 5GS Optimisation is enabled for this PDU Session the SMF sends the IPv6 Router Advertisement via the AMF for transmission to the UE using the Mobile Terminated Data Transport in Control Plane CIoT 5GS Optimisation procedures (see clause 4.24.2), otherwise the SMF sends the IPv6 Router Advertisement via N4 and the UPF.
20. When the trigger for 5GS Bridge/Router information available is armed, then the SMF may initiate the SM Policy Association Modification as described in clause 4.16.5.1.
SMF provides the 5GS Bridge/Router information (e.g. 5GS user-plane Node ID, port number for the PDU session, MAC address of the DS-TT Ethernet port for Ethernet PDU Session type, UE IP address for IP PDU Session type and UE-DS-TT Residence Time (if available) as provided by the UE) to PCF. In the case of Deterministic Networking, the SMF may also provide the MTU size for IPv4 or the MTU size for IPv6. If the SMF received a Port Management Information Container from either the UE or the UPF, then the SMF provides the Port Management Information Container and port number of the related port to the PCF as described in clause 5.28.3.2 of TS 23.501 [2].
If the SMF has received User Plane Node Management Information from the UPF, then the SMF provides the User Plane Node Management Information Container to the PCF as part of 5GS Bridge/Router information and as described in clause 5.28.3.2 of TS 23.501 [2].
To support IEEE TSN, the TSN AF calculates the bridge delay for each port pair, i.e. composed of DS-TT Ethernet port and NW-TT Ethernet port, using the UE-DS-TT Residence Time for all NW-TT Ethernet port(s) serving the 5GS Bridge indicated by the 5GS user-plane Node ID. Additionally, the TSN AF determines the 5GS bridge delay for port pair composed of two DS-TT ports connecting to the same 5GS Bridge as sum of bridge delays related to PDU Sessions of the two DS-TT ports.
21. If the PDU Session establishment failed after step 4, the SMF shall perform the following:
The SMF unsubscribes to the modifications of Session Management Subscription data for the corresponding (SUPI, DNN, S-NSSAI of the HPLMN), using Nudm_SDM_Unsubscribe (SUPI, Session Management Subscription data, DNN, S-NSSAI of the HPLMN), if the SMF is no more handling a PDU Session of the UE for this (DNN, S-NSSAI of the HPLMN). The UDM may unsubscribe to the modification notification from UDR by Nudr_DM_Unsubscribe (SUPI, Subscription Data, Session Management Subscription data, S-NSSAI of the HPLMN, DNN). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.2.2.2 Home-routed Roaming | This procedure is used in the case of home-routed roaming scenarios.
Figure 4.3.2.2.2-1: UE-requested PDU Session Establishment for home-routed roaming scenarios
1. This step is the same as step 1 in clause 4.3.2.2.1.
2. For NR satellite access, the AMF may decide to verify the UE location as described in clause 5.4.11.4 of TS 23.501 [2].
As in step 2 of clause 4.3.2.2.1 except that, if the UE does not include an S-NSSAI in the PDU Session request, both a Serving PLMN S-NSSAI (in the Allowed NSSAI or Partially Allowed NSSAI) and its corresponding HPLMN S-NSSAI values are selected by the AMF. Also, the AMF in the serving PLMN selects both an SMF in the Serving PLMN using the S-NSSAI of the Serving PLMN mapping to the S-NSSAIs of the HPLMN used for the PDU Session and additionally, an SMF and optionally H-SMF set ID in the HPLMN using the S-NSSAI of the HPLMN used for the PDU Session, as described in clause 4.3.2.2.3. The AMF may also receive alternative H-SMFs from the NRF. If Control Plane CIoT 5GS Optimisation is enabled for the PDU Session, the AMF selects V-SMF and H-SMF and optionally H-SMF set ID that supports the Control Plane CIoT 5GS Optimisation (see clause 6.3.2 of TS 23.501 [2]). The AMF stores the association of the S-NSSAI(s), the DNN, the PDU Session ID, the SMF ID in VPLMN as well as Access Type of the PDU Session. Whether to perform DNN replacement is based on operator agreement.
In step 3 of clause 4.3.2.2.1, in local breakout roaming case, if V-SMF responds to AMF indicating that V-SMF is not able to process some part of the N1 SM information, the AMF proceeds with home routed case from this step and may select an SMF in the VPLMN different from the V-SMF selected earlier.
3a. As in step 3 of clause 4.3.2.2.1 with the addition that:
- the AMF also provides the identity of the H-SMF and optionally the H-SMF set ID it has selected in step 2 and both the VPLMN S-NSSAI from the Allowed NSSAI or Partially Allowed NSSAI and the corresponding S-NSSAI of the HPLMN, which is in the mapping the VPLMN S-NSSAI from the Allowed NSSAI or Partially Allowed NSSAI. The H-SMF is provided when the PDU Session is home-routed. The AMF may also provide the identity of alternative H-SMFs, if it has received in step 2. If the AMF determines to replace the HPLMN S-NSSAI received from the UE with the HPLMN Alternative S-NSSAI or the AMF receives the HPLMN Alternative S-NSSAI and the HPLMN S-NSSAI provided by the UE, the AMF selects the H-SMF based on the HPLMN Alternative S-NSSAI.
- The V-SMF does not use DNN Selection Mode received from the AMF but relays this information to the H-SMF.
If the AMF is reusing an already established association with a V-SMF for the PDU Session ID provided by the UE (e.g. when Request Type indicates "existing PDU Session"), the AMF invokes the Nsmf_PDUSession_UpdateSMContext Request.
The AMF may include the H-PCF ID in this step and V-SMF will pass it to the H-SMF in step 6. This will enable the H-SMF to select the same H-PCF in step 9a.
If Control Plane CIoT 5GS Optimisation is used for the PDU Session and the "Invoke NEF indication" in the subscription data is set for the S-NSSAI / DNN combination, the AMF includes an "Invoke NEF" flag in Nsmf_PDUSession_CreateSMContext Request.
If Disaster Roaming service indication is received, the V-SMF stores the indication in PDU session context and includes the indication in charging data. V-SMF may also apply policy and charging control based on the indication according to roaming agreement.
3b: This step is the same as step 5 of clause 4.3.2.2.1. If the PDU Session Type is Unstructured and the V-SMF received an "Invoke NEF" flag in step 3a, then it skips steps 4 and 5.
4. The V-SMF selects a UPF in VPLMN as described in clause 6.3.3 of TS 23.501 [2].
5. The V-SMF initiates an N4 Session Establishment procedure with the selected V-UPF:
5a. The V-SMF sends an N4 Session Establishment Request to the V-UPF. The V-SMF provides Trace Requirements to the V-UPF if the V-SMF has received Trace Requirements from AMF. If V-SMF supports HR-SBO and receives HR-SBO allowed indication from AMF for this PDU session, V-SMF includes SUPI of the UE, HPLMN DNN and S-NSSAI, and an indication that the UE PDU session is working in HR-SBO mode.
5b. The V-UPF acknowledges by sending an N4 Session Establishment Response. The CN Tunnel Info is provided to V-SMF in this step.
6. V-SMF to H-SMF: Nsmf_PDUSession_Create Request (SUPI, GPSI (if available), V-SMF SM Context ID, DNN, S-NSSAI with the value defined by the HPLMN, [HPLMN Alternative S-NSSAI], PDU Session ID, V-SMF ID, V-CN-Tunnel-Info, PDU Session Type, PCO, Number Of Packet Filters, User location information, Access Type, RAT Type, PCF ID, [Small Data Rate Control Status], SM PDU DN Request Container, DNN Selection Mode, Control Plane CIoT 5GS Optimisation Indication, [Always-on PDU Session Requested], AMF ID, Serving Network, [ECS Address Configuration Information associated with PLMN ID of visited network], the QoS constraints from the VPLMN, Satellite backhaul category, Disaster Roaming service indication, [URSP rule enforcement reports]) or Nsmf_PDUSession_Update Request (V-CN-Tunnel-Info, PCO, User location information, Access Type, RAT Type, SM PDU DN Request Container, Control Plane CIoT 5GS Optimisation Indication, [Always-on PDU Session Requested], Serving Network, Satellite backhaul category, [URSP rule enforcement reports]). Protocol Configuration Options may contain information that H-SMF may needs to properly establish the PDU Session (e.g. SSC mode or SM PDU DN Request Container to be used to authenticate the UE by the DN-AAA as defined in clause 4.3.2.3). The H-SMF may use DNN Selection Mode when deciding whether to accept or reject the UE request. If the V-SMF does not receive any response from the H-SMF due to communication failure on the N16 interface, depending on operator policy the V-SMF may create the PDU Session to one of the alternative H-SMF(s) if additional H-SMF information is provided in step 3a, as specified in detail in TS 29.502 [36]. The Small Data Rate Control Status is included if received from the AMF. The Control Plane CIoT 5GS Optimisation Indication is set by the V-SMF, if the PDU Session is intended for Control Plane CIoT 5GS Optimisation. The QoS constraints from the VPLMN are specified in clause 5.7.1.11 of TS 23.501 [2]. The Disaster Roaming service indication is included if the indication is received from AMF in step 3a above.
NOTE 1: The QoS constraints from the VPLMN are provided by the VPLMN to avoid the risk that V-SMF rejects the PDU Session in step 13 when controlling SLA with the HPLMN.
V-SMF SM Context ID contains the addressing information it has allocated for service operations related with this PDU Session. The H-SMF stores an association of the PDU Session and V-SMF Context ID for this PDU Session for this UE.
If the H-SMF needs to use V-SMF services for this PDU Session (invoking Nsmf_PDUSession_Update Request) before step 13, at the first invocation of Nsmf_PDUSession_Update Request the H-SMF provides the V-SMF with the H-SMF SM Context ID it has allocated for service operations related with this PDU Session.
If the RAT type was included in the message, then the H-SMF stores the RAT type in SM Context.
ECS Address Configuration Information associated with PLMN ID of visited network is an optional information that may only be provided when HR-SBO is supported for roamers of HPLMN.
If the V-SMF has an association with the H-SMF for the indicated PDU Session ID, the V-SMF invokes Nsmf_PDUSession_Update Request. Otherwise the V-SMF invokes Nsmf_PDUSession_Create Request.
If the V-SMF receives the HPLMN Alternative S-NSSAI and the HPLMN S-NSSAI from the AMF, the V-SMF sends both the HPLMN Alternative S-NSSAI and the HPLMN S-NSSAI to the H-SMF.
If the V-SMF receives the URSP rule enforcement reports from UE, the V-SMF provides the URSP rule enforcement reports from roaming UE to H-SMF.
If an H-SMF set ID was received, the V-SMF further delegate the re-selection within the H-SMF set to the target PLMN as described in clause 4.17.10a.
7-12b. These steps are the same as steps 4-10 in clause 4.3.2.2.1 with the following differences:
- These steps are executed in Home PLMN;
- If the S-NSSAI of this PDU Session is subject to network slice usage control, according to operator's policy the H-SMF configures the PDU Session inactivity timer in the H-UPF as described in clause 5.15.15 of TS 23.501 [2]. Otherwise, the H-SMF does not provides the inactivity timer to the H-UPF as described in step 10a in clause 4.3.2.2.1.
- If the QoS constraints from the VPLMN is provided in step 6 and PCF is deployed, the H-SMF provides the QoS constraints from the VPLMN to PCF. The PCF takes this into account when making policy decisions. In case dynamic PCC is not deployed, the SMF takes this into account when generating the default QoS rule.
- Step 5 of clause 4.3.2.2.1 is not executed.
- If Disaster Roaming service indication is received, the SMF stores the indication in PDU session context and includes the indication in charging data. H-SMF may also apply policy and charging control based on the indication according to roaming agreement.
When PCF is deployed, the SMF shall further report the PS Data Off status to PCF if the PS Data Off event trigger is provisioned, the additional behaviour of SMF and PCF for 3GPP PS Data Off is defined in TS 23.503 [20].
12c. This step is the same as step 16c in clause 4.3.2.2.1 with the following difference:
- The H-SMF registers for the PDU Session with the UDM using Nudm_UECM_Registration (SUPI, DNN, S-NSSAI with the value defined by the HPLMN, PDU Session ID).
13. H-SMF to V-SMF: Nsmf_PDUSession_Create Response (QoS Rule(s), QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s), PCO including session level information that the V-SMF is not expected to understand, selected PDU Session Type and SSC mode, Reliable Data Service Support, H-CN Tunnel Info, QFI(s), QoS profile(s), Session-AMBR, Reflective QoS Timer (if available), information needed by V-SMF in the case of EPS interworking such as the PDN Connection Type, User Plane Policy Enforcement, [ECS Address Configuration Information for the serving PLMN]).
If the PDU Session being established was requested to be an always-on PDU Session, the H-SMF shall indicate to the V-SMF whether the request is accepted or not via the Always-on PDU Session Granted indication in the response message to V-SMF. If the PDU Session being established was not requested to be an always-on PDU Session but the H-SMF determines that the PDU Session needs to be established as an always-on PDU Session, the H-SMF shall indicate it to the V-SMF by including Always-on PDU Session Granted indication that the PDU Session is an always-on PDU Session.
The information that the H-SMF may provide is the same than defined for step 11 of Figure 4.3.2.2.1-1.
The H-CN Tunnel Info contains the tunnel information for uplink traffic towards H-UPF.
Multiple QoS Rules and QoS Flow level QoS parameters for the QoS Flow(s) associated with the QoS rule(s) may be included in the Nsmf_PDUSession_Create Response.
The V-SMF may apply VPLMN policies related with the SLA negotiated with the HPLMN or with QoS values supported by the VPLMN to evaluate the QoS parameters received from H-SMF; such policies may result in that V-SMF does not accept the PDU Session or does not accept some of the QoS Flows requested by the H-SMF. If the V-SMF does not accept the PDU Session, the V-SMF triggers the V-SMF initiated PDU Session Release procedure from step 1b-3b as defined in clause 4.3.4.3. When the V-SMF accepts at least one QoS flow, it transfers (via the AMF) the corresponding N2 (and NAS) request towards the 5G AN (and the UE) but does not issue requests for the QoS Flow(s) it has rejected due these policies. The V-SMF notifies the H-SMF about the rejected QoS Flows in step 23 below.
NOTE 2: QoS enforcement in V-UPF is not expected on the QoS parameters received from H-SMF.
If Control Plane CIoT 5GS Optimisation is enabled for the PDU Session, certain information, e.g. H-CN tunnel info, is not provided in the response to V-SMF.
V-SMF stores the indication of Small Data Rate Control applicability on this PDU Session, if it is received in Nsmf_PDUSession_Create Response.
13a-13b. The V-SMF initiates an N4 Session Modification procedure with the V-UPF. The V-SMF may provide N4 rules to the V-UPF for this PDU Session, including rules to forward UL traffic to the H-UPF.
14-18. These steps are the same as steps 11-15 in clause 4.3.2.2.1 with the following differences:
- These steps are executed in Visited PLMN;
- The V-SMF stores an association of the PDU Session and H-SMF ID for this PDU Session for this UE;
- If the H-SMF indicates the PDU Session can be established as an always-on PDU Session, the V-SMF shall further check whether the PDU Session can be established as an always-on PDU Session based on local policies. The V-SMF notifies the UE whether the PDU Session is an always-on PDU Session or not via the Always-on PDU Session Granted indication in the PDU Session Establishment Accept message.
- If the N2 SM information indicates failure of user plane resource setup and the V-SMF rejected the PDU session establishment as described in step 15 in clause 4.3.2.2.1, step 19 is skipped and instead the V-SMF releases the N4 Session with V-UPF.
- If an alternative H-SMF is selected for the PDU Session and the corresponding selected alternative H-SMF ID has not been previously provided to the AMF, the V-SMF provides the selected alternative H-SMF ID to the AMF.
NOTE 3: The selected alternative H-SMF ID can be provided to AMF earlier, e.g. in step 8 if PDU Session Authentication/Authorization is performed.
- If Control Plane CIoT 5GS Optimisation is enabled for the PDU Session, steps 19, 20 and 23 below are omitted.
19a. The V-SMF initiates an N4 Session Modification procedure with the V-UPF. The V-SMF may provide N4 rules to the V-UPF for this PDU Session, including rules to forward DL traffic to the AN.
19b. The V-UPF provides a N4 Session Modification Response to the V-SMF.
After this step, the V-UPF delivers any down-link packets to the UE that may have been buffered for this PDU Session.
20. This step is the same as step 17 in clause 4.3.2.2.1 with the following differences:
- The SMF is a V-SMF. The H-SMF and V-SMF subscribe to UE reachability event from AMF.
21. This step is same as step 18 in clause 4.3.2.2.1. In addition, if during the procedure, after step 14, the PDU Session establishment is not successful as specified in step 15 of clause 4.3.2.2.1, the V-SMF triggers the V-SMF initiated PDU Session Release procedure from step 1b-3b as defined in clause 4.3.4.3.
22. H-SMF to UE, via H-UPF and V-UPF in VPLMN: In the case of PDU Session Type IPv6 or IPv4v6, the H-SMF generates an IPv6 Router Advertisement and sends it to the UE via N4 and the H-UPF and V-UPF. If the Control Plane CIoT 5GS Optimisation is enabled for this PDU session the V-UPF forwards the IPv6 Router Advertisement to the V-SMF for transmission to the UE using the Mobile Terminated Data Transport in Control Plane CIoT 5GS Optimisation procedures (see clause 4.24.2).
23. If the V-SMF received in step18 an indication that the (R)AN has rejected some QFI(s) or if the V-SMF has rejected some QFI(s) in step 13, the V-SMF notifies the H-SMF via a Nsmf_PDUSession_Update Request. The H-SMF is responsible of updating accordingly the QoS rules and QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s) in the UE.
24. This step is the same as step 20 in clause 4.3.2.2.1 with the following differences:
- this step is executed in the Home PLMN;
- the SMF also deregisters for the given PDU Session using Nudm_UECM_Deregistration (SUPI, DNN, PDU Session ID). The UDM may update corresponding UE context by Nudr_DM_Update (SUPI, Subscription Data, UE context in SMF data).
NOTE 4: The SMF in HPLMN can initiate H-SMF initiated PDU Session Release procedure as defined in clause 4.3.4.3, already after step 13. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.2.2.3 SMF selection | 4.3.2.2.3.1 General
The SMF selection function, as described in clause 6.3.2 of TS 23.501 [2], is supported by the AMF and is used to allocate an SMF that manages the PDU Session.
The SMF selection function described in this clause does not apply to the selection of an SMF for Emergency services. For SMF selection for Emergency services is described in clause 5.16.4.5 of TS 23.501 [2].
Two main branches of deployment scenarios to consider:
- Non-roaming and roaming with local breakout, see clause 4.3.2.2.3.2
- Home routed roaming, see clause 4.3.2.2.3.3
In the case of non-roaming and local breakout, there are two operational scenarios dependent on the configuration of AMF and the deployment option of NSSF in the serving PLMN.
In the case of home-routed, there are two main options dependent on the operators' choices in terms of involvement of NRF, NSSF and configuration of AMF. The decision of which option to use is part of the roaming agreements.
NOTE: The use of NSI ID and the use of multiple NRFs in the network are optional and depend on the deployment choices of the operator.
4.3.2.2.3.2 Non-roaming and roaming with local breakout
Figure 4.3.2.2.3.2-1: SMF selection for non-roaming and roaming with local breakout scenarios
This procedure may be skipped altogether if SMF information is available in the AMF by other means (e.g. locally configured); otherwise:
- when the serving AMF is aware of the appropriate NRF to be used to select NFs/services within the corresponding Network Slice instance based on configuration or based on the Network Slice selection information received during Registration, only steps 3 and 4 in the following procedure are executed as described in Figure 4.3.2.2.3.2-1;
- when the serving AMF is not aware of the appropriate NRF to be used to select NFs/services within the corresponding Network Slice instance, all steps in the following procedure are executed as described in Figure 4.3.2.2.3.2-1.
1. The AMF invokes the Nnssf_NSSelection_Get service operation from the NSSF in serving PLMN with the S-NSSAI of the Serving PLMN from the Allowed NSSAI or Partially Allowed NSSAI requested by the UE, PLMN ID of the SUPI, TAI of the UE and the indication that the request is within a procedure of PDU Session establishment in either the non-roaming or roaming with local breakout scenario.
2. The NSSF in serving PLMN selects the Network Slice instance, determines and returns the appropriate NRF to be used to select NFs/services within the selected Network Slice instance and optionally may return a NSI ID corresponding to the Network Slice instance.
3. AMF queries the appropriate NRF in serving PLMN (including the scenario where SMF instances reside in a target PLMN as specified in clause 4.2.3 and clause 6.2.6.1 of TS 23.501 [2]) by issuing the Nnrf_NFDiscovery_Request including at least the S-NSSAI of the Serving PLMN for this PDU Session from the Allowed NSSAI or Partially Allowed NSSAI, PLMN ID of the SUPI, DNN and possibly NSI ID if the AMF has stored an NSI ID for the S-NSSAI of the Serving PLMN for this PDU Session from the Allowed NSSAI or Partially Allowed NSSAI.
NOTE: The list of parameters for SMF selection is defined in clause 6.3.2 of TS 23.501 [2]. See also clause 5.34.3 of TS 23.501 [2] for I-SMF selection.
4. The NRF in serving PLMN provides to the AMF, e.g. FQDN or IP address, of a set of the discovered SMF instance(s) or Endpoint Address(es) of SMF service instance(s) in Nnrf_NFDiscovery_Request response message and possibly an NSI ID for the selected Network Slice instance corresponding to the S-NSSAI for subsequent NRF queries.
4.3.2.2.3.3 Home routed roaming
The discovery and selection of the SMF in VPLMN is performed in the same way as for non-roaming and roaming with local breakout (see clause 4.3.2.2.3.2). The discovery and selection of the H-SMF in HPLMN, including the case of the Indirect Network Sharing scenario as described in clause 5.18 and clause 6.3.2 of TS 23.501 [2], is performed by means of either using NSSFs in VPLMN and HPLMN to discover a NRF in HPLMN (hNRF) or by having the hNRF configured in VPLMN. Which of these two options to use is based on local configuration in the VPLMN. The configuration depends on Service Level Agreements between the operators.
NOTE 1: The procedures described in this clause are not limited to SMF discovery and selection, but can be used to discover and select any NF/NF service in the HPLMN part of a Network Slice instance.
The discovery and selection of the H-SMF in HPLMN is performed by means of the procedure depicted in Figure 4.3.2.2.3.3-1 for the option where NSSFs are used for hNRF discovery. In this case the steps 1 to 4 in Figure 4.3.2.2.3.3-1 are required. In the option where VPLMN are having hNRF configured, then NRF in VPLMN (vNRF) has the endpoint(s) of the Nnrf_NFdiscovery service(s) of the hNRF(s) as described in Figure 4.3.2.2.3.3-2.
Figure 4.3.2.2.3.3-1: Option 1 for SMF selection for home-routed roaming scenarios
1. Based on the operator's configuration, if the AMF is not aware of the appropriate NRF to be used to discover NFs/NF services in the HPLMN, the AMF invokes the Nnssf_NSSelection_Get service operation from the NSSF in VPLMN (vNSSF) with the VPLMN S-NSSAI from the Allowed NSSAI or Partially Allowed NSSAI requested by the UE for this PDU Session, the HPLMN S-NSSAI that maps to the VPLMN S-NSSAI, PLMN ID of the SUPI, the TAI of the UE and the indication that the request is within a procedure of PDU Session establishment in the home-routed roaming scenario.
2. If slicing configuration information for the S-NSSAI in the HPLMN is not available (e.g. the vNSSF has no cached information), the vNSSF invokes the Nnssf_NSSelection_Get service operation from NSSF of the HPLMN (hNSSF) according to the PLMN ID of the SUPI by including the HPLMN S-NSSAI. The vNSSF may be configured with the address(es) of the Nnssf_NSSelection_Get service(s) of the hNSSF.
3. The NSSF in HPLMN may include the NSI ID, if needed, for the Network Slice instance in HPLMN selected for the corresponding S-NSSAI of the HPLMN in the Nnssf_NSSelection_Get response. The NSSF in HPLMN also includes the appropriate hNRF to be used to discover NFs/NF services within HPLMN in the Nnssf_NSSelection_Get response.
4. The vNSSF includes in the Nnssf_NSSelection_Get response all the information that has been received from the NSSF in HPLMN in the response to the AMF.
The steps 5-8 below apply SMF discovery of the general procedure for NF/NF service discovery across PLMNs in the case of discovery made by NF service consumer defined in clause 4.17.5.
5. The AMF queries the vNRF using the Nnrf_NFDiscovery_Request by including PLMN ID of the SUPI, the serving PLMN ID, DNN, HPLMN S-NSSAI, the hNRF (if discovered in steps 1-4 or cached) and possibly an HPLMN NSI ID for the selected Network Slice instance corresponding to the HPLMN S-NSSAI if available in the AMF (obtained from the HPLMN NSSF in steps 3 and 4 or cached from a previous H-NSSF query).
In the case of Indirect Network Sharing, the AMF may also include e.g. following query parameters, the service area/serving scope/preferred locality of SMF based on UE location as described in clause 6.3.2 of TS 23.501 [2].
NOTE 2: The list of parameters for SMF selection is further defined in clause 6.3.2 of TS 23.501 [2].
6. The vNRF invokes the Nnrf_NFDiscovery_Request service operation from hNRF (address aquired in step 5, or configured) according the procedure in Figure 4.17.4-1 to get the NF profiles of candidate H-SMF instance(s) in the HPLMN. As the vNRF sends an Nnrf_NFDiscovery request on behalf of the AMF, the vNRF shall not replace the information of the requesting NF ID, i.e. AMF ID, in the Nnrf_NFDiscovery_Request messag. If hNRF does not hold the NF profiles of the candidate H-SMF instances, hNRF may further interrogate other NRF(s) of the HPLMN to discovery H-SMF instances. For further information about NRF-NRF interactions, see clauses 5.3.2.2.4 and 5.3.2.2.5 of TS 29.510 [37].
7-8. The hNRF provides to the AMF (including the scenario where SMF instances reside in a target PLMN for traffic from certain UEs as specified in clause 4.2.4 and clause 6.2.6.1 of TS 23.501 [2]), via vNRF, the NF profiles of the discovered H-SMF instance(s) in Nnrf_NFDiscovery_Request response message, which may also include an NSI ID for the selected Network Slice instance corresponding to the S-NSSAI of the HPLMN, which can be used for subsequent NRF queries.
The second option is depicted in Figure 4.3.2.2.3.3-2.
Figure 4.3.2.2.3.3-2: Option 2 for SMF selection for home-routed roaming scenarios
1. Based on the operator's configuration, the AMF queries the vNRF with PLMN ID of the SUPI, PLMN ID of the serving PLMN, DNN, the HPLMN S-NSSAI that maps to the S-NSSAI from the Allowed NSSAI or Partially Allowed NSSAI of the Serving PLMN the UE has requested, the endpoint(s) of the discovery service(s) of hNRF if available and if applicable and available, an HPLMN NSI ID (if the AMF has stored hNRF information and if applicable and available, an HPLMN NSI ID for the selected Network Slice instance corresponding to the S-NSSAI of the HPLMN) and DNN.
In the case of Indirect Network Sharing, the AMF may also include e.g. following query parameters, service area/serving scope/preferred locality of SMF based on UE location as described in clause 6.3.2 of TS 23.501 [2].
2. The vNRF queries, on behalf of the AMF in VPLMN, the hNRF identified by means of the PLMN ID of the SUPI (if no endpoint address of hNRF discovery service is received from the AMF, the vNRF determines the endpoint address of hNRF based on local configuration using information received in step 1). The vNRF in VPLMN sends an Nnrf_NFDiscovery request to the hNRF according to the procedure in Figure 4.17.4-1 to get the NF profiles of candidate H-SMF(s). As the vNRF sends an Nnrf_NFDiscovery request on behalf of the AMF, the vNRF shall not replace the information of the requesting NF, i.e. AMF ID, in the Nnrf_NFDiscovery_Request message.
The steps 3a-3d below apply SMF discovery of the general procedure for NF/NF service discovery across PLMNs in the case of discovery made by NF service consumer defined in clause 4.17.5.
Depending on the available information and based on configuration, the hNRF may either execute steps in 3(A) or in 3(B).
3(A) The hNRF provides to the AMF, via vNRF, the NF profile(s) of the discovered SMF instance(s) and possibly an NSI ID for the selected HPLMN part of the Network Slice instance corresponding to the S-NSSAI of the HPLMN for subsequent NRF queries in Nnrf_NFDiscovery_Request response message(steps 3a and 3b).
3(B) The hNRF queries, on behalf of the AMF, another NRF (e.g. a slice level NRF in HPLMN or a NRF in a target PLMN for the scenario where NF instances reside in that target PLMN for certain UEs as specified in clause 4.2.4 and clause 6.2.6.1 of TS 23.501 [2]); the queried NRF provides NF profiles of SMF instance(s) and possibly an NSI ID for the selected HPLMN part of the Network Slice instance corresponding to the S-NSSAI of the HPLMN for subsequent NRF queries (steps 3a and 3b) that the hNRF returns, via vNRF, to the AMF (steps 3c and 3d).
NOTE 3: In 3(B) the NF profile is provided by a second NRF, however the candidate NF profile(s) might reside in a third or fourth NRF, etc. NRF-NRF interactions are described in clauses 5.3.2.2.4 and 5.3.2.2.5 of TS 29.510 [37].
NOTE 4: The detailed service operation parameters and the involvement of different NRFs are further described in TS 29.510 [37]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.2.2.4 Multiple PDU Sessions towards the same DNN and S-NSSAI | A UE may establish multiple PDU Sessions associated with the same DNN and S-NSSAI and the AMF may select the same SMF or different SMFs as specified in clause 6.3.2 of TS 23.501 [2].
During PDU Session establishment, the AMF checks if the SMF selection subscription data indicates that the same SMF is required for multiple PDU Sessions and if required, the AMF checks if any SMF is already selected for the same DNN and S-NSSAI, if so, the same SMF will be used for the additional PDU Session.
NOTE 1: The SMF ID can be notified from UDM to the AMF when one AMF is selected for 3GPP access in VPLMN and a different AMF is selected in HPLMN for non-3GPP access.
NOTE 2: The same SMF is selected for multiple PDU Sessions towards the same DNN and S-NSSAI to facilitate the selection of the same PCF e.g. for the purpose of usage monitoring. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.2.3 Secondary authorization/authentication by an DN-AAA Server during the PDU Session establishment | The PDU Session establishment authentication/authorization is optionally triggered by the SMF during a PDU Session establishment and performed transparently via a UPF or directly with the DN-AAA Server without involving the UPF if the DN-AAA Server is located in the 5GC and reachable directly, as described in clause 5.6.6 of TS 23.501 [2].
In the case of Home Routed Roaming, unless specified otherwise, the SMF in the information flow defined in this clause is the H-SMF.
Figure 4.3.2.3-1: PDU Session Establishment authentication/authorization by a DN-AAA Server
NOTE 1: Steps 2, 3a, 3f and 4 are not defined in this specification. Steps 3 can be repeated depending on the mechanism used.
NOTE 2: When the SMF directly communicates with the DN-AAA Server without involving the UPF, Step 1 is skipped and Step 2, 3a, 3f, 4 and 6 are executed without involving the UPF.
0. The SMF determines that it needs to contact the DN-AAA Server. The SMF identifies the DN-AAA Server based on local configuration or using the DN-specific identity (TS 33.501 [15]) provided by the UE inside the SM PDU DN Request Container provided by the UE in the PDU Session Establishment request or inside the EAP message in the PDU Session Authentication Complete message (TS 24.501 [25]).
NOTE 3: The content of the SM PDU DN Request Container is defined in TS 24.501 [25].
NOTE 4: When secondary authentication, using Default UE credentials for secondary authentication, is used in the context of the UE onboarding architecture in Figure 5.30.2.10.2.2-3 of TS 23.501 [2], the DCS can act as the DN-AAA server.
1. If there is no existing N4 session that can be used to carry DN-related messages between the SMF and the DN, the SMF selects a UPF and triggers N4 session establishment.
2. The SMF initiates the authentication procedure with the DN-AAA via the UPF to authenticate the DN-specific identity provided by the UE as specified in TS 29.561 [63].
When available, the SMF provides the GPSI in the signalling exchanged with the DN-AAA.
The UPF transparently relays the message received from the SMF to the DN-AAA Server.
3a. The DN-AAA Server sends an Authentication/Authorization message towards the SMF. The message is carried via the UPF.
3b. Transfer of DN Request Container information received from DN-AAA towards the UE.
In non-roaming and LBO cases, the SMF invokes the Namf_Communication_N1N2MessageTransfer service operation on the AMF to transfer the DN Request Container information within N1 SM information sent towards the UE.
In the case of Home Routed roaming, the H-SMF initiates a Nsmf_PDUSession_Update service operation to request the V-SMF to transfer DN Request Container to the UE and the V-SMF invokes the Namf_Communication_N1N2MessageTransfer service operation on the AMF to transfer the DN Request Container information within N1 SM information sent towards the UE. In Nsmf_PDUSession_Update Request, the H-SMF additionally includes the H-SMF SM Context ID.
3c: The AMF sends the N1 NAS message to the UE
3d-3e. Transfer of DN Request Container information received from UE towards the DN-AAA.
When the UE responds with a N1 NAS message containing DN Request Container information, the AMF informs the SMF by invoking the Nsmf_PDUSession_UpdateSMContext service operation. The SMF issues an Nsmf_PDUSession_UpdateSMContext response.
In the case of Home Routed roaming, the V-SMF relays the N1 SM information to the H-SMF using the information of PDU Session received in step 3b via a Nsmf_PDUSession_Update service operation.
3f: The SMF (In HR case it is the H-SMF) sends the content of the DN Request Container information (authentication message) to the DN-AAA Server via the UPF.
Step 3 may be repeated until the DN-AAA Server confirms the successful authentication/authorization of the PDU Session.
4. The DN-AAA Server confirms the successful authentication/authorization of the PDU Session. The DN-AAA Server may provide:
- an SM PDU DN Response Container to the SMF to indicate successful authentication/authorization;
- DN Authorization Data as defined in clause 5.6.6 of TS 23.501 [2];
- a request to get notified with the IP address(es) allocated to the PDU Session and/or with N6 traffic routing information or MAC address(es) used by the UE for the PDU Session; and
- an IP address (or IPV6 Prefix) for the PDU Session.
The N6 traffic routing information is defined in clause 5.6.7 of TS 23.501 [2].
After the successful DN authentication/authorization, a session is kept between the SMF and the DN-AAA. If the SMF receives a DN Authorization Data, the SMF uses the DN Authorization Profile Index to apply the policy and charging control (see clause 5.6.6 of TS 23.501 [2]).
5. The PDU Session establishment continues and completes. In the step 7b of the Figure 4.3.2.2.1-1, if the SMF receives the DN Authorization Profile Index in DN Authorization Data from the DN-AAA, it sends the DN Authorization Profile Index to retrieve the PDU Session related policy information (described in clause 6.4 of TS 23.503 [20]) and the PCC rule(s) (described in clause 6.3 of TS 23.503 [20]) from the PCF. If the SMF receives the DN authorized Session AMBR in DN Authorization Data from the DN-AAA, it sends the DN authorized Session AMBR within the Session AMBR to the PCF to retrieve the authorized Session AMBR (described in clause 6.4 of TS 23.503 [20]). For PDU Session of Ethernet type, the SMF may instruct the UPF to handle VLAN information of the Ethernet frames related with the PDU Session received and sent on N6 or N19 or internal interface, as described in clause 5.6.10.2 of TS 23.501 [2].
6. If requested so in step 4 or if configured so by local policies, the SMF notifies the DN-AAA with the IP/MAC address(es) and/or with N6 traffic routing information allocated to the PDU Session together with the GPSI.
Later on the SMF notifies the DN-AAA if the DN-AAA had requested to get notifications about:
- allocation or release of an IPV6 Prefix for the PDU Session of IP type or addition or removal of source MAC addresses for the PDU Session of Ethernet type (e.g. using IPV6 multi-homing as defined in clause 5.6.4.3 of TS 23.501 [2]);
- Change of N6 traffic routing information.
When later on the PDU Session gets released as described in clause 4.3.4, the SMF notifies the DN-AAA.
The DN-AAA Server may revoke the authorization for a PDU Session or update DN authorization data for a PDU Session. According to the request from DN-AAA Server, the SMF may release or update the PDU Session.
At any time after the PDU Session establishment, the DN-AAA Server or SMF may initiate Secondary Re-authentication procedure for the PDU Session as specified in clause 11.1.3 of TS 33.501 [15]. Step 3a to step 3f are performed to transfer the Secondary Re-authentication message between the UE and the DN-AAA Server. The Secondary Re-authentication procedure may start from step 3a (DN-AAA initiated Secondary Re-authentication procedure) or step 3b (SMF initiated Secondary Re-authentication procedure). For the DN-AAA Server initiated Secondary Re-authentication, the message in step 3a shall include GPSI, if available and the IP/MAC address(es) of the PDU session, for SMF to identify the corresponding UE and PDU session. If the Re-authentication result is unsuccessful then SMF may release the PDU session and notify the DN-AAA Server.
During Secondary Re-authentication, if the SMF receives an indication from the AMF that the UE is unreachable then it informs the DN-AAA Server that UE is not reachable for re-authentication. Based on this indication from SMF, the DN-AAA Server may decide to keep the PDU Session or request to release the PDU session.
DN-AAA may initiate DN-AAA Re-authorization without performing re-authentication based on local policy. DN-AAA Re-authorization procedure may start from step 4.
During Secondary Re-authentication/Re-authorization, if the SMF receives DN Authorization Profile Index and/or DN authorized Session AMBR, the SMF reports the received value(s) to the PCF (as described in TS 23.501 [2]) by triggering the Policy Control Request Trigger as described in TS 23.503 [20]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.2.4 Support of L2TP | L2TP may be used between UPF and the DN via N6 to carry traffic of a PDU Session, as defined in TS 23.501 [2]. The corresponding high level end to end signalling flow is described in this clause and further refined in TS 29.561 [63]. For the procedure described below, it is a prerequisite that the UE is already registered to the 5GC and both SMF and UPF support the L2TP feature.
NOTE 1: The scenario where the UE sends actual PPP frames/signalling towards the LAC, which involves back and forth message exchanges between the UE and LAC, for example for LCP Negotiation, is not in the scope of the present document.
NOTE 2: The UE does not need to be aware of the L2TP procedure.
Figure 4.3.2.4-1: Support of L2TP
1. This step is the same as step 1 in clause 4.3.2.2.1 or step 1 in clause 4.3.2.2.2.
The PDU session establishment may include in the PCO information authentication information for PAP and/or CHAP.
2. The SMF may determine that an L2TP session is required for the PDU Session based on local configuration (e.g. related with DNN/S-NSSAI). The SMF may retrieve the L2TP Tunnel parameters from the DN-AAA Server, as described in clause 4.3.2.3, or be configured locally with L2TP Tunnel parameters.
The L2TP Tunnel parameters may include information such as the LNS addressing information (e.g. IP address or hostname), as defined in TS 29.561 [63].
3. This step is the same as step 8 in clause 4.3.2.2.1 with the following additions:
If L2TP is required for the PDU Session, the SMF selects a UPF supporting L2TP.
4. This step is the same as step 10a in clause 4.3.2.2.1 with the following additions:
The SMF requests the UPF to setup an L2TP Session towards the L2TP server (LNS).
The SMF may send to the UPF as part of N4 signalling, L2TP Tunnel Information and L2TP Session Information to setup a L2TP session.
The L2TP Session Information includes specific information related to the PDU Session, e.g. a Calling Number which may be set to UE's SUPI, the Called Number for the L2TP Session which may be configured to contain the DNN, PAP/CHAP related parameters if included by the UE in PCO in step 1 etc. This information is defined in TS 29.561 [63].
5. If needed the UPF may decide to setup a new L2TP Tunnel, as described in TS 29.561 [63].
If the UPF decides to use an already existing L2TP Tunnel for the requested PDU Session from the SMF, it directly proceeds with step 6 below.
6. The UPF proceeds with L2TP Session setup towards the LNS, as described in TS 29.561 [63].
If the SMF has requested the UPF to allocate the UE IP address in step 4, the UPF may retrieve the UE IP address from the LNS.
7. This step is the same as step 10b in clause 4.3.2.2.1 with the following additions:
The status of the L2TP Session setup is sent by the UPF to the SMF in a N4 Session Establishment Response. This may indicate information provided by the LNS Server for the UE such as the DNS server address, etc.
8. This step is the same as steps 11 - 13 in clause 4.3.2.2.1. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.3 PDU Session Modification | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.3.1 General | The procedure is used when one or several of the QoS parameters exchanged between the UE and the network are modified and/or to send updated ECS Address Configuration Information as defined in clause 6.5.2 of TS 23.548 [74] to the UE and/or to send the updated DNS server address as defined in clause 6.2.3.2.3 of TS 23.548 [74].
NOTE 1: The conditions when to use this procedure for QoS change as well as the QoS parameters exchanged between the UE and the network are defined in clause 5.7 of TS 23.501 [2].
NOTE 2: The conditions when to use this procedure for the exchange of ECS Address Configuration Information are described in clause 6.5.2 of TS 23.548 [74].
NOTE 3: The conditions when to use this procedure for the update of DNS server address are described in clause 6.2.3.2.3 of TS 23.548 [74]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.3.2 UE or network requested PDU Session Modification (non-roaming and roaming with local breakout) | The UE or network requested PDU Session Modification procedure (non-roaming and roaming with local breakout scenario) is depicted in figure 4.3.3.2-1.
Figure 4.3.3.2-1: UE or network requested PDU Session Modification (for non-roaming and roaming with local breakout)
1. The procedure may be triggered by following events:
1a. (UE initiated modification) The UE initiates the PDU Session Modification procedure by the transmission of an NAS message (N1 SM container (PDU Session Modification Request (PDU session ID, Packet Filters, Operation, Requested QoS, Segregation, 5GSM Core Network Capability, Number Of Packet Filters, [URSP rule enforcement reports], [Always-on PDU Session Requested], [Requested Non-3GPP Delay Budget], [non-3GPP device connection information])), PDU Session ID, UE Integrity Protection Maximum Data Rate, [Port Management Information Container]) message. Depending on the Access Type, if the UE was in CM-IDLE state, this SM-NAS message is preceded by the Service Request procedure. The NAS message is forwarded by the (R)AN to the AMF with an indication of User location Information. The AMF invokes Nsmf_PDUSession_UpdateSMContext (SM Context ID, N1 SM container (PDU Session Modification Request)).
When the UE requests specific QoS handling for selected SDF(s), the PDU Session Modification Request includes Packet Filters describing the SDF(s), the requested Packet Filter Operation (add, modify, delete) on the indicated Packet Filters, the Requested QoS and optionally a Segregation indication. The Segregation indication is included when the UE recommends to the network to bind the applicable SDF(s) on a distinct and dedicated QoS Flow e.g. even if an existing QoS Flow can support the requested QoS. The network should abide by the UE request, but is allowed to proceed instead with binding the selected SDF(s) on an existing QoS Flow.
NOTE 1: Only one QoS Flow is used for traffic segregation. If UE makes subsequent requests for segregation of additional SDF(s), the additional SDF(s) are multiplexed on the existing QoS Flow that is used for segregation.
The UE shall not trigger a PDU Session Modification procedure for a PDU Session corresponding to a LADN when the UE is outside the area of availability of the LADN.
The PS Data Off status, if changed, shall be included in the PCO in the PDU Session Modification Request message.
For a PDU Session which was established in the EPS, when the UE moves from EPS to 5GS for the first time, the UE includes an Always-on PDU Session Requested indication in the PDU Session Modification Request message if it wants to change the PDU Session to an always-on PDU Session.
If UE supports to report URSP rule enforcement to network, when the UE associates a newly detected application to an existing PDU Session based on URSP evaluation result and the matched URSP rule included the Indication for reporting URSP rule enforcement, the UE may initiate PDU Session Modification procedure to provide URSP rule enforcement report as described in clause 6.6.2.4 of TS 23.503 [20].
When PCF is deployed, the SMF shall further report the PS Data Off status to PCF if the PS Data Off event trigger is provisioned, the additional behaviour of SMF and PCF for 3GPP PS Data Off is defined in TS 23.503 [20].
The 5GSM Core Network Capability is provided by the UE and handled by SMF as defined in clause 5.4.4b of TS 23.501 [2].
The UE Integrity Protection Maximum Data Rate indicates the maximum data rate up to which the UE can support UP integrity protection. It is set as defined in TS 23.501 [2].
The Number Of Packet Filters indicates the number of supported packet filters for signalled QoS rules as described in clause 5.17.2.2.2 of TS 23.501 [2].
When it moves from EPS to 5GS for the first time, a UE that supports EAS re-discovery as described in clause 6.2.3.3 of TS 23.548 [74], may indicate so in the PCO.
When it moves from EPS to 5GS for the first time, a UE that hosts the EDC functionality shall indicate in the PCO its capability to support the EDC functionality (see clause 5.2.1 of TS 23.548 [74]).
Port Management Information Container may be received from DS-TT and includes DS-TT port related management information as defined in clause 5.28.3 of TS 23.501 [2].
If the UE supports QoS differentiation of traffic for Non-3GPP Device Identifier and when the UE determines that QoS differentiation is required as described in clause 5.52 of TS 23.501 [2], the UE includes the Non-3GPP Device Identifier and the corresponding user plane address in the non-3GPP device connection information within the PDU Session Modification Request.
Editor's note: Details on how non-3GPP device connection information is included within PDU Session Modification Request are to be defined in stage 3.
1b. (PCF initiated SM Policy Association Modification) The PCF performs a PCF initiated SM Policy Association Modification procedure as defined in clause 4.16.5.2 to notify SMF about the modification of policies. This may e.g. have been triggered by a policy decision or upon AF requests, e.g. Application Function influence on traffic routing as described in step 5 in clause 4.3.6.2 or AF to provide Port management information Container.
If QoS Monitoring is requested by the AF, the PCF generates the QoS Monitoring policy for the corresponding service data flow and provides the policy in the PCC rules to the SMF in this step.
If Periodicity is provided by the AF, the PCF provides the Periodicity information in the PCC rules. Based on operator's local policies, the PCF sends to the SMF an indication in the PCC Rule to perform N6 Traffic Parameter Measurements for N6 Jitter and, if not received from the AF, also UL and/ or DL Periodicity measurements.
The PCF may provision a PDU Set Control Information and Protocol Description as described in clause 6.1.3.27.4 of TS 23.503 [20], clauses 5.37.5, 5.37.9.2 and 5.37.9.4 of TS 23.501 [2] and/or On-path N6 Signalling Information (as described in clause 5.37.9 of TS 23.501 [2] and clause 6.3.1 of TS 23.503 [20]) within PCC Rules based on the information provided by the AF and/or the local operator policies.
The PCF may provision a Data Burst Handing Information and DL Protocol Description as described in clause 6.3.1 of TS 23.503 [20] and clauses 5.37.8.3, 5.37.9.2 and 5.37.9.4 of TS 23.501 [2]) and/or On-pathN6 Signalling Information (as described in clause 5.37.9 of TS 23.501 [2] and clause 6.3.1 of TS 23.503 [20]) within PCC Rules based on the information provided by the AF and/or the local operator policies.
The PCF may provision two PCC rules with different QoS parameters for two service data flows with different Expedited Transfer Indication values as described in clause 5.37.10.3 of TS 23.501 [2] and 6.1.3.27.9 of TS 23.503 [20] based on the information provided by the AF.
If the PCF has received the notification from UDR via Nudr_DM_Notify that the Non-3GPP Device Identifier Information has been updated (e.g. update, delete), the PCF shall update the PCC rules associated with the Non-3GPP Device Identifier, if any.
1c. (SMF requested modification) The UDM updates the subscription data of SMF by Nudm_SDM_Notification (SUPI, Session Management Subscription Data). The SMF updates the Session Management Subscription Data and acknowledges the UDM by returning an Ack with (SUPI).
1d. (SMF requested modification) The SMF may decide to modify PDU Session. This procedure also may be triggered based on locally configured policy or triggered from the (R)AN (see clause 4.2.6 and clause 4.9.1). It may also be triggered if the UP connection is activated (as described in Service Request procedure) and the SMF has marked that the status of one or more QoS Flows are deleted in the 5GC but not synchronized with the UE yet. It may also be triggered to update QoS profile in the NG RAN and PDU Set information marking in the PSA UPF upon completion of mobility procedure as defined in clause 5.37.5.3 of TS 23.501 [2].
If interworking with TSN deployed in the transport network is supported and either the UPF supports CN-TL or NG-RAN supports AN-TL (see clause 4.4.8 of TS 23.501 [2]), the procedure may be triggered due to reception of Status group from TN CNC.
The SMF may decide to modify PDU Session to send updated ECS Address Configuration Information to the UE as defined in clause 6.5.2 of TS 23.548 [74].
The SMF may decide to modify PDU Session to send updated DNS server address to the UE as defined in clause 6.2.3.2.3 of TS 23.548 [74].
The SMF may decide to modify PDU Session to send the EAS rediscovery indication to the UE as defined in clause 6.2.3.3 of TS 23.548 [74].
If the SMF receives one of the triggers in step 1b ~ 1d, the SMF starts SMF requested PDU Session Modification procedure.
1e. (AN initiated modification) (R)AN shall indicate to the SMF when the AN resources onto which a QoS Flow is mapped are released irrespective of whether notification control is configured. (R)AN sends the N2 message (PDU Session ID, N2 SM information) to the AMF. The N2 SM information includes the QFI, User location Information and an indication that the QoS Flow is released. The AMF invokes Nsmf_PDUSession_UpdateSMContext (SM Context ID, N2 SM information).
(AN initiated notification control) If notification control is configured for a GBR QoS Flow, (R)AN sends a N2 message (PDU Session ID, N2 SM information) to SMF when the (R)AN decides the QoS targets of the QoS Flow cannot be fulfilled or can be fulfilled again, respectively. The N2 SM information includes the QFI and an indication that the QoS targets for that QoS Flow cannot be fulfilled or can be fulfilled again, respectively. When QoS targets cannot be fulfilled, the N2 SM information indicates a reference to the Alternative QoS Profile matching the values of the QoS parameters that the NG-RAN is currently fulfilling as specified in clause 5.7.2.4 of TS 23.501 [2]. If the QoS Flow has a TSCAI including Capability for BAT adaptation and without Burst Arrival Time, the N2 SM information can also include a BAT offset as described in clause 5.27.2.5 of TS 23.501 [2]. The AMF invokes Nsmf_PDUSession_UpdateSMContext (SM Context ID, N2 SM information). If the PCF has subscribed to the event, SMF reports this event to the PCF for each PCC Rule for which notification control is set in step 2.
1f. (AMF initiated modification) If the UE supports CE mode B and use of CE mode changes from restricted to unrestricted or vice versa in the Enhanced Coverage Restriction information in the UE context in the AMF and the UE has already established PDU sessions, then the AMF shall trigger a PDU session modification to the SMFs serving the UE's PDU sessions when the AMF determines that NAS-SM timer shall be updated due to the change of Enhanced Coverage Restriction and include the extended NAS-SM indication only if use of CE mode B is now unrestricted in the Enhanced Coverage Restriction information in the UE context in the AMF.
If the AMF, based on configuration, is aware that the UE is accessing over a gNB using GEO satellite backhaul and GEO Satellite ID needs to be updated to the SMF, the AMF may, based on configuration, include the latest GEO Satellite ID as described in clause 5.43.2 of TS 23.501 [2].
If the AMF is aware that the UE access is over a gNB onboard a satellite and the satellite ID needs to be updated to the SMF, the AMF includes the UE's latest serving satellite ID.
1g. (AMF initiated modification) the AMF informs the SMF of updates of the NWDAF ID(s) used for UE related Analytics and corresponding Analytics ID(s). Also, If the PCF provided PCF binding information and Request for notification of SM Policy Association establishment and termination and there is any PDU Session established to that DNN, S-NSSAI [PCF binding information, Request for notification of SM Policy Association establishment and termination].
1h. (AMF initiated modification) When the AMF determines that the S-NSSAI is to be replaced with an Alternative S-NSSAI (as described in clause 5.15.19 of TS 23.501 [2]), the AMF invokes Nsmf_PDUSession_UpdateSMContext Request (SM Context ID, S-NSSAI, Alternative S-NSSAI) to the SMF of the PDU session associated with the S-NSSAI.
(AMF initiated modification) When the AMF determines that the S-NSSAI is subject to area restriction, e.g. when the S-NSSAI is configured with an NS-AoS, or when the S-NSSAI is present in the Partially Allowed NSSAI, the AMF invokes Nsmf_PDUSession_UpdateSMContext Request (SM Context ID, S-NSSAI, Slice Area Restriction indication) to the SMF indicating that the PDU Session is subject to area restriction for the S-NSSAI. If the S-NSSAI is replaced with the Alternative S-NSSAI, the AMF checks the area restriction only for the Replaced S-NSSAI for this PDU Session.
Based on the extended NAS-SM timer indication, the SMF shall use the extended NAS-SM timer setting for the UE as specified in TS 24.501 [25].
2. The SMF may need to report some subscribed event to the PCF by performing an SMF initiated SM Policy Association Modification procedure as defined in clause 4.16.5.1. This step may be skipped if PDU Session Modification procedure is triggered by step 1b or 1d. If dynamic PCC is not deployed, the SMF may apply local policy to decide whether to change the QoS profile.
The PCF may make policy control decisions based on the awareness of URSP rule enforcement, as described in clause 6.1.1.5 in TS 23.503 [20].
Steps 2a to 7 are not invoked when the PDU Session Modification requires only action at a UPF (e.g. gating).
2a. The SMF may update the UPF with N4 Rules related to new or modified QoS Flow(s).
NOTE 2: This allows the UL packets with the QFI of a new or modified QoS Flow to be transferred.
If the SMF initiated the PDU Session Modification procedure in step 1b due to PCF initiated SM Policy Association Modification that adds one or more PCC Rule(s) with a TSC Assistance Container and if interworking with TSN deployed in the transport network is supported, the SMF may instruct the UPF to assign or remove a distinct N3 tunnel end point address for the QoS Flow(s) assigned with a TSC Assistance Container.
If the SMF initiated the PDU Session Modification procedure in step 1d due to reception of Status group from TN CNC, the SMF includes a TL-Container with a set-request to the N4 Session Modification request that is sent to the UPF, as described in clause 5.28a.2 of TS 23.501 [2].
If the SMF initiated the PDU Session Modification procedure in step 1b due to PCF initiated SM Policy Association Modification that adds one or more PCC Rule(s) with UL and/or DL Periodicity, the SMF composes the TSCAI with the periodicity information.
If the SMF initiated the PDU Session Modification procedure in step 1b due to PCF initiated SM Policy Association Modification that adds one or more PCC Rule(s) with an indication to perform N6 Traffic Parameter measurements (e.g. the N6 Jitter range associated with the DL Periodicity, and the UL/DL periodicity), the SMF instructs the UPF to perform N6 Traffic Parameter measurement associated with the DL Periodicity for the QoS Flow, as described in clause 5.37.8.2 of TS 23.501 [2].
If N6 Traffic Parameter measurements are requested and DL Periodicity is received in the PCC Rule, the SMF shall include the DL Periodicity as well as the indication of N6 Traffic Parameter measurement in the request to the UPF, see clause 5.8.5.11 of TS 23.501 [2].
If the PCC Rule includes a Protocol Description and PDU Set QoS parameters for DL and the SMF decides to enable PDU Set Identification and marking for PDU Set based Handling by PSA UPF, the SMF should provide the Protocol Description information, On-path N6 Signalling Information (if available) and PDU Set Marking indication to the UPF and request the UPF to mark the PDU Set Information in each PDU belonging to the PDU Sets as described in clauses 5.37.5.2, 5.37.9 and 5.8.5.4 of TS 23.501 [2].
If the SMF decides to enable End of Data Burst and/or Time to Next Burst marking by PSA UPF, the SMF should request the UPF to mark End of Data Burst and/or Time to Next Burst as described in clauses 5.37.8.3 and 5.37.10.2 of TS 23.501 [2] respectively. The SMF may instruct the UPF to identify and mark the Data Burst Size as described in clause 5.37.10.1 of TS 23.501 [2]. If the PCC Rule includes a Protocol Description and/or On-path N6 Signalling Information, the SMF should provide the Protocol Description information and/or On-path N6 Signalling Information to the UPF.
If the PDU Set information marking has been activated in the UPF for a QoS flow, the SMF may request the UPF to stop the marking of the PDU Set information based on the indication from the RAN or PCF, e.g. if the Target RAN does not support the PDU Set based handling as described in clause 5.37.5.3 of TS 23.501 [2].
If the PCC Rule indicates that Media over QUIC (MoQ) is requested by setting Protocol Description as Media over QUIC Transport and the PSA UPF supports the MoQ relay functionality, then the SMF requests the UPF to return the MoQ relay address via the N4 session management request procedures as described in clause 5.37.9.2 of TS 23.501 [2].
If the PCF initiated SM Policy Association Modification that adds one or more PCC Rule(s) with PDU Set Control Information, the SMF performs PDU Set based QoS handling, see clause 5.37.5 of TS 23.501 [2].
For Expedited Transfer with Reflective QoS the PCF may provide two PCC Rules with Expedited Transfer Indication in the service data flow descriptions. The SMF generates the PDRs as described in clause 5.37.10.2 of TS 23.501 [2].
If redundant transmission has not been activated to the PDU session and the SMF decides to perform redundant transmission for the QoS Flow, the SMF indicates to the UPF to perform packet duplication and elimination for the QoS Flow.
If redundant transmission has been activated on the PDU Session and the SMF decides to stop redundant transmission, the SMF indicates the UPF to release the CN Tunnel Info which is used as the redundancy tunnel of the PDU Session and also indicates the UPF to stop packet duplication and elimination for the corresponding QoS Flow(s).
NOTE 3: The method to perform elimination and reordering on RAN/UPF based on the packets received from the two GTP-U tunnels is up to RAN/UPF implementation. The two GTP-U tunnels are terminated at the same RAN node and UPF.
If redundant transmission has not been activated to the PDU Session and the SMF decides to perform redundant transmission for the QoS Flow with two I-UPFs between the PSA UPF and the NG-RAN, the SMF sends a N4 Session Establishment Request message to the I-UPFs including UL CN Tunnel Info of the PSA UPF and a request to allocate CN Tunnel Info.
SMF may make use of Redundant Transmission Experience analytics provided by NWDAF, when SMF takes a decision whether to perform redundant transmission, or stop redundant transmission if it had been activated, as described in clause 6.13 of TS 23.288 [50].
If the AMF initiated the PDU Session Modification procedure in step 1h due to network slice replacement with the Alternative S-NSSAI and if the SMF determines that the PDU Session is retained, the SMF sends N4 Session Modification request message to the UPF to replace the S-NSSAI with the Alternative S-NSSAI, as described in clause 5.15.19 of TS 23.501 [2].
2b. The UPF(s) respond to the SMF. If redundant transmission has not been activated to the PDU session and the SMF indicated the UPF to perform packet duplication and elimination for the QoS Flow in step 2a, the UPF allocates an additional CN Tunnel Info. The additional CN Tunnel Info is provided to the SMF.
If redundant transmission has not been activated to the PDU Session and the SMF decides to perform redundant transmission for the QoS Flow with two I-UPFs in step 2a, the UPFs allocate CN Tunnel Info. The CN Tunnel Info of each I-UPF is provided to the SMF.
If interworking with TSN deployed in the transport network is supported and the UPF supports CN-TL and received a TL-Container with a set-request from the SMF/CUC in step 2a (see clause 4.4.8 of TS 23.501 [2]), the UPF/CN-TL includes a TL-Container with a set-response to the N4 Session Modification response, as described in clause 5.28a.2 of TS 23.501 [2].
If requested by SMF in step 2a, the PSA UPF will initiate N4 Session Level reporting for N6 Traffic Parameter Measurement Report as described in clause 4.4.2.2. If N6 Traffic Parameter(s) are available then the response to the SMF in this step may include the N6 Traffic Parameter(s) (e.g. the N6 Jitter range associated with the DL Periodicity, and the UL/DL periodicity) for the QoS Flow (see clause 5.37.8.2 of TS 23.501 [2]). The SMF composes the TSCAI with the received N6 Traffic Parameters.
If the SMF has requested in step 2a the PSA UPF to provide the MoQ relay address, then the UPF returns the MoQ relay address via the N4 Session Establishment/Modification Response as described in clause 5.37.9.2 of TS 23.501 [2].
3a. For UE or AN initiated modification or AMF initiated modification, the SMF responds to the AMF through Nsmf_PDUSession_UpdateSMContext Response ([N2 SM information (PDU Session ID, QFI(s), QoS Profile(s), [Alternative QoS Profile(s)], Session-AMBR], [CN Tunnel Info(s)]), N1 SM container (PDU Session Modification Command (PDU Session ID, QoS rule(s) and associated UL Protocol Description(s) (if available), QoS rule operation, QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s), Session-AMBR, [Always-on PDU Session Granted], [Port Management Information Container], [Non-3GPP QoS Assistance Information Container]))). See clause 5.7 of TS 23.501 [2] for the QoS Profile, Alternative QoS Profile and QoS rule and QoS Flow level QoS parameters. Alternative QoS Profile is only valid for AN initiated modification.
If the PDU Session Modification was requested by the UE to modify a PDU Session to an always-on PDU Session, the SMF shall include an Always-on PDU Session Granted indication in the PDU Session Modification Command to indicate whether the PDU Session is to be changed to an always-on PDU Session or not via the Always-on PDU Session Granted indication in the PDU Session Modification Command.
The N2 SM information carries information that the AMF shall provide to the (R)AN. It may include the QoS profiles and the corresponding QFIs to notify the (R)AN that one or more QoS flows were added, or modified. It may include only QFI(s) to notify the (R)AN that one or more QoS flows were removed. The SMF may indicate for each QoS Flow whether redundant transmission shall be performed by a corresponding redundant transmission indicator. If the SMF decides to activate redundant transmission in step 2a, the SMF includes the allocated additional CN Tunnel Info in the N2 SM information. If the SMF decides to perform redundant transmission for new QoS Flow with two I-UPFs in step 2a, the SMF includes the allocated CN Tunnel Info of the two I-UPFs in the N2 SM information. If the PDU Session Modification was triggered by the (R)AN Release in step 1e the N2 SM information carries an acknowledgement of the (R)AN Release. If the PDU Session Modification was requested by the UE for a PDU Session that has no established User Plane resources, the N2 SM information provided to the (R)AN includes information for establishment of User Plane resources. For Network Slice Replacement if the SMF determines that the PDU Session is to be retained, the S-NSSAI in N2 SM information is set to Alternative S-NSSAI.
- If the SMF has received a Requested Non-3GPP Delay Budget for a QoS flow from the PEGC, the SMF may adjust the dynamic CN PDB signalled to the NG-RAN as defined in clause 5.44.3.4 of TS 23.501 [2].
If redundant transmission has been activated on the PDU Session and the SMF decides to stop redundant transmission in step 2a, the SMF indicates the (R)AN to release the AN Tunnel and stop packet duplication and elimination associated with the redundancy tunnel of the PDU Session.
The N1 SM container carries the PDU Session Modification Command that the AMF shall provide to the UE. It may include the QoS rules and associated UL Protocol Description(s) (if available), QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s) and corresponding QoS rule operation and QoS Flow level QoS parameters operation to notify the UE that one or more QoS rules were added, removed or modified. If the PCF provides the PCC rules with Protocol Description for UL in step 1b or step 2, based on operator policy, the SMF may additionally provide the Protocol Description for UL with the associated QoS rule as described in clause 5.37.5.1 of TS 23.501 [2].
For the AMF initiated the PDU Session Modification procedure in step 1h due to network slice replacement, and if the SMF determines that the PDU Session is to be retained, the SMF includes the Alternative S-NSSAI in the PDU Session Modification Command to the UE and a cause value indicating that the S-NSSAI of the PDU Session is replaced with the Alternative S-NSSAI.
If the AMF initiated the PDU Session Modification procedure in step 1h due to network slice replacement and if the PDU Session is SSC mode 3 and if the SMF determines that the PDU Session is to be re-established on the Alternative S-NSSAI, the SMF includes the Alternative S-NSSAI in the PDU Session Modification Command to the UE and a cause value indicating that a PDU Session re-establishment on the Alternative S-NSSAI is required. The UE re-establishes a new PDU Session on the Alternative S-NSSAI, as described in clause 5.15.19 in TS 23.501 [2]. If the PDU Session is SSC mode 1 or SSC mode 2, the SMF may initiate release of the PDU Session as described in clause 4.3.4.2.
If port number and a Port Management Information Container have been received from PCF in Step 2 and the port number matches the port number assigned for the DS-TT port for this PDU session, then SMF includes the Port Management Information Container in the N1 SM container.
The SMF may need to send transparently through NG-RAN the PDU Session Modification Command to inform the UE about changes in the QoS parameters (i.e. 5QI, GFBR, MFBR) that the NG-RAN is currently fulfilling after the SMF receives QoS Notification Control as defined in clause 5.7.2.4 of TS 23.501 [2]. When the SMF sends on the PDU Session Modification Command transparently through NG-RAN, the N2 SM information is not included as part of the Namf_Communication_N1N2MessageTransfer.
If the UE indicated in the PCO that it supports the EDC functionality, the SMF may indicate to the UE either that the use of the EDC functionality is allowed for the PDU Session or that the use of the EDC functionality is required for the PDU Session (see clause 5.2.1 of TS 23.548 [74]).
Based on the S-NSSAI and DNN for PIN, the SMF may provide the UE with per QoS-flow Non-3GPP QoS Assistance Information in the N1 SM container.
If SMF receives the indication indicating that the PDU Session is subject to area restriction for the S-NSSAI, and if SMF has not subscribed before, the SMF subscribes to "UE mobility event notification" event for reporting UE presence in Area of Interest by providing the S-NSSAI as an indicator for the Area Of Interest (see clauses 5.6.11 and 5.3.4.4 of TS 23.501 [2]).
If SMF does not receive the indication indicating that the PDU Session is subject to area restriction for the S-NSSAI, and if the SMF has subscribed the "UE mobility event notification" event in the AMF before, the SMF may unsubscribe "UE mobility event notification" event in the AMF.
If UE provided non-3gpp device connection information in step 1a and if the PCF indicates to the SMF that the Non-3GPP Device Identifier is not available for the UE as described in clause 6.1.3.31 of TS 23.503 [20], SMF shall reject the PDU Session modification with an appropriate cause code to notify that Non-3GPP Device Identifier is not available for the UE.
3b. For SMF requested modification, the SMF invokes Namf_Communication_N1N2MessageTransfer ([N2 SM information] (PDU Session ID, QFI(s), QoS Profile(s), [Alternative QoS Profile(s)], [DL PDU Set Information Marking Support Indication], Session-AMBR, [CN Tunnel Info(s)], QoS Monitoring indication, QoS Monitoring reporting frequency, QoS monitoring parameter, [Multi-modal Service ID(s)]), [TSCAI(s)], TL-Container(s), [ECN marking for L4S indicator(s)]), N1 SM container (PDU Session Modification Command (PDU Session ID, QoS rule(s) and associated UL Protocol Description(s) (if available), QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s), QoS rule operation and QoS Flow level QoS parameters operation, Session-AMBR, [Port Management Information Container]))).
- For each QoS Flow, the SMF may at most request one of the following to the NG-RAN:
- ECN marking for L4S indicator at NG-RAN in the case of ECN marking for L4S in RAN as described in clause 5.37.3 of TS 23.501 [2]; or
- Congestion information monitoring as described in clauses 5.45.3 and 5.37.4 of TS 23.501 [2]; or
- provide information for ECN marking for L4S at UPF in the case of ECN marking for L4S by PSA UPF as described in clause 5.37.3 of TS 23.501 [2].
- In the case of non-3GPP access, where the 5G-AN corresponds to an N3IWF or TNGF:
- For each QoS Flow, the SMF may request the following to the N3IWF or TNGF:
- ECN marking for L4S at N3IWF or TNGF in the case of ECN marking for L4S in non-3GPP access as described in clause 5.37.3 of TS 23.501 [2].
If the SMF initiated the PDU Session Modification procedure in step 1b due to PCF initiated SM Policy Association Modification that adds one or more PCC Rule(s) with a TSC Assistance Container and if interworking with TSN deployed in the transport network is supported, the SMF may instruct the NG-RAN to assign or remove a distinct N3 tunnel end point address for the QoS Flow(s) assigned with a TSC Assistance Container.
A DL PDU Set Information Marking Support Indication may be included by SMF as described in clause 5.37.5 of TS 23.501 [2].
The SMF may indicate for each QoS Flow whether redundant transmission shall be performed by a corresponding redundant transmission indicator. If the SMF decides to activate redundant transmission in step 2a, the SMF includes the allocated additional CN Tunnel Info in the N2 SM information. If the SMF decides to perform redundant transmission for new QoS Flow with two I-UPFs in step 2a, the SMF includes the allocated CN Tunnel Info of the two I-UPFs in the N2 SM information.
If redundant transmission has been activated on the PDU Session and the SMF decides to stop redundant transmission in step 2a, the SMF indicates the (R)AN to release the AN Tunnel and stop packet duplication and elimination associated with the redundancy tunnel of the PDU Session.
If port number and a Port Management Information Container have been received from PCF in step 1b and the port number matches the port number assigned for the DS-TT Ethernet port for this PDU session, then SMF includes the Port Management Information Container in the N1 SM container.
The SMF indicates the request for QoS Monitoring for the QoS Flow according to the information received from the PCF in step 1b, or based on SMF local policy, e.g. when the RAN rejected the creation of a specific QoS Flow. In the case of receiving the QoS Monitoring indication, the RAN enables the RAN part of UL/DL packet delay measurement for the QoS Flow and the QoS Monitoring reporting frequency is used by RAN to determine the packet delay measurement frequency of the RAN part. In the case of receiving a congestion information request, RAN initiates reporting of UL and/or DL QoS Flow congestion information to PSA UPF as defined in clause 5.45.3 of TS 23.501 [2]. In the case of receiving the Available Bitrate for a GBR QoS Flow Monitoring and the relevant thresholds as defined in clause 5.45.6 of TS 23.501 [2], the RAN initiates available bitrate for a GBR QoS Flow measurement and provides the measured available bitrate for a GBR QoS Flow as defined in clause 5.45.6 of TS 23.501 [2]. The TSCAI is defined in clause 5.27.2 of TS 23.501 [2].
If the SMF initiated the PDU Session Modification procedure in step 1d due to reception of Status group from TN CNC, the SMF includes a TL-Container with a set-request to the N2 SM information, as described in clause 5.28a.2 of TS 23.501 [2].
The SMF indicates EAS rediscovery indication to the UE, if that initiated the PDU Session Modification procedure in step 1d as defined in clause 6.2.3.3 of TS 23.548 [74].
If the UE is in CM-IDLE state and an ATC is activated, the AMF updates and stores the UE context based on the Namf_Communication_N1N2MessageTransfer and steps 4, 5, 6 and 7 are skipped. When the UE is reachable e.g. when the UE enters CM-CONNECTED state, the AMF forwards the N1 message to synchronize the UE context with the UE.
If the PCF provides the PCC rules with Protocol Description for UL in step 1b or step 2, based on operator policy, the SMF may provide the Protocol Description(s) for UL with the associated QoS rule(s) as described in clause 5.37.5.1 of TS 23.501 [2].
For each QoS Flow, when the received PCC rule contains the Multi-modal Service ID, the SMF provides the Multi-modal Service ID to the NG-RAN as described in clause 5.37.2 of TS 23.501 [2].
3c. For SMF requested modification due to updated SMF-Associated parameters from the UDM, the SMF may provide the SMF derived CN assisted RAN parameters tuning to the AMF. The SMF invokes Nsmf_PDUSession_SMContextStatusNotify (SMF derived CN assisted RAN parameters tuning) towards the AMF. The AMF stores the SMF derived CN assisted RAN parameters tuning in the associated PDU Session context for this UE.
3d. For SMF requested modification due to updated NWDAF ID, the SMF informs the AMF of updates of the NWDAF ID(s) used for UE related Analytics and corresponding Analytics ID(s).
4. The AMF may send N2 ([N2 SM information received from SMF], NAS message (PDU Session ID, N1 SM container (PDU Session Modification Command))) Message to the (R)AN.
5. The (R)AN may issue AN specific signalling exchange with the UE that is related with the information received from SMF. For example, in the case of a NG-RAN, an RRC Connection Reconfiguration may take place with the UE modifying the necessary (R)AN resources related to the PDU Session or if only N1 SM container is received in step 4 from AMF, RAN transports only the N1 SM container to the UE.
The (R)AN may consider the updated CN assisted RAN parameters tuning to reconfigure the AS parameters.
As part of this, the N1 SM container is provided to the UE. If the N1 SM container includes a Port Management Information Container then the UE provides the container to DS-TT.
If new DNS server address is provided to the UE in the PCO, the UE can refresh all EAS(s) information (e.g. DNS cache) bound to the PDU Session, based on UE implementation as described in clause 6.2.3.2.3 of TS 23.548 [74].
If EAS rediscovery indication is provided to the UE, the UE can trigger EAS rediscovery procedure as defined in clause 6.2.3.3 of TS 23.548 [74].
6. The (R)AN may acknowledge N2 PDU Session Request by sending a N2 PDU Session Ack (N2 SM information (List of accepted/rejected QFI(s), AN Tunnel Info, PDU Session ID, Secondary RAT usage data, TL-Container(s), BAT offset, Periodicity, established QoS Flows status (active/not active) (for one of the following: congestion information monitoring, ECN marking for L4S at PSA UPF, ECN marking for L4S at NG-RAN, ECN marking for L4S at N3IWF or TNGF), PDU Set Based Handling Support Indication), User location Information) Message to the AMF. In the case of Dual Connectivity, if one or more QFIs were added to the PDU Session, the Master RAN node may assign one or more of these QFIs to a NG-RAN node which was not involved in the PDU Session earlier. In this case the AN Tunnel Info includes a new N3 tunnel endpoint for QFIs assigned to the new NG-RAN node. Correspondingly, if one or more QFIs were removed from the PDU Session, a (R)AN node may no longer be involved in the PDU Session anymore and the corresponding tunnel endpoint is removed from the AN Tunnel Info. The NG-RAN may reject QFI(s) if it cannot fulfil the User Plane Security Enforcement information for a corresponding QoS Profile, e.g. due to the UE Integrity Protection Maximum Data Rate being exceeded. When receiving the request for QoS Monitoring, the (R)AN may indicate its rejection to perform QoS Monitoring, e.g. due to the (R)AN load condition. The (R)AN may reject the addition or modification of a QoS Flow, e.g. due to handling of the UE-Slice-MBR as described in clause 5.7.1.10 of TS 23.501 [2]. If the (R)AN rejects the addition or modification of a QoS Flow, the SMF is responsible of updating the QoS rules and QoS Flow level QoS parameters associated to that QoS Flow in the UE accordingly. 5G-AN includes the PDU Set Based Handling Support Indication in N2 SM information as defined in clause 5.37.5.3 of TS 23.501 [2]
If the PLMN has configured secondary RAT usage reporting, the NG-RAN node may provide RAN Usage Data Report. The User Location Information shall include the serving cell's ID and if Dual Connectivity is activated for the UE, the PSCell ID.
If the redundant transmission has not been activated to the PDU session and the SMF indicates to the RAN that one of the QoS Flow shall perform redundant transmission, the RAN includes an additional AN tunnel info in N2 SM information.
If interworking with TSN deployed in the transport network is supported and the NG-RAN supports AN-TL and received a TL-Container with a set-request from the SM/CUC in step 3b (see clause 4.4.8 of TS 23.501 [2]), the NG-RAN/AN-TL includes a TL-Container with a set-response to the N2 SM information, as described in clause 5.28a.2 of TS 23.501 [2].
If the NG-RAN has determined a BAT offset and optionally a periodicity as described in clause 5.27.2.5 of TS 23.501 [2], the NG-RAN provides the BAT offset and optionally the periodicity in the N2 SM information.
7. The AMF forwards the N2 SM information and the User location Information received from the AN to the SMF via Nsmf_PDUSession_UpdateSMContext service operation. The SMF replies with a Nsmf_PDUSession_UpdateSMContext Response.
If the N2 SM information indicates failure of whole N2 SM request (i.e. no part of the N2 SM request is successful in (R)AN), the SMF assumes that the NAS PDU, if provided in step 3, was not forwarded by NG-RAN to UE, as described in TS 38.413 [10]. In this case, if the PDU Session modification is UE triggered the SMF shall reject the PDU session modification by including a N1 SM container with a PDU Session Modification Reject message (see clause 8.3.3 of TS 24.501 [25]) in the Nsmf_PDUSession_UpdateSMContext Response in step 7b. Step 8 is skipped in this case.
Otherwise, the SMF assumes that the NAS PDU was sent to UE successfully. If the (R)AN rejects QFI(s), the SMF is responsible of updating the QoS rules and QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s) in the UE accordingly, i.e. the SMF shall trigger a separate NAS PDU Session Modification procedure after step 11 to align the SM context of this PDU Session in UE.
8. The SMF may update N4 session of the UPF(s) that are involved by the PDU Session Modification by sending N4 Session Modification Request message to the UPF (see NOTE 3).
The SMF may update the UPF with N4 Rules related to new, modified or removed QoS Flow(s), unless it was done already in step 2a.
NOTE 4: This allows the DL packets of the new or modified QoS Flow to be transferred.
If an additional AN Tunnel Info is returned by RAN in step 6, the SMF informs the UPF about this AN Tunnel Info for redundant transmission. In the case of redundant transmission with two I-UPFs, the SMF provides AN Tunnel Info to two I-UPFs. If CN Tunnel Info of two I-UPFs is allocated by the UPFs in step 2b, the SMF also provides the DL CN Tunnel Info of two I-UPFs to the UPF (PSA).
If the QoS Monitoring is enabled for the QoS Flow, the SMF provides the N4 rules containing the QoS Monitoring policy generated according to the information received in step 1b to the UPF via the N4 Session Modification Request message as defined in clause 5.45 of TS 23.501 [2].
If port number and a Port Management Information Container have been received from PCF in Step 2 and the port number matches the port number of the NW-TT port for this PDU session, then SMF includes the Port Management Information Container in the N4 Session Modification Request. If the N4 Session Modification Request includes a Port Management Information Container, then UPF also includes a Port Management Information Container in the N4 Session Modification Response.
If SMF decides to enable ECN marking for L4S by PSA UPF, a QoS Flow level ECN marking for L4S indicator shall be sent by SMF to PSA UPF over N4 as described in clause 5.37.3.3 of TS 23.501 [2].
If the N2 SM information includes the PDU Set Based Handling Support Indication and either there are PCC Rules with PDU Set QoS parameters for DL or the SMF has sent the DL PDU Set Information Marking Support Indication in step 3, the SMF configures PSA UPF to activate PDU set identification and marking for the QoS flow as described in clause 5.37.5.3 of TS 23.501 [2].
9. The UE acknowledges the PDU Session Modification Command by sending a NAS message (PDU Session ID, N1 SM container (PDU Session Modification Command Ack, [Port Management Information Container])) message.
10. The (R)AN forwards the NAS message to the AMF.
11. The AMF forwards the N1 SM container (PDU Session Modification Command Ack) and User Location Information received from the AN to the SMF via Nsmf_PDUSession_UpdateSMContext service operation. The SMF replies with a Nsmf_PDUSession_UpdateSMContext Response.
If the SMF initiated modification is to delete QoS Flows (e.g. triggered by PCF) which do not include QoS Flow associated with the default QoS rule and the SMF does not receive response from the UE, the SMF marks that the status of those QoS Flows is to be synchronized with the UE.
If interworking with TSN deployed in the transport network is supported, for any QoS Flow including a TSC Assistance Container, the SMF/CUC derives the merged stream requirements as described in Annex M of TS 23.501 [2]. If AN-TL and CN-TL are supported, the SMF/CUC uses the information provided in the get-responses stored during the PDU Session Establishment procedure to derive the merged stream requirements. The SMF/CUC interacts with the CNC deployed in the transport network and provides the merged stream requirements in the Talker and Listener groups to the TN CNC. The TN CNC uses the merged stream requirements as input to select respective path(s) and calculate schedules in TN.
Based on the processing results, the TN CNC provides a Status group that contains the merged end station communication-configuration back to the SMF/CUC.
12. The SMF may update N4 session of the UPF(s) that are involved by the PDU Session Modification by sending N4 Session Modification Request (N4 Session ID) message to the UPF. For a PDU Session of Ethernet PDU Session Type, the SMF may notify the UPF to add or remove Ethernet Packet Filter Set(s) and forwarding rule(s).
NOTE 5: The UPFs that are impacted in the PDU Session Modification procedure depends on the modified QoS parameters and on the deployment. For example in the case of the session AMBR of a PDU Session with an UL CL changes, only the UL CL is involved. This note also applies to the step 8.
13. If the SMF interacted with the PCF in step 1b or 2, the SMF notifies the PCF whether the PCC decision could be enforced or not by performing an SMF initiated SM Policy Association Modification procedure as defined in clause 4.16.5.1. If the trigger for 5GS Bridge/Router information available is armed and the SMF received a Port Management Information Container from either UE or UPF, then SMF provides the Port Management Information Container and the port number of the related port to the PCF in this step, as described in clause 5.28.3.2 of TS 23.501 [2]. If the trigger for 5GS Bridge/Router information available is armed and the SMF received the User Plane node Management Information Container from UPF, then the SMF provides the User Plane node Management Information Container to the PCF as described in clause 5.28.3.2 of TS 23.501 [2]. If trigger for Notification on BAT offset is armed and the SMF received BAT offset and/or Periodicity from the RAN, then the SMF provides the BAT offset and/or Periodicity to the PCF as described in clause 5.27.2.5 of TS 23.501 [2].
SMF notifies any entity that has subscribed to User Location Information related with PDU Session change.
If step 1b is triggered to perform Application Function influence on traffic routing by step 5 in clause 4.3.6.2, the SMF may reconfigure the User Plane of the PDU Session as described in step 6 in clause 4.3.6.2.
If interworking with TSN deployed in the transport network is supported and if the Status group from TN CNC to SMF/CUC in step 11 includes InterfaceConfiguration and if the AN-TL/CN-TL are supported, the SMF/CUC initiates a PDU Session Modification procedure as in step 1d. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.3.3 UE or network requested PDU Session Modification (home-routed roaming) | The UE or network requested PDU Session Modification procedure (home-routed roaming scenario) is depicted in figure 4.3.3.3-1.
Figure 4.3.3.3-1: UE or network requested PDU Session Modification (for home-routed roaming scenario)
1. The procedure is triggered by one of the following events:
1a. (UE or serving network requested) As in step 1a of clause 4.3.3.2 with the addition that:
- The V-SMF checks whether it can accept the request from the UE;
- The V-SMF invokes an Nsmf_PDUSession_Update Request (SM Context ID, UE request for PDU Session Modification or the QoS modification request from the VPLMN, UE location information, Time Zone, the current Access Type, PCO, [Always-on PDU Session Requested]) service operation to inform the H-SMF to update the PDU Session. The H-SMF responds to the request immediately. If the AMF notified the V-SMF that the access type of the PDU session can be changed, as described in the UE Triggered Service Request procedure in clause 4.2.3.2, the V-SMF shall also indicate that the access type can be changed.
The PS Data Off status, if changed, shall be included in PCO (Protocol Configuration Option) in the PDU Session Modification Request message.
When PCF is deployed, the SMF shall further report the PS Data Off status to PCF if the PS Data Off event trigger is provisioned, the additional behaviour of SMF and PCF for 3GPP PS Data Off is defined in TS 23.503 [20].
1b. (HPLMN requested) This step is the same as step 1b in clause 4.3.3.2. If the H-SMF received the indication that the access type of the PDU session can be changed, the H-SMF shall indicate the target access type to the PCF in the Access Type information of the Npcf_SMPolicyControl_Update Request.
1c. (HPLMN requested) This step is the same as step 1c in clause 4.3.3.2.
1d. (HPLMN requested) This step is the same as step 1d in clause 4.3.3.2.
1e. As in step 1e of clause 4.3.3.2 with addition that:
- The AMF invokes Nsmf_PDUSession_UpdateSMContext (SM context ID, N2 SM information) and sends it to the V-SMF;
- The V-SMF invokes an Nsmf_PDUSession_Update Request (SM context ID, ULI, AN type, QoS Flow to be released) service operation to inform the H-SMF to update the PDU Session. The H-SMF responds to the request immediately. For AN initiated notification control in step 1e of clause 4.3.3.2, the V-SMF includes also QoS Flow notification information as specified in clause 5.7 of TS 23.501 [2].
NOTE 1: SM Context ID between AMF and V-SMF and between V-SMF and H-SMF are different. SM Context ID has local significance per SMF instance.
1f. (Slice Replacement) As in step 1h of clause 4.3.3.2 with addition:
- When the AMF determines as described in clause 5.15.19 of TS 23.501 [2] that VPLMN S-NSSAI is to be replaced by an Alternative VPLMN S-NSSAI, and/or HPLMN S-NSSAI is to be replaced by an Alternative HPLMN S-NSSAI, the AMF invokes Nsmf_PDUSession_UpdateSMContext (SM context ID, VPLMN S-NSSAI, Alternative VPLMN S-NSSAI, HPLMN S-NSSAI, Alternative HPLMN S-NSSAI) and sends it to the V-SMF. If the AMF determines that the current PDU Session cannot be retained (e.g. the current V-SMF cannot support the Alternative VPLMN S-NSSAI), the AMF includes a release indication.
- If Alternative HPLMN S-NSSAI is received from the AMF, the V-SMF invokes an Nsmf_PDUSession_Update Request (SM context ID, HPLMN S-NSSAI, Alternative HPLMN S-NSSAI) service operation to inform the H-SMF. The H-SMF responds to the request immediately. The V-SMF forwards the release indication if it is received from the AMF.
2. This step is the same as steps 2 in clause 4.3.3.2 with the SMF is H-SMF.
3. (UE or serving network requested or HPLMN requested) The H-SMF invokes the Nsmf_PDUSession_Update Request (SM Context ID, QoS profiles, [Alternative QoS profile(s)], Session-AMBR, information needed to build the SM PDU Session Modification Command message towards the UE including the QoS rule(s) and QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s) and QoS rule operation and the QoS Flow level QoS parameters operation) service operation to the V-SMF.
Based on operator policies and roaming agreements, the V-SMF may decide to fully accept or reject the QoS information provided by the H-SMF. The V-SMF shall also be able to accept a subset of the QoS flows requested to be created or modified within a single H-SMF request i.e. V-SMF can accept some QoS flows and reject other QoS flows in same response to H-SMF.
If an Always-on PDU Session Granted indication was provided by the H-SMF to indicate that the PDU Session is to be changed to an always-on PDU Session, the V-SMF decides whether to accept or reject the request from the H-SMF based on local policies.
For network slice replacement, based on the information received from the V-SMF, the H-SMF determines whether to retain the PDU Session as described in clause 5.15.19 of TS 23.501 [2]. If the H-SMF decides to retain the PDU Session, the H-SMF includes the Alternative HPLMN S-NSSAI and a cause value indicating that the PDU Session is to be retained in the Nsmf_PDUSession_Update Request message. For SSC mode 3 PDU Session if the H-SMF decides to establish a new PDU Session on the Alternative HPLMN S-NSSAI, the H-SMF includes Alternative HPLMN S-NSSAI and a cause value indicating that a new PDU Session re-establishment on the Alternative HPLMN S-NSSAI is required in the Nsmf_PDUSession_Update Request message. For SSC mode 1 and SSC mode 2 PDU session if the H-SMF decides to establish a new PDU Session on the HPLMN Alternative S-NSSAI, the H-SMF initiates release of the PDU Session as described in clause 4.3.4.3.
3a-3b (HPLMN requested) These steps are executed if new QoS Flow(s) are to be created. The SMF updates the UPF with UL Packet Detection Rules of the new QoS Flow. These steps are executed if the HPLMN S-NSSAI is replaced by an Alternative HPLMN S-NSSAI and the PDU Session is retained. The SMF updates the UPF with Alternative S-NSSAI.
NOTE 2: This allows the UL packets with the QFI of the new QoS Flow to be transferred.
4a-4b. These steps are the same as step 3a-3b in clause 4.3.3.2 but controlled from the V-SMF. The V-SMF uses the information received in step 3 to generate any N1 and/or N2 signalling to be sent towards the UE and/or the (R)AN.
For network slice replacement in step 1f, the following applies:
- If the PDU Session is to be retained and only the VPLMN S-NSSAI is to be replaced by an Alternative VPLMN S-NSSAI, the V-SMF includes Alternative VPLMN S-NSSAI in the N1 PDU Session Modification Command message and a cause value to notify the UE that the VPLMN S-NSSAI of the PDU Session is replaced with the Alternative VPLMN S-NSSAI. The V-SMF also set the S-NSSAI in N2 SM information to Alternative VPLMN S-NSSAI.
- If the PDU Session is to be retained and only the HPLMN S-NSSAI is to be replaced by an Alternative HPLMN S-NSSAI, the V-SMF includes Alternative HPLMN S-NSSAI in the N1 PDU Session Modification Command message and a cause value to notify the UE that the HPLMN S-NSSAI is replaced with the Alternative HPLMN S-NSSAI
- If the PDU Session is to be retained and both VPLMN S-NSSAI and HPLMN S-NSSAI are to be replaced, the V-SMF includes Alternative HPLMN S-NSSAI and VPLMN Alternative S-NSSAI in the N1 PDU Session Modification Command message and a cause value to notify the UE that the HPLMN S-NSSAI is replaced with the Alternative HPLMN S-NSSAI and the VPLMN S-NSSAI of the PDU Session is replaced with Alternative VPLMN S-NSSAI. The V-SMF sets the S-NSSAI in N2 SM information to Alternative VPLMN S-NSSAI.
- If a new PDU Session establishment is required, the V-SMF includes Alternative HPLMN S-NSSAI and/or Alternative VPLMN S-NSSAI in the N1 PDU Session Modification Command message and a cause value to notify the UE that a new PDU Session establishment on the HPLMN Alternative S-NSSAI and/or Alternative VPLMN S-NSSAI is required.
5-7. These steps are the same as step 4-6 in clause 4.3.3.2.
8. This step is the same as step 7a in clause 4.3.3.2 with the difference that the SMF is V-SMF.
If the N2 SM information indicates modification failure and the V-SMF rejected the PDU session modification as described in step 7 in clause 4.3.3.2, step 9 is skipped.
9a-9b are the same as step 8a-8b in clause 4.3.3.2 but executed in Visited PLMN
10. This step is the same as step 7b in clause 4.3.3.2 with the difference that the SMF is V-SMF.
11-12. These steps are the same as steps 8-9 in 4.3.3.2.
13-14. These steps are the same as step 11a-11b in clause 4.3.3.2 but executed in Visited PLMN.
15. V-SMF responds to the H-SMF with an Nsmf_PDUSession_Update response carrying the information like PCO provided by the UE in the SM PDU Session Modification Command Ack message from the UE to the V-SMF, Secondary RAT usage data. The H-SMF shall modify the PDU Session context.
If the V-SMF has rejected QFI(s) (step3) or the (R)AN has rejected QFI(s) in step 6 of Figure 4.3.3.2-1, the H-SMF is responsible of later updating the QoS rules and QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s) in the UE.
16-17. These steps are the same as steps 12-13 in clause 4.3.3.2 with the difference that the SMF is H-SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.4 PDU Session Release | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.4.1 General | The PDU Session Release procedure is used to release all the resources associated with a PDU Session, including:
- The IP address/Prefixes allocated for an IP-based PDU Session; this may include the release of multiple Prefixes in the case of Multi-homing (as defined in TS 23.501 [2]).
- Any UPF resource (including N3/N9/N19 termination) that was used by the PDU Session. For N19 termination, the UPF resource may be released if all the PDU Sessions associated with the 5G VN group are released.
- Any access resource that was used by the PDU Session.
The SMF takes care to notify any entity associated with PDU Session: PCF, DN (e.g. when DN authorization has taken place at PDU Session establishment), etc. of a PDU Session Release. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.4.2 UE or network requested PDU Session Release for Non-Roaming and Roaming with Local Breakout | Figure 4.3.4.2-1 captures both the UE Requested PDU Session Release procedure and the network requested PDU Session Release procedure. The procedure allows the UE to request the release of one PDU Session. The procedure also allows the AMF, the SMF or the PCF to initiate the release of a PDU Session. In the case of LBO, the procedure is as in the case of non-roaming with the difference that the AMF, the SMF, the UPF and the PCF are located in the visited network.
Figure 4.3.4.2-1: UE or network requested PDU Session Release for non-roaming and roaming with local breakout
1. The procedure is triggered by one of the following events:
1a. (UE requested) The UE initiates the UE Requested PDU Session Release procedure by the transmission of an NAS message (N1 SM container (PDU Session Release Request (PDU session ID)), PDU Session ID). The NAS message is forwarded by the (R)AN to the AMF with an indication of User Location Information. This message is relayed to the SMF corresponding to the PDU Session ID via N2 and the AMF. The AMF invokes the Nsmf_PDUSession_UpdateSMContext service operation and provides the N1 SM container to the SMF together with User Location Information (ULI) received from the (R)AN.
NOTE 1: Depending on the Access Type, when the UE is in CM-IDLE state, the UE can trigger a Service Request procedure before being able to release the PDU Session.
1b. (PDU Session Release initiated by the PCF) The PCF may invoke an SM Policy Association Termination procedure as defined in clause 4.16.6 to request the release of the PDU Session.
1c. The AMF may invoke the Nsmf_PDUSession_ReleaseSMContext service operation to request the release of the PDU Session in the case of mismatch of PDU Session status between UE and AMF or other cases where neither N1 nor N2 SM signalling is needed before the releasing of SM context.
NOTE 2: The AMF invokes the Nsmf_PDUSession_ReleaseSMContext service operation when the AMF determines to release the PDU Session due to S-NSSAI is removed from Allowed NSSAI and the AMF separately updates the UE with a PDU Session status without the PDU Session, in a Registration Accept as specified in clause 4.2.2.2.2.
1d. (R)AN may decide to indicate to the SMF that the PDU Session related resource is released, e.g. when all the QoS Flow(s) of the PDU Session are released.
NOTE 3: In this case, it's up to SMF to decide whether to keep the PDU Session with user plane connection deactivated or release the PDU Session.
1e. (PDU Session Release initiated by the SMF).
The SMF may decide to release a PDU Session under the following scenarios:
- Based on a request from the DN (cancelling the UE authorization to access to the DN);
- Based on a request from the UDM (subscription change) or from the CHF;
- If the SMF received an event notification from the AMF that the UE is out of LADN service area;
- Based on locally configured policy (e.g. the release procedure may be related with the UPF re-allocation for SSC mode 2 / mode 3);
- If the SMF is notified by the (R)AN that the PDU Session resource establishment has failed during mobility procedure;
- The SMF initiates release of an emergency PDU Session when the UPF reports detection of PDU Session inactivity for a specified period as specified in clause 4.4.2.2;
- Based on PDU Session inactivity report from the UPF if the S-NSSAI of a PDU Session for non-roaming subscribers is subject to usage control as described in clause 5.15.15 of TS 23.501 [2]; or
- If the SMF is notified by the AMF that the S-NSSAI of the PDU Session with SSC mode 1 or SSC mode 2 is to be replaced with Alternative S-NSSAI, and if the SMF determines that a new PDU Session is to be established on the Alternative S-NSSAI, the SMF initiates release of the PDU Session, as described in clause 5.15.19 of TS 23.501 [2].
1f. The AMF may invoke the Nsmf_PDUSession_UpdateSMContext service operation with a release indication to request the release of the PDU Session where:
- N1 signalling is needed and N2 SM signalling may be needed before releasing the SM context with appropriate cause value (e.g. due to a change of the set of network slices for a UE where a network slice instance is no longer available as described in clause 5.15.5.2.2 of TS 23.501 [2];
- The AAA Server triggered Network Slice-Specific Re-authentication and Re-authorization procedure fails as specified in clause 4.2.9.2;
- The AAA Server triggered Slice-Specific Authorization Revocation takes place as specified in clause 4.2.9.4;
- AMF determines that Control Plane Only indication associated with PDU Session is not applicable any longer as described in clause 5.31.4.1 of TS 23.501 [2]);
- The MBSR authorization state is changed from "authorized" to "not authorized" as described in clause 5.35A.4 of TS 23.501 [2];
- The MWAB-UE BH PDU session release is triggered due to S-NSSAIs/DNNs related to BH PDU sessions being removed from subscription or invalid as described in clause 5.49.3 of TS 23.501 [2];
- The Network Slice instance is congested or not available as described in clause 5.15.5.3 of TS 23.501 [2].
- There is no LADN service area for the DNN and S-NSSAI of the PDU session and the AMF determines to configure the LADN service area configured per LADN DNN and S-NSSAI for the associated DNN and S-NSSAI (e.g. due to notification from UDM or local configuration update);
- The PDU session is subject to LADN per LADN DNN and S-NSSAI and the AMF determines the LADN service area for the DNN and S-NSSAI is removed (e.g. due to notification from UDM or local configuration update).
If the SMF receives one of the triggers in step 1a, 1b, 1c, 1e, or 1f, the SMF starts PDU Session Release procedure. If the cause value in step 1f indicates the Network Slice instance is congested or not available, the SMF triggers the impacted UE(s) to establish new PDU session(s) associated with the same S-NSSAI by using the procedures for PDU Session(s) of SSC mode 2 or SSC mode 3 as defined in clause 4.3.5.
If interworking with TSN deployed in the transport network is supported the SMF/CUC shall initiate the release of TN streams via UNI.
2. The SMF releases the IP address / Prefix(es) that were allocated to the PDU Session and releases the corresponding User Plane resources:
2a. The SMF sends an N4 Session Release Request (N4 Session ID) message to the UPF(s) of the PDU Session. The UPF(s) shall drop any remaining packets of the PDU Session and release all tunnel resource and contexts associated with the N4 Session.
If interworking with TSN deployed in the transport network is supported and the UPF supports CN-TL and TN streams are associated with the PDU session, the SMF/CUC shall initiate to the CN-TL the deletion of TN stream configurations.
2b. The UPF(s) acknowledges the N4 Session Release Request by the transmission of an N4 Session Release Response (N4 Session ID, [Small Data Rate Control Status], [APN Rate Control Status]) message to the SMF.
If UPF/CN-TL has performed the deletion of TN stream based on the request received from the SMF/CUC in step 2a, the UPF/CN-TL shall confirm the deletion of TN stream configurations.
The UPF includes Small Data Rate Control Status if the PDU Session used Small Data Rate Control.
If a NEF has been selected as anchor of the Control Plane CIoT 5GS Optimisation enabled PDU session which is Unstructured PDU Session Type as described in clause 4.3.2.2 and the SMF-NEF Connection is released for this PDU Session.
If interworking with TSN deployed in the transport network is supported and the NG-RAN supports AN-TL and TN streams are associated with the released PDU session, the SMF/CUC shall initiate to the AN-TL the deletion of TN stream configurations.
NOTE 4: If there are multiple UPFs associated with the PDU Session (e.g. due to the insertion of UL CL or Branching Point, or redundant I-UPFs if the redundant I-UPFs are used for URLLC), the Session Release Request procedure (steps 2a and 2b) is done for each UPF. In order to avoid charging of PDUs that later get dropped, the SMF performs the N4 Session Release first with the UPF(s) performing usage reporting, before releasing the other UPF(s) that forward traffic for the same user plane resources.
3 If the PDU Session Release is initiated by the PCF and SMF and the SMF has been notified by the AMF that UE is unreachable, e.g. due to the UE is in MICO mode or periodical registration failure, the procedure continues in step 11 by SMF notifying the AMF that the PDU Session is released by invoking the Nsmf_PDUSession_SMContextStatusNotify. The rest of step 3 and the steps 4-10 are skipped.
If the PDU Session Release procedure was triggered by steps 1a, 1b, 1d or 1e above, the SMF creates an N1 SM including PDU Session Release Command message (PDU Session ID, Cause, Alternative S-NSSAI). The Cause may indicate a trigger to establish a new PDU Session with the same characteristics (e.g. when procedures related with SSC mode 2 are invoked). .If the cause value indicates that a PDU Session re-establishment on the Alternative S-NSSAI is required the PDU Session Release Command message also includes the Alternative S-NSSAI. The UE establishes a new PDU Session on the Alternative S-NSSAI, as described in clause 5.15.19 of TS 23.501 [2].
If the User Plane connection of the PDU Session is activated, the message sent by the SMF to the AMF shall include N2 SM Resource Release request. If the User Plane connection of the PDU Session is not activated, the message sent by the SMF to the AMF shall not include N2 SM Resource Release request.
NOTE 5: SSC modes are defined in clause 5.6.9 of TS 23.501 [2].
3a. (If the PDU Session Release is initiated by the UE in step 1a or has been triggered by (R)AN in step 1d) The SMF responds to the AMF with the Nsmf_PDUSession_UpdateSMContext response (N2 SM Resource Release request, N1 SM container (PDU Session Release Command)). N2 SM Resource Release request is included if the PDU Session Release is initiated by the UE and if the UP connection of the PDU Session is active. Neither N2 SM Resource Release request nor N1 SM container is included if the PDU Session Release is triggered by (R)AN and the SMF decides to keep the PDU session with user plane connection deactivated and the subsequent steps are skipped.
3b. If the PDU Session Release is initiated by the SMF or the PCF, the SMF invokes the Namf_Communication_N1N2MessageTransfer service operation (N1 SM container (PDU Session Release Command), skip indicator).
If the UP connection of the PDU Session is active, the SMF shall also include the N2 Resource Release request (PDU Session ID) in the Namf_Communication_N1N2MessageTransfer, to release the (R)AN resources associated with the PDU Session.
The "skip indicator" tells the AMF whether it may skip sending the N1 SM container to the UE (e.g. when the UE is in CM-IDLE state). SMF includes the "skip indicator" in the Namf_Communication_N1N2MessageTransfer except when the procedure is triggered to change PDU Session Anchor of a PDU Session with SSC mode 2.
If the UE is in CM-IDLE state and "skip indicator" is included in the Namf_Communication_N1N2MessageTransfer service operation or if the UE is in CM-IDLE state and "skip indicator" is not included in the Namf_Communication_N1N2MessageTransfer service operation but the AMF detects that the UE context contains Paging Restriction Information indicating that all paging is restricted, the AMF acknowledges the step 3b by sending an Namf_Communication_N1N2MessageTransfer Response message ("N1 SM Message Not Transferred") to SMF and steps 4 to 10 are skipped.
3c. If the PDU Session Release is initiated by the AMF in step 1c, i.e. the SMF received the Nsmf_PDUSession_ReleaseSMContext Request from the AMF, the SMF responds to the AMF with the Nsmf_PDUSession_ReleaseSMContext response, optionally including the Small Data Rate Control Status and APN Rate Control Status.
If the UPF included APN Rate Control Status and/or Small Data Rate Control Status in step 2 then the SMF includes APN Rate Control and/or Small Data Rate Control Status and the AMF stores the Small Data Rate Control Status and/or the APN Rate Control Status in the UE context in AMF.
The AMF and SMF shall remove all contexts (including the PDU Session ID) associated with the PDU Session which are indicated as released at the UE. The SMF shall remove any event subscriptions on the AMF by the SMF that becomes no more needed due to the PDU Session Release. The steps 4 to 11 are skipped.
3d. If the PDU Session Release is initiated by the AMF in step 1f, i.e. the SMF received the Nsmf_PDUSession_UpdateSMContext Request from the AMF with a release indication to request the release of the PDU Session, the SMF responds to the AMF with the Nsmf_PDUSession_UpdateSMContext Response which may contain the N1 SM container (PDU Session Release Command) to release the PDU session at the UE.
If the UP connection of the PDU Session is active, the Nsmf_PDUSession_UpdateSMContext Response shall also include the N2 Resource Release request (PDU Session ID) to release the (R)AN resources associated with the PDU Session.
4. If the UE is in CM-IDLE state and "N1 SM delivery can be skipped" is not indicated, the AMF initiates the network triggered Service Request procedure to transmit the NAS message (PDU Session ID, N1 SM container) to the UE and the steps 6, 7 are skipped.
If the message received from the SMF in step 3 does not include N2 SM Resource Release request, the AMF transmits the NAS message (PDU Session ID, N1 SM container) to the UE and the steps 6, 7 are skipped.
If the PDU Session is Control Plane CIoT 5GS Optimisation enabled, the SMF shall not include N2 SM Resource Release request in the message sent to the AMF, the AMF transmits the NAS message (PDU Session ID, N1 SM container) to the UE and the steps 6, 7 are skipped.
If the UE is in CM-CONNECTED state and the received message from the SMF in step 3 includes N2 SM Resource Release request, the AMF transfers the SM information received from the SMF in step 4 (N2 SM Resource Release request, N1 SM container) to the (R)AN.
If the message from the SMF includes Small Data Rate Control Status then the AMF stores it in the UE Context in AMF.
5. When the (R)AN has received an N2 SM request to release the AN resources associated with the PDU Session it issues AN specific signalling exchange(s) with the UE to release the corresponding AN resources.
In the case of a NG-RAN, the NAS message is sent to the UE in an RRC message which may take place with the UE releasing the NG-RAN resources related to the PDU Session. If NG-RAN resources do not need to be released (i.e. the User Plane of the PDU Session is deactivated), the NAS message is sent to the UE in an RRC message which does not release the NG-RAN resources related to the PDU Session.
During this procedure, the (R)AN sends any NAS message (N1 SM container (PDU Session Release Command)) received from the AMF in step 4.
For PDU Session for non-roaming subscribers, if the S-NSSAI of the released PDU Session is subject to network slice usage control as described in clause 5.15.15 of TS 23.501 [2] and there is no other PDU Session using the S-NSSAI over which the Access Type the PDU Session was released, the UE starts slice deregistration inactivity timer for the S-NSSAI over the Access Type if the UE received slice deregistration inactivity timer for the S-NSSAI for that the Access Type.
6. [Conditional] If the (R)AN had received a N2 SM request to release the AN resources, the (R)AN acknowledges the N2 SM Resource Release Request by sending an N2 SM Resource Release Ack (User Location Information, Secondary RAT usage data) Message to the AMF.
If the PLMN has configured secondary RAT usage reporting, the NG-RAN node may provide RAN Usage Data Report.
If NG-RAN/AN-TL has performed the deletion of TN stream based on the request received from the SMF/CUC in step 3, the NG-RAN/AN-TL shall confirm the deletion of TN stream configurations.
7a. The AMF invokes the Nsmf_PDUSession_UpdateSMContext (N2 SM Resource Release Ack (Secondary RAT usage data), User Location Information) to the SMF.
7b. The SMF responds to the AMF with an Nsmf_PDUSession_UpdateSMContext response.
8. The UE acknowledges the PDU Session Release Command by sending a NAS message (PDU Session ID, N1 SM container (PDU Session Release Ack)) over the (R)AN.
9. [Conditional] The (R)AN forwards the NAS message from the UE by sending a N2 NAS uplink transport (NAS message (PDU Session ID, N1 SM container (PDU Session Release Ack)), User Location Information) to the AMF.
10a. The AMF invokes the Nsmf_PDUSession_UpdateSMContext (N1 SM container (PDU Session Release Ack, User Location Information) to the SMF.
10b. The SMF responds to the AMF with an Nsmf_PDUSession_UpdateSMContext response.
Steps 8-10 may happen before steps 6-7.
11. If steps 3a, 3b or 3d were performed, the SMF waits until it has received replies to the N1 and N2 information provided in step 3, as needed.
The SMF invokes Nsmf_PDUSession_SMContextStatusNotify to notify AMF that the SM context for this PDU Session is released. If the UPF included Small Data Rate Control Status and/or APN Rate Control Status in step 2 then the SMF includes Small Data Rate Control Status and/or APN Rate Control Status in its request to the AMF in this step. The AMF releases the association between the SMF ID and the PDU Session ID, DNN, as well as S-NSSAI and stores the Small Data Rate Control Status and/or the APN Rate Control Status in the UE context in AMF. The SMF shall remove any event subscriptions on the AMF that becomes no more needed due to the PDU Session Release.
NOTE 6: The UE and the 5GC will get synchronized about the status of the (released) PDU Session at the next Service Request or Registration procedure.
For PDU Session for non-roaming subscribers, if the S-NSSAI of the released PDU Session is subject to network slice usage control and if the SMF indicates cause of slice inactivity and there is no other PDU Session using the S-NSSAI over which the Access Type the PDU Session was released, then AMF may remove the S-NSSAI from the Allowed NSSAI or start slice deregistration inactivity timer for the S-NSSAI for that Access Type as described in clause 5.15.15.3 of TS 23.501 [2]. If the AMF did not provide slice deregistration inactivity timer of the S-NSSAI to the UE for the Access Type and S-NSSAI is removed from Allowed NSSAI, the AMF triggers UE Configuration Update procedure to provide the new Allowed NSSAI to the UE.
12. If Dynamic PCC applied to this session the SMF invokes an SM Policy Association Termination procedure as defined in clause 4.16.6 to delete the PDU Session.
13. SMF notifies any entity that has subscribed to User Location Information related with PDU Session change.
14. If it is the last PDU Session the SMF is handling for the UE for the associated (DNN, S-NSSAI), the SMF unsubscribes from Session Management Subscription data changes notification with the UDM by means of the Nudm_SDM_Unsubscribe (SUPI, DNN, S-NSSAI) service operation. The UDM may unsubscribe the subscription notification from UDR by Nudr_DM_Unsubscribe (SUPI, Subscription Data, Session Management Subscription data, DNN, S-NSSAI).
15. The SMF invokes the Nudm_UECM_Deregistration service operation including the DNN and the PDU Session ID. The UDM removes the association it had stored between the SMF identity and the associated DNN and PDU Session ID. The UDM may update this information by Nudr_DM_Update (SUPI, Subscription Data, UE context in SMF data). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.4.3 UE or network requested PDU Session Release for Home-routed Roaming | This procedure is used in the case of home-routed roaming scenarios.
Figure 4.3.4.3-1: UE or network requested PDU Session Release for home-routed roaming
1. The procedure is triggered by one of the following events:
1a. (UE initiated release) As in step 1a of clause 4.3.4.2 with the addition that:
- the V-SMF initiates N4 Session Modification to instruct the V-UPF to stop forwarding uplink traffic; and
- the V-SMF invokes the Nsmf_PDUSession_Update Request (SM Context ID, information from the SM message from the UE e.g. PCO, "Trigger PDU Session Release" indication, Time zone, User Location Information) service operation to request the H-SMF to release the PDU Session. The H-SMF responds to the request immediately.
1b. (Serving network initiated release) The serving network initiates the PDU Session Release during UE or serving network initiated Deregistration procedure as specified in clause 4.2.2.3. There is no NAS SM message between the UE and the V-SMF in this case. This step is the same as step 1c in clause 4.3.4.2, with the addition that:
- the V-SMF initiates N4 Session Modification to instruct the V-UPF to stop forwarding uplink traffic; and
- the V-SMF initiates the release of the PDU Session at the H-SMF by invoking the Nsmf_PDUSession_Release request.
The serving network also initiates the PDU Session Release where neither N1 nor N2 SM signalling is needed before releasing the SM context as in step 1c in clause 4.3.4.2 if e.g. due to the set of network slices for a UE changes where a network slice instance is no longer available (e.g. as described in clause 5.15.5.2.2 of TS 23.501 [2], or the AAA Server triggered Network Slice-Specific Re-authentication and Re-authorization procedure fails as specified in clause 4.2.9.2 or the AAA Server triggered Slice-Specific Authorization Revocation takes place as specified in clause 4.2.9.4).
1c. (HPLMN initiated release) This step is the same as step 1b in clause 4.3.4.2, with the addition that:
- the H-SMF initiates N4 Session Modification to instruct the H-UPF to stop forwarding downlink traffic.
1d. This step is the same as step 1d in clause 4.3.4.2, with the addition that:
- the V-SMF initiates N4 Session Modification to instruct the V-UPF to stop forwarding uplink traffic; and
- the V-SMF invokes the Nsmf_PDUSession_Update Request towards H-SMF.
1e. (HPLMN initiated release) This step is the same as step 1e in clause 4.3.4.2, with the addition that:
- if the H-SMF is notified by the V-SMF that the HPLMN S-NSSAI of the PDU Session with SSC mode 1 or SSC mode 2 is to be replaced with Alternative HPLMN S-NSSAI and if the H-SMF determines that a new PDU Session is to be established on the Alternative HPLMN S-NSSAI, the H-SMF initiates release of the PDU Session, as described in clause 5.15.19 of TS 23.501 [2];
- the H-SMF initiates N4 Session Modification to instruct the H-UPF to stop forwarding downlink traffic.
1f. This step is the same as step 1f in clause 4.3.4.2, with the addition that:
- the V-SMF initiates N4 Session Modification to instruct the V-UPF to stop forwarding uplink traffic; and
- the V-SMF invokes the Nsmf_PDUSession_Update Request towards H-SMF.
If the SMF receives one of the triggers in step 1a, 1c, 1e or 1f, the H-SMF starts PDU Session Release procedure.
When a SMF above initiates N4 Session Modification to instruct the UPF to stop forwarding traffic this means also to stop taking into account the traffic for usage monitoring.
2a-2b. (UE-, (R)AN- or Serving network initiated) This step is performed in case the PDU Session Release is triggered by a message from V-SMF. These steps are the same as steps 2a-2b in clause 4.3.4.2. The SMF is the SMF in HPLMN.
NOTE 1: This step 2a-2b can correspond to steps 1a, 1b, 1d, 1f.
3a. (UE or HPLMN initiated release) The H-SMF prepares the SM Release PDU Session Command message and initiates the PDU Session Release towards the UE by invoking the Nsmf_PDUSession_Update Request service operation towards the V-SMF. The Nsmf_PDUSession_Update Request contains necessary information to build the SM Release PDU Session Command by the V-SMF towards the UE (for example a Release Cause or PCO).
For network slice replacement as in step 1e, the H-SMF includes Alternative HPLMN S-NSSAI and a cause value indicating that a new PDU Session re-establishment on the Alternative HPLMN S-NSSAI is required.
3b. (Serving network initiated release) The H-SMF responds to the PDU release request from the V-SMF with a Nsmf_PDUSession_Release response.
If the UPF included Small Data Rate Control Status in step 2 then the SMF includes Small Data Rate Control Status in the request to the AMF.
If the Control Plane CIoT 5GS Optimisation is enabled for this PDU Session, the steps 4a and 4b are skipped.
4a-4b. The V-SMF releases the corresponding User Plane resources. This includes the same procedure in step 2 but controlled from the SMF in VPLMN.
5-13. These steps are the same as steps 3-10 in clause 4.3.4.2, with the addition that:
- In step 5c, for network slice replacement, based on information from H-SMF, the PDU Session Release Command message may include Alternative HPLMN S-NSSAI and/or Alternative VPLMN S-NSSAI and a cause value indicating that a PDU Session re-establishment on the Alternative HPLMN S-NSSAI and/or Alternative VPLMN S-NSSAI is required.
14. (UE or HPLMN initiated release) The V-SMF responds to the Nsmf_PDUSession_Update Request invoked at step 3a and confirms the PDU Session Release. The Nsmf_PDUSession_Update response may carry information such as PCO received from the UE in SM PDU Session Release Accept. as well as User Location Information, Time Zone and Secondary RAT Usage Data.
15a. (UE or HPLMN or Serving network initiated release) The H-SMF releases the SM policy control association with the PCF by invoking the SM Policy Association Termination procedure defined in clause 4.16.6. For serving network initiated PDU Session Release case, this step happens between step 1b and step 3b.
15b-15c. (HPLMN initiated release) In case the PDU Session Release is HPLMN-initiated (i.e. triggers in 1c, 1e), the H-SMF releases the corresponding User Plane resources. This includes the same procedure as in step 2.
15d. As in step 15 of clause 4.3.4.2, the SMF invokes the Nudm_UECM_Deregistration service operation.
NOTE 2: Step 15d does not necessarily take place after step 15c.
16. (UE or HPLMN initiated release) The H-SMF shall remove all contexts associated with the PDU Session:
16a. The H-SMF requests the V-SMF to release all contexts associated with the PDU Session by invoking the Nsmf_PDUSession_StatusNotify (Release) operation.
16b. The V-SMF requests the AMF to release all contexts associated with the PDU Session by invoking the Nsmf_PDUSession_SMContexStatusNotify (Release). The AMF releases the association between the SMF ID and the PDU Session ID. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.5 Session continuity, service continuity and UP path management | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.5.1 Change of SSC mode 2 PDU Session Anchor with different PDU Sessions | The following procedure is triggered by SMF in order to change the PDU Session Anchor serving a PDU Session of SSC mode 2 for a UE when neither multi-homing nor UL CL applies to the PDU Session. This procedure releases the existing PDU Session associated with an old PDU Session Anchor (i.e. UPF1 in figure 4.3.5.1-1) and immediately establishes a new PDU Session with a new PDU Session Anchor (i.e. UPF2 in figure 4.3.5.1-1) to the same DN.
Figure 4.3.5.1-1: Change of SSC mode 2 PSA for a PDU Session
1. The SMF determines that the serving UPF needs to be changed due to events that may benefit from such change.
1a. If the UPF (PSA) cannot connect to the target DNAI that SMF received from SM-PCF, the SMF invokes Nsmf_PDUSession_SMContextStatusNotify Request (target DNAI information) service operation to the AMF. The SMF also indicates the SMF selection is expected.
The target DNAI information is used for SMF selection which can control UPF connecting to that DNAI at next PDU session establishment towards the same DNN and S-NSSAI. Due to it is for SMF selection, the AMF stores the target DNAI information received from SMF. The target DNAI information is not transferred outside, e.g. to support the UE context transfer between AMFs for AMF relocation.
2. The PDU Session Release procedure is initiated as described in clause 4.3.4. The SMF sends an N1 SM Information to the UE via the AMF by invoking Namf_Communication_N1N2MessageTransfer as described in Step 3b of clause 4.3.4.2. The PDU Session Release Command message in N1 SM Information contains the PDU Session ID and Cause indicating that a PDU Session re-establishment to the same DN is required.
3. Upon reception of PDU Session Release Command with Cause indicating that a PDU Session re-establishment to the same DN is required as sent in step 2, the UE generates a new PDU Session ID and initiates PDU Session Establishment procedure as described in clause 4.3.2.2.
Then, the AMF selects an SMF as described in clause 6.4.2 of TS 23.501 [2] and the SMF can select a new UPF (i.e. UPF2) for the re-established PDU Session of SSC mode 2.
If the AMF has received target DNAI information from old SMF (i.e. SMF1), for the PDU Session toward same DNN and S-NSSAI the AMF selects the SMF using the stored target DNAI information. The AMF includes the target DNAI in the Nsmf_PDUSession_CreateSMContext Request and deletes the stored target DNAI information. The SMF selects the new PDU Session Anchor using the target DNAI. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.5.2 Change of SSC mode 3 PDU Session Anchor with multiple PDU Sessions | The following procedure is triggered by SMF in order to change the PDU Session Anchor serving a PDU Session of SSC mode 3 for a UE. This procedure releases the existing PDU Session associated with an old PDU Session Anchor (i.e. UPF1 in figure 4.3.5.2-1) after having established a new PDU Session to the same DN with a new PDU Session Anchor (i.e. UPF2 in figure 4.3.5.2-1), which is controlled by the same SMF. The SMF may determine that a new SMF needs to be reallocated.
Figure 4.3.5.2-1: Change of SSC mode 3 PDU Session Anchor with multiple PDU Sessions
1. The SMF determines that the serving UPF or the SMF needs to be changed. If the "Indication of application relocation possibility" attributes in the PCC rule indicates no DNAI change takes place once selected for this application, the SMF determines that the SMF can not be changed.
1a. If the UPF (PSA) cannot connect to the target DNAI(s) that SMF received from SM-PCF, the SMF invokes Nsmf_PDUSession_SMContextStatusNotify Request (target DNAI information) service operation to the AMF. The SMF also indicate the SMF selection is expected.
If the runtime coordination between 5GC and AF (Figure 4.3.6.3-1) is enabled, the SMF includes in the Nsmf_PDUSession_SMContextStatusNotify Request the SM Context ID as a reference to the SM Context that includes AF Coordination Information stored in the SMF.
The target DNAI information are used for SMF selection which can control UPF connecting to that DNAI at next PDU session establishment towards the same DNN and S-NSSAI. Due to it is for SMF selection, the AMF stores the target DNAI information received from SMF selection. The target DNAI information is not transferred outside, e.g. to support the UE context transfer between AMFs for AMF relocation.
2. If the SMF had sent an early notification to the AF and the runtime coordination between 5GC and AF is enabled based on local configuration as specified in clause 4.3.6.3, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF waits for a notification response from the AF. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure. This is defined in Figure 4.3.6.3-1.
The SMF invokes the Namf_Communication_N1N2MessageTransfer (PDU Session ID, SMF Reallocation requested indication, N1 SM container (PDU Session Modification Command (Cause, PCO (PDU Session Address Lifetime value)))) where PDU Session ID indicates the existing PDU Session to be relocated and Cause indicates that a PDU Session re-establishment to the same DN is required.
The SMF Reallocation requested indication indicates whether the SMF is requested to be reallocated.
The PDU Session Address Lifetime value is delivered to the UE upper layers in PCO and indicates how long the network is willing to maintain the PDU Session. The SMF starts a PDU Session Release timer corresponding to the PDU Session Address Lifetime value.
3a. The AMF forwards the NAS message to the UE. The UE can provide the release timer value to the upper layers if received in the PDU Session Modification Command.
3b. The UE acknowledges the PDU Session Modification Command.
3c. The AMF forwards the N1 SM container (PDU Session Modification Command ACK) received from the (R)AN to the SMF1 via Nsmf_PDUSession_UpdateSMContext service operation.
3d. The SMF1 replies with a Nsmf_PDUSession_UpdateSMContext Response.
4. If the UE receives PDU Session Modification Command, the UE may decide to initiate the PDU Session Establishment procedure described in clause 4.3.2.2, to the same DN with the following differences:
In Step 1 of clause 4.3.2.2.1, according to the SSC mode, UE generates a new PDU Session ID and initiates the PDU Session Establishment Request using the new PDU Session ID. The new PDU Session ID is included as PDU Session ID in the NAS request message and the Old PDU Session ID which indicates the existing PDU Session to be released is also provided to AMF in the NAS request message.
In Step 2 of clause 4.3.2.2.1, if SMF reallocation was requested in Step 2 of this clause, the AMF selects a different SMF. Otherwise, the AMF sends the Nsmf_PDUSession_CreateSMContext Request to the same SMF serving the Old PDU Session ID.
If target DNAI information has been received from old SMF (i.e. SMF1), for the PDU Session toward same DNN and S-NSSAI the AMF selects the new SMF using the stored target DNAI information. The AMF includes the target DNAI in the Nsmf_PDUSession_CreateSMContext Request and deletes the stored target DNAI information. If the AMF has received the SM Context ID from the old SMF, the AMF includes the SM Context ID in the Nsmf_PDUSession_CreateSMContext Request.
In Step 3 of clause 4.3.2.2.1, if the SMF is not to be reallocated, the AMF include both PDU Session ID and Old PDU Session ID in Nsmf_PDUSession_CreateSMContext Request. The SMF detects that the PDU Session establishment request is related to the trigger in step 2 based on the presence of an Old PDU Session ID in the Nsmf_PDUSession_CreateSMContext Request.
In Step 3 of clause 4.3.2.2.1, the SMF stores the new PDU Session ID and selects a new PDU Session Anchor (i.e. UPF2) for the new PDU Session.
If the new SMF receives an SM Context ID in the Nsmf_PDUSession_CreateSMContext Request, the new SMF retrieves the AF Coordination Information by sending a Nsmf_PDUSession_ContextRequest to the old SMF and indicates that "AF Coordination Information" part of 5G SM Context is requested.
If the SMF receives a target DNAI in the Nsmf_PDUSession_CreateSMContext Request, the SMF selects the new PDU Session Anchor using the target DNAI.
If the AF Coordination Information in the Nsmf_PDUSession_ContextRequest Response includes a notification correlation id associated with an "uplink buffering" indication, the SMF may also indicate PSA2 to buffer the uplink data associated with the same notification correlation id in the PCC Rules.
If the PCC Rules received from the PCF as in step 7b or step 9 in clause 4.3.2.2.1 indicate that a late notification is requested by the AF (directly or via NEF), the SMF sends a late notification to the AF before step 11 of clause 4.3.2.2.1 in Nsmf_EventExposure_Notify service operation, as in step 4a or step 4c in Figure 4.3.6.3-1 (directly or via NEF, respectively). The late notification contains the Source DNAI and the UE IP address in the Source DNAI included in the AF Coordination Information as received in the Nsmf_PDUSession_CreateSMContext Response from the old SMF.
If the SMF received a negative notification response from the AF, the SMF may stop the procedure. This is defined in Figure 4.3.6.3-1. Otherwise the SMF continue the following procedures to activate the UP path of the new PDU Session. The SMF may also indicate PSA2 to stop buffering and start forwarding uplink data.
5. After the new PDU Session is established the UE starts using the IP address/prefix associated with the new PDU Session for all new traffic and may also proactively move existing traffic flow (where possible) from the old PDU Session to the new PDU Session.
NOTE: The mechanisms used by the UE to proactively move existing traffic flows from one IP address/prefix to another are outside the scope of 3GPP specifications.
6. The old PDU Session is released as described in clause 4.3.4 either by the UE before the timer provided in step 3 expires (e.g. once the UE has consolidated all traffic on new PDU Session or if the session is no more needed) or by the SMF upon expiry of this timer. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.5.3 Change of SSC mode 3 PDU Session Anchor with IPv6 Multi-homed PDU Session | Clause 4.3.5.3 describes a procedure for service continuity with SSC mode 3 that uses the multi-homed PDU Session described in clause 5.6.4.3 of TS 23.501 [2]. In this case the SMF prepares a new PDU Session Anchor first and then notifies the UE of the existence of a new IP prefix, as depicted in figure 4.3.5.3-1. This procedure is applicable only to PDU Sessions of IPv6 type.
Figure 4.3.5.3-1: Change of PDU Session Anchor with IPv6 Multi homed PDU Session
The UE has an established PDU Session with the PDU Session Anchor (i.e. UPF1 in Figure 4.3.5.3-1). The PDU Session's User Plane involves at least the (R)AN and the PDU Session Anchor.
1. At some point the SMF decides to allocate the PDU Session with a new PDU Session Anchor.
2. The SMF selects a new UPF and using N4 configures the UPF as a new PDU Session Anchor (i.e. UPF2 in Figure 4.3.5.3-1) of the multi-homed PDU Session. In the process a new IPv6 prefix (IP@2) is allocated for the PDU Session. If the PCF has subscribed to the IP allocation/release event, the SMF performs a Session Management Policy Modification procedure as defined in clause 4.16.5 to provide the new allocated IPv6 prefix to the PCF. The PCF invokes Nbsf_Management_Update service operation to register the tuple (IPv6 prefix, PCF id) for the PDU session identified by (SUPI, DNN, S-NSSAI) in the BSF.
If the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF sends an early notification to the AF after the new UPF (new PSA) is selected and waits for a notification response from the AF. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure. This is further defined in Figure 4.3.6.3-1.
3. The SMF selects a Branching Point (BP) UPF as described in Clause of 6.3.3 of TS 23.501 [2]. The selection of BP UPF may consider the location of UPF1 and UPF2 to ensure a suitable location of the BP UPF relative to the UPF1 and the UPF2.
NOTE 1: If BP UPF is co-located with one of PDU Session Anchors, steps between SMF and BP UPF can be skipped.
4. The SMF configures via N4 the UPF selected in step 3 (BP UPF in Figure 4.3.5.3-1) as a Branching Point for the multi-homed PDU Session. It provides the Branching Point with the necessary UL traffic forwarding rules (related with the prefix of the IPv6 source address of UL traffic). Also, the SMF provides AN Tunnel Info for N3 tunnel setup and CN Tunnel Info for N9 tunnel setup to the BP UPF and obtains CN Tunnel Info from the BP UPF.
5-6. The SMF performs N4 Session Modification procedure with PSAs. During this procedure, the SMF provides CN Tunnel Info received from the BP UPF to set up an N9 tunnel between BP and PSAs. The SMF may also indicate local PSA2 to buffer the uplink data.
7. The SMF invokes the Namf_Communication_N1N2MessageTransfer service operation containing N2 SM Information with CN Tunnel Info for the N3 tunnel setup.
8. The AMF sends an N2 Request including N2 SM Information received from the SMF to the (R)AN. The (R)AN acknowledges to the AMF with an N2 Response.
9a. The AMF carries the N2 Response sent by the (R)AN to the SMF by invoking the Nsmf_PDUSession_UpdateSMContext service operation.
9b. The SMF responds to Nsmf_PDUSession_UpdateSMContext service operation from the AMF.
10-11. If the runtime coordination between 5GC and AF is enabled based on local configuration as specified in clause 4.3.6.3, according to the indication of "AF acknowledgment to be expected" is included in AF subscription to SMF events, the SMF sends a late notification to the AF and waits for a notification response from the AF. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure. This is further defined in Figure 4.3.6.3-1.
The SMF notifies the UE of the availability of the new IP prefix. This is performed using an IPv6 Router Advertisement message (RFC 4861 [6]). The SMF sends a Router Advertisement to the UE via the new PSA with a new prefix (IP@2) and sends another Router Advertisement to the UE via the old PSA with the old prefix (IP@1) and zero value in the preferred lifetime field and a value in the valid lifetime field according to RFC 4862 [8]. The UE shall update the valid lifetime of the old prefix (IP@1) to the signalled value regardless of the remaining lifetime. The valid lifetime value indicates the time how long the SMF is willing to keep the old prefix. The valid lifetime value may be decided by SMF based on local configuration.
The UE starts using IP@2 for all new traffic and may also proactively move existing traffic flow (where possible) from IP@1 to IP@2.
NOTE 2: The mechanisms used by the UE to proactively move existing traffic flows from one IP prefix to another are outside the scope of 3GPP specifications.
12. After the timer expires, the SMF releases the UE's old IPv6 prefix (IP@1). At this point the UE implicitly releases the old IP prefix. The SMF sends an N4 Session Modification Request to the BP to release UP resource for N9 tunnel between the BP and old PSA.
13. The SMF releases the old PDU Session context with the old PDU Session Anchor (UPF1 in Figure 4.3.5.3-1). If the PCF has subscribed to the IP allocation/release event, the SMF performs a Session Management Policy Modification procedure as defined in clause 4.16.5 to notify the PCF of the IPv6 prefix release. The PCF shall invoke Nbsf_Management_Update service operation to remove the tuple (IPv6prefix, PCF id) for the PDU session identified by (SUPI, DNN,S-NSSAI) in BSF.
14-18. The SMF may optionally release the Branching Point from the User Plane path. In step 14, the SMF may also indicate PSA2 to stop buffering and start forwarding uplink data. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.5.4 Addition of additional PDU Session Anchor and Branching Point or UL CL | Clause 4.3.5.4 describes a procedure to add a PDU Session Anchor and a Branching Point or UL CL for an established PDU Session.
Figure 4.3.5.4-1: Addition of additional PDU Session Anchor and Branching Point or UL CL
1. UE has an established PDU Session with a UPF including the PDU Session Anchor 1 (PSA1 in Figure 4.3.5.4-1). The PDU Session User Plane involves at least the (R)AN and the PDU Session Anchor 1.
2. At some point the SMF decides to establish a new PDU Session Anchor e.g. due to UE mobility, new flow detection. The SMF selects a UPF and using N4 establish the new PDU Session Anchor 2 (PSA2 in Figure 4.3.5.4-1) of the PDU Session. In the case of IPv6 multi-homing PDU Session, the SMF also ensures that a new IPv6 prefix corresponding to PSA2 is allocated and if the PCF has subscribed to the IP allocation/release event, the SMF performs the Session Management Policy Modification procedure as defined in clause 4.16.5 to provide the new allocated IPv6 prefix to the PCF.
If the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" is included in AF subscription to SMF events, the SMF sends an early notification to the AF after new PSA (PSA2 in Figure 4.3.5.4-1) is selected and waits for a notification response from the AF before configuring the new PSA. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure.
3. The SMF selects a UPF and using N4 establish the Branching Point (in the case of IPv6 multi-homing) or a UL CL for the PDU Session. It provides the necessary uplink forwarding rules towards PSA1 and PSA2 including the PSA1 CN Tunnel Info and the PSA2 CN Tunnel Info. In addition, the AN Tunnel Info is provided for downlink forwarding. In the case of IPv6 multi-homing, the SMF also provides traffic filters for the IPv6 prefixes corresponding to PSA1 and PSA2 indicating what traffic shall be forwarded towards PSA1 and PSA2 respectively.
In the case of UL CL, the SMF provides traffic filters indicating what traffic shall be forwarded towards PSA1 and PSA2 respectively. If the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" is included in AF subscription to SMF events, the SMF sends a late notification to the AF and waits for a notification response from the AF before configuring the UL CL. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure.
NOTE 1: If the Branching Point or UL CL and the PSA2 are co-located in a single UPF then steps 2 and 3 can be merged. If a Branching Point is already allocated, step 3 is skipped.
4. The SMF updates the PSA1 via N4. It provides the Branching Point or UL CL CN Tunnel Info for the downlink traffic.
NOTE 2: If the Branching Point or UL CL and the PSA1 are co-located in a single UPF then steps 3 and 4 can be merged.
5. The SMF updates PSA2 via N4. It provides the Branching Point or UL CL CN Tunnel Info for down-link traffic.
NOTE 3: If the Branching Point or UL CL and the PSA2 are co-located in a single UPF then step 5 is not needed.
6. The SMF updates (R)AN via N2 SM information over N11. It provides the new CN Tunnel Info corresponding to the UPF (Branching Point or UL CL). In the case of UL CL, if there is an existing UPF between the (R)AN and new inserted UL CL, the SMF updates the existing UPF via N4 instead of updating the (R)AN.
7. In the case of IPv6 multi-homing, the SMF notifies the UE of the availability of the new IP prefix @ PSA2. This is performed using an IPv6 Router Advertisement message (RFC 4861 [6]). Also, the SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix to the UE using an IPv6 Router Advertisement message (RFC 4191 [21]) as described in clause 5.8.2.2.2 of TS 23.501 [2].
If the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF sends a late notification to the AF and waits for a notification response from the AF before sending the new IP prefix to the UE. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure.
8. In the case of IPv6 multi-homing, the SMF may re-configure the UE for the original IP prefix @ PSA1,i.e. SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix to the UE using an IPv6 Router Advertisement message (RFC 4191 [21]) as described in clause 5.8.2.2.2 of TS 23.501 [2]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.5.5 Removal of additional PDU Session Anchor and Branching Point or UL CL | Clause 4.3.5.5 describes a procedure to remove a PDU Session Anchor and (optionally) remove Branching Point or UL CL for an established PDU Session.
Figure 4.3.5.5-1: Removal of additional PDU Session Anchor and Branching Point or UL CL
1. UE has an established PDU Session with a UPF including the Branching Point or UL CL, the PDU Session Anchor 1 (PSA1 in Figure 4.3.5.5-1) and the PDU Session Anchor 2 (PSA2 in Figure 4.3.5.5-1).
At some point the SMF decides to remove the PDU Session Anchor 1 e.g. due to UE mobility, flow terminated.
2. In the case of IPv6 multi-homing, the SMF notifies the UE to stop using the IPv6 prefix corresponding to PSA1. This is performed by IPv6 Router Advertisement message (RFC 4861 [6] and RFC 4862 [8]). Also, the SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix corresponding to PSA2 to the UE as described in clause 5.8.2.2.2 of TS 23.501 [2]. Based on the information provided in the Router Advertisement, the UE starts using the IPv6 prefix (corresponding to PSA2) for all the traffic.
4. If the Branching Point or UL CL is to be released, the SMF updates the (R)AN with the PSA2 CN Tunnel Info. In the case of UL CL, if there is an existing UPF between the (R)AN and the UL CL to be removed, the SMF updates the existing UPF via N4 instead of updating the (R)AN.
5. If the Branching Point or UL CL is to be released, the SMF updates via N4 the PSA2 providing the AN Tunnel Info. In the case of UL CL, if there is an existing UPF between the (R)AN and the UL CL to be removed, the SMF updates the PSA2 providing the UPF CN tunnel Info.
6. The SMF releases via N4 the PSA1. In the case of IPv6 multi-homing, the SMF also releases the corresponding IPv6 prefix and if the PCF has subscribed to the IP allocation/release event, the SMF performs the Session Management Policy Modification procedure as defined in clause 4.16.5 to notify the PCF of the IPv6 prefix release.
7. If steps 4 and 5 were executed, the SMF releases the Branching Point / UL CL. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.5.6 Change of additional PDU Session Anchor for IPv6 multi-homing or UL CL | The following procedure is triggered by an SMF when the SMF needs to modify IPv6 multi-homing or UL CL rule (i.e. traffic filter in the Branching Point or the UL CL) in order to move the some or whole traffic flows of the existing additional PDU Session Anchor which was established by the IPv6 multi-homing or the UL CL operations (i.e. PSA1 in figure 4.3.5.6-1) to a new additional PDU Session Anchor (i.e. PSA2 in figure 4.3.5.6-1) which is established under the same Branching Point or UL CL for a UE where the UE already has a PDU Session Anchor which was established before the event of Branching Point or UL CL insertion (i.e. PSA0 in figure 4.3.5.6-1). This procedure establishes a new additional PDU Session Anchor (i.e. PSA2) and conditionally releases the existing additional PDU Session Anchor (i.e. PSA1), while modifying IPv6 multi-homing or UL CL rule in the same Branching Point or UL CL under controlled by the same SMF.
Figure 4.3.5.6-1: Change of additional PSA for a PDU Session in IPv6 multi-homing or UL CL case
1. The SMF decides to change one additional PSA of a PDU Session with IPv6 multi-homing or UL CL, due to events that may benefit from such change or upon request from an Application Function.
2. If the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF sends an early notification to the AF after PSA2 is selected and waits for a notification response from the AF before configuring the PSA2. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure. This is defined in Figure 4.3.6.3-1.
The SMF sends an N4 Session Establishment Request to PSA2 and provides the tunnel ID of Branching Point or UL CL, Packet detection, enforcement and reporting rules to be installed on the PSA2 for this PDU Session. The SMF may also indicate local PSA2 to buffer the uplink data.
The PSA2 acknowledges by sending an N4 Session Establishment Response. The tunnel ID of PSA2 is provided to the SMF in this step.
In the case of IPv6 multi-homing PDU Session, a new IPv6 prefix corresponding to PSA2 is allocated (by the SMF or by the UPF depending on the deployment) and if the PCF has subscribed to the IP allocation/release event, the SMF performs the Session Management Policy Modification Procedure as defined in clause 4.16.5 to provide the new allocated IPv6 prefix to the PCF.
3a. In the case of PDU session with UL CL, if the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF sends a late notification to the AF and waits for a notification response from the AF. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure. This is further defined in Figure 4.3.6.3-1.
The SMF sends an N4 Session Modification Request to the Branching Point or UL CL to update the UL traffic filter according to new allocated IPv6 prefix allocated to PSA 2 or the UL CL rules regarding to the traffic flows that the SMF tries to move from PSA1 to PSA2. The N4 Session Modification Request message contains the identifications of traffic filter that needs to be updated and the tunnel ID of PSA2.
NOTE: The identification of a traffic filter can be either the index of the traffic filter, or a single value of the information field in traffic filter (e.g. the tunnel ID of next hop), or a combination value of some information field in the traffic filter (e.g. the tunnel ID of next hop with source port number).
3b. The Branching Point or the UL CL acknowledges by N4 Session Modification Response the Branching Point or when the UL CL successfully updates all the traffic filters that the SMF requests to modify.
3c. The SMF may also indicate PSA2 to stop buffering and start forwarding uplink data.
4. In the case of IPv6 multi-homing PDU Session, if the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF sends a late notification to the AF and waits for a notification response from the AF. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure. This is further defined in Figure 4.3.6.3-1.
In the case of IPv6 multi-homing PDU Session, The SMF notifies the UE of the availability of the new IP prefix @ PSA2. This is performed using an IPv6 Router Advertisement message (RFC 4861 [6]). Also, the SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix to the UE using an IPv6 Router Advertisement message (RFC 4191 [21]) as described in clause 5.8.2.2.2 of TS 23.501 [2]. The SMF may also indicate PSA2 to stop buffering and start forwarding uplink data.
5. In the case of IPv6 multi-homing PDU Session, The SMF may re-configure the UE for the original IP prefix @ PSA0,i.e. SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix to the UE using an IPv6 Router Advertisement message (RFC 4191 [21]) as described in clause 5.8.2.2.2 of TS 23.501 [2].
6. Step 6 occurs only if the Branching Point or UL CL does not have any traffic filter on the PDU Session which forwards a traffic flow to PSA1.
6a. The SMF sends an N4 Session Release Request with N4 session ID to PSA1. The PSA1 shall release all tunnel resources and contexts associated with the N4 session.
6b. PSA1 sends an N4 Session Release Response with N4 session ID to the SMF at the same moment that PSA1 successfully releases all tunnel resources and contexts associated with the N4 session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.5.7 Simultaneous change of Branching Point or UL CL and additional PSA for a PDU Session | Simultaneous change of UL CL or Branching Point and additional PSA can be performed after Xn based handover, N2 based handover and Service Request procedures.
The following procedure is triggered by SMF in order to change the Branching Point or the UL CL and additional PSA serving a PDU Session for a UE.
Figure 4.3.5.7-1: Simultaneous change of Branching Point or UL CL and additional PSA for a PDU Session
UE has an established PDU Session with a UPF including the PDU Session Anchor (Remote UPF). The PDU Session user plane involves at least the Source (R)AN, Source Branching Point or Source UL CL, local Source UPF (PSA2) and the Remote UPF (PDU Session Anchor, PSA1), where Source Branching Point or Source UL CL and PSA2 can be co-located.
1. At some point SMF decides to change the Branching Point or the UL CL due to UE mobility.
2. The SMF selects a local Target UPF (PSA3) and using N4 establishes the local Target UPF for the PDU Session.
In the case of IPv6 multi-homing PDU Session, a new IPv6 prefix corresponding to PSA3 is allocated (by the SMF or by the UPF depending on the deployment) and if the PCF has subscribed to the IP allocation/release event, the SMF performs the Session Management Policy Modification procedure as defined in clause 4.16.5 to provide the new allocated IPv6 prefix to the PCF.
The SMF may send an Early notification to the AF after PSA3 is selected. If the runtime coordination between 5GC and AF is enabled based on local configuration as specified in clause 4.3.6.3, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF waits for a notification response from the AF before configuring the PSA3. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure. This is defined in Figure 4.3.6.3-1.
3. The SMF selects a UPF and using N4 establishes the Target Branching Point or Target UL CL for the PDU Session. SMF provides the necessary uplink forwarding rules towards the PSA3 and PSA1 including the Tunnel Info for each UPF. If session continuity upon UL CL relocation is used, the SMF also uses N4 to establish an N9 forwarding tunnel between the Source UL CL and Target UL CL, including the Tunnel Info for each UPF. In addition, the AN Tunnel Info to target (R)AN is provided for downlink forwarding. In the case of UL CL, the SMF provides traffic filters indicating what traffic shall be forwarded towards PSA3, PSA1 and Source UL CL, respectively. In the case of IPv6 multi-homing, the SMF also provides traffic filters for the IPv6 prefixes corresponding to PSA3 and PSA1 indicating what traffic shall be forwarded towards PSA3 and PSA1 respectively. Target Branching Point or Target UL CL provides the CN Tunnel Info for downlink traffic.
NOTE 1: If the Target Branching Point or Target UL CL and the PSA3 are co-located in a single UPF then steps 2 and 3 can be merged.
NOTE 2: When session continuity upon UL CL relocation is used, the downlink traffic at this point goes through Source UL CL, Target UL CL and Target (R)AN.
4. The SMF updates the PSA1 via N4. It provides the PDU Session CN Tunnel Info for the downlink traffic.
5. The SMF updates the PSA3 via N4. It provides the CN Tunnel Info for downlink traffic. The SMF may also indicate PSA3 to buffer uplink data.
NOTE 3: If the Target Branching Point or the Target UL CL and the PSA3 are co-located in a single UPF then step 5 is not needed.
6. In the case of PDU session with UL CL, if the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF sends a late notification to the AF and waits for a notification response from the AF as described in step 9. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure and remove the Target Branching Point or Target UL CL and PSA3. This is further defined in Figure 4.3.6.3-1.
The SMF updates (R)AN via N2 SM information over N11. It provides the new CN Tunnel Info corresponding to the Target Branching Point or the Target UL CL. If there is an existing UPF between the Target (R)AN and Target Branching Point or Target UL CL, the SMF updates the existing UPF via N4 instead of updating the (R)AN.
NOTE 4: When session continuity upon UL CL relocation is used, the uplink traffic destined to PSA2 at this point goes through Target (R)AN, Target UL CL and Source UL CL.
7. In the case of IPv6 multi-homing PDU Session, if the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF sends a late notification to the AF and waits for a notification response from the AF as described in step 9. If the SMF receives a negative notification response from the AF, the SMF may stop the procedure. This is further defined in Figure 4.3.6.3-1.
In the case of IPv6 multi-homing, the SMF notifies the UE of the availability of the new IP prefix @ PSA3. This is performed using an IPv6 Router Advertisement message (RFC 4861 [6]). Also, the SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix to the UE using an IPv6 Router Advertisement message (RFC 4191 [21]) as described in clause 5.8.2.2.2 of TS 23.501 [2].
8. In the case of IPv6 multi-homing, the SMF may re-configure the UE for the original IP prefix @ PSA1, i.e. SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix to the UE using an IPv6 Router Advertisement message (RFC 4191 [21]) as described in clause 5.8.2.2.2 of TS 23.501 [2].
9. The SMF sends a Late Notification to the AF indicating a change of DNAI as described in clause 4.3.6.3. In cases where target local DN is associated with another AF instance, SMF also sends notification to target AF as described in 4.3.6.3 and cancels any future notification message to source AF as it is no longer involved. The SMF may also indicate PSA3 to stop buffering and start forwarding uplink data based on the positive response for the Late Notification.
NOTE 5: The message can include routing information to the application located in the target local DN. Alternatively the routing information to the application located in the target local DN can be determined by the AF based on the new DNAI, in which case the AF can invoke the AF triggered influence on traffic routing procedure targeting single UE as described in clause 4.3.6.4, which assists the SMF in generation of the routing rule on the Target UL CL towards PSA3 (i.e. towards the application located in the target local DN). It is up to network configuration whether the routing information to the application located in the target local DN is configured in the SMF or in the AF.
NOTE 6: When session continuity upon UL CL relocation is used the AF can also trigger mechanisms that are out of the scope of this specification (e.g. IP-level or HTTP-level redirection) by which the traffic is redirected towards the application in the target local DN. Based on this redirection the UE starts using a new destination IP address which leads the Target UL CL to force the traffic towards PSA3.
10. When session continuity upon UL CL relocation is used, detection of no active traffic over the N9 forwarding tunnel is performed during a time interval provisioned by SMF for User Plane inactivity report in order to release the N9 forwarding tunnel. The detection can be done by Source UL CL, which notifies the SMF of no active traffic over the N9 forwarding tunnel.
NOTE 7: It is up to network configuration whether the detection of no active traffic is performed by the Source UL CL or the Target UL CL. As an alternative to the detection of no active traffic, the AF can send an explicit notification to the SMF when traffic to/from this UE ceases to exist, leading the SMF to release the Source UL CL and the Source UPF (PSA2).
11. The SMF releases via N4 the PSA2.
12. The SMF releases the Source Branching Point or the Source UL CL.
NOTE 8: If the Source Branching Point or UL CL and the PSA2 are co-located in a single UPF then steps 11 and 12 can be merged. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.5.8 Ethernet PDU Session Anchor Relocation | This procedure allows for Ethernet PDU Sessions to change the PDU Session Anchor (PSA) while the session remains set up. Originally the Ethernet PDU Session goes via the Source UPF acting as the PSA. The Ethernet context which contains all Ethernet specific information including the MAC address of the UE and possibly its VLAN tag(s) is reported from the Source PSA UPF to the SMF. It is possible to report multiple MAC addresses (with their VLAN tag(s)) if these are reachable via the UE.
The SMF determines whether and when a serving PDU Session anchor for an Ethernet PDU Session needs to be changed and selects the Target PSA UPF, establishes the N4 session at the Target PSA UPF. The information within the Ethernet context is sent to the Target UPF. Based on the information in the Ethernet context, the Target PSA UPF may take action to update the Ethernet forwarding in the data network.
Figure 4.3.5.8-1: Ethernet PDU Session Anchor Relocation
Initially, the Ethernet PDU Session is established with the user data going via the Source UPF. The Source UPF acts as the PSA.
1. The Source UPF reports the Ethernet context which contains all Ethernet specific information including the MAC address of the UE and possibly its VLAN tag(s) that the UPF has learned from the UE side to the SMF. In the case of any changes in the Ethernet context, the change is updated to the SMF so that the SMF maintains an up-to-date state of the Ethernet context. This signalling is realized based on N4 reporting.
2. The UPF's report is acknowledged.
3-5. In the case of handover, the RAN handover preparation and execution is followed by path switch signalling to the AMF and corresponding signalling to SMF, as defined in clause 4.9.1.2.
6. The SMF decides that the PSA is to be changed for the Ethernet PDU Session and selects the Target UPF that will act as the new PSA. The decision may be triggered by a mobility event, such as receiving the message in step 5.
7. The Target UPF N4 session is established. The SMF provides the N3 tunnel endpoint used by RAN.
8. The establishment of the new N4 session is acknowledged from the Target UPF to the SMF. The UPF provides its N3 tunnel endpoint.
9-10. In the case of handover, the SMF signals to the RAN via the AMF to provide the Path Switch Request Ack, which includes the update of the uplink N3 tunnel endpoint to the target UPF. This signalling is defined in clause 4.9.1.2. In steps 9-10, an indication is sent from the SMF via the AMF to the RAN node indicating that the RAN node should not expect to receive an end marker packet. The RAN node may skip trying to reorder the downlink packets.
11-12. If there is no handover and the UE is in connected mode, the SMF sends PDU Session Modify Request message to the RAN via the AMF, which includes the update of the uplink N3 tunnel endpoint to the target UPF. The RAN acknowledges the message. The RAN node does not need to reorder the downlink packets.
NOTE 1: Due to the change in the end to end path, packet re-ordering can occur both for the handover and no handover cases. If necessary, upper layer protocols can ensure in sequence delivery.
After steps 9-10 or 11-12, uplink Ethernet frames pass via the target UPF. Downlink Ethernet frames may continue to be delivered from the source UPF to the RAN node. In the case of handover, the Ethernet frames are forwarded from the source RAN node to the target RAN node.
13-14. The SMF sends an N4 Session Modification Request to the Target UPF which includes the information in Ethernet context (i.e. MAC address and VLAN tag(s)) and a trigger for updating the Ethernet forwarding (next step). The Target UPF acknowledges by an N4 Session Modification Response.
15. The Target UPF may assist in the update of Ethernet forwarding tables of Ethernet switches in the DN via a variety of mechanisms, the use of which are specific to the DN and the specification of which are out-of-scope for 3GPP.
NOTE 2: The UPF acting as a switch in the DN, can for example issue a Gratuitous ARP (GARP) containing the MAC address(es) of the UE that has switched to the new anchor, or the UPF can send an unsolicited Neighbor Discovery Protocol (NDP) Neighbor Advertisement message indicating the UE MAC addresses, or the UPF can generate a uplink Ethernet frame with the UE's MAC addresses as source MAC addresses (and possibly its VLAN tag(s)) and configurable payload which will be dropped by endhosts, or the UPF can send another message or Ethernet frame compatible with DN protocols.
In the case of a central controller in the Ethernet network which sets the forwarding tables, the central controller can be instructed that the given MAC address is reachable at the new location.
When multiple MAC addresses are present in the Ethernet context, the update of the Ethernet forwarding is performed for each MAC address.
16. The N4 session is released at the Source UPF. The source UPF may wait for a configurable period before it stops delivering downlink Ethernet frames for the given PDU Session.
17. The N4 session release is acknowledged from the Source UPF to the SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6 Application Function influence on traffic routing, service function chaining and handling of payload headers | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.1 General | Clause 4.3.6 describes the procedures between an Application Function and the SMF to maintain an efficient user plane path and/or to provide N6-LAN service function chaining and/or to perform Handling of Payload Headers for Application Functions that require it.
As described in clauses 5.6.7, 5.6.16 and 5.6.17 of TS 23.501 [2], an Application Function may send requests to influence SMF routeing decisions for User Plane traffic of PDU Sessions. The AF requests may influence UPF (re)selection and allow routeing of user traffic to a local access (identified by a DNAI) to a Data Network and/or influence the steering of user traffic to service function chain(s) identified by SFC identifier(s) and/or request Handling of Payload Headers according to Header Handling Control Information. The AF may also provide in its request subscriptions to SMF events or UPF events. A V-SMF supporting HR-SBO provides, SUPI, an indication of support for HR-SBO, and HPLMN DNN and S-NSSAI related to the PDU session to the L-PSA UPF at PDU session establishment. The AF may also request N6 delay measurement for the delay sensitive application by providing the Indication of considering N6 delay.
NOTE 1: NEF uses the SUPI to derive PLMN ID of the UE.
The following cases can be distinguished:
NOTE 2: Such requests target an on-going PDU Session.
When receiving an AF request on Application Function influence on traffic routing targeting an individual UE IP address the NEF needs to determine whether the target PDU Session is working in HR-SBO mode. If the target PDU Session is NOT working in HR-SBO mode (non roaming or LBO PDU Session) then the NEF contacts the PCF of the PDU Session as further defined in the clause 4.3.6.4. If the target PDU Session is working in HR-SBO mode, the NEF does not contact the PCF of the PDU session but needs to store the AF request in UDR as defined in clause 4.3.6.5.
The NEF determines whether the PDU Session that the AF requests to influence is working in HR-SBO mode or not and in the former case determines the HPLMN of the UE, the DNN and S-NSSAI of the PDU Session as follows:
If the AF has determined based on procedure in clause 4.3.6.5.2 that the PDU session is home routed, the AF provides IP address of the UE (assigned by HPLMN) and HPLMN ID, HPLMN DNN and S-NSSAI, and the NEF determines if the PDU session is subject to HR-SBO using the provided information and proceeds according to clause 4.3.6.5.2.
If the AF has provided an IP address of the UE known to the AF (IP address not assigned by HPLMN), and DNN and S-NSSAI, the NEF determines if the PDU session is subject to HR-SBO based on local configuration. If PDU session is not subject to HR-SBO, the NEF proceeds according to clause 4.3.6.4. If PDU session is subject to HR-SBO the NEF determines the HPLMN and proceeds from according to clause 4.3.6.5.2, excluding step 0a.
NOTE 3: The DNN can be unique for a PLMN (see TS 23.003 [33]) and can be mapped to a HPLMN, or the IP address can be within a range that can be mapped to a HPLMN.
If the AF has not provided the (H)PLMN ID, DNN and S-NSSAI:
- If the IP address of the UE in the AF request is a private IP address, the NEF determines if the request relates to HR-SBO or not based on local configuration, or based on interactions with UPF, since the V-SMF shall have provided an indication that the PDU Session is working in HR-SBO mode, SUPI and the HPLMN DNN and S-NSSAI of the PDU Session to the L-PSA UPF. If the request relates to HR-SBO, the NEF proceeds according to clause 4.3.6.5.3, otherwise it proceeds according to clause 4.3.6.4.
NOTE 4: Whether or not NEF interact with UPF to determine if HR-SBO applies is based on configuration. If NEF does not interact with UPF, the 5GC NF (e.g. SMF/UPF, NEF) in PLMN can be configured to have separate private IP address ranges for HR-SBO PDU Sessions. This would allow NEF to distinguish AF request for influence on traffic routing for HR-SBO PDU Sessions from non-roaming and LBO PDU Sessions.
- If the IP address of the UE in the AF request is a public IP address:
- If this Public IP address belongs to an IP range not owned by the PLMN of the NEF, then the target PDU Session is working in HR-SBO mode and the NEF proceeds according to clause 4.3.6.5.4.
- If the UE IP Address in the AF request is an IP address NATed by the PLMN that the NEF belongs to, the NEF invokes steps 3 to 6 of clause 4.15.10 to get the corresponding private UE IP address. If HR-SBO applies, the V-SMF shall have provided an indication that the PDU Session is working in HR-SBO mode, SUPI and the HPLMN DNN and S-NSSAI of the PDU Session to the L-PSA UPF. Thus, the NEF can also receive these parameters and determines if the AF request relates to HR-SBO PDU Session, the NEF proceeds according to clause 4.3.6.5.3. Otherwise the NEF proceeds according to clause 4.3.6.4.
NOTE 5: In this Release, the HPLMN allows HR-SBO for a PDU session only if the UE IP address of the PDU Session has not been allocated in a range that may overlap with other PDU sessions to the same DNN and S-NSSAI of that HPLMN.
NOTE 6: It is assumed that the NEF is configured with the NATed IP range of its own PLMN. It is assumed that the NEF is configured based on HR-SBO roaming agreements for the Public IP address ranges with an HPLMN ID.
NOTE 7: Whether the AF needs to use the NEF or not is according to local deployment. If the AF request is expected to possibly address PDU Sessions in HR-SBO mode, then the AF sends its requests via the NEF.
When AF requests are routed (by the AF or by the NEF) to an individual PCF this may use the BSF. This case applies to both AF influence on traffic routing as well as AF influence on Service Function Chaining and Handling of Payload Headers. This is described in clause 4.3.6.4.
- AF requests described in clauses 5.6.7, 5.6.16, or 5.6.17 of TS 23.501 [2], targeting a group of UE(s), or any UE accessing a combination of DNN and S-NSSAI and optionally PLMN ID of the DNN and S-NSSAI, or targeting individual UE(s) by one or more GPSI(s) or targeting UEs with External Subscriber Category(s) which can be combined with External Group ID(s) or any UE as described in table 5.6.7-1. These AF requests may also affect UE(s) with an established PDU session. For such requests the AF shall contact the NEF and the NEF stores the AF request information in the UDR. For non-roaming and LBO cases, the PCF(s) receive a corresponding notification if they had subscribed to the create/update/delete operations of the AF request information corresponding to UDR Data Keys / Data Sub-Keys. This is defined in clause 6.3.7.2 of TS 23.501 [2] and further described in clause 4.3.6.2. For HR-SBO case, V-SMF(s) receive a corresponding notification if it has subscribed to the create/update/delete operation of the AF request information corresponding to UDR Data Keys /Data Sub-Keys, this is described in clause 4.3.6.5. For a single UE, NEF determines if HR-SBO applies for the PDU session based on the local configuration using the received GPSI. For "any UE", both PCF(s) and SMF(s) (via NEF) may need to subscribe to creates/updates/deletes of AF influence on traffic routing data in UDR depending on if a specific PLMN is targeted.
NOTE 8: Such requests can target on-going or future PDU Sessions.
If the AF request targets any UE the procedure described in clause 4.3.6.5 may also be performed. In that case if HPLMN ID, HPLMN DNN and HPLMN S-NSSAI have been provided (see clause 4.3.6.5.2), if the HPLMN ID, HPLMN DNN and HPLMN S-NSSAI have not been provided by the AF, the NEF determines the HPLMN DNN and HPLMN S-NSSAI as described in clause 4.3.6.5.5.
This Release of the specification does not support AF influence on traffic routing for HR-SBO PDU session, if the AF request targets an external group ID, or UE(s) identified by SUPI.
If the AF interacts with 5GC via the NEF, the NEF performs the following mappings or determinations where needed:
- Map the AF-Service-Identifier into DNN and S-NSSAI combination, determined by local configuration.
- Map the AF-Service-Identifier into a list of DNAI(s) and Routing Profile ID(s) determined by local configuration.
The NEF can only provide this mapping when the DNAI(s) being used by the applications are statically defined. When the DNAI(s) where applications are instantiated may vary dynamically, the AF should provide the target DNAI(s) in its request together with either Routing Profile ID(s) or with N6 traffic routing information.
- Map the GPSI in Target UE Identifier into SUPI, according to information received from UDM.
- Map the External Group Identifier in Target UE Identifier into Internal Group Identifier, according to information received from UDM.
- Map the External Subscriber Category(s) and any UE, or External Subscriber Category and External Group ID(s) to, Internal Group ID(s) or Internal Group ID(s) and Subscriber Category(s).
- Map the geographical area in Spatial Validity Condition into areas of validity, determined by local configuration.
- Determine whether an AF request targeting an UE IP address corresponds to HR-SBO and if yes determine the HPLMN of UE, the DNN/S-NSSAI of the PDU Session based on the description given above.
NOTE 9: As a user can be associated with multiple Subscriber Category(s), some values of Subscriber Category(s) can correspond to an SLA between an application provider represented by an AF and the 5GC operator. In the NEF API, the combination of application identifier and External Subscriber Category can also be used to refer to this SLA. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.2 Processing AF requests to influence traffic routing and/or Service Function Chaining and/or for Handling of Payload Headers for Sessions not identified by an UE address | Figure 4.3.6.2-1: Processing AF requests to influence traffic routing and/or Service Function Chaining for Sessions not identified by an UE address
NOTE 1: The 5GC functions used in this scenario are assumed to all belong to the same PLMN (HPLMN in non-roaming case or VPLMN in the case of a PDU Session in LBO mode).
0. The PCF(s) subscribe to modifications of AF requests (Data Set = Application Data; Data Subset = AF traffic influence request information, Data Key = S-NSSAI and/or DNN and/or Internal Group Identifier or SUPI) from the UDR.
1. To create a new request, the AF invokes a Nnef_TrafficInfluence_Create service operation. The content of this service operation (AF request) is defined in clause 5.2.6.7. The request contains also an AF Transaction Id. If it subscribes to events related with PDU Sessions the AF indicates also where it desires to receive the corresponding notifications (AF notification reporting information).
To update or remove an existing request, the AF invokes a Nnef_TrafficInfluence_Update or Nnef_TrafficInfluence_Delete service operation providing the corresponding AF Transaction Id.
The Nnef_TrafficInfluence_Create (initiated by target AF) or Nnef_TrafficInfluence_Update (initiated by source AF or target AF) service operation may be used for the case of AF instance change. If Nnef_TrafficInfluence_Update service operation is invoked, the NEF is required to update the subscription resource. The Nnef_TrafficInfluence_Update service operation may include an updated notification target address. The updated subscription resource is used by the target AF.
NOTE 2: If the source AF transfers the application context to the target AF, then target AF may create new subscription via Nnef_TrafficInfluence_Create operation or update existing subscription via Nnef_TrafficInfluence_Update. However, whether and how the application context transfer is done is out of this specification.
2. The AF sends its request to the NEF. If the request is sent directly from the AF to the PCF, the AF reaches the PCF selected for the existing PDU Session by configuration or by invoking Nbsf_management_Discovery service.
The NEF ensures the necessary authorization control, including throttling of AF requests and as described in clause 4.3.6.1, mapping from the information provided by the AF into information needed by the 5GC.
3. (in the case of Nnef_TrafficInfluence_Create or Update): The NEF stores the AF request information in the UDR (Data Set = Application Data; Data Subset, Data Key = AF Transaction Internal ID, S-NSSAI and DNN and/or Internal Group Identifier(s) and/or Subscriber Category(s) or SUPI). The Data Subset identifies whether the information relates to AF traffic influence request information for traffic routing, or to AF traffic influence request information for service function chaining, or to AF influence request for Handling of Payload Headers, as described in Table 5.2.12.2.1-1.
NOTE 3: Both the AF Transaction Internal ID and S-NSSAI and DNN and/or Internal Group Identifier(s) and/or Subscriber Category(s) or SUPI are regarded as Data Key when the AF request information are stored into the UDR, see Table 5.2.12.2.1-1. The Subscriber Category(s) is determined by NEF as described in clause 4.3.6.1.
(in the case of Nnef_TrafficInfluence_delete): The NEF deletes the AF requirements in the UDR (Data Set = Application Data; Data Subset, Data Key = AF Transaction Internal ID). The Data Subset identifies whether the information relates to AF traffic influence request information for traffic routing, or AF traffic influence request information for service function chaining, or to AF influence request for Handling of Payload Headers.
The NEF responds to the AF.
4. The PCF(s) that have subscribed to modifications of AF requests receive(s) a Nudr_DM_Notify notification of data change from the UDR. The Data Subset identifies whether the information relates to AF traffic influence request information for traffic routing or AF traffic influence request information for service function chaining.
5. The PCF determines if existing PDU Sessions are potentially impacted by the AF request. For each of these PDU Sessions, the PCF updates the SMF with corresponding new policy information about the PDU Session by invoking Npcf_SMPolicyControl_UpdateNotify service operation as described in steps 5 and 6 in clause 4.16.5.
The PCF validates whether the SFC identifier (if available) corresponds to an authorized SFC for the AF based on local configuration. If the validation has succeeded the PCF maps the SFC identifier to the corresponding Traffic Steering Policy identifier (i.e. TSP ID).
The PCF includes the Traffic Steering Policy ID(s) in the AF influence on traffic routing Enforcement Control information and/or N6-LAN Traffic Steering Enforcement Control information of the relevant PCC rule as defined in clause 6.3.1 of TS 23.503 [20]. The PCF also includes the Metadata in the N6-LAN Traffic Steering Enforcement Control information of the PCC rule when Metadata was provided by the AF.
If the AF request includes a notification reporting request for UP path change, the PCF includes in the PCC rule(s) the information required for reporting the event, including the Notification Target Address pointing to the NEF or AF and the Notification Correlation ID containing the AF Transaction Internal ID.
If the AF request includes an EAS Correlation indication or indication of traffic correlation, PCF includes in the PCC rule(s) an EAS Correlation indication or indication of traffic correlation and a Traffic Correlation ID corresponding to a set of UEs that AF request aims at, also if AF request includes a common EAS IP address or common DNAI for a set of UEs, PCC rule includes the common EAS IP address or common DNAI.
In the case of AF influence on traffic routing, the PCF may, optionally, use service experience analytics per UP path, as defined in clause 6.4.3 of TS 23.288 [50], to provide an updated list of DNAI(s) to the SMF.
The PCF may use the "Subscriber categories" as defined in "PDU Session policy control subscription information" in table 6.2-2 of TS 23.503 [20] to determine whether the PDU Session is impacted by the AF request.
If the AF request includes an Indication of considering N6 delay, the PCF includes the Indication of considering N6 delay in the corresponding PCC rule(s) as in clause 6.3.1 of TS 23.503 [20].
6. When the updated policy information about the PDU Session is received from the PCF, the SMF may take appropriate actions according to the policy information.
In the case of AF influence on traffic routing, SMF may take the appropriate actions to reconfigure the User plane of the PDU Session. Examples of actions are:
- The SMF may consider service experience analytics and/or DN Performance analytics per UP path (i.e. including UPF and/or DNAI and/or AS instance) as defined in clauses 6.4.3 and 6.14.3, respectively, of TS 23.288 [50] before taking any actions.
- Determining a target DNAI.
- Determining if a common DNAI needs to be used as a target DNAI.
- Adding, replacing or removing a UPF in the data path to e.g. act as an UL CL or a Branching Point e.g. as described in clause 4.3.5.
- Allocate a new Prefix to the UE (when IPv6 multi-Homing applies).
- Updating the UPF in the target DNAI with AF influence on traffic routing control parameters as described in clause 5.6.7.1 of TS 23.501 [2].
- Subscribe to notifications from the AMF for an Area of Interest via Namf_EventExposure_Subscribe service operation.
- Determining whether to relocate PSA UPF considering the user plane latency requirements provided by the AF (see clause 6.3.6 of TS 23.548 [74]).
- Triggers N6 delay measurement, and (re)selects the L-PSA UPF and EAS based on the measured N6 delay.
When the updated policy information about the PDU Session is received from the PCF, the SMF may take appropriate actions to assist the EAS discovery and re-discovery for PDU Session with Session Breakout connectivity model such as:
- Retrieve the EAS deployment information as defined in clause 6.2.3.4.1 of TS 23.548 [74].
- Providing DNS message handling rule to forward DNS messages of the UE and/or report when detecting DNS messages as defined in clause 6.2.3.2.2 of TS 23.548 [74].
In the case of AF influence on Service Function Chaining, the SMF may take appropriate actions to enforce the N6-LAN traffic steering control:
- Provide N6-LAN traffic steering control parameters to UPF as described in clause 5.6.16 of TS 23.501 [2].
In the case of AF influence on Handling of Payload Headers, the SMF may take appropriate actions by provisioning UPF with the Header Handling Control information, as described in clause 5.6.17 of TS 23.501 [2].
7. The SMF may decide whether it is required to send the target DNAI to the AMF for triggering SMF/I-SMF (re)selection and then inform the target DNAI information for the current PDU session or for the next PDU session to AMF via Nsmf_PDUSession_SMContextStatusNotify service operation. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.3 Notification of User Plane Management Events | The SMF may send a notification to the AF if the AF had subscribed to user plane management event notifications as described in clauses 4.3.6.2 and 4.3.6.4 and in clause 5.6.7 of TS 23.501 [2]. The following are the examples of such events:
- A PDU Session Anchor identified in the AF subscription request has been established or released.
- A DNAI has changed.
NOTE 1: To support UE-Satellite-UE (UE-SAT-UE) communication, the event that satellite identifier serving the UE has changed is represented by the event a DNAI has changed and the DNAI value can be derived from the satellite identifier.
- The SMF has received a request for AF notification and the on-going PDU Session meets the conditions to notify the AF.
- Ethernet PDU Session Anchor Relocation as defined in clause 4.3.5.8.
- Candidate DNAI(s) has changed.
- A common EAS has changed.
- The serving PLMN of PDU session has changed and local traffic offload is possible.
The SMF uses notification reporting information received from PCF to issue the notification either via an NEF (2a, 2b and 4a, 4b) or directly to the AF (2c and 4c).
In the case of the AF interacting with VPLMN in the HR-SBO case, the NF(s) in the procedure are located in VPLMN.
NOTE 2: 1a: In HR-SBO case, no PCF in VPLMN is involved.
In the case of AF interacting with HPLMN in the HR-SBO case (serving PLMN is VPLMN), the H-SMF provides Traffic influence related policies to V-SMF. N16 supports exchange of Traffic influence related policies and of early/late notification/subscription. The procedures for the case of AF interacting with HPLMN in the HR-SBO case are defined in clauses 6.7.3.2 and 6.7.4 of TS 23.548 [74].
The following flow depicts the sequence of events:
Figure 4.3.6.3-1: Notification of user plane management event
1. A condition for an AF notification has been met as described above. The SMF sends notification to the NF that is subscribed for SMF notifications. Further processing of the SMF notification depends on the receiving NF, as shown in steps 2a and 2c.
If immediate reporting flag is included in AF subscription for user plane management event as described in clause 5.6.7 of TS 23.501 [2], SMF sends notification, as shown in steps 2a or 2c.
2a. If early notification via NEF is requested by the AF, the SMF notifies the NEF of the target DNAI or candidate DNAI(s) of the PDU Session or indication of EAS rediscovery and may indicate capability of supporting EAS IP replacement in 5GC by invoking Nsmf_EventExposure_Notify service operation. The SMF may provide the target AF ID if it determines that the target DNAI is not supported by the source AF as specified in TS 23.548 [74]. The SMF may consider the UE location and available DNAI list provided by AF to select the closest available DNAI(s) as candidate DNAI(s). The SMF may also provide the candidate DNAI(s) in a prioritized order.
NOTE 2: For the reporting of candidate DNAIs from SMF/NEF to AF, only early notification is used.
2b. When the NEF receives Nsmf_EventExposure_Notify, the NEF performs information mapping (e.g. AF Transaction Internal ID provided in Notification Correlation ID to AF Transaction ID, SUPI to GPSI, etc.) as applicable according to clause 5.6.7 of TS 23.501 [2] and triggers the appropriate Nnef_TrafficInfluence_Notify message. In this case, step 2c is not applicable.
2c. If early direct notification is requested by the AF, the SMF notifies the AF of the target DNAI or candidate DNAI(s) of the PDU Session or indication of EAS rediscovery and may indicate capability of supporting EAS IP replacement in 5GC by invoking Nsmf_EventExposure_Notify service operation. The SMF may provide the target AF ID if it determines that the target DNAI is not supported by the source AF.
2c-a. To support UE-Satellite-UE (UE-SAT-UE) communication, if early notification is requested by the AF via PCF, the SMF notifies the PCF of the UE's serving satellite identifier change by invoking Nsmf_EventExposure_Notify service operation. In this case, step 2c-b follows.
2c-b. To support UE-Satellite-UE (UE-SAT-UE) communication, if early notification is requested by the AF via PCF, the PCF notifies the AF of the UE's serving satellite identifier change by invoking Npcf_PolicyAuthorization_Notify.
2d. The AF replies to Nnef_TrafficInfluence_Notify by invoking Nnef_TrafficInfluence_AppRelocationInfo service operation either immediately or after any required application relocation in the target DNAI is completed. The AF may include N6 traffic routing details corresponding to the target DNAI and /or the 'uplink buffering' indication to indicate that buffering of uplink traffic to the target DNAI is needed. The AF may include Information for EAS IP Replacement in 5GC. AF may reply in negative e.g. if the AF determines that the application relocation cannot be completed successfully and/or on time.
NOTE 3: The maximum time the new PSA is to buffer UL data relates to the maximum delay between steps 4a-4c and step 4f/4g of Figure 4.3.6.3-1. SMF local policies can control this maximum time.
NOTE 4: The traffic being buffered is the traffic associated with the PCC rule that has requested the notification.
2d-a. If information sent via Nnef_TrafficInfluence_Create is to be changed e.g. N6 traffic routing details corresponding to the target DNAI, the AF invokes Nnef_TrafficInfluence_update service operation in order for PCF to be able to include this information in PCC rules sent to SMF.
If the AF includes information such as N6 traffic routing details corresponding to the target DNAI in Nnef_TrafficInfluence_AppRelocationInfo it shall include the same information in Nnef_TrafficInfluence_update.
If common DNAI or common EAS is required for set of UEs and AF is used to select common DNAI or common EAS according to operator's configuration, the AF determines the common DNAI/EAS according to the candidate DNAI(s) of each UE of the set reported by SMF(s) serving the set of UEs, then informs SMF(s) of each UE of the selected common DNAI as clause 6.2.3.2.6 of TS 23.548 [74] or the selected common EAS as clause 6.2.3.2.5 of TS 23.548 [74].
2e. When the NEF receives Nnef_TrafficInfluence_AppRelocationInfo, the NEF triggers the appropriate Nsmf_EventExposure_AppRelocationInfo message.
2e-a. When the NEF receives Nnef_TrafficInfluence_update, the NEF triggers step 3a as in Figure 4.3.6.2-1 or step 2 of Figure 4.3.6.4-1 if targeting an individual UE by a UE address.
2f. The AF replies to Nsmf_EventExposure_Notify by invoking Nsmf_EventExposure_AppRelocationInfo service operation either immediately or after any required application relocation in the target DNAI is completed. The AF may include N6 traffic routing details corresponding to the target DNAI and /or the 'uplink buffering' indication to indicate that buffering of uplink traffic to the target DNAI is needed. The AF may include Information for EAS IP Replacement in 5GC. AF may reply in negative e.g. if the AF determines that the application relocation cannot be completed successfully on time.
2f-a. If the AF (i.e. P-CSCF) needs to acknowledge the notification as received in step 2c-b from PCF, the AF invokes Npcf_PolicyAuthorization_Update service operation. The AF (i.e. P-CSCF) may include N6 traffic routing details corresponding to the target DNAI and flow description information to configure ULCL for uplink traffic towards target DNAI in the request.
If information sent via Npcf_PolicyAuthorization_Create is to be changed e.g. N6 traffic routing details corresponding to the target DNAI, the AF invokes Npcf_PolicyAuthorization_Update service operation in order for PCF to be able to include this information in PCC rules sent to SMF.
If the AF includes information such as N6 traffic routing details corresponding to the target DNAI in Nsmf_EventExposure_AppRelocationInfo it shall include the same information in Npcf_PolicyAuthorization_Update.
2f-b. If the AF (i.e. P-CSCF) includes acknowledgement to the early notification in the Npcf_PolicyAuthorization_Update service, then the PCF triggers the Nsmf_EventExposure_AppRelocationInfo message.
3. The SMF enforces the change of DNAI or addition, change, or removal of a UPF. This may correspond to the mechanisms described in Figure 4.3.5.6-1 or in Figure 4.3.5.7-1.
If the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF may wait for a response from the AF to the early notification before this step. The SMF does not perform this step until it receives a positive response from the AF, as described in clause 5.6.7 of TS 23.501 [2].
4a. If late notification via NEF is requested by the AF, the SMF notifies the NEF of the target DNAI of the PDU Session or indication of EAS rediscovery or new serving PLMN ID, HPLMN DNN and S-NSSAI of the PDU session if serving PLMN is changed and local traffic offload is allowed and may indicate capability of supporting EAS IP replacement in 5GC by invoking Nsmf_EventExposure_Notify service operation. The SMF may provide the target AF ID if it determines that the target DNAI is not supported by the source AF.
If the runtime coordination between 5GC and AF is enabled based on local configuration, according to the indication of "AF acknowledgment to be expected" included in AF subscription to SMF events, the SMF may send late notification and wait for a positive response from the AF before activating the new UP path, as described in clause 5.6.7 of TS 23.501 [2].
4b. When the NEF receives Nsmf_EventExposure_Notify, the NEF performs information mapping (e.g. AF Transaction Internal ID provided in Notification Correlation ID to AF Transaction ID, SUPI to GPSI, etc.) as applicable according to clause 5.6.7 of TS 23.501 [2] and triggers the appropriate Nnef_TrafficInfluence_Notify message. In this case, step 4c is not applicable.
4c. If late direct notification is requested by the AF, the SMF notifies the AF of the target DNAI of the PDU Session or indication of EAS rediscovery or new serving PLMN ID, HPLMN DNN and S-NSSAI of the PDU session if serving PLMN is changed and local traffic offload is allowed and may indicate capability of supporting EAS IP replacement in 5GC by invoking Nsmf_EventExposure_Notify service operation. The SMF may provide the target AF ID if it determines that the target DNAI is not supported by the source AF.
4c-a. To support UE-Satellite-UE (UE-SAT-UE) communication, if late notification is requested by the AF via PCF, the SMF notifies the PCF of the UE's serving satellite identifier by invoking Nsmf_EventExposure_Notify service operation. In this case, step 4c-b follows.
4c-b. To support UE-Satellite-UE (UE-SAT-UE) communication, if late notification is requested by the AF via PCF, the PCF notifies the AF of the UE's serving satellite identifier by invoking Npcf_PolicyAuthorization_Notify.
4d. When the AF receives either the Nnef_TrafficInfluence_Notify message or the Nsmf_EventExposure_Notify message, the AF checks whether it can serve the target DNAI. If the AF instance change is needed, the AF determines the proper target AF for the target DNAI (e.g. based on locally configured information or the AF ID provided by the SMF in step 4a or 4c) and performs the AF migration.
NOTE 5: If the source AF is already locally configured with information associated with the target DNAI, the source AF is assumed to use the locally configured information, even if it has received from the SMF target AF ID in a previous step above.
NOTE 6: The determination of the target AF for the target DNAI and the AF migration to the target AF are out of the scope of this release.
4e. The AF replies to Nnef_TrafficInfluence_Notify by invoking Nnef_TrafficInfluence_AppRelocationInfo service operation either immediately or after any required application relocation in the target DNAI is completed. AF includes N6 traffic routing details corresponding to the target DNAI or new serving PLMN ID for traffic offload if serving PLMN is changed and local traffic offload is allowed. AF may reply in negative e.g. if the AF determines that the application relocation cannot be completed successfully on time. Nnef_TrafficInfluence_AppRelocationInfo with positive response may indicate that buffering of uplink traffic to the target DNAI is no more needed.
If SMF has sent an EAS re-discovery request to the UE as defined in TS 23.548 [74], e.g. due to change of common EAS, the SMF sends an indication to the AF that an EAS re-discovery request has been sent to the UE.
NOTE 7: The action taken by the AF when receiving such an indication that an EAS re-discovery request has been sent to the UE is out of scope of 3GPP specifications.
4e-a. If information sent via Nnef_TrafficInfluence_Create/Update is to be changed e.g. N6 traffic routing details corresponding to the target DNAI, the AF invokes Nnef_TrafficInfluence_Create or Nnef_TrafficInfluence_Update service operation in order for PCF to be able to include this information in PCC rules sent to SMF. The Nnef_TrafficInfluence_Create shall be used if the AF is notified (e.g. in step 4b) that the UE IP address is changed and the initial Nnef_TrafficInfluence_Create was targeted to an individual UE address, otherwise the Nnef_TrafficInfluence_Update may be used.
If the AF includes information such as N6 traffic routing details corresponding to the target DNAI in Nnef_TrafficInfluence_AppRelocationInfo it shall include the same information in Nnef_TrafficInfluence_Create or Nnef_TrafficInfluence_Update, whichever is appropriate.
4f. When the NEF receives Nnef_TrafficInfluence_AppRelocationInfo, the NEF triggers the appropriate Nsmf_EventExposure_AppRelocationInfo message.
4f-a. When the NEF receives Nnef_TrafficInfluence_Create/update, the NEF triggers step 3a as in Figure 4.3.6.2-1 or step 2 of Figure 4.3.6.4-1 if targeting an individual UE by a UE address.
4g. The AF replies to Nsmf_EventExposure_Notify by invoking Nsmf_EventExposure_AppRelocationInfo service operation either immediately or after any required application relocation in the target DNAI is completed. AF includes N6 traffic routing details corresponding to the target DNAI. AF may reply in negative e.g. if the AF determines that the application relocation cannot be completed successfully on time. Nsmf_EventExposure_AppRelocationInfo with positive response may indicate that buffering of uplink traffic to the target DNAI is no more needed.
4g-a. If information sent via Npcf_PolicyAuthorization_Create/Update is to be changed e.g. N6 traffic routing details corresponding to the target DNAI, the AF invokes Npcf_PolicyAuthorization_Create or Npcf_PolicyAuthorization_Update service operation in order for PCF to be able to include this information in PCC rules sent to SMF. The Npcf_PolicyAuthorization_Create shall be used if the AF is notified (e.g. in step 4c) that the UE IP address is changed, otherwise the Npcf_PolicyAuthorization_Update may be used.
If the AF includes information such as N6 traffic routing details corresponding to the target DNAI in Nsmf_EventExposure_AppRelocationInfo it shall include the same information in Npcf_PolicyAuthorization_Create or Npcf_PolicyAuthorization_Update, whichever is appropriate. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.4 Transferring an AF request targeting an individual UE address to the relevant PCF | Figure 4.3.6.4-1: Handling an AF request targeting an individual UE address to the relevant PCF
Depending on the AF deployment (see clause 6.2.10 of TS 23.501 [2]), the AF may send the AF request to PCF directly, in which case step 1 is skipped, or via the NEF.
1. [Conditional] If the AF sends the AF request via NEF, the AF sends Nnef_TrafficInfluenceCreate/Update/Delete Request targeting an individual UE address to the NEF. This request corresponds to an AF request to influence traffic routing to a local network and/or to a service function chain that targets an individual UE address.
When NEF receives an AF request from AF, the NEF ensures the necessary authorization control and as described in clause 4.3.6.1, mapping from the information provided by the AF into information needed by the 5GC. The NEF responds to the AF.
2. [Conditional] AF/NEF consumes Nbsf_Management_Discovery service operation (providing at least the UE address) to find out the address of the relevant PCF if the PCF address is not available on the NEF based on local configuration, otherwise step 1 is skipped.
NOTE 1: The AF/NEF finds the BSF based on local configuration or using the NRF.
3. BSF provides the PCF address in the Nbsf_Management_Discovery response to AF/NEF.
4. If step 1 was performed, NEF invokes the Npcf_PolicyAuthorization service to the PCF to transfer the AF request. If an AF sends the AF request directly to the PCF, AF invokes Npcf_PolicyAuthorization service and the PCF responds to the AF. To support the AF instance change, the Npcf_PolicyAuthorization_Create (initiated by target AF) or Npcf_PolicyAuthorization_Update (initiated by source AF or target AF) service operation may be used.
NOTE 2: If the source AF transfers the application context to the target AF, then target AF may create new subscription via Npcf_PolicyAuthorization_Create or update existing subscription via Npcf_PolicyAuthorization_Update. However, whether and how the application context transfer is done is out of this specification.
5. The PCF authorizes the AF request. If the PCF determines that the requirements can't be authorized, it rejects the AF request. Once the PCF authorizes the AF request, the PCF updates the SMF with corresponding new PCC rule(s) with PCF initiated SM Policy Association Modification procedure as described in clause 4.16.5.2.
The PCF includes the Traffic Steering Policy ID(s) for AF influence on traffic routing Enforcement Control information and/or N6-LAN Traffic Steering Enforcement Control information and/or Header Handling Control information in the relevant PCC rule as defined in clause 6.3.1 of TS 23.503 [20].
If the AF request includes a notification reporting request for UP path change, the PCF includes in the PCC rule(s) the information required for reporting the event, including the Notification Target Address pointing to the NEF or AF and the Notification Correlation ID containing the AF Transaction Internal ID.
If the PCF determines that the notification reporting request for UP path change is from P-CSCF, the PCF includes in the PCC rule(s) the information required for reporting the event, including the Notification Target Address pointing to the PCF and the Notification Correlation ID.
The PCF may, optionally, use service experience analytics per UP path, as defined in clause 6.4.3 of TS 23.288 [50], to provide a an updated list of DNAI(s) to the SMF.
If Npcf_PolicyAuthorization_Update service operation is invoked, the PCF is required to update the subscription resource. The Npcf_PolicyAuthorization_Update service operation may include an updated notification target address. The updated subscription resource is used by the target AF.
When a PCC rule is received from the PCF, the SMF may take appropriate actions, when applicable, to reconfigure the User plane of the PDU Session.
In the case of AF influence on traffic routing, examples of actions are:
- The SMF may consider service experience analytics and/or DN Performance analytics per UP path (i.e. including UPF and/or DNAI and/or AS instance) as defined in clauses 6.4.3 and 6.14.3, respectively, of TS 23.288 [50] before taking any actions.
- Determining a target DNAI and adding, replacing or removing UPF(s) in the data path, e.g. to act as UL CL, Branching Point and/or PDU Session Anchor e.g. as described in clause 4.3.5.
- Allocate a new Prefix to the UE (when IPv6 multi-Homing applies).
- Updating the UPF regarding the target DNAI with AF influence on traffic routing control parameters as described in clause 5.6.7.1 of TS 23.501 [2].
- Subscribe to notifications from the AMF for an Area of Interest via Namf_EventExposure_Subscribe service operation.
- Determining whether to relocate PSA UPF considering the user plane latency requirements provided by the AF (see clause 6.3.6 of TS 23.548 [74]).
In the case of AF influence on Service Function Chaining, the SMF may take appropriate actions to enforce the N6-LAN traffic steering control:
- Provide N6-LAN traffic steering control parameters to UPF as described in clause 5.6.16 of TS 23.501 [2].
In the case of AF influence on Handling of Payload Headers, the SMF may take appropriate actions by provisioning UPF with the Header Handling Control information, as described in clause 5.6.17 of TS 23.501 [2]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.5 Processing AF requests to influence traffic routing for HR-SBO session | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.5.1 General | Processing an AF requests to influence traffic routing for HR-SBO session are based on procedure described in clauses 4.3.6.5.2 - 4.3.6.5.5. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.5.2 AF traffic influence request includes HPLMN DNN, HPLMN S-NSSAI | Figure 4.3.6.5.2-1: Processing an AF request to influence traffic routing for HR-SBO session when AF provides HPLMN DNN and HPLMN S-NSSAI
0a. AF subscribes to H-SMF regarding the change of serving PLMN change event and is notified after V-SMF insertion/inter-PLMN V-SMF change as described in clause 6.7.2.6 of TS 23.548 [74]. The notification takes place as soon as the H-SMF has received an indication of Handover Complete.
0b. V-SMF supporting HR-SBO subscribes to notification of AF request by invoking Nnef_TrafficInfluenceData_Subscribe service from V-NEF (Data Set = Application Data; Data Subset = AF traffic influence request information; Data Key = HPLMN S-NSSAI and HPLMN DNN and HPLMN ID and UE IP address) and (Data Set = Application Data; Data Subset = AF traffic influence request information; Data Key = HPLMN S-NSSAI and HPLMN DNN and HPLMN ID and "any UE" indication) and (Data Set = Application Data; Data Subset = AF traffic influence request information; Data Key = HPLMN S-NSSAI and HPLMN DNN and SUPI).
NOTE 1: Using SUPI as a Data Key is for the case when AF request targeting GPSI.
- For any UE, the V-SMF supporting HR-SBO performs the above subscription using HPLMN ID, S-NSSAI and DNN and "any UE" indication as Data Key.
- For individual UE, when a PDU Session is authorized for HR-SBO as described in clause 6.7 of TS 23.548 [74], the V-SMF serving the PDU Session performs the above subscription using HPLMN ID, HPLMN S-NSSAI and DNN and UE IP address; and HPLMN S-NSSAI and HPLMN DNN and SUPI as Data Key.
V-NEF subscribes to notification of AF request by invoking Nudr_DM_Subscribe service from V-UDR using the same Data Set and Data Key as V-SMF.
1. As it is step 1 of Figure 4.3.6.2-1.
2. The AF sends its traffic influence request to V-NEF with HPLMN DNN and S-NSSAI of the UE. The AF request also includes HPLMN ID and UE IP address, or GPSI, or HPLMN ID and "any UE" indication as described in clause 4.3.6.1.
NOTE 2: To target an individual UE address, step 1 of Figure 4.3.6.4-1 is used with the above details.
3. Based on the provided HPLMN ID, HPLMN DNN and S-NSSAI as part of traffic influence request, V-NEF identifies that the AF request is targeting a HR-SBO PDU session via VPLMN as described in clause 4.3.6.1.
4a. V-NEF creates/updates/delete the information at V-UDR as follows:
- (in the case of Nnef_TrafficInfluence_Create or Update): The V-NEF stores the AF request information in the V-UDR (Data Set = Application Data; Data Subset, Data Key = AF Transaction Internal ID, HPLMN ID (not used if SUPI is used), HPLMN S-NSSAI and DNN and either, SUPI or UE IP address or "any UE" indication). The Data Subset identifies whether the information relates to AF traffic influence request information for traffic routing, as described in Table 5.2.12.2.1-1.
- (in the case of Nnef_TrafficInfluence_delete): The V-NEF deletes the AF requirements in the V-UDR (Data Set = Application Data; Data Subset, Data Key = AF Transaction Internal ID). The Data Subset identifies whether the information relates to AF traffic influence request information for traffic routing.
4b. The V-NEF responds to the AF.
5. The V-UDR notifies the subscribed V-NEF of the AF traffic influence request information.
6. The V-NEF notifies the subscribed V-SMF of the AF traffic influence request information.
7. As similar to step 6 of Figure 4.3.6.2-1, when V-SMF receives notification from V-NEF, the V-SMF may take appropriate actions to reconfigure the User plane of the PDU Session; and as step 7 of Figure 4.3.6.2-1, V-SMF sends Nsmf_PDUSession_SMContextStatusNotify to AMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.5.3 AF traffic influence request without HPLMN DNN, S-NSSAI information for a single UE, with private IP address or public IP address owned by VPLMN | Figure 4.3.6.5.3-1 Processing AF requests in VPLMN to influence traffic of a HR-SBO PDU Session
1. During HR-SBO PDU Session establishment procedure, the V-SMF provides an indication that the UE PDU session is working in HR-SBO mode, SUPI of the UE and the HPLMN DNN and HPLMN S-NSSAI of the PDU session to UPF (i.e. L-PSA in VPLMN). During the lifetime of the PDU session, if L-PSA changed or added, the V-SMF provides the above information to the new L-PSA.
2. V-SMF subscribes to Traffic Influence data to V-NEF (Data Set = Application Data; Data Subset = AF traffic influence request information. Data Key = HPLMN ID, HPLMN S NSSAI and DNN and UE IP address).
NOTE 1: HPLMN ID is derived from the SUPI by V-SMF.
3. The V-NEF subscribes to Traffic Influence data using the same Data Set and Data Key as step 2.
4. AF influence on traffic routing including IP address of the UE (e.g. public IP address within an IP address range owned by VPLMN, or VPLMN private IP address) known to the AF.
5. The V-NEF determines if the AF influence request relates to a HR-SBO according to clause 4.3.6.1.
6. If the step 4 was a create operation, V-NEF contacts UPF to get information related to the IP address received from AF (i.e. IEs provided by V-SMF in step 1, and additional private IP before NAT for NATed IP case) by invoking Nupf_GetUEPrivateIPaddrAndIdentifiers_Get request (IP address) as described in steps 3-6 of clause 4.15.10.
7 UPF returns the UE IP address, SUPI of the UE, an indication on if HR-SBO applies, and HPLMN DNN and HPLMN S-NSSAI for the PDU session, in the response.
8. The V-NEF creates/updates/deletes the AF Traffic Influence data in the UDR (Data Set = Application Data; Data Subset = AF traffic influence request information. Data Key = HPLMN ID, HPLMN S NSSAI and DNN and UE IP address).
NOTE 2: HPLMN ID is derived from the SUPI by V-NEF.
9. UDR notifies to V-NEF that Traffic Influence Data has been created/updated/deleted.
10. V-NEF notifies V-SMF of the created/updated/deleted Traffic Influence data.
11. Based on the Traffic Influence data the V-SMF may do traffic routing reconfiguration. Examples of such are listed in step 6 of clause 4.3.6.2.
NOTE 3: The V-NEF instance used by V-SMF and AF can be different. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.5.4 AF traffic influence request without HPLMN DNN, S-NSSAI information for a single UE, with UE IP address owned and assigned by HPLMN | Figure 4.3.6.5.4-1: Processing AF requests in VPLMN to influence traffic of a HR-SBO PDU Session
1. If HR-SBO applies to the PDU Session, the H-SMF may provide an indication that the PDU Session is working in HR-SBO mode, SUPI, HPLMN DNN and S-NSSAI of the PDU session to UPF.
2. V-SMF subscribes to Traffic Influence data from V-NEF (Data Set = Application Data; Data Subset = AF traffic influence request information. Data Key = HPLMN ID, HPLMN S NSSAI and DNN and UE IP address).
NOTE 1: HPLMN ID is derived from the SUPI by V-SMF.
3. The V-NEF subscribes to Traffic Influence data using the same Data Set and Data Key as step 2.
4. AF request for traffic routing including IP address of the UE know by the AF (i.e. public IP address within an IP address range owned by HPLMN).
5. The V-NEF determines if the AF influence request relates to a HR-SBO according to clause 4.3.6.1.
If service operation is a create, then the procedure continues at step 6, else it continues at step 10.
6. V-NEF contacts H-NEF to get data related to the IP address received from AF by Nnef_UEId_Get request service operation (IP address).
7. H-NEF contacts H-UPF to get data related to the IP address received from AF by Nupf_GetUEPrivateIPaddrAndIdentifiers_Get request (IP address).
8 H-UPF returns the UE IP address, and optionally HPLMN DNN and S-NSSAI for the PDU session, in the response. If H-UPF does not provide HPLMN DNN and S-NSSAI, H-NEF may be configured with those parameters.
9. H-NEF responds with Nnef_UEId_Get response (UE IP address, and optionally HPLMN DNN and S-NSSAI). If H-NEF does not provide the HPLMN DNN and S-NSSAI in the response, V-NEF needs to be configured with those parameters.
NOTE 2: Whether H-NEF or V-NEF is responsible for assigning HPLMN DNN and S-NSSAI depends on roaming agreements.
10. The V-NEF creates/updates/deletes the AF Traffic Influence data in the UDR (Data Set = Application Data; Data Subset = AF traffic influence request information. Data Key = HPLMN ID, HPLMN S NSSAI and DNN and UE IP address).
11. UDR notifies to V-NEF that Traffic Influence Data has been created/updated/deleted.
12. V-NEF notifies V-SMF of the created/updated/deleted Traffic Influence data.
13. Based on the Traffic Influence data the V-SMF may do traffic routing reconfiguration. Examples of such are listed in step 6 of clause 4.3.6.2.
NOTE 3: The V-NEF instance used by V-SMF and AF can be different. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.6.5.5 AF traffic influence request for GPSI or any UE | If target is GPSI, the NEF determines PLMN owning the GPSI (i.e. HPLMN of the UE). If the PLMN owning the GPSI is not the serving PLMN of the NEF, the NEF determines that HR-SBO applies for the PDU session. Then the NEF in VPLMN contacts NEF of the PLMN owning the GPSI by invoking Nnef_UEId_Get service, and the NEF of the PLMN owning the GPSI retrieves the SUPI from UDM, and assigns HPLMN DNN and S-NSSAI based on local configuration, and provides these parameters to the NEF of VPLMN.
NOTE: If the GPSI is in the form of External Identifier (see TE 23.003 [33]) the NEF can determine the HPLMN of UE based on Domain Identifier in the GPSI.
When SUPI is retrieved by NEF in VPLMN or "any UE" is provided by AF, the procedure of clause 4.3.6.2 applies with the following differences:
- SMF and PCF(s) in Figure 4.3.6.2-1 are replaced with V-SMF
- Step 0: PCF(s) is replaced with V-SMF(s) and V-SMF(s) may add HPLMN ID in the subscription Data Key if target is "any UE". V-SMF subscribes to UDR via NEF in VPLMN.
- Step 2: AF always uses NEF. AF may add HPLMN ID, HPLMN DNN and HPLMN S-NSSAI in the request.
- Step 2a (new step): V-NEF interacts with H-NEF as described above.
- Step 4: UDR notifies V-SMF via NEF.
- Step 5: Does not apply. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.7 CN-initiated selective deactivation of UP connection of an existing PDU Session | The following procedure is used to deactivate UP connection (i.e. data radio bearer and N3 tunnel) for an established PDU Session of a UE in CM-CONNECTED state.
For an always-on PDU Session, the SMF should not configure the UPF to report inactivity.
Figure 4.3.7-1: CN-initiated deactivation of UP connection for an established PDU Session
1. The SMF determines that the UP connection of the PDU Session can be deactivated in following cases:
- During handover procedure, if all the QoS Flows of a PDU Session are rejected by the target NG-RAN (as described in clause 4.9.1), or if a PDU Session is failed to setup indicated by the AMF (see step 7 of clause 4.9.1.3.3). SMF proceeds with step 2 and step 3, the steps 5 to 9 are skipped;
- The UPF detects that the PDU Session has no data transfer for a specified Inactivity period as described in clause 4.4.2.2;
- For PDU sessions belonging to a network slice that is in the Partially Allowed NSSAI (see clause 5.15.17 in TS 23.501 [2]), or with Network Slice Area of Service not matching deployed Tracking Areas (see clause 5.15.18 of TS 23.501 [2]) the AMF notifies to the SMF that it has detected that the UE moved out of the network slice area of support or availability;
- For a LADN PDU Session, the AMF notifies to the SMF that the UE moved out of the LADN service area; or
- The AMF notifies to the SMF that the UE moved out of the Allowed Area.
The SMF may decide to release the UPF of N3 terminating point. In that case the SMF proceeds with step 2 and step 3. Otherwise, if the SMF decides to keep the UPF of N3 terminating points, the SMF proceeds with step 4. To assist SMF in this decision the SMF may make use of UE presence pattern in LADN service area based on UE mobility analytics from the NWDAF as described in clause 6.7.2 of TS 23.288 [50].
The SMF may make use of UE Communication analytics provided by NWDAF, as described in clause 6.7.3 of TS 23.288 [50], to determine the value of an Inactivity Timer for a PDU Session provided to the UPF.
2. The SMF may initiate an N4 Session Release procedure to release the intermediate UPF of N3 terminating point. If there are multiple intermediate UPFs, this step can be performed for each UPFs to be released. The SMF needs to initiate N4 Session Modification procedure to the UPF (i.e. N9 terminating point or PDU Session Anchor) connecting to the released UPF in step 3.
3. If the intermediate UPF(s) of N3 terminating point is released in step 2, the SMF initiates an N4 Session Modification procedure towards the UPF (PDU Session Anchor or another intermediate UPF) connecting to the released UPF, indicating the need to remove CN Tunnel Info for N9 tunnel of the corresponding PDU Session. In this case, the UPF connecting to the released UPF buffers the DL packets for this PDU Session or drops the DL packets for this PDU session or forwards the DL packets for this PDU session to the SMF, based on buffering instruction provided by the SMF as described in clause 5.8.3.2 or clause 5.8.3.3 of TS 23.501 [2]. If the PDU Session corresponds to a LADN and the UE moved out of the LADN service area, the SMF may notify the UPF connecting to the released UPF to discard downlink data for the PDU Sessions and/or to not provide further Data Notification messages.
Otherwise, N4 Session Modification procedure occurs toward N3 terminating point.
4. If the UPF of N3 terminating point is not released in step 2, the SMF initiates an N4 Session Modification procedure indicating the need to remove AN Tunnel Info for N3 tunnel of the corresponding PDU Session. In this case, the UPF buffers the DL packets for this PDU Session or drops the DL packets for this PDU session or forwards the DL packets for this PDU session to the SMF, based on buffering instruction provided by the SMF as described in clause 5.8.3.2 or clause 5.8.3.3 of TS 23.501 [2]. If the PDU Session corresponds to a LADN and the UE moved out of the LADN service area, the SMF may notify the UPF to discard downlink data for the PDU Sessions and/or to not provide further Data Notification messages.
5. The SMF invokes the Namf_Communication_N1N2MessageTransfer service operation (PDU Session ID, N2 SM Information (N2 Resource Release Request (PDU Session ID))) to release the NG-RAN resources associated with the PDU Session.
6. The AMF sends the N2 PDU Session Resource Release Command including N2 SM information (N2 Resource Release Request (PDU Session ID)) received from the SMF via N2 to the NG-RAN.
7. The NG-RAN may issue NG-RAN specific signalling exchange (e.g. RRC Connection Reconfiguration) with the UE to release the NG-RAN resources related to the PDU Session received from the AMF in step 5. When a User Plane connection for a PDU Session is released, the AS layer in the UE indicates it to the NAS layer.
If the UE is in RRC_INACTIVE state, this step is skipped. When the UE becomes RRC_CONNECTED state from RRC_INACTIVE state, the NG-RAN and UE synchronize the released radio resources for the deactivated PDU Session as described in TS 36.331 [16] and TS 38.331 [12].
8. The NG-RAN acknowledges the N2 PDU Session Resource Release Command to the AMF including N2 SM Resource Release Ack (User Location Information, Secondary RAT Usage Data).
9. The AMF invokes the Nsmf_PDUSession_UpdateSMContext service operation (N2 SM Information(Secondary RAT Usage Data)) to acknowledge the Namf service received in step 5. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.3.8 Change of Network Slice instance for PDU Sessions | When a Network Slice instance for the existing PDU Session is required to be changed as described in clause 5.15.5.3 of TS 23.501 [2], the AMF deletes the old NSI ID corresponding to the Network Slice instance that is congested or no longer available and informs the SMF of the PDU Session(s) which is selected by using such old NSI ID to release this PDU session with appropriate cause value as described in clause 4.3.4.2. If so, the SMF triggers the impacted UE(s) to establish new PDU session(s) associated with the same S-NSSAI by using the procedures for PDU Session(s) of SSC mode 2 or SSC mode 3 as defined in clause 4.3.5.
When UE initiates PDU Session Establishment procedure, the AMF may select a new Network Slice instance for the given S-NSSAI during PDU Session Establishment by querying the NSSF as described in the clause 4.3.2.2.3. If there is no Network Slice instance available, the network may change the related network slice(s) for the UE as described in clause 5.15.5.2.2 of TS 23.501 [2]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4 SMF and UPF interactions | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.1 N4 session management procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.1.1 General | N4 session management procedures are used to control the functionality of the UPF. The SMF can create, update and remove the N4 session context in the UPF, which is described in clause 5.8.2 of TS 23.501 [2].
The following N4 session management procedures exist: N4 Session Establishment procedure, N4 session Modification procedure and N4 session release procedure. All of them are initiated by the SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.1.2 N4 Session Establishment procedure | The N4 Session Establishment procedure is used to create the initial N4 session context for a PDU Session at the UPF. The SMF assigns a new N4 Session ID and provides it to the UPF. The N4 Session ID is stored by both entities and used to identify the N4 session context during their interaction. The SMF also stores the relation between the N4 Session ID and PDU Session for a UE.
Figure 4.4.1.2-1: N4 Session Establishment procedure
1. SMF receives the trigger to establish a new PDU Session or change the UPF for an established PDU Session.
2. The SMF sends an N4 session establishment request message to the UPF that contains the structured control information which defines how the UPF needs to behave. If the SMF is a V-SMF and it supports HR-SBO for the PDU session, V-SMF includes SUPI, HPLMN DNN and S-NSSAI, and an indication that the UE PDU session is working in HR-SBO mode.
If the UPF supports Nupf_EventExposure service, the SMF should include DNN and S-NSSAI in the N4 Session Establishment procedure.
NOTE 1: If SMF does not provide DNN and S-NSSAI to UPF it could result in rejections for the Nupf_EventExposure_Subscribe service operations, unless UPF is configured with a DNN and S-NSSAI for a specific IP address range.
3. The UPF responds with an N4 session establishment response message containing any information that the UPF has to provide to the SMF in response to the control information received.
If the UPF (by configuration or other means) utilizes an NWDAF, UPF adds the NWDAF serving the UE identified by the NWDAF instance ID. Per NWDAF service instance the Analytics ID(s) are also included.
NOTE 2: The SMF can use this NWDAF related information and can forward it to the PCF using the SMF initiated SM Policy Modification procedure, as a result of a Policy Control Request Trigger.
4. The SMF interacts with the network function which triggered this procedure (e.g. AMF or PCF). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.1.3 N4 Session Modification procedure | The N4 Session Modification procedure is used to update the N4 session context of an existing PDU Session at the UPF, which is executed between SMF and UPF whenever PDU Session related parameters have to be modified.
Figure 4.4.1.3-1: N4 Session Modification procedure
1. SMF receives the trigger to modify the existing PDU Session.
2. The SMF sends an N4 session modification request message to the UPF that contains the update for the structured control information which defines how the UPF needs to behave.
3. The UPF identifies the N4 session context to be modified by the N4 Session ID. Then, the UPF updates the parameters of this N4 session context according to the list of parameters sent by the SMF. The UPF responds with an N4 session modification response message containing any information that the UPF has to provide to the SMF in response to the control information received.
4. The SMF interacts with the network entity which triggered this procedure (e.g. AMF or PCF). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.1.4 N4 Session Release procedure | The N4 session release procedure is used to remove the N4 session context of an existing PDU Session at the UPF.
Figure 4.4.1.4-1: N4 Session Release procedure
1. SMF receives the trigger to remove the N4 session context for the PDU Session.
2. The SMF sends an N4 session release request message to the UPF.
3. The UPF identifies the N4 session context to be removed by the N4 Session ID and removes the whole session context. The UPF responds with an N4 session release response message containing any information that the UPF has to provide to the SMF.
4. The SMF interacts with the network entity which triggered this procedure (e.g. AMF or PCF). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.2 N4 Reporting Procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.2.1 General | The N4 reporting procedure is used by the UPF to report events to the SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.2.2 N4 Session Level Reporting Procedure | This procedure is used by the UPF to report events related to an N4 session for an individual PDU Session. The triggers for event reporting were configured on the UPF during N4 Session Establishment/Modification procedures by the SMF.
Figure 4.4.2.2-1: N4 Session Level Reporting procedure
1. The UPF detects that an event has to be reported. The reporting triggers include the following cases:
(1) Measurement information reporting (Usage Report).
Measurement information shall be collected in the UPF and reported to the SMF as defined in clause 5.8 and clause 5.12 of TS 23.501 [2].
NOTE 1: The Usage Report is also used for the reporting of other events or information. For details refer to clause 7.5.8.3 of TS 29.244 [69].
(2) Start of traffic detection (Usage Report).
When traffic detection is requested by SMF and the start of traffic is detected for a Packet Detection Rule (PDR) as described in clause 5.8 of TS 23.501 [2], the UPF shall report the start of traffic detection to the SMF and indicate the corresponding PDR rule ID.
(3) Stop of traffic detection (Usage Report).
When traffic detection is requested by SMF and the end of traffic is detected for a PDR as described in clause 5.8 of TS 23.501 [2], the UPF shall report the stop of traffic detection to the SMF and indicate the corresponding PDR rule ID.
(4) Detection of 1st downlink packet for a QoS Flow of a PDU Session with UP Connection deactivated (Downlink Data Report).
When UPF receives the first downlink packet for a QoS Flow but no N3/N9 tunnel for downlink data transmission exists and the buffering is performed by the UPF, it shall report the detection of 1st downlink packet to SMF also indicating the QoS Flow for which the downlink packet was received (for the purpose of downlink data notification). The UPF shall also report the DSCP of the packet if the PDU Session type is IP (to support the Paging Policy Differentiation feature described in clause 5.4.3 of TS 23.501 [2]).
(5) Detection of PDU Session Inactivity for a specified period (User Plane Inactivity Report).
When an Inactivity Timer for a PDU Session is provided by SMF during N4 Session Establishment/Modification procedure and the UPF detects the PDU Session has no data transfer for a period specified by the Inactivity Timer, it shall report PDU Session Inactivity to the SMF.
NOTE 2: As described in clause 4.3.7, an Inactivity Timer to the UPF is not provided by the SMF for always-on PDU Sessions.
(6) QoS Monitoring Report (Session Report).
When the QoS Monitoring is enabled for the QoS Flow, performs the necessary actions as described in clauses 5.8.2.18 and 5.45 of TS 23.501 [2]. The details about when and how the UPF sends the QoS Monitoring reports are described in clause 5.8.2.18 of TS 23.501 [2]. When receiving the QoS monitoring reports from the UPF, the SMF sends the reports to the target NF according to the information for QoS Monitoring received in the PCC rules as described in TS 23.503 [20].
(7) TSC Management Information available (TSC Management Information).
When TSC management information is available, the UPF shall provide the TSC management information in the TSC Management Information to the SMF as defined in clause 5.8.5.14 of TS 23.501 [2].
(8) Discard Downlink Traffic detection (Downlink Data Report).
When discarded downlink traffic detection is requested by SMF for a PDR and the first downlink packet is discarded after being buffered for this PDR as described in clause 5.8.3.2 of TS 23.501 [2], the UPF shall report the discarded downlink traffic detection to the SMF and indicate the corresponding PDR rule ID (for the purpose of downlink data delivery status notification).
(9) Buffered Downlink Traffic detection (Downlink Data Report).
When buffered downlink traffic detection is requested by SMF for a PDR and the first downlink packet is buffered for this PDR as described in clause 5.8.3.2 of TS 23.501 [2], the UPF shall report the buffered downlink traffic detection to the SMF and indicate the corresponding PDR rule ID (for the purpose of downlink data delivery status notification).
(10) N6 Traffic Parameter Measurement Report (Session Report).
When the N6 Traffic Parameters measurement report is requested by SMF for a QoS Flow as described in clause 5.37.8.2 of TS 23.501 [2], the UPF shall report to the SMF the N6 Traffic Parameter(s) for the specified QoS Flow (i.e. the N6 jitter range associated with the DL periodicity and conditionally, the UL/DL periodicity).
2. The UPF sends an N4 session report message (N4 Session ID, list of [Usage Report, Downlink Data Report, Session Report, User Plane Inactivity Report, TSC Management Information]) to the SMF.
3. The SMF identifies the N4 session context based on the received N4 Session ID and applies the reported information for the corresponding PDU Session. The SMF responds with an N4 session report ACK message. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.3 N4 Node Level Procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.3.1 N4 Association Setup Procedure | The N4 Association Setup procedure is used to setup an N4 association between the SMF and the UPF, to enable the SMF to use the resources of the UPF subsequently to establish N4 Sessions. The SMF and UPF may exchange the supported functionalities on each side during these procedures.
The setup of an N4 association is initiated by the SMF. SMF and UPF may additionally support an N4 association initiated by UPF.
The SMF should only establish an N4 association with a UPF that supports F-TEID allocation at the UPF.
The SMF initiates the N4 Association Setup procedure to request to setup an N4 association towards a UPF prior to establishing a first N4 session on this UPF.
When receiving an N4 Association Setup Request, the UPF shall send an N4 Association Setup Response.
N4 Association Setup procedure can be used to request the UPF to measure and report the clock drift between the external time and 5GS time for one or more external time domains by provisioning External Clock Drift Report and providing the corresponding Time Domain number(s) as specified in TS 29.244 [69]. The SMF may omit the Time domain number in the request; in this case the UPF shall report the clock drift for all Time domains the UPF is connected to.
N4 Association Setup procedure may be used to request the UPF to measure the N6 delay for the connection between the UPF and the endpoint in the DN (e.g. EAS) as described in clause 5.8.2.23 of TS 23.501 [2].
Figure 4.4.3.1-1: N4 association setup procedure initiated by SMF
The UPF may initiate the N4 Association Setup procedure to request to setup an N4 association towards a SMF prior to establishing a first N4 session on this UPF.
When receiving an N4 Association Setup Request, the SMF shall send an N4 Association Setup Response.
Figure 4.4.3.1-2: N4 association setup procedure initiated by UPF |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.3.2 N4 Association Update Procedure | The N4 Association Update procedure shall be used to modify an existing N4 association between the SMF and the UPF. It may be initiated by the UPF or by the SMF to update the supported features or available resources of the UP function.
N4 Association Update procedure can be used by the SMF to update the provisioning of External Clock Drift Report as specified in clause 4.4.3.1.
N4 Association Update procedure may be used by the SMF to provide or update the provisioning of measurement assistance information of N6 delay for the connection between the UPF and the endpoint in the DN (e.g. EAS) as specified in clause 5.8.2.23 of TS 23.501 [2].
Figure 4.4.3.2-1: SMF initiated N4 association update procedure
Figure 4.4.3.2-2: UPF initiated N4 association update procedure |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.3.3 N4 Association Release Procedure | The N4 Association Release procedure shall be used to terminate the N4 association between the SMF and the UPF due to e.g. OAM reasons. The N4 Association Release Request may be initiated by the SMF or UPF.
Figure 4.4.3.3-1: SMF initiated N4 association release procedure
Figure 4.4.3.3-2: UPF initiated N4 association release procedure |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.3.4 N4 Report Procedure | The N4 Report procedure shall be used by the UPF to report information to the SMF which is not related to a specific N4 session, e.g. to report a user plane path failure affecting all the N4 sessions towards a remote GTP-U peer.
N4 Report procedure can be used by the UPF to report the clock drift between the external time and 5GS time for one or more external working domains as specified in TS 29.244 [69].
N4 Report procedure may be used by the UPF to report the N6 delay measurements for the connection between the UPF and the endpoint in the DN as described in clause 5.8.2.23 of TS 23.501 [2].
Figure 4.4.3.4-1: N4 report procedure
The UPF detects that an event has to be reported and starts the procedure by sending an N4 Report message (UPF ID, list of [event, status]) to the SMF. The SMF responds with an N4 report ACK message (SMF ID). The event parameter contains the name of the event and UPF ID. The status parameter contains the actual information the control plane function is interested in. If the UPF detects clock drifting between 5G time and one or more time working domains, the UPF reports the corresponding external domain number and the time offset and cumulative rate Ratio according to the provisioning from the SMF as defined in clause 5.27.2 of TS 23.501 [2]. If the UPF detects that the configured reporting periodicity or reporting threshold is reached on N6 delay measurements, the UPF reports the corresponding N6 delay measurement information and the corresponding endpoint address as defined in clause 5.8.2.23 of TS 23.501 [2]. The UPF includes the Network Instance (if available) and the combination of DNN and S-NSSAI (if available) in the report.
NOTE: When the UPF supports more than one NW-TT, the SMF can use the Network Instance or DNN/S-NSSAI to associate the report with the corresponding N4 sessions and NW-TT. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.3.5 N4 PFD management Procedure | This N4 procedure is used by the SMF to provision or remove all PFD(s) belonging to an Application Identifier in the UPF. PFD sets belonging to different Application Identifiers can be managed with the same PFD management request message.
The N4 PFD management procedure is a node level procedure, i.e. independent of any PDU Session.
Figure 4.4.3.5-1: PFD management in the UPF
1. The SMF is triggered to provision or remove the PFD set belonging to an Application Identifier in the following cases:
When the caching timer expires and there's no active PCC rule that refers to the corresponding application identifier, the SMF informs the UPF to remove the PFD(s) identified by the Application Identifier.
When a PCC rule is provided for an Application Identifier corresponding to the PFD(s) that are not already provided to the UPF, the SMF shall provide the PFD(s) to the UPF (if there are no PFD(s) cached, the SMF retrieves them from the NEF (PFDF), as described in TS 23.503 [20]).
When any update of the PFD(s) is received from NEF (PFDF) and there are still active PCC rules in UPF for the Application Identifier.
2. The SMF sends a PFD management request to the UPF to provision/remove the PFD(s) corresponding to the Application Identifier(s).
3. The UPF updates the PFD(s) according to the request and acknowledges by responding with a PFD management response message. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.4.4 SMF Pause of Charging procedure | The SMF Pause of Charging procedure aims for the SMF charging and usage monitoring data to more accurately reflect the downlink traffic actually sent to the AN.
The following are example triggers for the SMF to enable the pause of charging
- Operator specified criteria/threshold (e.g. number/fraction of packets/bytes dropped at UPF in downlink since last time the N3 tunnel towards the AN was released). The SMF requests the UPF to notify the SMF whenever the criteria/threshold is met.
- Indication of "Radio Link Failure" (see clause 4.2.6).
Based on operator policies, if the trigger for the SMF to enable the pause of charging is met, the SMF shall pause the charging. When the SMF pauses charging the following applies:
- Towards the UPF(s) where the Usage Reporting is configured, the SMF shall modify the Usage Reporting Rules for the PDU Session so that the usage collection for charging is stopped.
- The SMF may request the UPF to limit the rate of downlink traffic sent to the downstream UPF or the AN.
NOTE 1: A consequence of using this procedure is that SMF charging data does not correspond to the volume that traversed the UPF and it is therefore not possible to count the downlink packets dropped between the PDU Session Anchor (PSA) UPF and the downstream UPF.
NOTE 2: In this release of the specification, pause of charging procedure does not address the issue of packets dropped by the NG-RAN.
In home routed roaming scenarios, based on operator's policy, the H-SMF may indicate to the V-SMF if the feature is to be enabled on a per PDU Session basis. This is indicated to the V-SMF by a "PDU Session Charging Pause Enabled" Indication in the Nsmf_PDUSession_Create Response during the PDU Session Establishment procedure. This is an indication to the V-SMF that when the criteria for pause of SMF charging are met at the VPLMN (as described further down in this clause) charging at the H-SMF can be paused.
The H-SMF shall stop any charging and usage monitoring actions for the PDU Session upon receiving a "Start Pause of Charging" Indication in a Nsmf_PDUSession_Update request from the V-SMF. When the H-SMF receives a Nsmf_PDUSession_Update request for a PDU Session with a "Stop Pause of Charging" Indication, then the H-SMF shall resume charging for the PDU Session.
Regardless of operator policy/configuration, the downlink user plane packets received at the (V-)UPF shall trigger Data Notifications as described in clause 4.2.3.3.
When the (V-)SMF receives a Nsmf_PDUSession_UpdateSMContext request or a Namf_EventExposure_Notify about UE reachability, the (V-)SMF shall consider the PDU Session charging as being unpaused if it had been paused previously.
Figure 4.4.4-1: SMF Pause of charging procedure
1. The UPF receives downlink data packets for a PDU Session that does not have an N3 tunnel and the UPF sends data notification to the SMF. The packets are buffered or discarded in the UPF based on operator policy.
2. Based on operator policy/configuration the SMF triggers the procedure to pause PDU Session charging. Triggering criteria are based on SMF operator policy/configuration.
3. SMF sends a N4 Session Modification Request message to the UPF where the Usage Reporting is configured, modifying the Usage Reporting Rules for the PDU Session so that the usage collection for charging is stopped. In home routed roaming scenarios, the V-SMF sends a Nsmf_PDUSession_Update request to the H-SMF with a "Start Pause of Charging" Indication. The H-SMF then requests the H-UPF to stop usage collection as mentioned before.
4. UPF confirms with a N4 Session Modification Response message. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.5 User Profile management procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.5.1 Subscriber Data Update Notification to AMF | Whenever the user profile is changed for a user in the UDM/UDR and the changes affect the user profile in the AMF, the UDM shall notify these changes to the affected AMF by the means of invoking Nudm_SDM_Notification service operation. Then the AMF adds or modifies the user profile.
The Nudm_SDM_Notification service operation specified in clause 5.2.3.3 is used by the UDM to update subscriber data stored in the AMF.
The AMF takes appropriate action according to the changed subscriber data as follows, e.g.:
- initiating an AMF initiated Deregistration procedure if the updated subscription data indicates the UE is not allowed to roam in this network; and
- updating UE context stored at AN to modify the UE-AMBR.
- updating UE context stored at RAN to modify the UE-Slice-MBR corresponding to an S-NSSAI.
- initiating UE Configuration Update procedure as defined in clause 4.2.4.2.
- initiating UE Parameters Update via UDM Control Plane Procedure as defined in clause 4.20.
UDM can also use the Nudm_SDM_Notification service operation to update the Steering of Roaming information stored in the UE via the AMF (i.e. a list of preferred PLMN/access technology combinations and/or Credentials Holder controlled prioritized lists of preferred SNPNs and GINs and/or Credentials Holder controlled prioritized lists of preferred SNPNs and GINs for accessing Localized Services or HPLMN/Credentials Holder indication that 'no change of the above list(s) stored in the UE is needed'). UDM can include an indication for the UE to send an acknowledgement of the reception of this information. The AMF provides the acknowledgement sent from the UE to UDM using the Nudm_SDM_Info service operation. For more details regarding the handling of Steering of Roaming information refer to TS 23.122 [22].
When the subscribed S-NSSAIs change, UDM provides a Network Slicing Subscription Change Indication to the UE via the AMF. Once the AMF updates the UE and obtains an acknowledgment from the UE, the AMF informs the UDM that the UE received the Network Slicing Subscription Change Indication using the Nudm_SDM_Info service operation.
When the CAG information in the subscription data changes, or when the SUPI and PEI association changes, UDM provides a CAG information Subscription Change Indication to the AMF. Once the AMF updates the UE and obtains an acknowledgment from the UE, the AMF informs the UDM that the UE received the CAG information using the Nudm_SDM_Info service operation.
If the AMF received a changed Service Gap Time parameter in the updated subscription data and if the UE has indicated Service Gap Control capability the AMF shall provide the new Service Gap Time value to the UE in the next Registration Accept message, or, if the UE does not send any Registration Request within a certain time period that shall be longer than any MICO mode or eDRX interval used by the UE, the AMF may initiate a UE Configuration Update procedure. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.5.2 Session Management Subscriber Data Update Notification to SMF | Whenever the session management subscriber data is changed for a user in the UDM/UDR and if the SMF subscribed for the update of the session management subscriber data to be notified, the UDM shall notify these changes to the affected SMF by the means of invoking Nudm_SDM_Notification service operation. Then the SMF modifies the session management subscriber data in the UE SM context.
The Nudm_SDM_Notification service operation specified in clause 5.2.3.3 is used by the UDM to update session management subscriber data stored in the SMF.
The SMF initiates appropriate action according to the changed subscriber data, e.g. including:
- initiating an SMF initiated PDU Session Modification procedure; or
- initiating an SMF initiated PDU Session Release procedure. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.5.3 Purge of subscriber data in AMF | An AMF may, as an implementation option, purge the subscriber data and MM context of a UE after the implicit or explicit Deregistration of the UE. In this case, the AMF shall unsubscribe and deregister from the UDM, where UDM may further do corresponding operation from UDR, by the means of following "Purge of subscriber data in AMF" procedure.
Figure 4.5.3-1: Purge of Subscriber Data in AMF
1. After purging the subscriber data and MM context of a deregistered UE, the AMF unsubscribes to changes to subscription data using Nudm_SDM_Unsubscribe request operation (see clause 5.2.3.3.4), for the data the AMF has previously subscribed (see clause 4.2.2.2.2, step 14b). The UDM unsubscribes the AMF from the data indicated.
The UDM may unsubscribe to changes to subscription data from UDR by using Nudr_DM_Unsubscribe for the data the UDM has previously subscribed (see clause 4.2.2.2.2, step 14b).
2. The UDM sends a response back using Nudm_SDM_Unsubscribe response operation.
3. The AMF deregisters from UDM using Nudm_UECM_Deregistration request (SUPI, NF ID, Access Type) operation (see clause 5.2.3.2.3). The UDM may update UE context in UDR by Nudr_DM_Update (SUPI, Subscription Data).
4. The UDM sets the UE Purged flag associated with the Access Type and acknowledges with a Nudm_UECM_Deregistration response operation. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.6 Security procedures | Security procedures for the 5GS are specified in 33.501 [15]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.7 ME Identity check procedure | The AMF initiates Mobile Equipment Identity Check procedure by invoking the N5g-eir_MEIdentityCheck_Get service operation as defined in clause 5.2.4.2.2. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8 RAN-CN interactions | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8.1 Connection Inactive and Suspend procedure | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8.1.1 Connection Inactive procedure | This procedure may be initiated by the serving NG-RAN node when the UE is in CM-CONNECTED with RRC_CONNECTED state and has received the "RRC Inactive Assistance Information" from the AMF as defined in clause 5.3.3.2.5 of TS 23.501 [2]. NG-RAN initiates the transition to RRC_INACTIVE state as defined in TS 38.300 [9].
4.8.1.1a Connection Inactive procedure with CN based MT communication handling
This procedure may be initiated by the serving NG-RAN node when CN based mobile terminating (MT) communication handling is requested for a UE that is configured with eDRX cycle value longer than 10.24 seconds for RRC_INACTIVE state and has at least one PDU session with active user plane as defined in clause 5.31.7 of TS 23.501 [2].
Figure 4.8.1.1a-1: NG-RAN initiated Connection Inactive procedure with CN based MT communication handling
0. The UE is registered in the network with negotiated eDRX parameters for CM-IDLE state and is in CM-CONNECTED with RRC_CONNECTED state. The AMF provides the eDRX values for CM-IDLE state to NG-RAN as part of the RRC Inactive Assistance Information as defined in clause 5.3.3.2.5 of TS 23.501 [2].
1. NG-RAN determines eDRX values for UE in RRC_INACTIVE state and decides to initiate Connection Inactive with CN based MT communication handling as specified in clause 5.31.7.2.4 of TS 23.501 [2].
1a. Optionally the NG-RAN may initiate state transition from RRC_CONNECTED to RRC_INACTIVE with RRC configuring eDRX value as specified in TS 38.300 [9]. The NG-RAN may send the request in step 2 towards CN immediately following step 1a or the NG-RAN may delay this request towards CN as specified in clause 5.31.7.2.1 of TS 23.501 [2].
2. Either immediately following step 1a or after having delayed the request for NG-RAN based on implementation, the NG-RAN sends N2 MT Communication Handling request message to AMF indicating the UE is transitioning to RRC_INACTIVE state. The CN takes the NG-RAN request into consideration and handles MT communication. The NG-RAN also provides the determined eDRX values for RRC_INACTIVE to AMF. The NG-RAN also provides the List of PDU sessions with active user plane resource.
If the NG-RAN receives DL NAS message and the UE is in RRC_INACTIVE with RRC configured eDRX and is considered not reachable, NG-RAN indicates to the AMF a NAS non-delivery and then initiates for the CN to handle mobile terminated (MT) communication.
3. For each of the PDU sessions with user plane resources as indicated by NG-RAN in step 2, the AMF invokes Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID, Cause, Operation type, User Location Information, Age of Location Information, N2 SM Information (Secondary RAT usage data), CN based MT handling indication) towards SMF. The Operation Type is set to a value that indicates to stop user plane DL data transmissions towards the UE and enable data buffering. The SMF starts data buffering for MT data if the data buffering is handled in SMF. Based on local policy and/or an indication from the AMF, e.g. the RAT type is REDCAP or the CN based MT handling indication, the SMF triggers data size reporting in the case of DL data arrival.
4. If data buffering is handled in the UPF, the SMF updates the UPF with proper rules for MT data handling and DL data size reporting in the case of DL data arrival.
5. The SMF sends the Nsmf_PDUSession_UpdateSMContext response.
6. The AMF sends N2 MT Communication Handling response message to NG-RAN acknowledging the NG-RAN request and indicating the AMF has taken the NG-RAN request into account. The AMF considers the UE is in CM-CONNECTED with RRC_INACTIVE state.
7. If the UE connection is not released as specified in step 1a, the NG-RAN initiates state transition from RRC_CONNECTED to RRC_INACTIVE with RRC configuring the eDRX values as specified in TS 38.300 [9]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8.1.2 Connection Suspend procedure | This procedure may be initiated by the serving NG-RAN node when the UE is in CM-CONNECTED and has at least one PDU session with active user plane connection and NG-eNB has received indication from the AMF that User Plane CIoT 5GS Optimisation, as defined in clause 5.31.18 of TS 23.501 [2], is supported for the UE.
Figure 4.8.1.2-1: NG-RAN initiated Connection Suspend procedure
1. NG-RAN to AMF: The NG-RAN sends the N2 Suspend Request message to the AMF, see TS 38.413 [10]. The AMF enters CM-IDLE with Suspend indicator. Context information related to the NGAP UE association, UE Context and PDU session context, necessary to resume the connection is stored in the UE, NG-RAN node and in the AMF. The NG-RAN may include the Suspend cause and the N2 SM information.
If the UE is served by an NG-eNB that supports WUS, then the NG-eNB should include the Information On Recommended Cells And RAN nodes For Paging in the N2 Suspend Request message; otherwise NG-RAN may include the Information On Recommended Cells And NG-RAN For Paging in the N2 Suspend Request message. If available, the AMF shall store this information to be used when paging the UE.
The NG-RAN includes Information for Enhanced Coverage, if available, in the N2 Suspend Request message.
If Service Gap Control is being applied to the UE (see clause 4.3.17.9) and the Service Gap timer is not already running, the Service Gap timer shall be started in the AMF when entering CM-IDLE, unless the connection was initiated after a paging of an MT event, or after a mobility registration procedure without Follow-on Request indication or after a mobility registration procedure for regulatory prioritized services like Emergency services or exception reporting.
2. AMF to SMF: For each of the PDU Sessions in the N2 Suspend Request, the AMF invokes Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID, Cause, Operation type, User Location Information, Age of Location Information, N2 SM Information (Secondary RAT usage data)). The Operation Type is set to "UP Suspend" to indicate suspend of user plane resources for the PDU Session.
3. SMF to UPF: N4 Session Modification Request (AN Tunnel Info to be suspended, Buffering on/off).
The SMF initiates an N4 Session Modification procedure indicating the need to release the tunnel info of AN terminating N3 between AN and UPF. Buffering on/off indicates whether the UPF shall buffer incoming DL PDU or not.
The UPF sends N4 Session Modification Response to acknowledge the SMF request.
The SMF shall maintain the N3 tunnel info (including both AN Tunnel Info and the CN Tunnel Info).
NOTE: The UPF maintains the CN tunnel info as it may receive uplink packets from the AN.
4. SMF to AMF: The SMF sends Nsmf_PDUSession_UpdateSMContext response to the AMF.
5. AMF to NG-RAN: After response for each PDU session in step 4, the AMF sends N2 Suspend Response to NG-RAN to successfully terminate the Connection Suspend procedure initiated by the NG-RAN, see TS 38.413 [10].
6. The NG-RAN sends RRC message to suspend the RRC Connection towards the UE including UE Resume ID, see TS 36.300 [46]).
If Service Gap Control is applied for the UE (see clause 5.31.16 of TS 23.501 [2]) and the Service Gap timer is not already running, the Service Gap timer shall be started in the UE when entering CM-IDLE, unless the connection was initiated as a response to paging of an MT event, or after a mobility registration procedure without Follow-on Request Indication set or after a mobility registration procedure for regulatory prioritized services like Emergency services or exception reporting. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8.2 Connection Resume procedure | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8.2.1 General | The Connection Resume procedure is used by a UE to request the establishment of a secure connection between a UE and the network when the UE is in CM-CONNECTED with RRC_INACTIVE state, or in CM-IDLE with Suspend indicator for the UE supporting User Plane CIoT 5GS Optimisation. The UE initiates the procedure when upper layers or the AS (when responding to RAN paging or upon triggering RNA updates) requests the resumption of a suspended RRC connection. NG-RAN details are specified in TS 38.300 [9] and TS 38.331 [12] for NR and in TS 36.300 [46] and TS 36.331 [16] for E-UTRA. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8.2.2 UE Triggered Connection Resume in RRC_INACTIVE procedure | The Connection Resume procedure is used by the UE in RRC_INACTIVE state, e.g. to transition to RRC_CONNECTED state or for Small Data Transmission while in RRC_INACTIVE as specified in TS 38.300 [9]. Triggers for the UE to initiate this procedure are defined in clause 5.3.3.2.5 of TS 23.501 [2].
Figure 4.8.2.2-1: Connection Resume in RRC_INACTIVE
1. UE to NG-RAN: RRC message (Resume ID).
The UE initiates connection resume from RRC_INACTIVE state, see TS 38.300 [9]. The UE provides its Resume ID needed by the NG-RAN to access the UE's stored Context.
2. [Conditional] NG-RAN performs UE Context Retrieval.
UE Context Retrieval is performed when the UE Context associated with the UE attempting to resume its connection is not locally available at the accessed NG-RAN. The UE Context Retrieval procedure via NG-RAN is specified in TS 38.300 [9].
3. NG-RAN to UE: RRC messages.
NG-RAN determines whether the UE shall be transitioned to RRC_CONNECTED state or kept in RRC_INACTIVE (e.g. the latter in the case of Small Data Transmission as defined in TS 38.300 [9]).
4a. [Conditional] N2 Path switch procedure.
If the accessed NG-RAN is different from the last serving NG-RAN and is able to retrieve the UE Context, the accessed NG-RAN node initiates N2 Path Switch procedure, i.e. steps 1 to 8 of clause 4.9.1.2.2 and including Xn data forwarding.
If the Connection Resume procedure is a response to RAN paging which is triggered by 5GC due to an N2 interface procedure, NG-RAN and 5GC handle the N2 interface procedure as a collision described in clause 4.9.1.2.
If Connection Inactive procedure with CN based MT communication handling (see clause 4.8.1.1a) has been performed previously then when the path switch procedure is performed downlink data or signalling delivery is triggered, if there is any.
If NG-RAN supports PDU Set based handling, then NG-RAN includes PDU Set Based Handling Support Indication in N2 Path Switch request message as described in clause 5.37.5.3 of TS 23.501 [2]. With the indication, the SMF may determine to activate PDU Set based Handling as described in clause 5.37.5.3 of TS 23.501 [2].
4b. [Conditional] N2 Notification:
4b.1 If the accessed NG-RAN is the same as the NG-RAN that configured RRC_INACTIVE and still has the UE context, NG-RAN sends:
- an N2 Notification to the AMF indicating the UE is in RRC_CONNECTED, if an AMF requested N2 Notification (see clause 4.8.3); or
- an MT Communication Handling request to the AMF indicating the UE is now reachable for downlink data and/or signalling if Connection Inactive procedure with CN based MT communication handling (see clause 4.8.1.1a) has been performed previously. The NG-RAN also provides the List of PDU sessions with active user plane resource.
4b.2 The AMF invokes Nsmf_PDUSession_UpdateSMContext Request towards SMF indicating the Downlink data delivery for each PDU session with active user plane as indicated by NG-RAN in step 4b.1, if the AMF has requested data buffering as described in clause 4.8.1.1a.
4b.3 N4 session modification procedure is triggered by the SMF. If data buffering is handled in the UPF, the SMF updates the UPF with appropriate rules to trigger data delivery.
4b.4 The SMF sends the Nsmf_PDUSession_UpdateSMContext response.
4b.5 The AMF sends the N2 MT Communication Handling response message to NG-RAN.
If NG-RAN determines that the connection resume is for Small Data Transmission as defined in TS 38.300 [9] and step 4a or steps 4b.1 to 4b.5 have been performed, then NG-RAN keeps the UE in RRC_INACTIVE state and the UL/DL Small Data are transferred via the NG-RAN. Based on the procedures defined in TS 38.300 [9], if the UE is re-configured with RRC Inactive with eDRX>10.24s, the NG-RAN may send an N2 message to 5GC as described in step 2 in clause 4.8.1.1a so the CN can then handle mobile terminated (MT) communication.
4.8.2.2a Network Triggered Connection Resume in RRC_INACTIVE procedure
The Network Triggered Connection Resume in RRC_INACTIVE procedure is used when the NG-RAN needs to send data (e.g. the N1 NAS PDU and/or downlink user plane PDU) to a UE in the RRC_INACTIVE state. During the procedure, the NG-RAN sends a RAN Paging to the UE in order to trigger the Connection Resume in RRC_INACTIVE procedure in clause 4.8.2.2.
Figure 4.8.2.2a-1: Network Triggered Connection Resume for UE in RRC_INACTIVE
1. The NG-RAN receives downlink data (e.g. the N1 NAS PDU and/or the user plane PDU) for a UE in RRC_INACTIVE State, the NG-RAN buffers the downlink data and triggers RAN Paging message.
If the NG RAN supports the Paging Cause Indication for Voice Service feature and if the UE context in NG-RAN indicates that the UE supports the Paging Cause Indication for Voice Service feature, the NG RAN shall provide the Voice Service Indication in the RAN Paging message for the UE when it detects that the downlink data which triggers the RAN Paging message is related to voice service, as specified in clause 5.38.3 of TS 23.501 [2].
For MPS, based on receipt of an ARP (see clause 5.4.3.3 of TS 23.501 [2]), or based on receipt of service priority (also called RAN Paging Priority in TS 38.413 [10]) with values indicative of MPS priority handling, the NG-RAN shall handle the request with MPS priority.
2. The NG-RAN sends the RAN Paging message to the UE.
3. If the UE is in RRC_INACTIVE State, based on the RAN paging and the UE decides to accept the paging, the UE initiates the UE Triggered Connection Resume in RRC_INACTIVE procedure (see clause 4.8.2.2).
4.8.2.2b Network Triggered Connection Resume in RRC_INACTIVE with CN based MT communication handling
When the UE is in CM-CONNECTED with RRC_INACTIVE state with CN based mobile terminating (MT) communication handling, high latency communication as described in clause 5.31.8 of TS 23.501 [2] is applied.
This procedure may be triggered by MT data, or a N1 procedure from SMF and UPF as shown in Figure 4.8.2.2b-1. When the procedure is triggered by other NFs (e.g. SMSF, LMF, GMLC), the UPF (or SMF) in the following figure should be replaced by the respective NF (the corresponding service operations used by other NFs when they communicate with AMF may also be different from the service operations used by SMF/UPF). For MT-SMS delivery request from SMSF, see also procedures defined in clause 4.13.3.6, clause 4.13.3.7 and clause 4.13.3.8.
During the procedure, the NG-RAN (i.e. gNB) performs RAN paging towards the UE based on the N2 message from the AMF in order to trigger the UE triggered Connection Resume procedure in clause 4.8.2.2.
Figure 4.8.2.2b-1: Network Triggered Connection Resume for UE in RRC_INACTIVE with CN based MT communication handling
1a. When downlink data is received and the SMF/UPF is requested to perform buffering as specified in clause 4.8.1.1a, the UPF/SMF checks with AMF for the possibility of data delivery, similar to step 2 of clause 4.24.2 with the following differences:
- The UPF provides the DL data size information of the QoS Flow when sending Data Notification to SMF if the UPF has received instruction from SMF.
NOTE 1: The DL data size corresponds to the cumulative size of all the buffered packets in the UPF at the time when the UPF triggers the Data Notification. This is typically the size of the first DL packet, unless multiple DL packets arrive in a single burst before the UPF triggers the Data Notification.
- In the Namf_MT_EnableUEReachability the SMF may also send the following parameters the PPI, the ARP and the 5QI, DL data size and/or QFI for the QoS Flow of the PDU Session which triggered the request for paging policy differentiation as defined in clause 5.4.3.2 of TS 23.501 [2].
- The AMF determines if the UE is reachable based on the stored eDRX values for RRC_INACTIVE state provided by NG-RAN in clause 4.8.1.1a. If the UE is unreachable, the AMF stores the information received in the Namf_MT_EnableUEReachability request and provides the Estimated Maximum Wait time in the reject response message based on the eDRX values for RRC_INACTIVE in AMF (steps 2-5 are postponed until the UE becomes reachable). If the UE is considered reachable, step 2 is executed immediately.
NOTE 2: This handling is similar to CM-IDLE with eDRX. When the AMF provides the Estimated Maximum Wait time, it can consider the time needed for RRC level procedures (e.g. RRC RNA update procedure) when UE wakes up from the eDRX cycle.
NOTE 3: The other NFs can use the Namf_Communication_N1N2MessageTransfer service operation to deliver the MT signalling.
If the SMF, after the reception of reject response in step 1.a.3 and while waiting for UE triggered Connection Resume indication (within the Estimated Maximum Wait time) from the AMF, receives any additional Data Notification message due to additional data packets for another QoS Flow associated with a higher priority (i.e. ARP priority level) than the priority indicated to the AMF in the previous Namf_MT_EnableUEReachability, or the SMF derive a different Paging Policy Indicator according to the additional Data Notification, the SMF invokes a new Namf_MT_EnableUEReachability indicating the higher priority or different Paging Policy Indicator to the AMF. The information contained in the new Namf_MT_EnableUEReachability request may override the information from the previous Namf_MT_EnableUEReachability request that is stored in the AMF based on local configuration. If the SMF receives any additional Data Notification messages due to additional data packets for another QoS Flow associated with same or lower priority than the priority indicated to the AMF in the previous Namf_MT_EnableUEReachability or if the SMF has sent the second Namf_MT_EnableUEReachability message indicating the higher priority, based on local configuration, the SMF either buffers these Data Notification messages and does not send a new Namf_MT_EnableUEReachability message, or the SMF sends a new Namf_MT_EnableUEReachability message to AMF. If AMF receives DL data sizes for different QoS Flows from SMF, based on local configuration, the AMF may store the DL data size information for each QoS Flows and provides the information per QoS Flow to NG-RAN as in step 2 below.
2. When the AMF determines that the UE is reachable, the AMF sends a RAN Paging Request message to NG-RAN with the request for the UE's RRC connection to be resumed. The AMF may include the following parameters in the RAN Paging Request message to trigger and enable RAN paging:
- On per QoS Flow basis the PPI, the ARP, DL data size, the 5QI and/or QFI for the QoS Flow(s) of the PDU Session; and/or
A DL Signalling indication if the AMF receives MT signalling (i.e. via Namf_Communication_N1N2MessageTransfer) in step 1a.
3. NG-RAN performs RAN paging towards the UE considering the parameters provided by the AMF. Based on the QFI and/or the DL data size for QoS Flow(s), if provided, the NG-RAN determines whether to set the MT-SDT indication as defined in TS 38.300 [9]).
4. When the UE receives RAN paging, it initiates the UE triggered Connection Resume procedure and NG-RAN notifies CN as specified in clause 4.8.2.2 including the N2 Notification in step 3b. If the Namf_MT_EnableUEReachability response was not sent in step 1.a.3 (i.e. the AMF has considered the UE is reachable in step 1), then the AMF sends the Namf_MT_EnableUEReachability response to the SMF along with step 4 of the UE triggered Connection Resume in RRC_INACTIVE procedure (see clause 4.8.2.2).
5. The UPF triggers downlink data delivery if there is any. The AMF sends downlink NAS messages if there is any. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8.2.3 Connection Resume in CM-IDLE with Suspend procedure | For the UE supporting User Plane CIoT 5GS Optimisation, the Connection Resume procedure is used by the UE to perform RRC_IDLE with Suspend to RRC_CONNECTED state transition. Triggers for the UE to initiate this procedure are defined in clause 5.31.18 of TS 23.501 [2].
Figure 4.8.2.3-1: Connection Resume in CM-IDLE with Suspend
1. UE to NG-RAN: RRC message (Resume ID).
The UE initiates the transition from CM-IDLE and RRC_IDLE state with Suspend to CM-CONNECTED and RRC_CONNECTED state, see TS 36.300 [46]. The UE provides its Resume ID needed by the NG-RAN to access the UE's stored Context.
2. [Conditional] NG-RAN performs UE Context Retrieval.
UE Context Retrieval may be performed when the UE Context associated with the UE attempting to resume its connection is not locally available at the accessed NG-RAN. The UE Context Retrieval procedure via NG-RAN is specified in TS 38.300 [9].
3. NG-RAN and UE continues the resume procedure and access stratum configuration synchronization is performed between the UE and the network. UE enters CM-CONNECTED and RRC_CONNECTED.
4. NG-RAN to AMF:
a) If the NG-RAN is the same as the NG-RAN when UE is suspended, the NG-RAN sends N2 Resume Request to AMF including Resume cause and N2 SM information which indicates the PDU sessions successfully resumed and PDU sessions failed or partially failed to resume the user plane resource.
b) If the NG-RAN is different from the NG-RAN when UE is suspended and the new NG-RAN is able to retrieve the UE Context from the old NG-RAN, the new NG-RAN node initiates N2 Path Switch Request towards AMF, i.e. Steps 1b of clause 4.9.1.2.2.
5. AMF to SMF: For each of the PDU Sessions indicated in step 4, the AMF invokes Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID, Cause, Operation type, User Location Information, Age of Location Information, N2 SM Information). The Operation Type is set to "UP Resume" to indicate resume of user plane resources for the PDU Session.
For PDU Session(s) to be switched to the new NG-RAN, upon receipt of the Nsmf_PDUSession_UpdateSMContext request, the SMF determines whether the existing UPF can continue to serve the UE. If the existing UPF cannot continue to serve the UE, steps 3 to 7 of clause 4.9.1.2.3 or clause 4.9.1.2.4 are performed depending on whether the existing UPF is a PDU Session Anchor and flow continues in step 7. Otherwise, step 6 is performed if the existing UPF can continue to serve the PDU Session.
If the RRC connection is resumed and the UE is accessing via the NB-IoT RAT with the RRC resume cause set to "MO exception data" the AMF updates all (H-)SMFs. If AMF indicates "MO exception data" then it includes the MO Exception Data Counter. The AMF maintains the MO Exception Data Counter for Small Data Rate Control purposes as described in clause 5.31.14.3 of TS 23.501 [2]. Each (H-)SMF should be updated for every RRC Connection which is triggered for "MO exception data".
In the home-routed roaming case, if Small Data Rate Control applies, the V-SMF waits for H-SMF response before proceeding with the N3 establishment.
6. SMF to UPF: N4 Session Modification Request (AN Tunnel Info to be resumed, Buffering on/off).
The SMF initiates an N4 Session Modification procedure indicating the resume of AN tunnel. Buffering on/off indicates whether the UPF shall buffer incoming DL PDU or not.
If step 4a) is performed, the AN tunnel info is the one maintained by the SMF during Connection Suspend procedure, step 3 of clause 4.8.1.2. If step 4b) is performed, the AN tunnel info is part of the N2 SM information received by SMF in step 5.
The UPF sends N4 Session Modification Response to acknowledge the SMF request.
7. SMF to AMF: The SMF sends Nsmf_PDUSession_UpdateSMContext response to the AMF.
If new CN tunnel information is allocated for the PDU session, i.e. in the case of new AN tunnel is received in step 6, the SMF includes the new CN tunnel information as part of the N2 SM information.
If the resume for PDU session is unsuccessful, the SMF shall include the resume failure as part of the N2 SM information.
8. AMF to NG-RAN: After response for each PDU session in step 7, the AMF sends N2 Resume Response to NG-RAN and indicates success, including N2 SM information for PDU session received in step 7, if at least one PDU session is resumed successfully. If none of the PDU sessions is resumed successfully, AMF indicates failure to NG-RAN.
The AMF sends N2 Path Switch Acknowledge with PDU session resume information, if Path Switch Request is received in step 4.
The AMF may provide Extended Connected Time value to the NG-RAN. If the NG-RAN receives the Extended Connected Time value, the NG-RAN may take this information into account when determining user inactivity.
9. [Conditional] NG-RAN to UE: RRC message.
The NG-RAN may reconfigure the RRC connection based on resume result received from AMF.
10. If the AMF has paged the UE to trigger the Connection Resume procedure, the AMF shall initiate the UE configuration update procedure as defined in clause 4.2.4.2 to assign a new 5G-GUTI. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8.2.4 Connection Resume in CM-IDLE with Suspend and MO EDT procedure | The Connection Resume with Early Data Transmission procedure is used by the UE to optimise sending user data in a single uplink packet and single uplink followed by single downlink packet cases for a UE in CM-IDLE with Suspend.
Figure 4.8.2.4-1: Connection Resume in RRC_IDLE with Suspend with EDT
1. UE to NG-eNB: RRC message (Resume ID, AS RAI) with UL EDT.
The UE initiates the transition from RRC_IDLE with Suspend state to RRC_CONNECTED state, see TS 36.300 [46].
The UE may include AS Release Assistance information indicating:
- No further Uplink and Downlink Data transmission, or
- Only a single Downlink Data transmission subsequent to the Uplink transmission.
2. The NG-eNB deciphers the EDT UL data received from the UE and forwards it to the UPF using the N3 UL TEID in the AS context.
3. The NG-eNB sends N2 Resume Request to AMF including Resume cause and N2 SM.
If the UE included AS Release Assistance information indicating No further Uplink and Downlink Data transmission in step 1, NG-eNB may request for immediate transition to RRC_IDLE with Suspend.
If the NG-eNB requests for immediate transition to RRC_IDLE with Suspend, the NG-eNB should include Paging Assistance Data for CE capable UE in the N2 Resume Request message. If the NG-eNB supports WUS and requests for immediate transition to RRC_IDLE with Suspend, the NG-eNB should include Information on Recommended Cells and RAN Nodes for Paging in the N2 Resume Request message. The AMF stores this information in the UE context for subsequent Paging procedure.
4. [Conditional] The AMF interacts with SMF to establish the N3 tunnel, except for the case:
- The AMF receives a request for immediate transition to RRC_IDLE with Suspend in step 3; and
- the AMF is not aware of any downlink data or signalling pending.
5. The AMF sends an N2 Resume Response to NG-eNB.
If the AMF received a request for immediate transition to RRC_IDLE with Suspend in step 3 and there is no downlink data or signalling pending, the AMF includes a Suspend indication, keeps the UE in CM-IDLE with Suspend and restarts the Periodic Registration Timer unless the Strictly Periodic Registration Timer Indication has been provided to the UE during the previous registration procedure.
Otherwise the AMF sends an N2 Resume Response to NG-eNB after the N3 Connectivity has been established and moves the UE to CM-CONNECTED. If the AMF knows of mobile terminating data or signalling pending, the AMF may include the Extended Connected Time value to the RAN
6. [Conditional] RRC procedure:
6a. If the AMF included the Suspend indication, the NG-eNB releases the RRC Connection with Suspend. The procedure is complete and following steps are skipped.
6b. If the AMF did not include the Suspend indication and:
- The UE did not include AS Release Assistance Indication; or
- The AMF included the Extended Connected Time value.
the NG-eNB sends an RRC Resume message to the UE and the UE moves to CM-CONNECTED and RRC_CONNECTED. The procedure is complete and the following steps are skipped.
6c. Otherwise, if the AMF did not include Extended Connected Time value and the UE included AS Release Assistance information with only a single Downlink Data transmission subsequent to the Uplink transmission, the NG-eNB waits for the DL data to arrive and proceeds to steps 7-10.
7-9. The NG-eNB releases the N3 connectivity by sending an N2 Suspend Request to AMF including Suspend cause and N2 SM. Steps 2-4 of Connection Suspend procedure in clause 4.8.1.2 is executed.
10. [Conditional] NG-eNB to UE: RRC message (with DL data).
The NG-eNB ciphers received DL data.
The NG-eNB releases the RRC Connection with Suspend including the DL EDT data. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.8.3 N2 Notification procedure | This procedure is used by an AMF to request the NG-RAN to report RRC state information, when the target UE is in CM-CONNECTED state. When AMF has requested reporting of subsequent state changes, the need for the NG-RAN to continue reporting ceases when the UE transitions to CM-IDLE or the AMF sends a cancel indication. This procedure may be used for services that require RRC state information (e.g. 5GC MT control and paging assistance, O&M and collection of statistics), or for subscription to the service by other NFs. See TS 38.413 [10] for details of the procedure.
Reporting of RRC state transitions can be requested per UE by AMF. Continuous reporting of all RRC state transitions can be enabled by operator local configuration.
Figure 4.8.3-1: RRC state transition notification
1. The AMF sends a UE State Transition Notification Request to the NG-RAN as described in TS 38.413 [10]. The UE State Transition Notification Request message shall identify the UE for which notification(s) are requested and may contain a reporting type. The reporting type either indicates subsequent state transitions shall be notified at every RRC state transition (i.e. from RRC_CONNECTED state to RRC_INACTIVE state, or from RRC_INACTIVE to RRC_CONNECTED state), or it indicates Single RRC_CONNECTED state notification.
2. The NG-RAN sends the UE Notification message to report the current RRC state for the UE (i.e. RRC_INACTIVE state or RRC_CONNECTED state). The current UE location information (i.e. TAI + Cell Identity) is always included when RRC state information is reported.
2b. When the AMF has requested reporting about subsequent state transitions, the NG-RAN sends subsequent UE Notification messages to the AMF at every RRC state transition until the UE transitions to CM-IDLE or NG-RAN receives a Cancel UE State Notification message from the AMF.
When the AMF has requested reporting for Single RRC_CONNECTED state notification and UE is in RRC_CONNECTED state, the NG-RAN sends one UE Notification message but no subsequent messages. If UE is in RRC_INACTIVE state, the NG-RAN sends one UE Notification message plus one subsequent UE Notification message when RRC state transits to RRC_CONNECTED.
3. The AMF can send a Cancel UE State Notification message to inform the NG-RAN that it should terminate notifications for a given UE. This message should only be used when notification(s) about subsequent state transitions was requested at every RRC state transition. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9 Handover procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1 Handover procedures in 3GPP access | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.1 General | These procedures are used to hand over a UE from a source NG-RAN node to a target NG-RAN node using the Xn or N2 reference points. This can be triggered, for example, due to new radio conditions, load balancing or due to specific service e.g. in the presence of QoS Flow for voice, the source NG-RAN node being NR may trigger handover to E-UTRA connected to 5GC.
As defined in TS 38.413 [10] a generic mechanism exists for the source NG-RAN node to retrieve information on the level of support for a certain feature at the target NG-RAN side associated with an NGAP IE. The mechanism makes use of the Source to Target and Target to Source transparent containers.
The Inter NG-RAN node N2 based handover procedure specified in clause 4.9.1.3 may also be used for intra-NG-RAN node handover.
NOTE: One use case for intra-NG-RAN handover to be performed by the Inter NG-RAN node N2 based handover procedure is when an NG-RAN node serves a satellite access system that covers more than one country. In such a situation, the UE might move from a "cell" in one country into a "cell" in another country and the NG-RAN node may need to cause the AMF to change to an AMF serving the UE's new country.
The RRC Inactive Assistance Information is included in N2 Path Switch Request Ack message for Xn based handover or Handover Request message for N2 based handover (see clause 5.3.3.2.5 of TS 23.501 [2]). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.2 Xn based inter NG-RAN handover | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.2.1 General | Clause 4.9.1.2 includes details regarding the Xn based inter NG-RAN handover with and without UPF re-allocation.
Xn handovers are only supported for intra-AMF mobility. New AMF can be selected by the target NG-RAN node as specified in clause 5.21.2 of TS 23.501 [2].
The handover preparation and execution phases are performed as specified in TS 38.300 [9], in the case of handover to a shared network, source NG-RAN determines a PLMN or an SNPN to be used in the target network as specified by TS 23.501 [2]. If the serving PLMN or SNPN changes during Xn-based handover, the source NG-RAN node shall indicate to the target NG-RAN node (in the Mobility Restriction List) the selected PLMN ID or SNPN ID to be used in the target network. During Xn based handover into a shared NG-RAN node the source NG RAN node shall include the serving NID (if available) in the Mobility Restriction List to be used by the target NG-RAN node.
If the AMF generates the N2 downlink signalling during the ongoing handover and receives a rejection to a N2 interface procedure (e.g. Location Reporting Control; DL NAS message transfer; etc.) from the NG-RAN with an indication that a Xn based handover procedure is in progress, the AMF may reattempt the same N2 interface procedure either when the handover is complete or the handover is deemed to have failed, when possible. The failure is known by expiry of the timer guarding the N2 interface procedure.
Upon reception for an SMF initiated N1 and/or N2 request(s) with an indication that the request has been temporarily rejected due to handover procedure in progress, the SMF starts a locally configured guard timer. Any NF (e.g. the SMF) should hold any signalling messages targeted towards AMF for a given UE during the handover preparation phase unless it detects that the handover execution is completed or handover has failed/cancelled. The NF (e.g. the SMF) may re-attempt, up to a pre-configured number of times, when either it detects that the handover is completed or has failed using message reception or at expiry of the guard timer.
For the MBSR mobility as specified in clause 5.35A.3 of TS 23.501 [2], the MBSR-UE may operate without any PDU session. In that case, the NG-RAN and the AMF behave as specified in clause 5.35A.3.4 of TS 23.501 [2]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.2.2 Xn based inter NG-RAN handover without User Plane function re-allocation | This procedure is used to hand over a UE from a source NG-RAN to Target NG-RAN using Xn when the AMF is unchanged and the SMF decides to keep the existing UPF. The UPF referred in this clause 4.9.1.2.2 is the UPF which terminates N3 interface in the 5GC for non-roaming or local breakout roaming scenario, V-UPF which terminates N3 interface in 5GC for home routed roaming scenario. The SMF referred in this clause 4.9.1.2.2 is the V-SMF for home routed roaming scenario. The presence of IP connectivity between the Source UPF and Target NG-RAN is assumed.
The call flow is shown in figure 4.9.1.2.2-1.
Figure 4.9.1.2.2-1: Xn based inter NG-RAN handover without UPF re-allocation
1a. If the PLMN has configured secondary RAT usage reporting, the source NG-RAN node during the handover execution phase may provide RAN usage data Report (N2 SM Information (Secondary RAT usage data), Handover Flag, Source to Target transparent container) to the AMF. The source NG-RAN node shall provide this only when the Target NG-RAN has confirmed handover over Xn interface. The Handover Flag indicates to the AMF that it should buffer the N2 SM Information containing the usage data report before forwarding it.
If the source NG RAN and Target NG RAN support RACS as defined in TS 23.501 [2], the source NG-RAN provides the UE's UE Radio Capability ID to the Target NG-RAN. If the source NG-RAN has knowledge that the Target NG-RAN might not have a local copy of the Radio Capability corresponding to the UE Radio Capability ID (i.e. because the source NG-RAN had itself to retrieve the UE's Radio Capability from the AMF) then the source NG-RAN may also send some or all of the UE's Radio Capability to the Target NG-RAN (the size limit based on local configuration) in Xn signalling as defined in TS 38.423 [72] . In the case of inter-PLMN handover, when the source and Target NG-RAN support RACS as defined in TS 23.501 [2] and the source NG-RAN determines based on local configuration that the Target PLMN does not support the UE Radio Capability ID assigned by the source PLMN, then the source NG-RAN shall provide the UE radio access capabilities to the Target NG-RAN and shall not send the UE Radio Capability ID. If, as permitted in TS 38.423 [72], the Target NG-RAN during the handover preparation received the UE radio access capabilities but did not receive the UE Radio Capability ID, NG-RAN shall proceed with handover using the received UE radio access capabilities. If the Target NG-RAN received both the UE radio access capabilities and the UE Radio Capability ID, then the Target NG-RAN shall use any locally stored UE radio access capability information corresponding to the UE Radio Capability ID. If none are stored locally, the Target NG-RAN may request the full UE radio access capability information from the core network. If the full UE radio access capability information is not promptly received from the core network, or the Target NG-RAN chooses not to request them, then the Target NG-RAN shall proceed with the UE radio access capabilities sent by the source NG-RAN. The Target NG-RAN shall not use the UE radio access capability information received from the source NG-RAN for any other UE with the same the UE Radio Capability ID.
1b. Target NG-RAN to AMF: N2 Path Switch Request (List of PDU Sessions To Be Switched with N2 SM Information, List of PDU Sessions that failed to be established with the failure cause given in the N2 SM information element, UE Location Information, established QoS Flows status (active/not active) (for one of the following: congestion information monitoring, ECN marking for L4S at PSA UPF ECN marking for L4S at NG-RAN), PDU Set Based Handling Support Indication included in the N2 SM information).
The Target NG-RAN sends an N2 Path Switch Request message to an AMF to inform that the UE has moved to a new Target cell and provides a List Of PDU Sessions To Be Switched. AN Tunnel Info for each PDU Session to be switched is included in the N2 SM Information.
If redundant transmission is performed for one or more QoS Flows in the PDU Session, two AN Tunnel Info are provided by the Target NG-RAN and the Target NG-RAN indicates to the SMF one of the AN Tunnel Info is used as the redundancy tunnel of the PDU Session as described in clause 5.33.2.2 of TS 23.501 [2]. If only one AN Tunnel Info is provided by the Target NG-RAN for the PDU session, the SMF may release these QoS Flows by triggering PDU Session Modification procedure as specified in clause 4.3.3 after the handover procedure.
The serving PLMN ID is included in the message. The Target NG-RAN shall include the PDU Session in the PDU Sessions Rejected list:
- If none of the QoS Flows of a PDU Session are accepted by the Target NG-RAN; or
- If the corresponding network slice is not supported in the Target NG-RAN; or
- When the NG-RAN cannot set up user plane resources fulfilling the User Plane Security Enforcement with a value Required, the NG-RAN rejects the establishment of user plane resources for the PDU Session.
If the NG-RAN cannot set up user plane resources fulfilling the User Plane Security Enforcement with a value Preferred, the NG-RAN establishes the user plane resources for the PDU session and shall include the PDU Session in the PDU Sessions Modified list.
PDU Sessions Rejected contains an indication of whether the PDU session was rejected because User Plane Security Enforcement is not supported in the Target NG-RAN. Depending on the type of target cell, the Target NG-RAN includes appropriate information in this message.
For the PDU Sessions to be switched to the Target NG-RAN, the N2 Path Switch Request message shall include the list of accepted QoS Flows. For each QoS Flow accepted with an Alternative QoS Profile as specified in TS 23.501 [2], the N2 SM Information shall include a reference to the fulfilled Alternative QoS Profile.
The NG-RAN includes the PDU Set Based Handling Support Indication in N2 SM information as defined in clause 5.37.5.3 of TS 23.501 [2].
2. AMF to SMF: Nsmf_PDUSession_UpdateSMContext Request (N2 SM information received from T-RAN in step 1b and N2 SM Information from source NG-RAN (Secondary RAT usage data), UE Location Information, UE presence in LADN service area). The N2 SM Information here from source NG-RAN is the one buffered at step 1a when applicable.
The AMF sends N2 SM information by invoking the Nsmf_PDUSession_UpdateSMContext request service operation for each PDU Session in the lists of PDU Sessions received in the N2 Path Switch Request.
The Nsmf_PDUSession_UpdateSMContext Request contains either an indication that the PDU Session Is To Be Switched (together with information on the N3 addressing to use and on the transferred QoS flows) or an indication that the PDU Session is to be Rejected (together with a rejection cause).
If the AMF, based on configuration, as described in clause 5.43.4 of TS 23.501 [2], is aware that satellite backhaul category has changed due to the handover and needs to be updated to the SMF, the AMF includes the new Satellite backhaul category as described in clause 5.43.4 of TS 23.501 [2].
If the AMF, based on configuration, as described in clause 5.43.2 of TS 23.501 [2], is aware that the UE is accessing over a gNB using GEO satellite backhaul and GEO Satellite ID needs to be updated to the SMF, the AMF may include the latest GEO Satellite ID as described in clause 5.43.2 of TS 23.501 [2].
For a PDU Sessions to be switched to the Target NG-RAN, upon receipt of the Nsmf_PDUSession_UpdateSMContext request, the SMF determines whether the existing UPF can continue to serve the UE. If the existing UPF cannot continue to serve the UE, steps 3-11 of clause 4.9.1.2.3 or 4.9.1.2.4 are performed depending on whether the existing UPF is a PDU Session Anchor. Otherwise, the following steps 3 to 6 are performed if the existing UPFs can continue to serve the PDU Session.
In the case that the AMF determines that the PDU Session is related to a LADN, then the AMF provides the "UE presence in LADN service area" to the SMF. If the AMF does not provide the "UE presence in LADN service area" indication and the SMF determines that the DNN corresponds to a LADN, then the SMF considers that the UE is OUT of the LADN service area. The SMF takes actions for the LADN PDU Session as defined in clause 5.6.5 of TS 23.501 [2] based on the "UE presence in LADN service area" indication.
If a PDU Session is rejected by the Target NG-RAN with an indication that the PDU session was rejected because User Plane Security Enforcement is not supported in the Target NG-RAN and the User Plane Enforcement Policy indicates "Required" as described in clause 5.10.3 of TS 23.501 [2], the SMF triggers the release of this PDU Session. In all other cases of PDU Session rejection, the SMF can decide whether to release the PDU Session or to deactivate the UP connection of this PDU Session.
If some of the QoS Flows of a PDU Session are not accepted by the Target NG-RAN, the SMF shall initiate the PDU Session Modification procedure to remove the non-accepted QoS Flows from the PDU Session(s) after the handover procedure is completed.
For the PDU Session(s) that do not have active N3 UP connections before handover procedure, the SMF(s) keep the inactive status after handover procedure.
If the UE moves into a non-Allowed Area, the AMF also notifies via Namf_EventExposure_Notify to each NF Consumer (e.g. SMFs of the established PDU Sessions) which has subscribed for UE reachability event, that the UE is only reachable for regulatory prioritized services. The SMF then deactivates the PDU session if this PDU Session is not for emergency service.
3. SMF to UPF: N4 Session Modification Request (AN Tunnel Info)
For PDU Sessions that are modified by the Target NG-RAN, the SMF sends an N4 Session Modification Request message to the UPF. The SMF may notify the UPF that originated the Data Notification to discard downlink data for the PDU Sessions and/or to not provide further Data Notification messages.
Depending on the network deployment, the CN Tunnel Info of UPF used for connection to Target NG-RAN and connection to Source NG-RAN may be different, e.g. due to Source and Target NG-RAN are in different IP domains. In this case the SMF may ask the UPF to allocate new CN Tunnel Info, providing the target Network Instance.
4. UPF to SMF: N4 Session Modification Response (CN Tunnel Info)
For the PDU Sessions that are switched, the UPF returns an N4 Session Modification Response message to the SMF after requested PDU Sessions are switched. Tunnel identifiers for UL traffic are included only for PDU Sessions whose user plane resources are not being released and was requested by the SMF. If redundant transmission is performed for one or more QoS Flows of a PDU Session and different CN Tunnel Info were requested by the SMF, the UPF allocates two different CN Tunnel Info and indicates the SMF that one CN Tunnel Info is used as the redundancy tunnel of the PDU session as described in clause 5.33.2.2 of TS 23.501 [2]. For the PDU Sessions that are deactivated, the UPF returns an N4 Session Modification Response message to the SMF after the N3 (R)AN tunnel information is released.
5. In order to assist the reordering function in the Target NG-RAN, the UPF (as specified in clause 5.8.2.9 of TS 23.501 [2]) sends one or more "end marker" packets for each N3 tunnel on the old path immediately after switching the path. The UPF starts sending downlink packets to the Target NG-RAN.
6. SMF to AMF: Nsmf_PDUSession_UpdateSMContext Response (N2 SM information)
The SMF sends an Nsmf_PDUSession_UpdateSMContext response (N2 SM Information (CN Tunnel Info, updated CN PDB for the accepted QoS Flows, Updated TSCAIs for the accepted QoS Flows)) to the AMF for PDU Sessions which have been switched successfully. The CN Tunnel Info of UPF send to AMF is used to setup N3 tunnel. If redundant transmission is performed for one or more QoS Flows of a PDU Session, two CN Tunnel Info are sent and the SMF indicates to the Target NG-RAN one of the CN Tunnel Info is used as the redundancy tunnel of the PDU Session as described in clause 5.33.2.2 of TS 23.501 [2]. The SMF sends an Nsmf_PDUSession_UpdateSMContext response without including the CN Tunnel Info to the AMF for the PDU Sessions for which user plane resources are deactivated or released and then the SMF releases the PDU Session(s) which is to be released using a separate procedure as defined in clause 4.3.4. For each accepted GBR QoS Flow of Delay-critical resource type, the dynamic CN PDB and TSCAI may be updated and sent to the Target NG-RAN by the SMF. The SMF may update the CN PDB and TSCAI in the response or using a separate PDU Session Modification procedure, based on local configuration.
If the Source NG-RAN does not support Alternative QoS Profiles (see TS 23.501 [2]) and the Target NG-RAN supports them, the SMF sends the Alternative QoS Profiles (see TS 23.501 [2]) to the Target NG-RAN on a per QoS Flow basis, if available.
NOTE: Step 6 can occur any time after receipt of N4 Session Modification Response at the SMF.
7. AMF to NG-RAN: N2 Path Switch Request Ack (N2 SM Information, Failed PDU Sessions, UE Radio Capability ID).
Once the Nsmf_PDUSession_UpdateSMContext response is received from all the SMFs, the AMF aggregates received CN Tunnel Info and sends this aggregated information as a part of N2 SM Information along with the Failed PDU Sessions in N2 Path Switch Request Ack to the Target NG-RAN. If none of the requested PDU Sessions have been switched successfully, the AMF shall send an N2 Path Switch Request Failure message to the Target NG-RAN.
If the UE Radio Capability ID is included in the N2 Path Switch Request Ack message, when there is no corresponding UE radio capabilities set for UE Radio Capability ID at the Target NR-RAN, the Target NG-RAN shall request the AMF to provide the UE radio capabilities set corresponding to UE Radio Capability ID to the Target NG-RAN.
If Energy Saving Indicator is in the UE context, the AMF includes Energy Saving Indicator in the N2 message carrying the Path Switch Request Ack.
Editor's note: Whether the Energy Saving Indicator is provided to the NG-RAN is FFS.
8. By sending a Release Resources message to the Source NG-RAN, the Target NG-RAN confirms success of the handover. It then triggers the release of resources with the Source NG-RAN.
9. [Conditional] The UE may initiate Mobility Registration Update procedure if one of the triggers of registration procedure applies as described in clause 4.2.2.2.2. In this case, only steps 1, 2, 3, 17 and 21 in clause 4.2.2.2.2 are performed.
For the mobility related events as described in clause 4.15.4, the AMF invokes the Namf_EventExposure_Notify service operation.
Upon reception of the Namf_EventExposure_Notify with an indication that UE is reachable only for regulatory prioritized service, the SMF deactivates the PDU Session if the service of the PDU Session is not regulatory prioritized. For home routed roaming case, the V-SMF triggers the deactivation of the PDU Session, in addition, the H-SMF refrains from sending downlink signalling if the signalling is not related to regulatory prioritized service upon receiving the notification. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.2.3 Xn based inter NG-RAN handover with insertion of intermediate UPF | This procedure is used to hand over a UE from a Source NG-RAN to a Target NG-RAN using Xn when the AMF is unchanged and the SMF decides that insertion of a new additional intermediate UPF is needed. If redundant transmission is performed for one or more QoS Flows of a PDU Session to be switched to the Target NG-RAN, the SMF may select two Intermediate UPFs (I-UPFs) and set up two N3 and N9 tunnels between the Target NG-RAN and the UPF (PSA) via the two I-UPFs as described in clause 5.33.2.2 of TS 23.501 [2].
In the case of using UL CL, the I-UPF can be regarded as UL CL and additional PSA providing local access to a DN. In the case of using Branching Point, the I-UPF can be regarded as BP.
It is assumed that the PDU Session for the UE comprises of only one UPF that acts as a PDU Session Anchor at the time of this Handover procedure for non-roaming and local breakout roaming scenario. In the case of home routed roaming scenario, the PDU Session of the UE comprises of at least one UPF in the VPLMN and one UPF in the HPLMN at the time of this handover procedure. In this case, additional insertion of an N3 terminating intermediate UPF will not have impact on the connectivity between the UPF in VPLMN and UPF in HPLMN. The presence of IP connectivity between the UPF (PDU Session Anchor) and Source NG-RAN, between the UPF (PDU Session Anchor) and Target NG-RAN and between the intermediate UPF (I-UPF) and Target NG-RAN, is assumed. (If there is no IP connectivity between UPF (PDU Session Anchor) and Target NG-RAN, it is assumed that the N2-based handover procedure in clause 4.9.1.3 shall be used instead).
The call flow is shown in figure 4.9.1.2.3-1.
Figure 4.9.1.2.3-1: Xn based inter NG-RAN handover with insertion of intermediate UPF
Steps 1-2 are the same as described in clause 4.9.1.2.2.
3a. [Conditional] SMF to UPF (PSA): N4 Session Modification Request.
If the SMF selects a new UPF to act as intermediate UPF for the PDU Session and the different CN Tunnel Info need be used, the SMF sends N4 Session Modification Request message to UPF (PSA).
3b. [Conditional] UPF (PSA) to SMF: N4 Session Modification Response.
The UPF (PSA) sends an N4 Session Modification Response message to the SMF. The UPF provides CN Tunnel Info (on N9) to the SMF. If redundant transmission is performed for one or more QoS Flows of the PDU Session, the UPF (PSA) provides two CN Tunnel Info (on N9) to the SMF and indicates the SMF that one CN Tunnel Info is used as redundancy tunnel of the PDU Session as described in in clause 5.33.2.2 of TS 23.501 [2]. The UPF (PSA) associate the CN Tunnel Info (on N9) with UL Packet detection rules provided by the SMF.
4a. SMF to I-UPF: N4 Session Establishment Request (Target NG-RAN Tunnel Info, CN Tunnel Info of the PDU Session Anchor)
For PDU Sessions to be updated, if the UE has moved out of the service area of UPF connecting to the serving NG-RAN node, the SMF then selects an I-UPF based on UPF Selection Criteria according to clause 6.3.3 of TS 23.501 [2]. An N4 Session Establishment Request message is sent to the I-UPF. The CN Tunnel Info of the PDU Session Anchor, which is used to setup N9 tunnel, is included in the N4 Session Establishment Request message.
4b. I-UPF to SMF: N4 Session Establishment Response.
The I-UPF sends an N4 Session Establishment Response message to the SMF. The UL and DL CN Tunnel Info of I-UPF is sent to the SMF.
If SMF select two Intermediate UPFs (I-UPFs) to perform redundant transmission for a PDU session, step 4a and 4b are performed between the SMF and each I-UPF.
5. SMF to PDU Session Anchor: N4 Session Modification Request (DL CN Tunnel Info of the I-UPF).
The SMF sends N4 Session Modification Request message to the PDU Session Anchor.
If a different CN Tunnel Info is used on N9 in UPF (PSA), the SMF starts a timer to release the CN Tunnel for N3. Otherwise the SMF does not need to start a timer to release the CN Tunnel Info used on N3 in UPF(PSA) (i.e. CN Tunnel Info is common for both N3 and N9).
If redundant transmission is performed for one or more QoS Flows of the PDU Session, the SMF provides two DL CN Tunnel Info (for N9) to the UPF (PSA) and indicates to the UPF (PSA) one of the DL CN Tunnel Info is used as redundancy tunnel of the PDU Session.
6. PDU Session Anchor to SMF: N4 Session Modification Response.
The PDU Session Anchor responds with the N4 Session Modification Response message after requested PDU Sessions are switched. At this point, PDU Session Anchor starts sending downlink packets to the Target NG-RAN via I-UPF.
7. In order to assist the reordering function in the Target NG-RAN, the PDU Session Anchor sends one or more "end marker" packets for each N3 tunnel on the old path immediately after switching the path, the source NG-RAN shall forward the "end marker" packets to the Target NG-RAN.
8. SMF to AMF: Nsmf_PDUSession_UpdateSMContext Response (N2 SM Information (UL CN Tunnel Info of the I-UPF, updated QoS parameters for accepted QoS Flows)).
The SMF sends an Nsmf_PDUSession_UpdateSMContext response to the AMF.
Steps 8-11 are same as steps 6-9 defined in clause 4.9.1.2.2.
12. After the timer set in step 5 expires, the SMF informs the PDU Session Anchor to remove the CN Tunnel for N3 via N4 Session Modification procedure. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.2.4 Xn based inter NG-RAN handover with re-allocation of intermediate UPF | This procedure is used to hand over a UE from a Source NG-RAN to a Target NG-RAN using Xn when the AMF is unchanged and the SMF decides that the intermediate UPF (I-UPF) is to be changed. In the case of using UL CL, the I-UPF can be regarded as UL CL and additional PSA provides local access to a DN, the simultaneous change of UL-CL and the additional PSA is described in clause 4.3.5.7. In the case of using Branching Point, the I-UPF can be regarded as BP.
It is assumed that the PDU Session for the UE comprises of a UPF that acts as a PDU Session Anchor and an intermediate UPF at the time of this Handover procedure for non-roaming and local breakout roaming scenario. In the case of home routed roaming scenario, the PDU Session of the UE comprises of at least one UPF in the VPLMN and UPF in the HPLMN which acts as a PDU Session Anchor at the time of this handover procedure. The Source UPF referred in this clause 4.9.1.2.4 is the UPF which terminates N3 interface in the 5GC. The presence of IP connectivity between the Source UPF and Source NG-RAN, between the source UPF and Target NG-RAN and between the Target UPF and Target NG-RAN, is assumed. (If there is no IP connectivity between source UPF and Target NG-RAN, it is assumed that the N2-based handover procedure in clause 4.9.1.3 shall be used instead).
The call flow is shown in figure 4.9.1.2.4-1.
Figure 4.9.1.2.4-1: Xn based inter NG-RAN handover with intermediate UPF re-allocation
Steps 1-4 are same as steps 1-4 described in clause 4.9.1.2.3 except that the I-UPF in clause 4.9.1.2.3 is replaced by Target UPF.
5. [Conditional] The SMF sends N4 Session Modification Request message to the PDU Session Anchor. The DL CN Tunnel Info of the Target UPF is included in this message. If redundant transmission is performed for one or more QoS Flows of the PDU Session, the SMF provides two DL CN Tunnel Info (for N9) to the UPF (PSA) and indicates to the UPF (PSA) one of the DL CN Tunnel Info is used as redundancy tunnel of the PDU Session.
In the case of home routed roaming, if the N9 terminating V-UPF, which is connected to with home UPF, is changed, the V-SMF invokes an Nsmf_PDUSession_Update Request (DL CN Tunnel Info) service operation toward the H-SMF.
6. [Conditional] The SMF associated with the PDU Session Anchor responds with the N4 Session Modification Response message. In the case of home routed roaming, the H-SMF responds with the Nsmf_PDUSession_Update Response service operation toward the V-SMF once H-UPF is updated with the DL Tunnel Info of the T-UPF. At this point, PDU Session Anchor starts sending downlink packets to the Target NG-RAN via Target UPF.
Steps 7-11 are same as steps 7-11 described in clause 4.9.1.2.3 except that the I-UPF in clause 4.9.1.2.3 is replaced by Target UPF.
If the Source UPF acts as a UL CL or BP, the SMF indicates to only one of the PDU Session Anchors to send the "end marker" packets. To ensure the "end marker" is the last user plane packet on the old path, the SMF should modify the path on other PDU Session Anchors before it indicates the PDU Session Anchor to send the "end marker" packets.
11. The timer is started in step 4 if the source UPF is not the PSA UPF. When this timer is expired, the SMF initiates Source UPF(s) Release procedure by sending an N4 Session Release Request (Release Cause).
12. The Source UPF(s) acknowledges with an N4 Session Release Response message to confirm the release of resources. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.3 Inter NG-RAN node N2 based handover | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.3.1 General | Clause 4.9.1.3 includes details regarding the inter NG-RAN node N2 based handover without Xn interface.
The source NG-RAN decides to initiate an N2-based handover to the target NG-RAN. This can be triggered, for example, due to new radio conditions or load balancing, if there is no Xn connectivity to the target NG-RAN, an error indication from the target NG-RAN after an unsuccessful Xn-based handover (i.e. no IP connectivity between T-RAN and S-UPF), or based on dynamic information learnt by the S-RAN. NTN NR supports additional trigger conditions i.e. time-based trigger condition, upon which UE may execute conditional handover to a candidate cell, as defined in TS 38.331 [12].
The availability of a direct forwarding path is determined in the source NG-RAN and indicated to the SMFs. If IP connectivity is available between the source and target NG-RAN and security association(s) is in place between them, a direct forwarding path is available.
If a direct forwarding path is not available, indirect forwarding may be used. The SMFs use the indication from the source NG-RAN to determine whether to apply indirect forwarding.
If both source NG-RAN and source AMF support DAPS the source NG-RAN may decide that some of the DRBs are subject for DAPS handover as defined in TS 38.300 [9]; in this case, the source NG-RAN provides the DAPS information indicating the request concerns a DAPS handover for the DRB as part of the Source to Target (NG-RAN) Transparent Container. If the target NG-RAN accepts that the request concerns DAPS handover and both Target NG-RAN and Target AMF support DAPS, the DAPS handover will be performed and target NG-RAN provides DAPS response information as part of the Target to Source (NG-RAN) Transparent Container.
In the case of handover to a shared network, the source NG-RAN determines a PLMN (or PLMN ID and NID, see clause 5.30 of TS 23.501 [2]) to be used in the target network as specified by TS 23.501 [2]. The source NG-RAN shall indicate the selected PLMN ID to be used in the target network to the AMF as part of the Tracking Area sent, or the selected SNPN ID to be used in the target network to the AMF, in the HO Required message.
NOTE: In the case of Indirect Network Sharing, when UE handover is triggered between the shared network area and an area of its home network, a V-SMF can be inserted or removed, as described in clause 4.23.7.
If the AMF generates the N2 downlink signalling during the ongoing handover and receives a rejection to a N2 interface procedure (e.g. DL NAS message transfer; Location reporting control; etc.) from the NG-RAN with an indication that an Inter NG-RAN node handover procedure is in progress, the AMF may reattempt the same N2 interface procedure either when the handover is complete or the handover is deemed to have failed if the AMF is still the serving AMF, when possible. If the Inter NG-RAN node handover changes the serving AMF, the source AMF shall terminate any other ongoing N2 interface procedures except the handover procedure.
In order to minimize the number of procedures rejected by NG-RAN, the AMF should pause non-handover related N2 interface procedures (e.g. DL NAS message transfer, Location Report Control, etc.) while a handover is ongoing (i.e. from the time that a Handover Required has been received until either the Handover procedure has succeeded (Handover Notify) or failed (Handover Failure)) and continue them once the Handover procedure has completed if the AMF is still the serving AMF.
If during the handover procedure the AMF detects that the AMF needs be changed, the AMF shall reject any SMF initiated N2 request received since handover procedure started and shall include an indication that the request has been temporarily rejected due to handover procedure in progress.
Upon reception for an SMF initiated N1 and/or N2 request(s) with an indication either from the NG-RAN (via N2 SM Info) or AMF that the request has been temporarily rejected due to handover procedure in progress, the SMF starts a locally configured guard timer. The SMF should hold any signalling messages targeted towards AMF for a given UE during the handover preparation phase unless it detects that the handover execution is completed or handover has failed/cancelled. The SMF may re-attempt, up to a pre-configured number of times, when either it detects that the handover is completed or has failed using message reception or at expiry of the guard timer.
In the case of N2 handover within the VPLMN in a home routed roaming scenario, the SMF in the Inter NG-RAN node N2 based handover procedure (Figure 4.9.1.3.2-1 and Figure 4.9.1.3.3-1) interacting with the S-UPF, T-UPF, S-AMF and T-AMF is the V-SMF and the SMF (Figure 4.9.1.3.3-1) interacting with the UPF (PSA) is the H-SMF.
In the case of inter-PLMN N2 handover in a home routed roaming scenario, the procedures in clause 4.23 apply.
For the MBSR mobility as specified in clause 5.35A.3 of TS 23.501 [2], the MBSR-UE may operate without any PDU session. In that case, the NG-RAN and the AMF behave as specified in clause 5.35A.3.4 in TS 23.501 [2]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.3.2 Preparation phase | Figure 4.9.1.3.2-1: Inter NG-RAN node N2 based handover, Preparation phase
1. S-RAN to S-AMF: Handover Required (Target ID, Source to Target transparent container, SM N2 info list, PDU Session IDs, intra system handover indication).
NOTE 1: When applicable the message includes the selected NID, see TS 38.413 [10] for the IE that includes the selected NID. The T-AMF, ensures that the selected NID is forwarded to SMF.
Source to Target transparent container includes NG-RAN information created by S-RAN to be used by T-RAN and is transparent to 5GC. It also contains for each PDU session the corresponding QoS flows/DRBs information subject to data forwarding. It may also contain DAPS Information if DAPS handover is supported by S-RAN and S-AMF and DAPS handover is requested for one or more DRBs as described in TS 38.300 [9]. It may also contain the time-based handover parameters when time-based trigger condition is used.
All PDU Sessions handled by S-RAN (i.e. all existing PDU Sessions with active UP connections) shall be included in the Handover Required message, indicating which of those PDU Session(s) are requested by S-RAN to handover. The SM N2 info includes Direct Forwarding Path Availability if direct data forwarding is available.
Direct Forwarding Path Availability indicates whether direct forwarding is available from the S-RAN to the T-RAN. This indication from S-RAN can be based on e.g. the presence of IP connectivity and security association(s) between the S-RAN and the T-RAN.
If the source NG RAN and target NG RAN support RACS as defined in TS 23.501 [2], the Source to Target transparent container need not carry the UE radio access capabilities (instead the UE Radio Capability ID is supplied from the CN to the T-RAN). However, if the source NG-RAN has knowledge that the target NG-RAN might not have a local copy of the Radio Capability corresponding to the UE Radio Capability ID (i.e. because the source NG-RAN had itself to retrieve the UE's Radio Capability from the AMF) then the source NG-RAN may also send some (or all) of the UE's Radio Capability to the target NG-RAN (the size limit based on local configuration). In the case of inter-PLMN handover, when the source and target NG-RAN support RACS as defined in TS 23.501 [2] and the source NG-RAN determines based on local configuration that the target PLMN does not support the UE Radio Capability ID assigned by the source PLMN, then the source NG-RAN includes the UE radio access capabilities in the Source to Target transparent container.
2. T-AMF Selection: When the S-AMF can't serve the UE anymore, the S-AMF selects the T-AMF as described in clause 6.3.5 on "AMF Selection Function" in TS 23.501 [2].
3. [Conditional] S-AMF to T-AMF: Namf_Communication_CreateUEContext Request (N2 Information (Target ID, Source to Target transparent container, SM N2 information list, PDU Session IDs), UE context information (SUPI, Service area restriction, Allowed NSSAI for each Access Type and Partially Allowed NSSAI if available, Tracing Requirements, LTE M Indication, the list of PDU Session IDs along with the corresponding SMF information and the corresponding S-NSSAI(s), PCF ID(s), DNN, UE Radio Capability ID and UE Radio Capability Information, N2 Notify URI). If the subscription information includes Tracing Requirements, the old AMF provides the target AMF with Tracing Requirements.
If the old AMF was a consumer of UE related NWDAF services, the old AMF includes information about active analytics subscriptions, i.e. the Subscription Correlation ID(s), NWDAF identifier(s) (i.e. Instance ID or Set ID), Analytics ID(s) and associated Analytics specific data in the Namf_Communication_UEContextTransfer request. Usage of the analytics information by the new AMF is specified in TS 23.288 [50].
In inter PLMN handover case, UE context information includes HPLMN S-NSSAIs corresponding to the Allowed NSSAI for each Access Type and Partially Allowed NSSAI, without Allowed NSSAI and Partially Allowed NSSAI of source PLMN. The target AMF may determine the Allowed NSSAI and Partially Allowed NSSAI based on the HPLMN S-NSSAIs received in step 3, or else the target AMF queries the NSSF by invoking Nnssf_NSSelection_Get service operation with the HPLMN S-NSSAIs and PLMN ID of SUPI. Based on the query result returned from the NSSF, the target AMF determines whether the AMF re-allocation need be triggered and if needed reselects another target AMF. In this case the target AMF selected by the S-AMF is the Initial AMF. And another reselected target AMF is the final target AMF (i.e. T-AMF).
The S-AMF initiates Handover resource allocation procedure by invoking the Namf_Communication_CreateUEContext service operation towards the target AMF.
When the S-AMF can still serve the UE, this step and step 12 are not needed.
If target AMF re-allocation is needed, e.g. due to the inter PLMN handover, the initial AMF invokes Namf_Communication_CreateUEContext request (SUPI, Target 5GAN Node ID, Source to Target Transparent Container, 5GS MM Context, PDU Session ID and its associated S-NSSAI of the VPLMN value for each PDU Session, the corresponding S-NSSAI of HPLMN value for home routed PDU Session(s), Allowed NSSAI, N2 Notify URI) to the selected final target AMF. The N2 Notify URI is the N2 Notify URI of the source AMF, which is used by the T-AMF to send N2 handover notify to the S-AMF. If the information about active analytics subscriptions are received from S-AMF, it is also included them in the Namf_Communication_CreateUEContext request.
If Service area restrictions are available in the S-AMF, they may be forwarded to the T-AMF as described in clause 5.3.4.1.2 of TS 23.501 [2].
If both Home and Visited PCF ID(s) are provided by the S-AMF, the T-AMF contacts the (V-) PCF identified by the (V-)PCF ID. If the (V-)PCF identified by the (V-)PCF ID is not used or there are no PCF ID(s) received from the S-AMF, the T-AMF may select the PCF(s) as described in clause 6.3.7.1 of TS 23.501 [2] and according to the V-NRF to H-NRF interaction described in clause 4.3.2.2.3.3. The T-AMF informs the S-AMF that the PCF ID is not used, as defined in step 12 and then the S-AMF terminates the AM Policy Association with the PCF identified by the PCF ID.
4. [Conditional] T-AMF to SMF: Nsmf_PDUSession_UpdateSMContext (PDU Session ID, Target ID, T-AMF ID, N2 SM Information).
For each PDU Session indicated by S-RAN, the AMF invokes the Nsmf_PDUSession_UpdateSMContext Request to the associated SMF. However, if the S-NSSAI associated with PDU Session is not available in the T-AMF, the T-AMF does not invoke Nsmf_PDUSession_UpdateSMContext for this PDU Session.
PDU Session ID indicates a PDU Session candidate for N2 Handover. Target ID corresponds to Target ID provided by S-RAN in step 1. SM N2 Info includes the Direct Forwarding Path Availability if the direct data forwarding is available between the S-RAN and the T-RAN and has been inserted by the S-RAN.
If the (T-)AMF detects that the UE moves into a non-allowed area based on Service area restrictions, the (T‑)AMF notifies each NF consumer which has subscribed for UE reachability event (e.g. SMFs corresponding to the list of PDU Sessions received in UE Context from (S-)AMF via Namf_EventExposure_Notify that the UE is only reachable for regulatory prioritized services.
5. [Conditional] SMF checks if the Target ID is within the service area of the UPF connecting to NG-RAN. If UE has moved out of the service area of the UPF connecting to NG-RAN, SMF selects a new intermediate UPF according to clause 6.3.3 of TS 23.501 [2], if available. If redundant transmission is performed for one or more QoS Flows of the PDU Session, the SMF selects two new Intermediate UPFs to support the redundant transmission based on two N3 and N9 tunnels between the T-RAN and the UPF (PSA) as described in clause 5.33.2.2 of TS 23.501 [2]. In this case, step 6c and 6d are performed between SMF and each T-UPF.
6a. [Conditional] SMF to UPF (PSA): N4 Session Modification Request.
If the SMF selects a new UPF to act as intermediate UPF for the PDU Session and the different CN Tunnel Info need be used, the SMF sends N4 Session Modification Request message to UPF (PSA). The SMF provides the CN Tunnel Info (on N9) if the CN Tunnel Info is allocated by the SMF and UL Packet detection rules associate the CN Tunnel Info (on N9) to be installed on the UPF (PSA).
If redundant transmission is performed for one or more QoS Flows of the PDU Session and the different CN Tunnel Info need be used, the SMF provides two CN Tunnel Info (on N9) to the UPF (PSA) if the CN Tunnel Info is allocated by the SMF and indicates to the UPF (PSA) one of the CN Tunnel Info is used as redundancy tunnel of the PDU Session.
6b. [Conditional] UPF (PSA) to SMF: N4 Session Modification Response.
The UPF (PSA) sends an N4 Session Modification Response message to the SMF. If the UPF (PSA) allocates CN Tunnel Info (on N9) of UPF (PSA), it provides CN Tunnel Info (on N9) to the SMF. If redundant transmission is performed for one or more QoS Flows of the PDU Session, the UPF (PSA) provides two CN Tunnel Info (on N9) of UPF (PSA) to the SMF and indicates the SMF that one CN Tunnel Info is used as redundancy tunnel of the PDU Session as described in in clause 5.33.2.2 of TS 23.501 [2]. The UPF (PSA) associate the CN Tunnel Info (on N9) with UL Packet detection rules provided by the SMF.
6c. [Conditional] SMF to T-UPF (intermediate): N4 Session Establishment Request.
If the SMF selects a new intermediate UPF, i.e. the target UPF (T-UPF), for the PDU Session and if CN Tunnel Info is allocated by the T-UPF, an N4 Session Establishment Request message is sent to the T-UPF, providing Packet detection, enforcement and reporting rules to be installed on the T-UPF. The CN Tunnel Info (on N9) of UPF (PSA) for this PDU Session, which is used to setup N9 tunnel, is also provided to the T-UPF.
6d. T-UPF (intermediate) to SMF: N4 Session Establishment Response.
The T-UPF sends an N4 Session Establishment Response message to the SMF with DL CN Tunnel Info and UL CN Tunnel Info (i.e. N3 tunnel info). The SMF starts a timer to release the resource of S-UPF, which is to be used in step 13a of the Execution Phase.
7. SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response (PDU Session ID, N2 SM Information, Reason for non-acceptance).
If at step 5 the SMF has determined that the UPF connecting to NG-RAN can still be used after the handover or has selected a new intermediate UPF, the SMF includes in the Nsmf_PDUSession_UpdateSMContext response the N2 SM Information containing the N3 UP address and the UL CN Tunnel ID of the UPF, the QoS parameters, TSCAI and the User Plane Security Enforcement information for the Target NG-RAN. If redundant transmission is performed for one or more QoS Flows of the PDU Session, two UL CN Tunnel Info are included in the N2 SM Information. If the N2 SM information received at step 4 does not include the Direct Forwarding Path Availability and the SMF knows that there is no indirect data forwarding connectivity between source and target, the N2 SM Information includes a Data forwarding not possible indication. If the SMF indicated that Direct Forwarding is available in step 4, the SMF should further include a "Direct Forwarding Path Availability" indication in the N2 SM information container. The SMF sends the Alternative QoS Profiles, request for congestion information monitoring or request for information for ECN marking for L4S at PSA UPF or request for ECN marking for L4S at NG-RAN for QoS Flow (see clauses 5.45.3, 5.37.4 and 5.37.3 of TS 23.501 [2]) to the Target NG-RAN on a per QoS Flow basis, if available.
If the SMF failed to find a suitable I-UPF at step 5, the SMF does not include any N2 SM Information regarding the PDU Session to avoid establishment of radio resources at the target NG-RAN. Instead of that, the SMF provides a reason for non-acceptance. The SMF decides to (based on local policies) either:
- trigger re-establishment of PDU Session. After handover procedure, SMF sends N1 message to the UE via the AMF by invoking Namf_Communication_N1N2MessageTransfer containing the cause indicating PDU Session re-establishment is required for the UE; or
- keep the PDU Session (the User Plane connection being deactivated); or
- release the PDU Session after handover procedure.
If the SMF has received notification from (T-)AMF that the UE is only reachable for regulatory prioritized services, the SMF does not include any N2 SM info regarding the PDU Session for non-regulatory prioritized services to avoid establishment of radio resources at the target NG-RAN. If the SMF receives notification from (T-)AMF that UE is only reachable for regulatory prioritized service after this step via Namf_EventExposure_Notify, the SMF deactivates the PDU Session after handover procedure finish if the PDU Session is not for regulatory prioritized services.
8. AMF supervises the Nsmf_PDUSession_UpdateSMContext Response messages from the involved SMFs. The lowest value of the Max delay indications for the PDU Sessions that are candidates for handover gives the maximum time AMF may wait for Nsmf_PDUSession_UpdateSMContext Response messages before continuing with the N2 Handover procedure. At expiry of the maximum wait time or when all Nsmf_PDUSession_UpdateSMContext Response messages are received, AMF continues with the N2 Handover procedure (Handover Request message in step 9).
NOTE 2: The delay value for each PDU Session is locally configured in the AMF and implementation specific.
9. T-AMF to T-RAN: Handover Request (Source to Target transparent container, N2 MM Information, N2 SM Information list, Tracing Requirements, UE Radio Capability ID). If the subscription information includes Tracing Requirements, the target AMF provides the target RAN with Tracing Requirements in the Handover Request.
T-AMF determines T-RAN based on Target ID. T-AMF may allocate a 5G-GUTI valid for the UE in the AMF and target TAI.
Source to Target transparent container is forwarded as received from S-RAN. N2 MM Information includes e.g. security information and Mobility Restriction List if available in the T-AMF.
N2 SM Information list includes N2 SM Information received from SMFs for the T-RAN in the Nsmf_PDUSession_UpdateSMContext Response messages received within allowed max delay supervised by the T-AMF mentioned in step 8.
T-AMF provides the UE Radio Capability ID to T-RAN if RACS is supported. If the UE Radio Capability ID is included in the Handover Request message and no UE radio access capabilities are provided in the Source to Target transparent container, when there is no corresponding UE radio capabilities set for UE Radio Capability ID at T-RAN, T-RAN shall request the T-AMF to provide the UE radio capabilities set corresponding to UE Radio Capability ID to the T-RAN. If the Source to Target transparent container contains the UE radio access capabilities and the T-RAN did not receive the UE Radio Capability ID from the T-AMF, NG-RAN shall proceed with handover using the received UE radio access capabilities. If the T-RAN received both the UE radio access capabilities and the UE Radio Capability ID, then the T-RAN shall use any locally stored UE radio access capability information corresponding to the UE Radio Capability ID. If none are stored locally, the T-RAN may request the full UE radio access capability information from the core network. If the full UE radio access capability information is not promptly received from the core network, or the T-RAN chooses not to request them, then the T-RAN shall proceed with the UE radio access capabilities sent by the source RAN node. The T-RAN shall not use the UE radio access capability information received from the source RAN node for any other UE with the same the UE Radio Capability ID.
If Energy Saving Indicator is in the UE context, the AMF includes Energy Saving Indicator in the Handover Request.
Editor's note: Whether the Energy Saving Indicator is provided to the NG-RAN is FFS.
10. T-RAN to T-AMF: Handover Request Acknowledge (Target to Source transparent container, List of PDU Sessions to Hand-over with N2 SM information, List of PDU Sessions that failed to be established with the failure cause given in the N2 SM information element, PDU Set Based Handling Support Indication included in the N2 SM information).
Target to Source transparent container includes a UE container with an access stratum part and a NAS part. The UE container is sent transparently via T-AMF, S-AMF and S-RAN to the UE. If DAPS handover is supported by the T-RAN and T-AMF and the DAPS Information for one or more DRBs had been received in the Source to Target Transparent Container, the T-RAN includes the DAPS Response information in the Target to Source Transparent Container as described in TS 38.300 [9].
T-RAN creates List Of PDU Sessions failed to be setup and reason for failure (e.g. T-RAN decision, S-NSSAI is not available, unable to fulfil User Plane Security Enforcement) based on T-RAN determination. The information is provided to the S-RAN.
The N2 SM information in the List Of PDU Sessions to Hand-over, contains per each PDU Session ID T-RAN N3 addressing information i.e. N3 UP address and Tunnel ID of T-RAN for the PDU Session.
If redundant transmission is performed for one or more QoS Flows of the PDU Session, the T-RAN provides two AN Tunnel Info for the PDU Session in the N2 SM information. The T-RAN indicates to the SMF one of the AN Tunnel Info is used as the redundancy tunnel of the PDU session as described in clause 5.33.2.2 of TS 23.501 [2]. If only one AN Tunnel Info is provided by the Target NG-RAN for the PDU session, the SMF may release these QoS Flows by triggering PDU Session Modification procedure as specified in clause 4.3.3 after the handover procedure.
The N2 SM information may also include:
- an Indication whether UP integrity protection is performed or not on the PDU Session based on User Plane Security Enforcement information received in N2 SM information in step 9.
- if the PDU Session has at least one QoS Flow subject for data forwarding, N3 UP address and Tunnel ID of T-RAN for receiving forwarded data. The T-RAN provides data forwarding addresses for each data forwarding tunnel which it decided to setup.
- For each QoS Flow accepted with an Alternative QoS Profile (see TS 23.501 [2]), the Target NG-RAN shall include a reference to the fulfilled Alternative QoS Profile.
- For each accepted QoS Flow, established QoS Flows status (active/not active) for one of the following: congestion information monitoring, ECN marking for L4S at PSA UPF, ECN marking for L4S at NG-RAN.
- PDU Set Based Handling Support Indication as described in clause 5.37.5.3 of TS 23.501 [2].
11a. AMF to SMF: Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID, N2 SM response received from T-RAN in step 10).
For each N2 SM response received from the T-RAN (N2 SM information included in Handover Request Acknowledge), AMF sends the received N2 SM response to the SMF indicated by the respective PDU Session ID.
If no new T-UPF is selected, SMF stores the N3 tunnel info of T-RAN from the N2 SM response if N2 handover is accepted by T-RAN.
The SMF/UPF allocates the N3 UP address and Tunnel IDs for indirect data forwarding corresponding to the data forwarding tunnel endpoints established by T-RAN.
If a PDU Session is indicated as a rejected PDU Session by the Target NG-RAN with an indication that the PDU session was rejected because User Plane Security Enforcement is not supported in the Target NG-RAN and the User Plane Enforcement Policy indicates "Required" as described in clause 5.10.3 of TS 23.501 [2], the SMF triggers the release of this PDU Session. In all other cases of PDU Session rejection, the SMF can decide whether to release the PDU Session (possibly triggering the re-establishment of the PDU Session as described in step 5) or to deactivate the UP connection of this PDU Session.
If some of the QoS Flows of a PDU Session are not accepted by the Target NG-RAN, the SMF shall initiate the PDU Session Modification procedure to remove the non-accepted QoS Flows from the PDU Session(s) after the handover procedure is completed.
11b. [Conditional] SMF to T-UPF: N4 Session Modification Request (T-RAN SM N3 forwarding Information list, indication to allocate DL forwarding tunnel(s) for indirect forwarding)
If the SMF selected a T-UPF in step 6a, the SMF updates the T-UPF by providing the T-RAN SM N3 forwarding information list by sending a N4 Session Modification Request to the T-UPF.
If indirect forwarding applies based on indication from the S-RAN and the UPF is re-allocated and if the SMF decides to setup the indirect forwarding tunnel on the same T-UPF, the SMF also requests in the N4 Session Modification Request message to the T-UPF, to allocate DL forwarding tunnel(s) for indirect forwarding.
Indirect forwarding may be performed via a UPF which is different from the T-UPF, in which case the SMF selects a T-UPF for indirect forwarding.
11c. [Conditional] T-UPF to SMF: N4 Session Modification Response (T-UPF SM N3 forwarding Information list).
The T-UPF allocates Tunnel Info and returns an N4 Session Modification Response message to the SMF.
The T-UPF SM N3 forwarding info list includes T-UPF N3 address, T-UPF N3 Tunnel identifiers for forwarding data
11d. [Conditional] SMF to S-UPF: N4 Session Modification Request (T-RAN SM N3 forwarding Information list or T-UPF SM N3 forwarding Information list, indication to allocate DL forwarding tunnel(s) for indirect forwarding).
If the UPF is re-allocated, this message includes the T-UPF SM N3 forwarding info list. If the UPF is not re-allocated, this message includes the T-RAN SM N3 forwarding info list.
If indirect forwarding applies based on indication from NG-RAN and UPF allocates tunnel identities, the SMF indicates in the N4 Session Modification Request message to the S-UPF to allocate DL forwarding tunnel(s) for indirect forwarding.
Indirect forwarding may be performed via a UPF which is different from the S-UPF.
11e. [Conditional] S-UPF to SMF: N4 Session Modification Response (S-UPF SM N3 forwarding Information list).
The S-UPF allocates Tunnel Info and returns an N4 Session establishment Response message to the SMF.
The S-UPF SM N3 forwarding Information list includes S-UPF N3 address, S-UPF N3 Tunnel identifiers for DL data forwarding.
11f. SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response (N2 SM Information).
The SMF sends an Nsmf_PDUSession_UpdateSMContext Response message per PDU Session to T-AMF.
The SMF creates an N2 SM information containing the DL forwarding Tunnel Info to be sent to the S-RAN by the AMF. The SMF includes this information in the Nsmf_PDUSession_UpdateSMContext response. The DL forwarding Tunnel Info can be one of the following information:
- If direct forwarding applies, then the SMF includes the T-RAN N3 forwarding information the SMF received in step 11a.
- If the indirect forwarding tunnel is setup in step 11b or 11d, then the SMF includes the T-UPF or S-UPF DL forwarding information containing the N3 UP address and the DL Tunnel ID of the UPF.
12. [Conditional] T-AMF to S-AMF: Namf_Communication_CreateUEContext Response (N2 information necessary for S-AMF to send Handover Command to S-RAN including Target to Source transparent container, PDU Sessions failed to be setup list, N2 SM information (N3 DL forwarding Information, PCF ID), [Target AMF ID]).
T-AMF supervises the Nsmf_PDUSession_UpdateSMContext Response message from the involved SMFs. At expiry of the maximum wait time or when all Nsmf_PDUSession_UpdateSMContext Response messages are received, T-AMF sends the Namf_Communication_CreateUEContext Response to the S-AMF.
The PDU Sessions failed to be setup list includes the List Of PDU Sessions failed to be setup received from target RAN in step 10 and the Non-accepted PDU session List generated by the T-AMF.
Non-accepted PDU Session List includes following PDU Session(s) with proper cause value:
- Non-accepted PDU Session(s) by the SMF(s);
- Non-accepted PDU Session(s) by the AMF due to no response from the SMF within maximum wait time; and
- Non-accepted PDU Session(s) by the AMF due to non-available S-NSSAI in the T-AMF, which is decided at step 4.
The Target to Source transport container is received from the T-RAN. The N2 SM Information is received from the SMF in step 11f.
If target AMF re-allocation is executed in step 3, the selected final target AMF, i.e. T-AMF, invoke Namf_Communication_CreateUEContext Response (Cause, N2 information necessary for S-AMF to send Handover Command to S-RAN including Target to Source transparent container, N2 SM information (PDU Sessions failed to setup list, N3 DL forwarding Information), PCF ID, PCF reselected indication, target AMF ID) to the initial AMF. The cause indicates whether the Relocate UE Context (hand-Over) succeeded or failed. If the target NG RAN has rejected the Handover Request in step 10, the cause indicates a failure due to RAN rejection. The target AMF ID is used for S-AMF to transfer RAN Status to T-AMF directly. Based on the receiving Namf_Communication_CreateUEContext Response, the initial AMF invokes Namf_Communication_CreateUEContext Response towards S-AMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.3.3 Execution phase | Figure 4.9.1.3.3-1: inter NG-RAN node N2 based handover, execution phase
NOTE 1: Registration of serving AMF with the UDM is not shown in the figure for brevity.
1. S-AMF to S-RAN: Handover Command (Target to Source transparent container, List Of PDU Sessions to be handed-over with N2 SM information containing information received from T-RAN during the handover preparation phase, List Of PDU Sessions failed to be setup).
Target to Source transparent container is forwarded as received from S-AMF. If DAPS Response information for one or more DRBs is received by S-RAN and indicates that DAPS handover is accepted, the execution phase for DAPS handover procedure as described in clause 4.9.1.3.3a is performed.
The SM forwarding info list includes T-RAN SM N3 forwarding info list for direct forwarding or S-UPF SM N3 forwarding info list for indirect data forwarding
S-RAN uses the PDU Sessions failed to be setup list and the indicated reason for failure to decide whether to proceed with the N2 Handover procedure.
If the S-RAN supports and receives a reference to an Alternative QoS Profile for an accepted QoS Flow, it shall take it into account for deciding whether or not to proceed with the N2 Handover procedure (see TS 23.501 [2]).
2. S-RAN to UE: Handover Command (UE container).
UE container is a UE part of the Target to Source transparent container which is sent transparently from T-RAN via AMF to S-RAN and is provided to the UE by the S-RAN.
2a0. If the PLMN has configured secondary RAT usage reporting and the source NG-RAN has Secondary RAT usage data to report, the source NG-RAN node may provide RAN usage data report message (N2 SM Information (Secondary RAT usage data), Handover Flag) as in clause 4.21 to the AMF. The Handover Flag indicates to the AMF that it should buffer the N2 SM Information containing the usage data report before forwarding it.
NOTE 2: This step is not shown in this figure but the secondary RAT usage data reporting procedure is shown in figure 4.21-1 in clause 4.21.
2a. - 2c. The S-RAN sends the Uplink RAN Status Transfer message to the S-AMF, as specified in TS 36.300 [46] and TS 38.300 [9]. The S-RAN may omit sending this message if none of the radio bearers of the UE shall be treated with PDCP status preservation. In the case of time-based handover, the S-RAN sends the Uplink RAN Early Status Transfer message to the S-AMF as specified in TS 38.413 [10].
If there is an AMF relocation, the S-AMF sends this information to the T-AMF via the Namf_Communication_N1N2MessageTransfer service operation and the T-AMF acknowledges. The S-AMF or, if the AMF is relocated, the T-AMF, sends the information to the T-RAN via the Downlink RAN Status Transfer message, as specified in TS 36.300 [46] and TS 38.300 [9]. In the case of time-based handover, the T-AMF sends the Downlink RAN Early Status Transfer message to the T-RAN as specified in TS 38.413 [10].
For Inter PLMN handover, if the target AMF has been relocated in Preparation phase, e.g. due to the inter PLMN handover, the S-AMF send this information to the indicated T-AMF, which is derived from the target AMF ID received in step 12 of clause 4.9.1.3.2.
3. Uplink packets are sent from T-RAN to T-UPF and UPF (PSA). Downlink packets are sent from UPF (PSA) to S-RAN via S-UPF. The S-RAN should start forwarding of downlink data from the S-RAN towards the T-RAN for QoS Flows or DRBs subject to data forwarding. This may be either direct (step 3a) or indirect forwarding (step 3b).
4. UE to T-RAN: Handover Confirm.
After the UE has successfully synchronized to the target cell, it sends a Handover Confirm message to the T-RAN. Handover is by this message considered as successful by the UE.
5. T-RAN to T-AMF: Handover Notify.
Handover is by this message considered as successful in T-RAN.
6a. [Conditional] T-AMF to S-AMF: Namf_Communication_N2InfoNotify.
The T-AMF notifies to the S-AMF about the N2 handover notify received from the T-RAN by invoking the Namf_Communication_N2InfoNotify.
A timer in S-AMF is started to supervise when resources in S-RAN shall be release.
6b. [Conditional] S-AMF to T-AMF: Namf_Communication_N2InfoNotify ACK (N2 SM Information (Secondary RAT usage data)).
The S-AMF acknowledges by sending the Namf_Communication_N2InfoNotify ACK to the T-AMF. The N2 SM Information here is the one buffered at step 2a0 when applicable.
6c. [Conditional] S-AMF to SMF: Nsmf_PDUSession_ReleaseSMContext Request (SM Context ID, N2 SM Information (Secondary RAT Usage Data)).
If the PDU Session(s) is not accepted by the T-AMF (e.g. S-NSSAI associated with the PDU Session is not available in the T-AMF), S-AMF triggers PDU Session Release procedure as specified in clause 4.3.4.2 after the S-AMF is notified for the reception of N2 Handover Notify in step 6a.
7. T-AMF to SMF: Nsmf_PDUSession_UpdateSMContext Request (Handover Complete indication for PDU Session ID, UE presence in LADN service area, N2 SM Information (Secondary RAT usage data)). The N2 SM Information here is the one received at step 6b when applicable.
Handover Complete indication is sent per each PDU Session to the corresponding SMF to indicate the success of the N2 Handover.
When an Nsmf_PDUSession_UpdateSMContext Response message arrived too late during the handover preparation phase (see step 8 of clause 4.9.1.3.2), or the PDU Session with SMF involvement is not accepted by T-RAN, Nsmf_PDUSession_UpdateSMContext Request (SM Context ID, Operation Type) is sent to the corresponding SMF allowing the SMF to deallocate a possibly allocated N3 UP address and Tunnel ID of the selected UPF. A PDU Session handled by that SMF is considered deactivated and handover attempt is terminated for that PDU Session.
In the case that the AMF determines that the PDU Session is related to a LADN then the AMF provides the "UE presence in LADN service area". If the AMF does not provide the "UE presence in LADN service area" indication and the SMF determines that the DNN corresponds to a LADN, then the SMF considers that the UE is OUT of the LADN service area.
The SMF takes actions for the LADN PDU Session as defined in clause 5.6.5 of TS 23.501 [2] based on the "UE presence in LADN service area" indication.
For each QoS Flow for which the SMF has received a reference to the fulfilled Alternative QoS Profile in step 10 of clause 4.9.1.3.2, the SMF notifies the PCF and the UE as described in TS 23.501 [2].
8a. [Conditional] SMF to T-UPF (intermediate): N4 Session Modification Request.
If new T-UPF is inserted or an existing intermediate S-UPF is re-allocated, the SMF shall send N4 Session Modification Request indicating DL AN Tunnel Info of T-RAN to the T-UPF.
8b. [Conditional] T-UPF to SMF: N4 Session Modification Response.
The T-UPF acknowledges by sending N4 Session Modification Response message to SMF.
9a. [Conditional] SMF to S-UPF (intermediate): N4 Session Modification Request.
If UPF is not re-allocated, the SMF shall send N4 Session Modification Request indicating DL AN Tunnel Info of T-RAN to the S-UPF.
9b. [Conditional] S-UPF to SMF: N4 Session Modification Response.
The S-UPF acknowledges by sending N4 Session Modification Response message to SMF.
10a. [Conditional] SMF to UPF (PSA): N4 Session Modification Request.
For non-roaming or local breakout roaming scenario, the SMF sends N4 Session Modification Request message to PDU Session Anchor UPF, UPF (PSA), providing N3 AN Tunnel Info of T-RAN or the DL CN Tunnel Info of T-UPF if a new T-UPF is inserted or an existing intermediate S-UPF is re-allocated. If redundant transmission is performed for one or more QoS Flows of the PDU Session, two N3 AN Tunnel Info of T-RAN or two DL CN Tunnel Info of two T-UPFs are provided and the SMF indicates to the UPF (PSA) one of the AN/CN Tunnel Info is used as redundancy tunnel of the PDU Session. If the existing intermediate S-UPF terminating N9 toward the H-UPF (PDU Session Anchor) is re-allocated for the home routed roaming scenario, the V-SMF invokes an Nsmf_PDUSession_Update Request (DL CN Tunnel Info) service operation toward the H-SMF.
In the case of the S-UPF acts as a UL CL or BP, the SMF indicates only one of the PDU Session Anchors to send the "end marker" packets. To ensure the "end marker" is the last user plane packet on the old path, the SMF should modify the path on other PDU Session Anchors before it indicates the PDU Session Anchor to send the "end marker" packets.
If T-UPF is not inserted or an existing intermediate S-UPF is not re-allocated, step 10a and step 10b are skipped.
10b. [Conditional] UPF (PSA) to SMF: N4 Session Modification Response.
The UPF (PSA) sends N4 Session Modification Response message to SMF. In order to assist the reordering function in the T-RAN, the UPF (PSA) sends one or more "end marker" packets for each N3 tunnel on the old path immediately after switching the path, the source NG-RAN shall forward the "end marker" packets to the Target NG-RAN. At this point, UPF (PSA) starts sending downlink packets to the T-RAN, via T-UPF if a new T-UPF is inserted or an existing intermediate S-UPF is re-allocated. In the case of home routed roaming scenario, the H-SMF responds with the Nsmf_PDUSession_Update Response service operation to V-SMF once the H-UPF (PDU Session Anchor) is updated with the UL Tunnel Info of the T-UPF.
When there are multiple UPFs(PSA), step 10a and step 10b are performed for each UPFs(PSA).
11. SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response (PDU Session ID).
SMF confirms reception of Handover Complete.
If indirect data forwarding applies, the SMF starts an indirect data forwarding timer, to be used to release the resource of indirect data forwarding tunnel.
12. The UE initiates Mobility Registration Update procedure as described in clause 4.2.2.2.2.
The target AMF knows that it is a Handover procedure and therefore the target AMF performs only a subset of the Registration procedure, specifically the steps 4, 5 and 10 in the Registration procedure for the context transfer between source AMF and target AMF are skipped.
The target AMF, based on the S-NSSAIs subject to Network Slice-Specific Authentication and Authorization status information from source AMF in step 3 of clause 4.9.1.3.2, may decide to skip step 25 in the Registration procedure (i.e. NSSAA procedure) or whether to perform it if the status is pending.
13a. [Conditional] SMF to S-UPF (intermediate): N4 Session Release Request.
If there is a source intermediate UPF, the SMF initiates resource release, after timer in step 6 or indirect data forwarding timer expires, by sending an N4 Session Release Request (Release Cause) to source UPF. This message is also used to release the indirect data forwarding resource in S-UPF.
13b. S-UPF to SMF: N4 Session Release Response.
The S-UPF acknowledges with an N4 Session Release Response message to confirm the release of resources.
In the case of indirect data forwarding, the resource of indirect data forwarding is also released.
14a. AMF to S-RAN: UE Context Release Command ().
After the timer in step 6a expires, the AMF sends UE Context Release Command.
14b. S-RAN to AMF: UE Context Release Complete ().
The source NG-RAN releases its resources related to the UE and responds with a UE Context Release Complete () message.
15a. [Conditional] SMF to T-UPF: N4 Session Modification Request.
If indirect forwarding applies and UPF is re-allocated, after timer of indirect data forwarding expires, the SMF sends N4 Session Modification Request to T-UPF to release the indirect data forwarding resource.
15b. [Conditional] T-UPF to SMF: N4 Session Modification Response.
The T-UPF acknowledges with an N4 Session Modification Response message to confirm the release of indirect data forwarding resources.
If the AMF is subscribed to Mobility Event by other NFs, the AMF notifies the event to the corresponding NFs by invoking the Namf_EventExposure_Notify service operation as described in clause 4.15.4.2.
Upon reception of the Namf_EventExposure_Notify with an indication that UE is reachable only for regulatory prioritized service, the SMF deactivates the PDU Session if the service of the PDU Session is not regulatory prioritized. For home routed roaming case, the V-SMF triggers the deactivation of the PDU Session, in addition, the H-SMF refrains from sending downlink signalling if the signalling is not related to regulatory prioritized service upon receiving the notification.
4.9.1.3.3a Execution phase for DAPS handover
This procedure applies only if at the end of the Preparation phase it has been determined that at least one DRB of the UE is subject to a DAPS related Handover.
Figure 4.9.1.3.3a-1: inter NG-RAN node N2 based DAPS handover, execution phase
1 to 2. Same as step 1 to step 2 in clause 4.9.1.3.3 with the following difference.
DAPS Response information received in the Target to Source Transparent Container indicates the DAPS handover is accepted for one or more DRBs.
2a to 2c. The S-RAN sends the Uplink RAN Early Status Transfer message to the S-AMF as specified in TS 38.413 [10]. For the DRBs not subjecting to DAPS, steps 2a to 2c in clause 4.9.1.3.3 may be performed.
If there is an AMF change, the S-AMF sends this information to the T-AMF via the Namf_Communication_N1N2MessageTransfer service operation and the T-AMF acknowledges. The S-AMF or, if the AMF is relocated, the T-AMF, sends the information to the T-RAN via the Downlink RAN Early Status Transfer message, as specified in TS 38.413 [10].
3. Same as step 3 in clause 4.9.1.3.3.
4. Same as step 4 in clause 4.9.1.3.3.
5. T-RAN to T-AMF: same as step 5 in clause 4.9.1.3.3 with the difference that the Handover Notify includes a Notify Source NG-RAN node information which is used to notify the S-RAN that the UE has successfully accessed the T-RAN.
6a. [Conditional] T-AMF to S-AMF: Namf_Communication_N2InfoNotify.
The T-AMF notifies the S-AMF as in step 6a in clause 4.9.1.3.3 with the difference that Notify Source NG-RAN node information is included.
6b. [Conditional] S-AMF to T-AMF: Namf_Communication_N2InfoNotify ACK.
The S-AMF acknowledges by sending the Namf_Communication_N2InfoNotify ACK to the T-AMF as in step 6b in clause 4.9.1.3.3.
7. S-AMF to S-RAN: Handover Success.
The S-AMF informs the S-RAN node that the UE has successfully accessed the T-RAN as described in TS 38.413 [10], S-RAN stops the UL data transfer for the UE.
8a to 8c. The S-RAN initiates step 8a. Step 8a to 8c are the same as step 2a to 2c in clause 4.9.1.3.3 for the DRB(s) subject to DAPS.
9. Step 6c to step 15 in clause 4.9.1.3.3 are performed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.1.4 Inter NG-RAN node N2 based handover, Cancel | Prior to sending a Handover Command to the UE, the source NG-RAN node may attempt cancellation of handover during the handover procedure. The reason for cancellation may include timer expiration, internal failure within the source NG-RAN node or UE returned to source cell etc. The handover cancellation is initiated by sending a Handover Cancel request to the source AMF. This is done in order to release the resources reserved for the handover in the target system.
The AMF shall cancel the handover resources as defined in clause 4.11.1.2.3 for case the source RAN is NG-RAN. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2 Handover of a PDU Session procedure between 3GPP and untrusted non-3GPP access | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2.0 General | The procedures in this clause are used to hand over a PDU Session between 3GPP access and non-3GPP access. This can be triggered, for example, due to radio conditions, user interaction, etc. When the UE triggers handover of a PDU Session between 3GPP access and non-3GPP access and the procedure fails due to e.g. not allowed by policy or AN rejected resource setup, etc. the network should not release the PDU Session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2.1 Handover of a PDU Session procedure from untrusted non-3GPP to 3GPP access (non-roaming and roaming with local breakout) | Clause 4.9.2.1 specifies how to hand over a UE from a source Untrusted non-3GPP access to a target 3GPP access and how a UE can handover a PDU Session from untrusted non-3GPP access to 3GPP access. It is based on the PDU Session Establishment procedure for 3GPP access as specified in clause 4.3.2.
Figure 4.9.2.1-1: Handover of a PDU Session procedure from untrusted non-3GPP access to 3GPP access (non-roaming and roaming with local breakout)
1. If the UE is not registered via 3GPP access, the UE shall initiate Registration procedure as defined in clause 4.2.2.2.2.
2. The UE performs a PDU Session Establishment procedure with the PDU Session ID of the PDU Session to be moved as specified clause 4.3.2.2.1 (PDU Session Establishment for Non-roaming and Roaming with Local Breakout).
When sending the PDU Session Establishment Accept, within the N1 SM container and in the N2 SM information, the SMF shall include all QoS information (e.g. QoS Rule(s) in N1 SM container, QFI(s) and QoS Profile(s) in N2 SM information) for the QoS Flow(s) that are applicable to the PDU Session for the target access.
3. If the User Plane of the PDU Session is activated in non-3GPP access, the SMF executes the release of resources in non-3GPP access by initiating a Namf_Communication_N1N2MessageTransfer (to send N2 resource release request) which triggers performing steps 4 to 7 specified in clause 4.12.7, followed by step 7a/7b specified in clause 4.3.4.2 in order to release the resources over the source non-3GPP access. Because the PDU Session shall not be released, the SMF shall not send the PDU Session Release Command to the UE. Hence, in steps 4 and 7 of clause 4.12.7 as well as in step 7a of clause 4.3.4.2, the messages do not include the N1 SM container but only the N2 Resource Release Request (resp. Ack). Since the PDU Session is not to be released, the SMF shall not execute step 11 of clause 4.3.4.2 and the SM context between the AMF and the SMF is maintained.
If the User Plane of the PDU Session is deactivated in non-3GPP access, this step is skipped.
The steps 2 and 3 shall be repeated for all PDU Sessions to be moved from to untrusted non-3GPP access to 3GPP access.
If the UE is moving to the NB-IoT RAT type of 3GPP access, the PDU Session Establishment request would be rejected by AMF when the UP resources exceeds the UE's maximum number of supported UP resources as described in clause 5.4.5.2.4 of TS 24.501 [25]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2.2 Handover of a PDU Session procedure from 3GPP to untrusted non-3GPP access (non-roaming and roaming with local breakout) | Clause 4.9.2.2 specifies how to hand over a UE from a source 3GPP access to a target Untrusted non-3GPP access and how a UE can handover a PDU Session from 3GPP access to untrusted non-3GPP access. It is based on the PDU Session Establishment procedure for non-3GPP access as specified in clause 4.12.5.
Figure 4.9.2.2-1: Handover of a PDU Session from 3GPP access to untrusted non-3GPP access (non-roaming and roaming with local breakout)
1. If the UE is not registered via untrusted non-3GPP access, the UE shall initiate Registration procedure as defined in clause 4.12.2.
2. The UE performs PDU Session Establishment procedure with the PDU Session ID of the PDU Session to be moved as specified in clause 4.12.5.
When sending the PDU Session Establishment Accept, within the N1 SM container and in the N2 SM information, the SMF shall include all QoS information (e.g. QoS Rule(s) in N1 SM container, QFI(s) and QoS Profile(s) in N2 SM information) for the QoS Flow(s) that are applicable to the PDU Session for the target access.
3. If the User Plane of the PDU Session is activated in 3GPP access, the SMF executes the release of resource in 3GPP access by performing step 3b, then steps 4 to 7a/7b specified in clause 4.3.4.2 (UE or network requested PDU Session Release for Non-Roaming and Roaming with Local Breakout) in order to release the resources over the source 3GPP access. Because the PDU Session shall not be released, the SMF shall not send the PDU Session Release Command to the UE. Hence, in steps 3b, 4, 6 and 7a of clause 4.3.4.2, messages do not include the N1 SM container but only the N2 Resource Release Request (resp. Ack). Since the PDU Session is not to be released, the SMF shall not execute step 11 of clause 4.3.4.2 and the SM context between the AMF and the SMF is maintained.
If the User Plane of the PDU Session is deactivated in 3GPP access, this step is skipped.
The steps 2 and 3 shall be repeated for all PDU Sessions to be moved from 3GPP access to untrusted non-3GPP access.
If the PDU Session is associated with Control Plane Only Indication, the AMF shall reject the PDU Session establishment request as the Control Plane CIoT Optimisation feature is not supported over non-3GPP accesses as described in clause 5.4.5.2.5 of TS 24.501 [25]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2.3 Handover of a PDU Session procedure from untrusted non-3GPP to 3GPP access (home routed roaming) | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2.3.1 The target AMF is in the PLMN of the N3IWF | Figure 4.9.2.3.1 -1: Handover of a PDU Session procedure from untrusted non-3GPP access to 3GPP access (home routed roaming)
1. If the UE is not registered via 3GPP access, the UE shall initiate Registration procedure as defined in clause 4.2.2.2.2. The NG-RAN selects the same AMF as the one used via non-3GPP access.
2. The UE performs a PDU Session Establishment procedure with the PDU Session ID of the PDU Session to be moved as specified clause 4.3.2.2.2 (PDU Session Establishment for Home Routed Roaming). The AMF selects the same V-SMF as the one used via non-3GPP access.
In the Nsmf_PDUSession_Update Response the H-SMF shall include all QoS information for the QoS Flow(s) applicable to the PDU Session for the target access so that when sending the PDU Session Establishment Accept, within the N1 SM container and in the N2 SM information, the V-SMF can include all QoS information (e.g. QoS Rule(s) in N1 SM container, QFI(s) and QoS Profile(s) in N2 SM information) for the QoS Flow(s) acceptable according to VPLMN policies. In case of Handover for a PDU Session eligible to EPS Interworking, the Nsmf_PDUSession_Update Response should also contain: EPS bearer context(s), linked EBI.
3. If the User Plane of the PDU Session is activated in non-3GPP access, the V-SMF executes the release of resource in non-3GPP access by initiating a Namf_Communication_N1N2MessageTransfer (to send N2 resource release request) which triggers performing steps 4 to 7 specified in clause 4.12.7, followed by step 7a/7b specified in clause 4.3.4.2 in order to release the resources over the source non-3GPP access. Because the PDU Session shall not be released, the SMF shall not send the PDU Session Release Command to the UE. Hence, in steps 4 and 7 of clause 4.12.7 as well as in step 7a of clause 4.3.4.2, the messages do not include the N1 SM container but only the N2 Resource Release Request (resp. Ack). Since the PDU Session is not to be released, the SMF shall not execute step 11 of clause 4.3.4.2 and the SM context between the AMF and the SMF is maintained.
If the User Plane of the PDU Session is deactivated in non-3GPP access, this step is skipped.
The steps 2 and 3 shall be repeated for all PDU Sessions to be moved from to untrusted non-3GPP access to 3GPP access. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2.3.2 The target AMF is not in the PLMN of the N3IWF (i.e. N3IWF in HPLMN) | Figure 4.9.2.3.2-1: Handover of a PDU Session procedure from untrusted non-3GPP access with N3IWF in the HPLMN to 3GPP access (home routed roaming)
1. If the UE is not registered via 3GPP access, the UE shall initiate Registration procedure as defined in clause 4.2.2.2.2. This includes the retrieval of the SMF-IDs corresponding to each of the PDU Sessions.
2. The UE performs a PDU Session Establishment procedure with the PDU Session ID of the PDU Session to be moved as specified clause 4.3.2.2.2 (PDU Session Establishment for Home Routed Roaming).
In the Nsmf_PDUSession_Create Response the H-SMF shall include all QoS information for the QoS Flow(s) applicable to the PDU Session for the target access so that when sending the PDU Session Establishment Accept, within the N1 SM container and in the N2 SM information, the V-SMF can include all QoS information (e.g. QoS Rule(s) in N1 SM container, QFI(s) and QoS Profile(s) in N2 SM information) for the QoS Flow(s) acceptable according to VPLMN policies.
3. The H-SMF executes the release of resources in non-3GPP AN by performing steps 3-12 specified in clause 4.12.7 with the following exceptions:
- the H-SMF interfaces the source AMF (in the home PLMN). The H-SMF shall not send the N1 SM Container (PDU Session Release Command) to the UE;
- The Npcf_SMPolicyControl_Delete service operation to PCF shall not be performed.
- Nsmf_PDUSession_SMContexStatusNotify service operation invoked by the H-SMF to the source AMF indicates the PDU Session is moved to different access.
The steps 2 and 3 shall be repeated for all PDU Sessions to be moved from to untrusted non-3GPP access to 3GPP access. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2.4 Handover of a PDU Session procedure from 3GPP to untrusted non-3GPP access (home routed roaming) | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2.4.1 The selected N3IWF is in the registered PLMN | Figure 4.9.2.4.1-1: Handover of a PDU Session procedure from 3GPP access to untrusted non-3GPP access (home routed roaming)
1. If the UE is not registered via untrusted non-3GPP access, the UE shall initiate Registration procedure as defined in clause 4.12.2. The N3IWF selects the same AMF as the one used via 3GPP access.
2. The UE performs PDU Session Establishment procedure with the PDU Session ID of the PDU Session to be moved as specified in clause 4.12.5. The AMF selects the same V-SMF as the one used via 3GPP access.
In the Nsmf_PDUSession_Update Response the H-SMF shall include all QoS information for the QoS Flow(s) applicable to the PDU Session for the target access so that when sending the PDU Session Establishment Accept, within the N1 SM container and in the N2 SM information, the V-SMF can include all QoS information (e.g. QoS Rule(s) in N1 SM container, QFI(s) and QoS Profile(s) in N2 SM information) for the QoS Flow(s) acceptable according to VPLMN policies.
3. If the User Plane of the PDU Session is activated in 3GPP access, the V-SMF executes the release of resources in 3GPP access by performing step 5c to 10 specified in clause 4.3.4.3 (UE or network requested PDU Session Release for Home Routed Roaming) in order to release the resources over the source 3GPP access. Because the PDU Session shall not be released, the SMF shall not send the PDU Session Release Command to the UE. Hence, in steps 5c, 6, 8 and 9 of clause 4.3.4.3, the messages do not include the N1 SM container but only the N2 Resource Release Request (resp. Ack). Since the PDU Session is not to be released, the SMF shall not execute step 11 of clause 4.3.4.2 and the SM context between the AMF and the SMF is maintained.
If the User Plane of the PDU Session is deactivated in 3GPP access, this step is skipped.
The steps 2 and 3 shall be repeated for all PDU Sessions to be moved from 3GPP access to untrusted non-3GPP access. |
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