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fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.2.4.2 The UE is roaming and the selected N3IWF is in the home PLMN | Figure 4.9.2.4.2-1: Handover of a PDU Session procedure from 3GPP access to untrusted non-3GPP access with N3IWF in the HPLMN (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. This includes the retrieval of the SMF-IDs corresponding to each of the PDU Sessions.
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.
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 source V-SMF, V-UPF, V-AMF and 3GPP AN by performing steps 3a, 5c to 16b specified in clause 4.3.4.3 with the following exceptions:
- the H-SMF indicates in the Nsmf_PDUSession_Update Request that the UE shall not be notified. This shall result in the V-SMF not sending the N1 Container (PDU Session Release Command) to the UE;
- Nsmf_PDUSession_StatusNotify service operation invoked by H-SMF to V-SMF indicates PDU Session is moved to different access;
- Nsmf_PDUSession_SMContexStatusNotify service operation invoked by the V-SMF to the AMF indicates the PDU Session is moved to different access;
- The Npcf_SMPolicyControl_Delete service operation to PCF shall not be performed.
The steps 2 and 3 shall be repeated for all PDU Sessions to be moved from 3GPP access to untrusted non-3GPP access. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.3 Handover of a PDU Session procedure between 3GPP and trusted non-3GPP access | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.9.3.0 General | The handover of a PDU Session between 3GPP access and trusted non-3GPP access shall be supported as specified in clause 4.9.2 for all types of handover of a PDU Session between 3GPP access and untrusted non-3GPP access, with the following modifications and clarifications:
- The untrusted non-3GPP access is substituted by a trusted non-3GPP access point (TNAP).
- The N3IWF is substituted by the TNGF.
- The registration via untrusted non-3GPP access is substituted by the registration via trusted non-3GPP access as specified in clause 4.12a.2.2.
- A PDU Session is activated over trusted non-3GPP access as specified in clause 4.12a.5. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.10 NG-RAN Location reporting procedures | This procedure is used by an AMF to request the NG-RAN to report where the UE is currently located when the target UE is in CM-CONNECTED state. The need for the NG-RAN to continue reporting ceases when the UE transitions to CM-IDLE or the AMF sends cancel indication to NG-RAN. This procedure may be used for services that require accurate cell identification (e.g. emergency services, lawful intercept, charging), or for subscription to the service by other NFs. When Dual Connectivity is activated, PSCell information is only reported if requested by the AMF.
Figure 4.10-1: NG-RAN Location Reporting Procedure
1. AMF to NG-RAN: Location Reporting Control (Reporting Type, Location Reporting Level, (Area Of Interest, Request Reference ID)).
The AMF sends a Location Reporting Control message to the NG-RAN. The Location Reporting Control message shall identify the UE for which reports are requested and shall include Reporting Type and Location Reporting Level. The Location Reporting Control message may also include Area Of Interest and Request Reference ID. Location Reporting Level could be TAI+ Cell Identity. Reporting Type indicates whether the message is intended to trigger a single standalone report about the current Cell Identity serving the UE or start the NG-RAN to report whenever the UE changes cell, or ask the NG-RAN to report whenever the UE moves out or into the Area Of Interest. If the Reporting Type indicates to report whenever the UE changes cell and if PScell reporting is requested and Dual Connectivity is in use, the Master RAN node shall also report to the AMF whenever the PSCell changes. If the Reporting Type indicates to start the NG-RAN to report when UE moves out of or into the Area Of Interest, the AMF also provides the requested Area Of Interest information in the Location Reporting Control message. The AMF may include a Request Reference ID in the Location Report Control message to identify the request of reporting for an Area Of Interest. If multiple Areas Of Interest are included in the message, the Request Reference ID identifies each Area of Interest.
NOTE 1: Requesting reports whenever the UE changes cell can increase signalling load on multiple interfaces. Requesting reports for all changes in PSCell ID can further increase signalling load. Hence it is recommended that any such reporting is only applied for a limited number of subscribers.
2. NG-RAN to AMF: Location Report (UE Location, UE Presence in Area Of Interest, Request Reference ID, Timestamp).
The NG-RAN sends a Location Report message informing the AMF about the location of the UE which shall be represented as the requested Location Reporting Level. If PSCell reporting is requested and Dual Connectivity is activated, then the Master NG-RAN node shall also include the PSCell ID. With NR satellite access, cell and TAI reporting by NG-RAN refer to a fixed cell and fixed TA in which a UE is geographically located. As part of the User Location Information, NG_RAN also reports one or more TACs for the Selected PLMN as described in TS 38.413 [10], but it is not guaranteed that the UE is always located in one of these TACs.
When UE is in CM-CONNECTED with RRC_INACTIVE state, if NG-RAN has received Location Reporting Control message from AMF with the Reporting Type indicating single stand-alone report, the NG-RAN shall perform NG-RAN paging before reporting the location to the AMF. The NG-RAN should send the Location Report promptly and shall not wait to attempt to create a Dual Connectivity configuration. However, if PSCell reporting is requested and the PSCell ID is known to the Master RAN node, then it shall be included in the Location Report. In the case of RAN paging failure, the RAN reports UE's last known location with time stamp.
When UE is in CM-CONNECTED with RRC_INACTIVE state, if NG-RAN has received Location Reporting Control message from AMF with the Reporting Type indicating continuous reporting whenever the UE changes cell, the NG-RAN shall send a Location Report message to the AMF including the UE's last known location with time stamp. If the UE was using Dual Connectivity immediately before entering CM-CONNECTED with RRC_INACTIVE state and PSCell reporting is requested, then the Location Report shall also include the PSCell ID.
When UE is in CM-CONNECTED, if NG-RAN has received Location Reporting Control message from AMF with the Reporting Type of Area Of Interest based reporting, the NG-RAN shall track the UE presence in Area Of Interest and send a Location Report message to AMF including the UE Presence in the Area Of Interest (i.e. IN, OUT, or UNKNOWN) as described in clause D.2 and the UE's current location (including the PSCell ID if PSCell reporting is requested and Dual Connectivity is activated) when the UE is in RRC_CONNECTED state, or, when the UE is in RRC_INACTIVE state, the UE's last known location (including the PSCell ID if PSCell reporting is requested and the UE was using Dual Connectivity immediately before entering CM-CONNECTED with RRC_INACTIVE state) with time stamp if the NG-RAN perceives that the UE presence in the Area Of Interest is different from the last one reported. When the NG-RAN detects that the UE has moved out of or into multiple areas of interest, it sends multiple pairs of UE Presence in the Area Of Interest and the Request Reference ID in one Location Report message to AMF. If UE transitions from RRC_INACTIVE state to RRC_CONNECTED state, NG-RAN shall check the latest location (including the PSCell ID if PSCell reporting is requested and Dual Connectivity is activated) of UE and follow the rules when UE is in RRC_CONNECTED.
The AMF may receive Location Report even if the UE presence in Area Of Interest is not changed. The AMF stores the latest received PSCell ID with its associated timestamp. The AMF stores the latest received PSCell ID with its associated timestamp, when available.
In addition to the above, if the UE is served by an authorized MSBR and the AMF serving this UE receives the Location Report including the TAI/NR CGI for the MBSR that UE is accessing, the AMF shall, if supported, update the corresponding Warning Area List NG-RAN specified in TS 23.041 [86]
In addition to the above, if the UE is served by an MWAB-gNB, the MWAB-gNB shall report ULI and Additional ULI as specified in clause 5.49.4 of TS 23.501 [2].
In addition to the above, if the UE is served by an MWAB-gNB and the AMF serving this UE receives the Location Report including the TAI/NR CGI for the MWAB that UE is accessing, the AMF shall, if supported, update the corresponding Warning Area List NG-RAN specified in TS 23.041 [86].
3. AMF to NG-RAN: Cancel Location Report (Reporting Type, Request Reference ID).
The AMF can send a Cancel Location Reporting message to inform the NG-RAN that it should terminate the location reporting for a given UE corresponding to the Reporting Type or the location reporting for Area Of Interest indicated by Request Reference ID. This message is needed when the reporting type was requested for continuously reporting or for the Area Of Interest. The AMF may include the Request Reference ID which indicates the requested Location Reporting Control for the Area Of Interest, so that the NG-RAN should terminate the location reporting for the Area Of Interest.
NOTE 2: Location reporting related information of the source NG-RAN node is transferred to the target NG-RAN node during Xn handover.
In this release the location reporting procedure is applicable only to 3GPP access. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11 System interworking procedures with EPC | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.0 General | Clause 4.11 includes the following:
- Procedures for interworking with EPS based on N26 interface (clause 4.11.1) and interworking without N26 interface (clause 4.11.2);
- Handover procedures between EPS and 5GC-N3IWF (clause 4.11.3), handover procedures between EPS and 5GC-TNGF (clause 4.11.3a) and handover procedures between EPC/ePDG and 5GS (clause 4.11.4);
- Impact to 5GC procedure due to interworking with EPC (clause 4.11.5);
- Interworking for common network exposure (clause 4.11.6).
In clause 4.11, UEs are assumed to support both 5GC NAS and EPC NAS unless explicitly stated otherwise.
The procedures in clause 4.11 are not applicable for Disaster Roaming service (see clause 5.40 of TS 23.501 [2]).
Interworking between EPS and 5GS and between EPC/ePDG and 5GS is supported with IP address preservation by assuming SSC mode 1. Interworking between EPS and 5GS and between EPC/ePDG and 5GS is not supported for PDU Sessions with SSC mode 2 or SSC mode 3.
NOTE: For a PDU Session with SSC mode 2 or SSC mode 3, the UE can request establishment of a new PDN Connection in EPC towards the same APN/DNN.
4.11.0a Impacts to EPS Procedures
4.11.0a.1 General
This clause captures changes to procedures in TS 23.401 [13] that are common to interworking based on N26 and interworking without N26.
4.11.0a.2 Interaction with PCC
When interworking with 5GS is supported and a "SMF+PGW-C" is selected for a PDN connection, policy interactions between PDN GW and PCRF specified in TS 23.401 [13] are replaced by equivalent interactions between SMF+PGW-C and PCF as follows:
- IP-CAN Session Establishment procedure defined in TS 23.203 [24] is replaced by SM Policy Association Establishment Procedure as described in clause 4.16.4.The SMF+PGW-C includes the information elements received in Create Session Request message into the Npcf_SMPolicyControl_Create Service as follows: the SUPI contains the IMSI, the DNN contains the APN, the PEI contains either the IMEISV or IMEI, the Session AMBR contains the APN-AMBR and the default QoS information that contains the default EPS bearer QoS, note that QCI values are mapped into 5QI values. The SMF+PGW-C may receive PCC Rules and PDU Session Policy Information, 5G QoS information in the PCC Rule and in PDU Session Policy Information are mapped into EPS QoS information as defined in clause 4.11.1.1 and Annex C.
- (PCEF-initiated) IP-CAN Session Modification procedure defined in TS 23.203 [24] is replaced by SM Policy Association Modification procedure as described in clause 4.16.5.1. The Policy Control Request Triggers are specified in clause 6.1.3.5 of TS 23.503 [20].
- The SMF+PGW-C includes the QoS related information elements received in Modify Bearer Request or Modify Bearer Command message into the Npcf_SMPolicyControl_Update Service with the following modifications, the subscribed Session AMBR includes the subscribed APN-AMBR and subscribed default QoS information includes the default EPS bearer QoS, note that QCI values are mapped into 5QI values. The SMF+PGW-C may receive PCC Rules and PDU Session Policy Information, 5G QoS information in the PCC Rule and in PDU Session Policy Information are mapped into EPS QoS information as defined in clause 4.11.1.1 and Annex C.
- The SMF+PGW-C includes the location related information received in Modify Bearer Request (as specified in clause 5.9.2 of TS 23.401 [13]) into Npcf_SMPolicyControl_Update if the corresponding Policy Control Request Triggers (i.e. Location change, Change of UE presence in Presence Reporting Area) are provisioned.
- The SMF+PGW-C includes the information elements received in Delete Bearer Command message into the Npcf_SMPolicyControl_Update Service.
- (PCRF-initiated) IP-CAN Session Modification procedure defined in TS 23.203 [24] is replaced by SM Policy Association Modification procedure as described in clause 4.16.5.2. The SMF+PGW-C may receive PCC Rules and PDU Session Policy Information, 5G QoS information in the PCC Rule and in PDU Session Policy Information are mapped into EPS QoS information as defined in clause 4.11.1.1 and Annex C.
- IP-CAN Session Termination procedure defined in TS 23.203 [24] is replaced by SM Policy Association Termination procedure as described in clause 4.16.6. The SMF+PGW-C includes the information elements received in Delete Session Request message by the SMF+PGW-C into the Npcf_SMPolicyControl_Delete Service.
URSP provisioning may be supported in EPS and the procedures are specified in clause 4.11.0a.2a.
4.11.0a.2a Interaction with PCC for URSP delivery via EPS
4.11.0a.2a.0 General
This clause captures the enhancement to the interaction with PCC to support URSP delivery via EPS.
To Support URSP provisioning in EPS, the SMF+PGW-C receives the Indication of URSP Provisioning Support from the UE as defined in TS 23.501 [2]. If the SMF+PGW-C also supports URSP Provisioning Support in EPS and ePCO, it selects a PCF which also supports URSP Provisioning in EPS to establish the SM Policy Association based on the received Indication of URSP Provisioning Support in EPS PCO and local configuration. The SMF+PGW-C then provides the "Indication of URSP Provisioning Support in EPS" in the ePCO to the UE.
When the SMF+PGW-C receives the UE Policy Container ePCO in Bearer Resource Command during UE requested bearer resource modification procedure, it forwards transparently the UE Policy Container to PCF for the PDU Session in the Npcf_SMPolicyControl_Update Request including indication that "UE Policy Container received" PCRT was met. When the PCF for Session Management receives UE Policy Container from PCF for the UE, it forwards the UE Policy Container to SMF+PGW-C in Npcf_SMPolicyControl_UpdateNotify Request. The PCF for the PDU Session retrieves the PCRTs for UE Policy from PCF for the UE and subscribe to the applicable PCRTs in EPC to SMF+PGW-C.
During initial attach or PDN connection establishment procedure, if SMF+PGW-C supports URSP provisioning in EPS, PCF for the UE and PCF for the PDU session may be discovered as indicated in clause 5.2.7.3.2 by indicating the URSP delivery in EPS capability to NRF.
During initial registration in 5GS, if 5GS supports URSP provisioning in EPS, PCF for the UE and PCF for the PDU session may be discovered as indicated in clause 5.2.7.3.2 by indicating the URSP delivery in EPS capability to NRF. During 5GS to EPS mobility, PCF for the PDU session discovers PCF for the UE is in BSF.
When URSP Provisioning is supported in EPS, the PCF for the PDU Session may establish the UE Policy Association with PCF for the UE:
- When the first UE Policy Container is received from the UE for an SM Policy association.
- During 5GS to EPS mobility with N26 when the SMF+PGW-C notifies the PCF for the PDU Session about a RAT-Type change via Npcf_SMPolicyControl_Update.
NOTE 1: If there are more than one PCF for the PDU session handling PDU sessions for the UE, during the 5GS to EPS mobility every involved PCF for the PDU session can establish a UE Policy Association with the PCF for the UE.
The PCF for the UE triggers the re-evaluation of applicable URSPs in the cases as described in clause 6.1.2.2.3 of TS 23.503 [20] and determines whether an update of URSP is needed for the UE. The PCF for the UE generates the URSP and sends it to the PCF for the PDU Session in the UE Policy Container via Npcf_UEPolicyControl_UpdateNotify Request.
The procedures for the UE Policy association defined in clauses 4.16.11, 4.16.12 and 4.16.13 apply in EPS with the main differences below:
- AMF is replaced by the PCF for the PDU Session.
- Delivery of UE Policy Containers from the PCF for the UE to the PCF for the PDU Session is done via Npcf_UEPolicyControl service instead of via UE Configuration Update procedure.
- Delivery of UE Policy Containers from the SMF+PGW-C to the UE is done via PDN GW initiated bearer modification without QoS update procedure as specified in clause 4.11.0a.2a.10.
URSP delivery via EPS is also supported in roaming scenarios, both for a PDN connection established in Home Routed and for a PDN connection established in LBO.
NOTE 2: If the PCF for the PDU Session is the same as the PCF for the UE, the interactions between them are internal to the PCF.
4.11.0a.2a.1 SM Policy Association Establishment
The following additions are applicable to clause 4.16.4 (SM Policy Association Establishment procedure):
- In addition to step 4 the PCF determines whether the PDN connection supports the provisioning of URSP rules in EPS by checking URSP delivery in EPS support indication provided by the SMF+PGW-C. The SMF+PGW-C provides that indication based on local capabilities and operator policies. The PCF may receive the URSP delivery in EPS support indication provided by the SMF+PGW-C and store the indication for the following use (for example, URSP rule provision to UE during 5GS to EPS mobility).
4.11.0a.2a.1a SM Policy Association Establishment in EPS
The following enhancement is applicable to clause 4.11.0a.2 which refers to clause 4.16.4 (SM Policy Association Establishment):
- Step 1 of clause 4.16.4: If the SMF+PGW-C receives URSP Provisioning Support indication, the SMF+PGW-C selects the PCF based on the URSP delivery in EPS capability of the PCF, as defined in clause 6.3.7.1 of TS 23.501 [2].
4.11.0a.2a.2 SMF initiated SM Policy Association Modification
4.11.0a.2a.2.1 SMF initiated SM Policy Association Modification due to UE requested bearer resource modification procedure
When SMF+PGW-C receives the UE Policy Container in the UE requested bearer resource modification procedure, the SMF+PGW-C provides the UE Policy Container to the PCF.
The SM Policy Association Modification procedure in clause 4.16.5.1 applies with the following enhancements is executed with the following differences, applicable between step 4 and step 5:
If the PCF receives both the indication that the PCRT "UE Policy Container received" was met and the UE Policy Container, steps 4a to 4c below are executed.
- Step 4a: The PCF for the PDU Session discovers the PCF for the UE by querying the BSF, using Nbsf_Management_Discovery for the SUPI. If no result is obtained from the BSF the PCF for the PDU Session selects the PCF for the UE by querying NRF, using the URSP delivery in EPS capability of the PCF, as defined in clause 6.3.7.1 of TS 23.501 [2].
- Step 4b: The PCF for the PDU Session establishes a UE Policy Association towards the PCF for the UE as described in clause 4.11.0a.2a.5.
- Step 4c: If the PCF for the UE provides any Policy Control Request Trigger parameters in the Npcf_UEPolicyControl Create Response the PCF for the PDU Session takes them into account for the generation of Policy Control Request Triggers to the SMF+PGW-C.
4.11.0a.2a.2.2 SMF initiated SM Policy Association Modification at mobility between 5GS and EPS
During 5GS to EPS mobility procedure, the PCF for the PDU Session establishes a UE Policy Association towards the PCF for the UE if it exists otherwise, it performs PCF discovery and selection then establishes a UE Policy Association. During EPS to 5GS mobility procedure the PCF for the PDU Session terminates the UE Policy Association, if established during 5GS to EPS mobility.
NOTE: If there are more than one PCF for the PDU session handling PDU sessions for the UE every involved PCF for the PDU session can establish a UE Policy Association with the PCF for the UE.
The following enhancements are applicable to clause 4.16.5.1 (SMF initiated SM Policy Association Modification procedure):
In addition to step 4 in clause 4.16.5.1, the PCF determines that 5GS to EPS or EPS to 5GS mobility applies by checking a change in RAT and Access-Type.
- If 5GS to EPS mobility applies, , in non-roaming and Home Routed roaming the (H-)PCF for the PDU Session determines whether the UE supports provisioning of URSP Rules in EPS by checking indication of support of URSP delivery in EPS in UDR and in LBO roaming the V-PCF for the PDU Session determine whether the UE supports provisioning of URSP rules in EPS based on local configuration, e.g. using the PEI, given that the V-PCF has no access to UDR at the HPLMN. The (H-)PCF or the V-PCF determines if the SMF+PGW-C supports delivery of URSP Rules in EPS as reported by the SMF+PGW-C. If the PCF determines that the UE and the SMF+PGW-C support provisioning of URSP Rules in EPS, the PCF for the PDU Session finds the PCF for the UE using Nbsf_Management_Discovery for the SUPI and then performs UE Policy Association Establishment procedure as specified in clause 4.11.0a.2a.5. If no result is obtained from the BSF, the PCF for the PDU Session selects the PCF for the UE by querying NRF, using the URSP delivery in EPS capability of the PCF, as defined in clause 6.3.7.1 of TS 23.501 [2].
- If EPS to 5GS mobility applies, the PCF for the PDU Session requests the termination of the UE Policy association as described in clause 4.11.0a.2a.8.
4.11.0a.2a.2.3 SMF initiated SM Policy Association Modification for UE reporting URSP update result
When the UE reports the result of URSP rule update, the following enhancements are applicable to clause 4.16.5.1 (SM Policy Association Modification procedure):
In addition to step 4 in clause 4.16.5.1 if the PCF for the PDU Session receives the "UE Policy" Policy Control Request Trigger and associated UE Policy Container, steps 4a to 4b below are executed:
- Step 4a: The PCF for the PDU Session determines that a UE Policy association has been already established towards the PCF for the UE for the SM Policy Association as described in clause 4.11.0a.2a.7.
- Step 4b: The PCF for the PDU Session forwards the UE Policy Container to the PCF for the UE in Npcf_UEPolicyControl_Update Request.
4.11.0a.2a.3 PCF initiated SM Policy Association Modification
For the purpose of URSP delivery in EPS, PCF initiated SM Policy Association Modification procedure is triggered by an interaction from the PCF for the UE.
The following enhancements are applicable to clause 4.16.5.2 (PCF initiated SM Policy Association Modification procedure):
- Step 4: The PCF for the PDU Session may receive a UE Policy Container from the PCF for the UE and/or an update in the Policy Control Request Triggers applicable to the UE as described in clause 4.11.0a.2a.6:
- If a UE Policy Container is received from the PCF for the UE, the PCF for the PDU Session selects one of the ongoing PDU Sessions for this UE that supports URSP Rule delivery in EPS according to clause 4.11.0a.2a.1 and includes that UE Policy Container in Npcf_SMPolicyControl_UpdateNotify request.
If an update in the Policy Control Request Triggers applicable to the UE is received, the PCF for the PDU Session determines whether an update on the current Policy Control Request Triggers needs to be sent to the SMF+PGW-C in Npcf_SMPolicyControl_UpdateNotify request.
4.11.0a.2a.4 Void
4.11.0a.2a.5 UE Policy Association establishment
To support the delivery of URSP rule in EPS as described in clause 6.1.2.2.3 of TS 23.503 [20], the PCF for the PDU Session may establish a UE Policy Association towards the PCF for the UE.
This procedure may be triggered by the following procedures:
1. UE requested bearer resource modification.
2. 5GS to EPS handover or 5GS to EPS Idle Mode mobility.
Figure 4.11.0a.2a.5-1: UE Policy Association establishment procedure
In the non-roaming case, the V-PCF for the UE is not involved, and the PCF for the PDU Session interacts with the PCF for the UE. For the Home Routed roaming scenario, the V-PCF for the UE is not involved and the H-PCF for the PDU Session interacts with the H-PCF for the UE. For the LBO roaming scenario, the V-PCF for the PDU Session interacts with the V-PCF for the UE and the V-PCF for the UE interacts with the H-PCF for the UE.
The procedure is based on clause 4.16.11.1 for a UE in 5GC with the following differences:
1. The PCF for the PDU Session determines the need of establishment of a UE Policy Association when:
- A UE Policy Container is received from the UE during SM Policy Association Update at UE requested bearer resource modification as described in clause 4.11.0a.2a.2.1; or
- During 5GS to EPS mobility as described in clause 4.11.0a.2a.2.2.
2. Same as step 2 in clause 4.16.11, with the following exceptions:
The PCF for the PDU Session includes the UE Policy Container in case of SM Policy Association update at UE requested bearer resource modification or 5GS to EPS Mobility indication in case of SM Policy Association update at 5GS to EPS mobility.
For LBO roaming the V-PCF for the PDU Session discovers and selects an instance of the V-PCF for the UE based on the available PCF instances obtained from the NRF or locally configured information in the V-PCF, depending on operator's policies, as described in clause 6.3.7.1 of TS 23.501 [2]. The V-PCF for the PDU Session contacts the V-PCF for the UE and steps 3 and 4 are executed.
For non-roaming or Home Routed roaming the (H-)PCF for the PDU Session contacts the (H-)PCF for the UE and step5 follows.
3. Same as step 3 in clause 4.16.11.1, with the following exceptions:
The UE Policy Container is received at SM Policy Association instead of initial registration. When the UE Policy Association is being established due to 5GS to EPS mobility as described in clause 4.11.0a.2a.2.2, the V-PCF for the UE in the VPLMN needs to discover and select the same H-PCF for the UE that is serving the UE in the H-PLMN for 5GS by querying the BSF in the HPLMN. This is to be able to recover the information about the list of PSIs in the UE and the subscribed PCRTs from former UE Policy Association for the UE in 5GS as described in step 6. Therefore, the V-PCF for the UE in the VPLMN needs first to discover the BSF in the HPLMN.
NOTE 1: For Home Routed roaming, the V-PCF for the UE is not involved, therefore in this roaming scenario it is not possible to retrieve the Application guidance on URSP Rule for inbound roamers of the PLMN and provide it to the H-PCF for the UE to be used as input for the generation of the URSP rules for the UE as described in clause 6.6.2.2.3 of TS 23.503 [20].
4. Same as in clause 4.16.11.1.
5. Same as in clause 4.16.11.1 step 5, with the following exceptions:
The subscription to notification of N1 message delivery of policy information to the UE using Namf_Communication_N1N2MessageSubscribe service is not applicable.
6. The Same as step 6 in clause 4.16.11.1, with the following difference:
If "5GS to EPS Mobility" indication was received in Npcf_UEPolicyControl_Create in step 2 instead, the (H-)PCF recovers the information about the list of PSIs for the UE, the subscribed PCRTs in 5GS from former UE Policy Association for the UE and the indication about the support of provisioning of URSP rules in EPS. If the UE does not support the provisioning of URSPs in EPS, the H-PCF rejects the establishment of the UE Policy Association.
NOTE 2: In LBO roaming the V-PCF for the UE may trigger the establishment of the UE Policy Association for a UE that does not support the provisioning of URSP in EPS, as described in step 4a in clause 4.11.0a.2a.2.2.
The (H-)PCF provides the UE Policy Container in the Npcf_UEPolicyControl_UpdateNotify Request.
7. Same as in clause 4.16.11.
NOTE 3: Steps 8 and 9 are executed only in LBO roaming scenario.
8. The V-PCF for the UE forwards the UE Policy Container to the V-PCF for the PDU Session by invoking Npcf_UEPolicyControl_UpdateNotify Request. The V-PCF for the UE checks the size limit as described in clause 6.1.2.2.2 of TS 23.503 [20].
9. The V-PCF for the PDU Session sends a response to the V-PCF for the UE.
10. If the UE provides a UE Policy Container with the result of the URSP update to the PCF for the PDU Session as described in clause 4.11.0a.2a.2.3 the PCF for the PDU Session forwards the UE Policy Container to the (V-) PCF for the UE invoking Npcf_UEPolicyControl_Update Request.
11. The (V-) PCF for the UE sends a response to the (V-) PCF for the PDU Session.
NOTE 4: Steps 12 and 13 are executed only in LBO roaming.
12. The V-PCF for the UE forwards the notification response to the H-PCF by invoking Npcf_UEPolicyControl_Update Request.
13. The H-PCF sends a response to the V-PCF for the UE.
4.11.0a.2a.6 UE Policy Association Modification initiated by the PCF for the UE
The following impacts are applicable to clause 4.16.12.2 (UE Policy Association Modification initiated by the PCF procedure):
In the non-roaming case, the V-PCF is not involved, the AMF is replaced by the PCF for the PDU Session, and the role of the H-PCF is performed by the PCF for the UE.
For the Home Routed roaming scenarios, the V-PCF is not involved, the AMF is replaced by the H-PCF for the PDU Session, and the role of the H-PCF is performed by the H-PCF for the UE.
For the LBO roaming scenarios, the AMF is replaced by the V-PCF for the PDU Session, the role of the V-PCF is performed by the V-PCF for the UE and the role of the H-PCF is performed by the H-PCF for the UE.
- Steps 1a, 1c, 2a, 2c and 2d: These steps are not applicable for Home Routed roaming, since the V-PCF is not involved.
- Step 3: The (H-)PCF may create the UE policy container including UE policy information as defined in clause 6.1.2.2.2 of TS 23.503 [20]. The (H-) PCF checks whether the UE Policy Association for the UE is established for a UE in EPS by checking the RAT-Type of the UE Policy Association and in this case the (H-)PCF may send the UE Policy Container in the Npcf_UEPolicyControl_UpdateNotify Request. The (H-)PCF may provide updated PCRTs over the UE policy association.
For Home Routed roaming, the V-PCF for the UE is not involved, therefore the Service Parameters provided by the AF from the VPLMN are not used by the H-PCF as input for the generation of the URSP rules.
NOTE: Steps 5 and 6 are executed only in LBO roaming.
- Step 5: In case the UE Policy Association is for a UE in EPS, the (V-) PCF for the UE provides the UE Policy Container and/or policy control triggers to the (V-) PCF for the PDU Session.
- Step 6: The (V-) PCF for the PDU session sends a response to the (V-) PCF for the UE.
- Steps 7, 8 and 9 are replaced by steps 10-13 of procedure UE Policy Association Establishment in EPS from clause 4.11.0a.2a.5.
4.11.0a.2a.7 UE Policy Association Modification initiated by the PCF for the PDU Session
This procedure addresses the scenario where a Policy Control Request Trigger condition is met by the PCF for the PDU Session.
The procedure is based on the one defined in clause 4.16.12.1.1 with the following differences:
In the non-roaming case, the V-PCF is not involved, the AMF is replaced by the PCF for the PDU Session, and the role of the H-PCF is performed by the PCF for the UE.
For the Home Routed roaming scenarios, the V-PCF is not involved, the AMF is replaced by the H-PCF for the PDU Session, and the role of the H-PCF is performed by the H-PCF for the UE.
For the LBO roaming scenarios, the AMF is replaced by the V-PCF for the PDU Session, the role of the V-PCF is performed by the V-PCF for the UE and the role of the H-PCF is performed by the H-PCF for the UE.
- Step 1: Same as in clause 4.16.12.1.1 step 1, with the following exceptions:
In LBO roaming the V-PCF for the PDU Session contacts the V-PCF for the UE and steps 2 and 3 are executed. The V-PCF for the UE contacts with the H-PCF for the UE discovered during the establishment of the UE Policy association as described in clause 4.11.0a.2a.5.
For non-roaming or Home Routed roaming the (H-)PCF for the PDU Session contacts the (H-)PCF for the UE and step 4 follows.
- Steps 2, 3,4: Same as in clause 4.16.12.1.1.
- Step 5: The (H-)PCF may create the UE policy container including UE policy information as defined in clause 6.6 of TS 23.503 [20]. The (H-) PCF checks whether the UE Policy Association for the UE is established for a UE in EPS by checking the RAT-Type of the UE Policy Association and in this case the (H-)PCF may send the UE Policy Container in the Npcf_UEPolicyControl_UpdateNotify Request.
- Step 6: Same as in clause 4.16.12.1.1.
- Steps 7, 8 and 9 are replaced by steps 10-13 of procedure UE Policy Association Establishment in EPS from clause 4.11.0a.2a.5.
4.11.0a.2a.8 UE Policy Association Termination initiated by PCF for PDU session
The following case is considered for UE Policy Association Termination:
1. UE Detach from the EPS.
2. The last PDN connection for UE which supports URSP delivery in EPS according to clause 4.11.0a.2a.1 is released.
3. Changing of RAT type from EPS to 5GS, notified to PCF for the PDU Session by SMF+P-GW-C.
Figure 4.11.0a.2a.8-1: UE Policy Association termination in EPS
This procedure applies for non-roaming scenarios, LBO roaming scenarios and Home Routed roaming scenario.
In the non-roaming case, the V-PCF for the UE is not involved, the role of the V-PCF for the PDU session is performed by the PCF for the PDU session and the role of the H-PCF for the UE is performed by the PCF for the UE. For the LBO roaming scenarios, the V-PCF for the PDU session interacts with the V-PCF for the UE and the V-PCF for the UE interacts with the H-PCF for the UE.
In the Home Routed roaming scenario, the V-PCF for the UE is not involved, the role of the V-PCF for the PDU session is performed by the PCF for the PDU session in HPLMN and the role of the H-PCF for the UE is performed by the PCF for the UE in HPLMN.
1. The (V-)PCF for the PDU session terminates a UE Policy Association with the (V-)PCF for the UE when:
- The SMF+P-GW-C notifies the changing of RAT type from EPS to 5GS; or
- The last PDN connection for UE which supports URSP delivery in EPS according to clause 4.11.0a.2a.1 is released, either due to UE detached from EPS or other reason.
2. Same as in clause 4.16.13.1 step 2, replace AMF with (V-)PCF for the PDU session.
3. Same as in clause 4.16.13.1 step 3, replace AMF with (V-)PCF for the PDU session.
4. Same as in clause 4.16.13.1 step 4.
5. Same as in clause 4.16.13.1 step 5.
4.11.0a.2a.9 UE Policy Association termination initiated by the PCF for the UE
The procedure is based on clause 4.16.13.2 (UE Policy Association Termination initiated by the PCF procedure) with the following differences:
In the non-roaming case, the V-PCF is not involved, the AMF is replaced by the PCF for the PDU Session, and the role of the H-PCF is performed by the PCF for the UE.
For the LBO roaming scenarios, the AMF is replaced by the V-PCF for the PDU Session, the role of the V-PCF is performed by the V-PCF for the UE.
In the Home Routed roaming scenario, the V-PCF is not involved. The AMF is replaced by the PCF for PDU Session in HPLMN, and the role of the H-PCF for the UE is performed by the PCF for the UE in HPLMN.
When the UE is in EPS, the UE Policy Association has been established by the (V-) PCF for PDU Session as described in clause 4.11.0a.2a.5.
- Step 4: Change the AMF to the PCF for PDU Session. The PCF for UE may notify the PCF for PDU Session of the removal of the UE Policy Association via Npcf_UEPolicyControl_UpdateNotify service operation.
- Step 5: Change the AMF to the PCF for PDU Session.
- Step 6: Change AMF to the PCF for PDU Session and refer to the step 2 to step 5 in clause 4.11.0a.2a.8.
4.11.0a.2a.10 UE Policy Container delivery via EPS
This procedure is initiated when the PCF for the UE decides to update URSP and to provide to the UE via EPS. Based on UE Policy Association Modification initiated by the PCF for the UE in 4.11.0a.2a.6 and PCF initiated SM Policy Association Modification in 4.11.0a.2a.3, the updated URSP Rule included UE Policy Container is received by SMF+PGW-C. The SMF+PGW-C transfers the received UE Policy Container via ePCO to the UE by initiating the bearer modification without QoS update procedure as described in clause 5.4.3 of TS 23.401 [13].
Figure 4.11.0a.2a.10-1: UE Policy Container delivery via EPS procedure
0. PCF for the UE decides to update UE policy.
1. The PCF for the UE creates the UE Policy Container including UE policy information, selects one of the ongoing UE Policy Associations for the UE in EPS in case more than one exists and sends the UE Policy Container in the Npcf_UEPolicyControl_UpdateNotify Request over the selected UE Policy Association as described in step 3 of clause 4.11.0a.2a.6. If the PCF for the UE has not subscribed to be notified by the PCF for the PDU Session, the PCF for the UE subscribes to the PCF for the PDU Session to be notified about the UE response to an update of UE policy information by including "Result of UE Policy Container delivery via EPS" PCRT in this message. If the AF requested to PCF for the UE to report on the outcome of the UE Policies delivery as specified in clause 4.15.6.7, "Result of UE Policy Container delivery via EPS" PCRT shall be included in this message.
2. The PCF for the PDU Session sends a response to the PCF for the UE.
3. The PCF for the PDU Session initiates SM Policy Association Modification procedure as described in step 4 of clause 4.11.0a.2a.3. The PCF for the PDU Session transfers the UE Policy Container by Npcf_SMPolicyControl_UpdateNotify Request for the selected PDN connection for the related UE in EPC. If the PCF for the PDU Session received "Result of UE Policy Container delivery via EPS" PCRT in step 1, the PCF for the PDU Session subscribes to the SMF+PGW-C with "Result of UE Policy Container delivery via EPS" PCRT.
4. The SMF+PGW-C sends a response to the PCF for the PDU Session.
5. The SMF+PGW-C initiates the bearer modification without bearer QoS update procedure, as described in clause 5.4.3 of TS 23.401 [3]. The UE includes the result of UE Policy delivery in response via ePCO.
NOTE: The ePCO container for UE Policy delivery response is specified by Stage 3.
6. The SMF+PGW-C transparently forwards the response of the UE to the PCF for the PDU Session by using Npcf_SMPolicyControl_Update Request. The message includes the indication that "Result of UE Policy Container delivery via EPS" PCRT was met.
If the SMF+PGW-C received rejection (e.g. due to paging failure) from Update Bearer Request message in step 5, then the SMF+PGW-C sends the delivery failure result with an appropriate reason (e.g. such that UE is temporarily not reachable) and the indication of "Result of UE Policy Container delivery via EPS" PCRT was met to the PCF for the PDU Session.
7. The PCF for the PDU Session transparently forwards the response from the UE, or the delivery failure result provided by SMF+PGW-C to the PCF for the UE by using Npcf_UEPolicyControl_Update Request. The message includes the indication of "Result of UE Policy Container delivery via EPS" PCRT was met.
If the AF requested to PCF for the UE to report on the outcome of the UE Policies delivery as specified in clause 4.15.6.7, the PCF for the UE reports the outcome of the UE Policies delivery to the AF with the received result from the PCF for the PDU Session.
8. The PCF for the UE sends a response to the PCF for the PDU Session.
9. The PCF for the PDU Session sends a response to the SMF+PGW-C.
4.11.0a.3 Mobility Restrictions
The UE's subscription may include access restriction for NR in 5GS and restriction for Core Network Type (5GC). If so, the HSS provides these restrictions to the MME. The MME includes these restrictions in the Handover Restriction List to the E-UTRAN. The MME and E-UTRAN use these restrictions to determine if mobility of the UE to 5GS or NR connected to 5GS should be permitted.
4.11.0a.4 PGW Selection
When the UE requests to establish a non-emergency PDN connection to an APN, the MME may use the UE's support for 5GC NAS indication included in the UE Network Capability and/or UE's subscription from HSS that includes UE's mobility restriction parameters related to 5GS and/or indication of support for interworking with 5GS for this APN to determine if SMF+PGW-C or a standalone PGW-C should be selected. If both PGW-C and SMF+PGW-C is available, then MME may select SMF+PGW-C when UE's subscription from HSS indicate support for interworking with 5GS for the APN.
NOTE: If restriction for Core Network Type indicates that the UE can access to 5GC, it implies that the UE has 5G subscription data.
When the UE performs emergency attach or requests to establish an emergency PDN connection, the MME may use the UE's support for 5GC NAS indication included in the UE Network Capability and/or local configuration to determine if an emergency SMF+PGW-C or a standalone emergency PGW-C should be selected. An emergency SMF+PGW-C needs to be configured in Emergency Configuration Data in the MME if it is to be selected.
To enable a differentiation of the emergency gateway based on UE´s support of 5GC NAS, the Emergency Configuration Data in the MME defined in TS 23.401 [13] is extended with the IE listed in Table 4.11.0a.4-1.
Table 4.11.0a.4-1: MME Emergency Configuration Data Extensions
Field
Description
Emergency SMF+PGW-C identity
The statically configured identity of a combined SMF+PGW-C used for emergency APN. The SMF+PGW-C identity may be either an FQDN or an IP address. (NOTE)
NOTE: The FQDN always resolves to one SMF+PGW-C.
4.11.0a.5 PDN Connection Establishment
During establishment of non-emergency PDN connection in the EPC, the UE and the SMF+PGW-C exchange information via PCO as described in clause 5.15.7 of TS 23.501 [2]. For UE with 5GC NAS capability disabled (i.e. N1 mode is disabled), the UE may also allocate a PDU Session ID and send it to the SMF+PGW-C via PCO. If the SMF+PGW-C supports more than one S-NSSAI and the APN is valid for more than one S-NSSAI, before the SMF+PGW-C provides an S-NSSAI to the UE, the SMF+PGW-C should check such that the selected S-NSSAI is among the UE's subscribed S-NSSAIs which supports interworking with EPC and that the S-NSSAI is not subject to Network Slice-Specific Authentication and Authorization, by retrieving the Subscribed S-NSSAI from UDM using the Nudm_SDM_Get service operation (the SMF+PGW-C discovers and selects a UDM as described in clause 6.3.8 of TS 23.501 [2]). If the SMF+PGW-C is in a VPLMN, the SMF+PGW-C uses the Nnssf_NSSelection_Get service operation to retrieve a mapping of the Subscribed S-NSSAIs to Serving PLMN S-NSSAI values. If the S-NSSAIs supported by the SMF+PGW-C are all subject to NSSAA, then the SMF+PGW-C should reject the PDN connection establishment. If the selected S-NSSAI is subject to NSAC and EPS counting is required for the S-NSSAI, the SMF+PGW-C uses the Nnsacf_NSAC_NumberOfUEsUpdate services operation and/or the Nnsacf_NSAC_NumberOfPDUsUpdate services operation to check if the selected S-NSSAI is available as described in clause 4.11.5.9. The SMF+PGW-C uses the Nudm_SDM_Subscribe service operation to subscribe the change of the Session Management Subscription data. If the SMF+PGW-C is notified from UDM with subscription data change, the SMF+ PGW-C takes actions for the PDN connection as described in clause 5.17.2.1 of TS 23.501 [2].
As described in TS 23.548 [74], during establishment of a PDN connection, a UE that hosts EEC(s) may indicate to the SMF+PGW-C, 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). If the UE indicated in the PCO that it supports the ability to receive ECS address(es) via NAS, the SMF+PGW-C 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+PGW-C may derive the Edge Configuration Server Information based on local configuration, the UE's location and/or UE subscription information.
The SMF+PGW-C may use the bearer modification procedure without bearer QoS update to send the UE a PCO with updated ECS Address Configuration Information as defined in clause 6.5.2 of TS 23.548 [74] to the UE.
During establishment of non-emergency PDN connection in the EPC, if PGW-C+SMF is selected for a UE that has 5GS subscription, the SMF may be configured to obtain the subscribed IP index from UDM as part of subscription data using the Nudm_SDM_Get service operation (the PGW-C+SMF discovers and selects a UDM as described in clause 6.3.8 of TS 23.501 [2]).
During establishment of non-emergency PDN connection in EPC, if PGW-C+SMF is selected for a UE that has 5GS subscription, the SMF may be configured to obtain the subscribed User Plane Security Policy from UDM as part of subscription data using the Nudm_SDM_Get service operation (the PGW-C+SMF discovers and selects a UDM as described in clause 6.3.8 of TS 23.501 [2]). The SMF uses the subscribed User Plane Security Policy as described in clause 5.10.3 of TS 23.501 [2].
During establishment of non-emergency PDN connection in the EPC, if SMF+PGW-C is selected for a UE that has 5GS subscription but does not support 5GC NAS and is accessing via EPC/E-UTRAN and if the SMF+PGW-C supports more than one S-NSSAI and the APN is valid for more than one S-NSSAI, the SMF+PGW-C+PGW-C may proceed as specified in first paragraph of this clause or select any S-NSSAI associated with the APN of the PDN connection. The SMF+PGW-C shall not provide any 5GS related parameters to the UE.
NOTE 1: The SMF+PGW-C knows that the UE does not support 5GS NAS if the UE does not provide PDU Session ID in PCO (see clause 5.15.7 of TS 23.501 [2]).
During establishment of emergency PDN connection:
- The SMF+PGW-C is to be derived from the emergency APN or to be statically configured in the Emergency Configuration Data in MME.
- 5GC interworking support with N26 or without N26 is determined based on UE's 5G NAS capability and local configuration (in the Emergency Configuration Data in MME).
- The S-NSSAI configured for the emergency APN in SMF+PGW-C is not sent to the UE by the SMF+PGW-C. One S-NSSAI is configured for the emergency APN.
During establishment of non-emergency PDN connection and emergency PDN connection, if SMF+PGW-C is selected for a UE that does not support 5GC NAS, the SMF+PGW-C creates unique PDU Session ID for each PDN connection of the UE.
- The unique PDU Session ID can be created based on the EPS Bearer IDs assigned by the MME for the PDN Connections associated with the UE and not be in the range of PDU Session ID values that can be created by a 5GC NAS capable UE.
- If handover between EPS and EPC/ePDG (as specified in clause 8.6 of TS 23.402 [26]) is required, the SMF+PGW-C, based on operator configuration, may perform the following to ensure the uniqueness of PDU Session ID:
- the SMF+PGW-C queries the UDM for any PDU Session ID(s) that are already registered in the UDM for the UE by invoking Nudm_UECM_Get service operation.
- the SMF+PGW-C creates a PDU session ID that does not collide with the received PDU session ID(s).
- When the SMF+PGW-C establishes the PDN connection successfully, the SMF+PGW-C performs UDM registration using the Nudm_UECM_Registration service operation.
NOTE 2: If the scenario that a UE handovers a PDN connection with APN1 established via MME to ePDG and then establishes a second PDN connection with APN2 via MME needs to be supported in a given deployment, then, based on operator configuration, the SMF+PGW-C can query the UDM to avoid that the same PDU Session ID value of first PDN connection would be assigned by the SMF+PGW-C for the second PDN connection.
When the SMF+PGW-C establishes the PDN connection successfully, the SMF+PGW-C provides the ID of the PCF ID selected for the PDN connection in the UDM using the Nudm_UECM_Registration service operation.
A SMF+PGW-C may support L2TP as described in clause 4.3.2.4. In this case step 1 and step 7 of Figure 4.3.2.4‑1 correspond to a PDN Connection establishment and a SMF+PGW-C replaces the SMF in that Figure.
To support User Plane Integrity Protection with EPS and policies that Require User Plane integrity protection to be used, at PDN connection establishment, the MME shall indicate to the SMF+PGW-C (via the Serving GW) whether the UE, the current eNB and the MME support User Plane Integrity Protection in EPS. If the MME and the UE support User Plane Integrity Protection, then the SMF+PGW-C informs the MME of the User Plane integrity protection policy (Required, Preferred, Not Needed) applicable to the PDN connection on a per-EPS bearer basis. In turn, the MME informs the eNB.
To support URSP Provisioning in EPS, during Initial Attach with default PDN connection establishment procedure in EPS, the UE provides the "Indication of URSP Provisioning Support in EPS" in the PCO or in the ePCO in the PDN connectivity request as described in clause 5.17.8 of TS 23.501 [2]. If the SMF+PGW-C supports URSP Provisioning in EPS and the ePCO capability, it provides the "Indication of URSP Provisioning Support in EPS" in the ePCO in the Create Session Response. If the UE receives the "Indication of URSP Provisioning Support in EPS" in the ePCO from SMF+PGW-C provided in the PDN Connectivity Accept message, the UE initiates the UE requested bearer resource modification procedure and includes the UE Policy Container in the ePCO in the Request Bearer Resource Modification message, see clause 4.11.0a.10. If the default PDN connection is not established during Initial Attach procedure, the aforementioned procedure happens during the first request for PDN connectivity. If the negotiation of the support of URSP provisioning in EPS fails for the first PDN connection the UE may retry the aforementioned procedure successively for the next PDN connectivity requests until it succeeds for one of them as specified in clause 5.17.8 of TS 23.501 [2] When the UE receives an indication of URSP provisioning support in EPS in the PDN Connectivity Accept message or in PDU Session Establishment Accept (as described in clause 4.11.5.3) and this PDN connection or the corresponding transferred PDN connection after 5GS to EPS handover is not released, then for any subsequent PDN connectivity requests the UE does not include an indication of URSP Provisioning Support in EPS.
4.11.0a.6 Network Configuration
To avoid the need for identifier coordination between MMEs, AMFs and SGSNs, the MME provides to the eNB its served GUMMEIs by separating the values between native MME GUMMEI values, values mapped from AMF and values mapped from SGSN.
4.11.0a.7 Interactions with DN-AAA Server
EAP-based secondary authentication and authorization at PDU Session establishment is supported as defined in clause 4.3.2.3. EAP-based secondary authentication and authorization at PDN connection establishment is supported as defined in Annex H.
This clause 4.11.0a.7 defines the support of secondary authorization over EPS without EAP-based authentication when one of the UE, the 5GC and the DN does not support (or is configured not to use) the mechanisms defined in Annex H.
NOTE 1: This implies that when data connectivity to the DN is initiated as a PDU Session over 5GC it can be subject to EAP based secondary authentication mechanism (see TS 33.501 [15]) whereas, when data connectivity to the same DN is initiated as a PDN connection over EPC it cannot be subject to EAP based secondary authentication mechanism. This discrepancy occurs regardless of whether the data connection is later on moved between EPC and 5GC.
NOTE 2: Secondary authorization without authentication means no signalling exchange with the UE.
If secondary authentication and authorization has been performed for the PDU Session while the UE was in 5GS and the UE has moved to EPS, the following applies:
- DN-AAA re-authorization (without re-authentication signalling) can be performed even when the UE is in EPS, e.g. to provide new parameters from the DN-AAA Server to SMF+PGW-C.
- Re-authentication cannot be performed while the UE is in EPS because there is no support of the related signalling in EPS. In case the SMF+PGW-C receives a re-authentication request from the DN-AAA, the SMF+PGW-C informs the DN-AAA Server that the UE is not available for re-authentication at the moment. The SMF+PGW-C should not initiate PDN connection release at this point: the DN-AAA decides the actions to take, based on the reply from SMF+PGW-C and local policy which may also trigger a DN-AAA Server request to release the PDU Session/PDN connection of the UE.
4.11.0a.8 5GC NAS capability (re-)enabled and disabled
When 5G NAS (i.e. N1 mode) capability is (re-)enabled, the UE triggers Tracking Area Update procedure as specified in clause 5.3.3.0 of TS 23.401 [13].
If the MME determines that interworking with 5GS is changed to Supported and if the MME has selected a standalone PGW, the MME may initiate PDN disconnection with reactivation required as specified in clause 5.10.3 of TS 23.401 [13] at the end of the tracking area update procedure.
NOTE 1: MME requesting PDN disconnection with reactivation required is to allow MME to select a SMF+PGW-C so that session continuity can be achieved when UE moves to 5GS.
If a UE disables its support of N1 mode and moves from 5GS to EPS, the UE and the SMF+PGW-C maintain the mapped 5GS parameters for PDU session(s) that are transferred to EPS.
NOTE 2: The mapped 5GS parameters are used when the UE re-enables N1 mode and moves back to 5GS.
4.11.0a.9 PDN Connection Release
If the SMF+PGW-C has registered with the UDM, the SMF+PGW-C shall deregister with UDM (using Nudm_UECM_Deregistration) during the PDN Connection Release procedure.
NOTE: SMF+PGW-C registration in the UDM is specified in clause 4.11.0a.5 or clause 4.3.2.
4.11.0a.10 UE requested bearer resource modification procedure
To support URSP Provisioning in EPS, the following enhancement to clause 5.4.5 of TS 23.401 [13] applies:
- Steps 1, if the UE received the Indication of URSP Provisioning Support in EPS in ePCO from SMF+PGW-C in the PDN Connectivity Accept message (as described in clause 4.11.0a.5), the UE includes the UE Policy Container ePCO in the Request Bearer Resource Modification message.
- Step 4 (replaced by SM Policy Association Modification procedure as described in clause 4.11.0a.2a.2.1), SMF+PGW-C forwards the UE Policy Container received from the UE to the PCF for the PDU Session, which triggers UE Policy Association establishment as specified in clause 4.11.0a.2a.5.
4.11.0a.11 SMF+PGW-C initiated bearer modification without bearer QoS update
To support URSP Provisioning in EPS, the following enhancement to clause 5.4.3 of TS 23.401 [13] applies:
- Step 1 The PCF provides UE Policy Container, which is received from the PCF for the UE as specified in clause 4.11.0a.2a.6, to the SMF+PGW-C in (PCF-initiated) IP-CAN Session Modification procedure as specified in clause 4.11.0a.3.
- Steps 2~5 The UE Policy Container in ePCO is sent by the SMF+PGW-C to the UE via SGW and MME
- Steps 6~9 The UE sends UE Policy delivery result to the SMF+PGW-C via MME and SGW.
- Steps 10 The SMF+PGW-C reports the UE Policy delivery result to the PCF as specified in clause 4.11.0a.2a.2.3. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1 N26 based Interworking Procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.1 General | N26 interface is used to provide seamless session continuity for single registration mode UE.
Interworking between EPS and 5GS is supported with IP address preservation by assuming SSC mode 1. Interworking between EPS and 5GS is not supported for PDU Sessions with SSC mode 2 or SSC mode 3.
When the UE is served by the 5GC, during PDU Session establishment and GBR QoS Flow establishment, SMF+PGW-C performs EPS QoS mappings, from the 5G QoS parameters obtained from the PCF and allocates TFT with the PCC rules obtained from the PCF if PCC is deployed. Otherwise, EPS QoS mappings and TFT allocation are mapped by the SMF+PGW-C locally. The PGW+SMF ignores 5G QoS parameters that are not applicable to EPC (e.g. QoS Notification control). If a TFT is to be allocated for a downlink unidirectional EPS bearer mapped from a downlink only QoS Flow, the SMF+PGW-C shall allocate a TFT packet filter that effectively disallows any useful uplink packet as specified in TS 23.401 [13]. EPS Bearer IDs are allocated by the serving AMF requested by the SMF if the SMF determines that EPS Bearer IDs need to be assigned to the QoS Flows. For each PDU Session, EPS bearer IDs are allocated to the default EPS bearer and dedicated bearers. The SMF shall be able to determine the QoS flows that require EPS Bearer IDs, based on the QoS profile and operator policies.
NOTE 1: Based on operator policies, an SMF can map all non-GBR QoS flows to default EPS bearer in which case it requests only one EBI for all the non-GBR QoS flows. Alternatively, an SMF can also map one non-GBR QoS flow to one dedicated EPS bearer in which case it requests a dedicated EBI for non-GBR QoS flow that should be mapped to dedicated EPS bearer. In between these two extreme cases, the SMF can also map more than one (but not all) non-GBR QoS Flow to the same EPS bearer (either default EPS bearer or dedicated EPS bearer).
NOTE 2: To reduce the probability of AMF revoking the EBI corresponding to the QoS Flow associated with the default QoS rule, ARP priority level of dedicated QoS Flows can be set to higher value than that of the QoS Flow associated with the default QoS rule within the same PDU Session.
When a new QoS Flow needs to be mapped to an EPS Bearer ID that has already been assigned for an existing QoS Flow, the SMF includes the already assigned EPS Bearer ID in the QoS Flow description sent to the UE.
If there is a possibility to run into a restriction regarding the number of TFT packet filters that can be allocated for the PDU Session,
- in the case that PCC is deployed, the PCF may include in the PCC rules the Precedence for TFT packet filter allocation parameter, which determines the order of the PCC rules in allocation of TFT packet filter(s) by the SMF+PGW-C.
- in the case that PCC is deployed but the Precedence for TFT packet filter allocation parameter is not received, or in the case that PCC is not deployed, the SMF+PGW-C makes the decision how to allocate TFT packet filter(s) based on operator policy or implementation.
NOTE 3: An EPS bearer can have up to 16 TFT packet filters.
For Ethernet and Unstructured PDU Session Types, only EPS Bearer ID for the default EPS Bearer is allocated. The EPS Bearer IDs for these EPS bearers are provided to the SMF+PGW-C by the AMF and are provided to the UE and NG-RAN by the SMF+PGW-C using N1 SM NAS message and N2 SM message. The UE is also provided with the mapped QoS parameters. The UE and the SMF+PGW-C store the association between the QoS Flow and the corresponding EBI and the EPS QoS parameters. When the QoS Flow is deleted e.g. due to PDU Session status synchronization or PDU Session Modification, the UE and the SMF+PGW-C delete any possibly existing EPS QoS parameters associated with the deleted QoS Flow.
In this release, for a PDU Session for a LADN or for Multi-homed IPv6 PDU Session, the SMF doesn't allocate any EBI or mapped QoS parameters.
For PDU Sessions with UP integrity protection of UP Security Enforcement Information set to Required, the SMF does not allocate any EBI or mapped QoS parameters unless the UE support User Plane Integrity Protection with EPS and the AMF supports the associated functionality.
If the UE supports User Plane Integrity Protection with EPS, as indicated in the S1 UE network capability and the AMF supports the related functionality, the AMF indicates the UE support for EPS User Plane Integrity Protection to SMF. Then, for PDU Sessions with UP integrity protection of UP Security Enforcement Information set to Required, the SMF may perform the EPS bearer ID allocation procedure as described in clause 4.11.1.4.
If the MME indicates support for EPS User Plane Integrity Protection to SMF+PGW-C, the SMF+PGW-C provides User Plane Security Enforcement Information for the EPS bearer contexts to the MME (via the SGW).
When the UE is served by the EPC, during PDN connection establishment, the UE allocates the PDU Session ID and sends it to the SMF+PGW-C via PCO. During PDN Connection establishment and dedicated bearer establishment, SMF+PGW-C performs EPS QoS mappings, from the 5G QoS parameters obtained from the PCF and allocates TFT with the PCC rules obtained from the PCF if PCC is deployed. Otherwise, EPS QoS mappings and TFT allocation are mapped by the SMF+PGW-C locally. Other 5G QoS parameters corresponding to the PDN connection, e.g. Session AMBR and QoS rules and QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s), are sent to UE in PCO. The UE and the SMF+PGW-C store the association between the EPS Context and the PDU Session Context to use it in the case of handover from EPS to 5GS. During the EPS bearer establishment/modification procedure, QoS rules corresponding to the related EPS bearers are allocated and sent to UE in PCO. The 5G QoS parameters are stored in the UE and are to be used when the UE is handed over from EPS to the 5GS. The 5G QoS parameters may be provided to SMF+PGW-C by the PCF, if PCC is deployed. On mobility from EPS to 5GS, the UE sets the SSC mode of the mapped PDU Session to SSC mode 1. The UE and the SMF+PGW-C store the association between the EPS bearer and the corresponding 5G QoS Rules and QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s). When the EPS bearer is deleted e.g. due to EPS bearer status synchronization or bearer deactivation, the UE and the SMF+PGW-C delete any possibly existing 5G QoS Rule(s) and QoS Flow level QoS parameters if any for the QoS Flow(s) associated with the QoS rule(s) associated with the deleted EPS bearer.
In the roaming case, if the VPLMN supports interworking with N26, the UE shall operate in Single Registration mode.
During the 5GS-EPS handover, indirect forwarding may apply for the downlink data forwarding performed as part of the handover. From its configuration data the AMF knows whether indirect forwarding applies and it requests to allocate downlink data forwarding paths on UPFs for indirect forwarding. From its configuration data the MME knows whether indirect forwarding applies and it requests to allocate downlink data forwarding paths on Serving GWs for indirect forwarding. It is configured on AMF and MME whether indirect downlink data forwarding does not apply, applies always or applies only for inter PLMN inter RAT handovers.
During the 5GS-EPS handover, direct forwarding may apply for the downlink data forwarding performed as part of the handover. From its configuration data the source RAN node knows whether direct forwarding applies and indicates to source CN the direct data forwarding is available.
During 5GS-EPS handover, on the target side, the CN informs the target RAN node whether data forwarding is possible or not.
During interworking from EPS to 5GS, as the SMF+PGW-C may have different IP addresses when being accessed over S5/S8 and N11/N16 respectively, the AMF shall discover the SMF instance by an NF/NF service discovery procedure using the FQDN for the S5/S8 interface received from the MME as a query parameter.
This is required for both non-roaming and roaming with local breakout, as well as for home routed roaming.
NOTE 4: As the AMF is not aware of the S-NSSAI assigned for the PDN Connection, the NF/NF service discovery used to find the SMF instance can use PLMN level NRF.
During interworking from 5GS to EPS, for QoS Flows without EPS bearer ID(s) assigned or for QoS Flows with PCC rules that do not have allocated TFT packet filters, the SMF+PGW-C deletes the PCC rules associated with those QoS Flows and informs the PCF about the removed PCC rule(s).
During interworking from 5GS to EPS, as a PDU Session may be released while the UE is served by EPS, if Small Data Rate Control is used the SMF+PGW-C obtains the Small Data Rate Control Status from the PGW-U+UPF in the N4 Session Modification procedure or from the SCEF+NEF and passes the Small Data Rate Control Status in the PDU Session Context Response to the AMF, for the AMF to store. The time to store the Small Data Rate Control Statuses is implementation specific. If the UE and PGW-U+UPF / SCEF+NEF have stored APN Rate Control parameters and optionally APN Rate Control Status they are only applied when the UE is served by EPS.
During interworking from 5GS to EPS, for PDU Sessions with UP integrity protection of UP Security Enforcement Information set to Required, the SMF+PGW-C does not provide the EPS bearer context unless both the UE, the target eNB and the target MME support User Plane Integrity Protection with EPS.
During interworking from EPS to 5GS the UE and PGW-U+UPF / SCEF+NEF store the APN Rate Control parameters and APN Rate Control Status while the UE is served by 5GS, so they can be used if the UE moves back to EPS.
At EPS to 5GS mobility:
- The UE considers the PDN connections released if those PDN connections were established over EPS and for which the UE has not received mapped 5GS QoS parameters from the network.
NOTE 5: UE not receiving mapped 5GS QoS parameters from the network covers the case that a UE did not provide a PDU Session ID to the network when establishing a PDN connection while UE's N1 mode is disabled and the case that a UE provided PDU Session ID where the network (SMF+PGW-C) does not provide mapped 5GS parameters.
- The MME does not transfer to 5GS a PDN connection that does not support 5GS interworking, e.g. PDN connection was established on a stand-alone PGW, or 5GS interworking is restricted by subscription data. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.2 Handover procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.2.1 5GS to EPS handover using N26 interface | Figure 4.11.1.2.1-1 describes the handover procedure from 5GS to EPS when N26 is supported.
In the case of handover to a shared EPS network, the source NG-RAN determines a PLMN 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 TAI sent in the HO Required message.
In the case of handover from a shared NG-RAN, the AMF may provide the MME with an indication that the 5GS PLMN is a preferred PLMN at later change of the UE to a 5GS shared networks.
During the handover procedure, as specified in clause 4.9.1.3.1, the source AMF shall reject any SMF+PGW-C 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 of a rejection for an SMF+PGW-C initiated N2 request(s) with an indication that the request has been temporarily rejected due to handover procedure in progress, the SMF+PGW-C behaves as specified in TS 23.401 [13].
Figure 4.11.1.2.1-1: 5GS to EPS handover for single-registration mode with N26 interface
The procedure involves a handover to EPC and setup of default EPS bearer and dedicated bearers for QoS Flows that have EBI assigned, in EPC in steps 1-16 and re-activation, if required, of dedicated EPS bearers for non-GBR QoS Flows that have no EBI assigned, in step 19. This procedure can be triggered, for example, due to new radio conditions, load balancing or in the presence of QoS Flow for normal voice or IMS emergency voice, the source NG-RAN node may trigger handover to EPC.
For Ethernet and Unstructured PDU Session Types, the PDN Type Ethernet and non-IP respectively are used, when supported, in EPS.
When EPS supports PDN Type non-IP but not PDN type Ethernet, PDN type non-IP is used also for Ethernet PDU sessions. The SMF shall also set the PDN Type of the EPS Bearer Context to non-IP in this case. After the handover to EPS, the PDN Connection will have PDN Type non-IP, but it shall be locally associated in UE and SMF to PDU Session Type Ethernet or Unstructured respectively.
In the roaming home routed case, the SMF+PGW-C always provides the EPS Bearer ID and the mapped QoS parameters to UE. The V-SMF caches the EPS Bearer ID and the mapped QoS parameters obtained from H-SMF for this PDU session. This also applies in the case that the HPLMN operates the interworking procedure without N26.
NOTE 1: The IP address preservation cannot be supported, if SMF+PGW-C in the HPLMN doesn't provide the mapped QoS parameters.
1. NG-RAN decides that the UE should be handed over to the E-UTRAN. If NG-RAN is configured to perform Inter RAT mobility due to IMS voice fallback triggered by QoS flow setup and request to setup QoS flow for IMS voice was received, NG-RAN responds indicating rejection of the QoS flow establishment because of mobility due to fallback for IMS voice via N2 SM information and triggers handover to E-UTRAN. The NG-RAN sends a Handover Required (Target eNB ID, Direct Forwarding Path Availability, Source to Target Transparent Container, inter system handover indication) message to the AMF. NG-RAN indicates bearers corresponding to the 5G QoS Flows for data forwarding in Source to Target Transparent Container.
If the source NG RAN and target E-UTRAN 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 target E-UTRAN). However, if the source NG-RAN has knowledge that the target E-UTRAN 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 E-UTRAN (the size limit based on configuration). In the case of inter-PLMN handover, when the source NG-RAN and target E-UTRAN support RACS as defined in TS 23.501 [2] and TS 23.401 [13] and the source NG-RAN determines that the target PLMN does not support the UE Radio Capability ID assigned by the source PLMN based on local configuration, then the source NG-RAN includes the UE radio access capabilities in the Source to Target transparent container.
Direct Forwarding Path Availability indicates whether direct forwarding is available from the NG-RAN to the E-UTRAN. This indication from NG-RAN can be based on e.g. the presence of IP connectivity and security association(s) between the NG-RAN and the E-UTRAN.
If the handover is triggered due to Emergency fallback, the NG-RAN may forward the Emergency indication to the target eNB in the Source to Target Transparent Container and the target eNB allocates radio bearer resources taking received indication into account.
2a-2c. The AMF determines from the 'Target eNB Identifier' IE that the type of handover is Handover to E-UTRAN. The AMF selects an MME as described in clause 4.3.8.3 of TS 23.401 [13].
The AMF determines for a PDU Session whether to retrieve context including mapped UE EPS PDN Connection from the V-SMF (in the case of HR roaming) or the SMF+PGW-C (in the case of non roaming or LBO roaming) as follows:
- If the AMF determines that one or more of the EBI(s) can be transferred, the AMF sends Nsmf_PDUSession_ContextRequest to the V-SMF or SMF+PGW-C and includes in the message EBI value(s) if any that cannot be transferred.
- The EBI values(s) that cannot be transferred is determined by the AMF if the target MME does not support 15 EPS bearers, i.e. the AMF determines the EBI values in range 1-4 as not to be transferred to EPS and if there are still more than 8 EBI values associated with PDU Sessions, the AMF then determines EBI value(s) not to be transferred to EPS based on S-NSSAI and ARP as specified in clause 5.17.2.2.1 of TS 23.501 [2].
- The AMF does not retrieve the context for a PDU Session that cannot be transferred to EPS due to no EBI allocated, or allocated EBIs not transferrable, or combination of the two.
When the AMF sends Nsmf_PDUSession_ContextRequest the AMF provides also the target MME capability to the V-SMF or the SMF+PGW-C to allow it to determine whether to include EPS Bearer context for Ethernet PDN Type or non-IP PDN Type or not.
When the AMF sends Nsmf_PDUSession_ContextRequest to the V-SMF or the SMF+PGW-C, the AMF indicates whether the target MME supports User Plane Integrity Protection with EPS.
NOTE 2: The AMF knows the MME capability to support 15 EPS bearers, Ethernet PDN type and/or non-IP PDN type or not through local configuration. The AMF knows the MME capability to support User Plane integrity protection through local configuration but the actual EPS support may depend on the target E-UTRAN coverage (see step 14).
When Nsmf_PDUSession_Context Request is received in the V-SMF or the SMF+PGW-C, the V-SMF or the SMF+PGW-C provides context that includes the mapped EPS PDN Connection as follows:
- If there is EBI list not to be transferred and the EBI value of the QoS Flow associated with the default QoS Rule is included in that list, the V-SMF or the SMF+PGW-C shall not return the PDN Connection context (which implies the whole PDU Session is not transferred to EPS), otherwise if the EBI value of the QoS Flow associated with the default QoS Rule is not included in EBI list not to be transferred, the V-SMF or PGW C+SMF shall not provide the EPS bearer context(s) mapped from QoS Flow(s) associated with the EBI list not to be transferred.
- For PDU Sessions with PDU Session Type Ethernet, if the UE and target MME supports Ethernet PDN type, the V-SMF or the PGW C+SMF provides Context for Ethernet PDN Type, otherwise if the target MME does not support Ethernet Type but support non-IP Type, the V-SMF or the PGW C+SMF provides Context for non-IP PDN Type. For PDU Sessions with PDU Session Type Unstructured, the V-SMF or the SMF+PGW-C provides Context for non-IP PDN Type.
- If the UP integrity protection policy for the EPS bearer context is set to "Required", the V-SMF or the PGW C+SMF shall not provide the EPS bearer context unless the MME capability indicates support for User Plane Integrity Protection with EPS and the UE supports User Plane Integrity Protection with EPS.
In the case of non roaming or LBO roaming, when Nsmf_PDUSession_ContextRequest is received in PGW C+SMF, if the SMF+PGW-C determines that EPS Bearer Context can be transferred to EPS and the CN Tunnel Info for EPS bearer(s) have not been allocated before, the SMF+PGW-C sends N4 Session modification to the PGW-U+UPF to establish the CN tunnel for each EPS bearer and provides EPS Bearer Contexts to AMF, as described in step 8 of clause 4.11.1.4.1. The PGW-U+UPF is ready to receive the uplink packet from E-UTRAN.
This step is performed with all the SMF+PGW-Cs corresponding to PDU Sessions of the UE which are associated with 3GPP access and have at least one EBI(s) determined to be transferred to EPS.
NOTE 3: The AMF knows the MME capability to support 15 EPS bearers, Ethernet PDN type and/or non-IP PDN type or not through local configuration.
In home routed roaming scenario, the UE's EPS PDN Contexts are obtained from the V-SMF. If Small Data Rate Control applies on PDU Session, the V-SMF retrieves the SM Context, including Small Rate Control Status information from the H-SMF using Nsmf_PDUSession_Context Request.
3. The AMF sends a Forward Relocation Request as in step 3 in clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13], with the following modifications and clarifications:
- Parameter "Return preferred" may be included. Return preferred is an optional indication by the MME of a preferred return of the UE to the 5GS PLMN at a later access change to a 5GS shared network. An MME may use this information as specified by TS 23.501 [2].
- The SGW address and TEID for both the control-plane or EPS bearers in the message are such that target MME selects a new SGW.
- The AMF determines, based on configuration and the Direct Forwarding Path Availability, the Direct Forwarding Flag to inform the target MME whether direct data forwarding is applicable.
- The AMF includes the mapped SM EPS UE Contexts for PDU Sessions with and without active UP connections.
- Subject to operator policy if the secondary RAT access restriction condition is the same for EPS and 5GS, the AMF may set EPS secondary RAT access restriction condition based on the UE's subscription data.
4-5. Steps 4 and 4a respectively in clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13].
6. Step 5 (Handover Request) in clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13] with the following modification:
- Handover Request may contain information Handover Restriction List with information about PLMN IDs as specified by clause 5.2a of TS 23.251 [35] for eNodeB functions.
- The target eNB should establish E-RABs indicated by the list of EPS bearer to be setup provided by the MME, even if they are not included in the source to target container.
7-9. Step 5a through 7 in clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13].
10a. If data forwarding applies, the AMF sends the Nsmf_PDUSession_UpdateSMContext Request (data forwarding information) to the SMF+PGW-C. If multiple SMF+PGW-Cs serves the UE, the AMF maps the EPS bearers for Data forwarding to the SMF+PGW-C address(es) based on the association between the EPS bearer ID(s) and PDU Session ID(s). In home-routed roaming case, the AMF requests the V-SMF to create indirect forwarding tunnel if indirect forwarding applies.
10b. If indirect data forwarding applies, the SMF+PGW-C may select an intermediate PGW-U+UPF for data forwarding. The SMF+PGW-C maps the EPS bearers for Data forwarding to the 5G QoS flows based on the association between the EPS bearer ID(s) and QFI(s) for the QoS flow(s) in the SMF+PGW-C and then sends the QFIs, Serving GW Address(es) and TEID(s) for data forwarding to the PGW-U+UPF. The CN Tunnel Info is provided by the PGW-U+UPF to SMF+PGW-C in this response. In home-routed roaming case, the V-SMF selects the V-UPF for data forwarding.
The SMF+PGW-C deactivates PDU Set based handling at PGW-U+UPF if it is activated during the UE was registered to 5GS as described in clause 5.37.5.3 of TS 23.501 [2].
10c. The SMF+PGW-C returns an Nsmf_PDUSession_UpdateSMContext Response (Cause, Data Forwarding tunnel Info, QoS flows for Data Forwarding). Based on the correlation between QFI(s) and Serving GW Address(es) and TEID(s) for data forwarding, the PGW-U+UPF maps the QoS flow(s) into the data forwarding tunnel(s) in EPC.
11. The AMF sends the Handover Command to the source NG-RAN (Transparent container (radio aspect parameters that the target eNB has set-up in the preparation phase), Data forwarding tunnel info, QoS flows for Data Forwarding). The source NG-RAN commands the UE to handover to the target Access Network by sending the HO Command. The UE correlates the ongoing QoS Flows with the indicated EPS Bearer IDs to be setup in the HO command. The UE locally deletes the PDU Session if the QoS Flow associated with the default QoS rule in the PDU Session does not have an EPS Bearer ID assigned. If the QoS Flow associated with the default QoS rule has an EPS Bearer ID assigned, the UE keeps the PDU Session (PDN connection) and for the remaining QoS Flow(s) that do not have EPS bearer ID(s) assigned, the UE locally deletes the QoS rule(s) and the QoS Flow level QoS parameters if any associated with those QoS Flow(s) and notifies the impacted applications that the dedicated QoS resource has been released. The UE deletes any UE derived QoS rules. The EPS Bearer ID that was assigned for the QoS flow of the default QoS rule in the PDU Session becomes the EPS Bearer ID of the default bearer in the corresponding PDN connection.
If indirect data forwarding is applied, Data forwarding tunnel info includes CN tunnel info for data forwarding per PDU session. For the QoS Flows indicated in the "QoS Flows for Data Forwarding", NG-RAN initiate data forwarding via to the PGW-U+UPF based on the CN Tunnel Info for Data Forwarding per PDU Session. Then the PGW-U+UPF maps data received from the data forwarding tunnel(s) in the 5GS to the data forwarding tunnel(s) in EPS and sends the data to the target eNodeB via the Serving GW.
If direct data forwarding is applied, Data forwarding tunnel info includes E-UTRAN tunnel info for data forwarding per EPS bearer. NG-RAN initiate data forwarding to the target E-UTRAN based on the Data Forwarding Tunnel Info for Data Forwarding per EPS bearer.
12-12c. Step 13 to step 14 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13] with the following clarification:
- The AMF requests the release of the PDU Session which is associated with 3GPP access and not expected to be transferred to EPC, i.e. the AMF requests the release of:
- PDU Session(s) whose corresponding SMF+PGW-C(s) are not contacted by AMF for SM context because the AMF determines that none of EBI(s) for the PDU Session can be transferred to EPS at step 2a; and
- PDU Session(s) for which the SM context retrieval failed at step 2c.
12d. The AMF acknowledges MME with Relocation Complete Ack message. A timer in AMF is started to supervise when resource in NG-RAN shall be released.
12e. In the case of home routed roaming, the AMF invokes Nsmf_PDUSession_ReleaseSMContext Request (V-SMF only indication) to the V-SMF. This service operation request the V-SMF to remove only the SM context in V-SMF, i.e. not release PDU Session context in the SMF+PGW-C.
The V-SMF starts a timer and releases the SM context on expiry of the timer.
13. Step 15 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13].
14a. Step 16 (Modify Bearer Request) from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13] with the following clarification:
- If the PDU Session (PDN connection) has QoS Flows that do not have EPS bearer ID(s) assigned, or QoS Flow(s) for which the mapped EPS bearers are not included in Modify Bearer Request, the SMF+PGW-C deletes the PCC rule(s) associated with those QoS Flows and informs the PCF about the removed PCC rule(s). If there are QoS Flow(s) with PCC rule(s) that do not have allocated TFT packet filters, the SMF+PGW-C deletes those PCC rule(s) and informs the PCF about the removed PCC rule(s).
NOTE 4: If the QoS flow is deleted, the IP flows of the deleted QoS rules will continue flowing on the default EPS bearer if it does not have an assigned TFT. If the default EPS bearer has an assigned TFT, the IP flows of the deleted QoS Flow may be interrupted until step 19 when dedicated bearer activation is triggered by a request from the PCF.
The SMF+PGW-C 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.
If the MME does not indicate support of User Plane integrity protection, or the new eNB does not support User Plane integrity protection, or the UE does not support User Plane Integrity Protection with EPS and the UP integrity protection policy is set to "Required" then the SMF+PGW-C releases the bearers associated with the PDN CONNECTION.
15. The SMF+PGW-C initiates a N4 Session Modification procedure towards the UPF+PGW-U to update the User Plane path, i.e. the downlink User Plane for the indicated PDU Session is switched to E-UTRAN. The SMF+PGW-C releases the resource of the CN tunnel for PDU Session in UPF+PGW-U.
16. Step 16a (Modify Bearer Response) from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13]. At this stage the User Plane path is established for the default bearer and the dedicated EPS bearers between the UE, target eNodeB, Serving GW and the PGW-U+UPF. The SMF+PGW-C uses the EPS QoS parameters as assigned for the dedicated EPS bearers during the QoS Flow establishment. SMF+PGW-C maps all the other IP flows to the default EPS bearer (see NOTE 4).
If indirect forwarding tunnel(s) were previously established, the SMF+PGW-C starts a timer, to be used to release the resource used for indirect data forwarding.
17. Step 17 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13].
18. The UE initiates a Tracking Area Update procedure as specified in step 18 of clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13].
This includes the deregistration of the old AMF for 3GPP access from the HSS+UDM as specified in clause 4.11.1.5.3. Any registration associated with the non-3GPP access in the old AMF is not removed (i.e. an AMF that was serving the UE over both 3GPP and non-3GPP accesses does not consider the UE as deregistered over non 3GPP access and will remain registered and subscribed to subscription data updates in UDM).
NOTE 5: The behaviour whereby the HSS+UDM cancels location of CN node of the another type, i.e. AMF, is similar to HSS behaviour for MME and Gn/Gp SGSN registration (see TS 23.401 [13]). The target AMF that receives the cancel location from the HSS+UDM is the one associated with 3GPP access.
When the UE decides to deregister over non-3GPP access or the old AMF decides not to maintain a UE registration for non-3GPP access anymore, the old AMF then deregisters from UDM by sending a Nudm_UECM_Deregistration service operation, unsubscribes from Subscription Data updates by sending an Nudm_SDM_Unsubscribe service operation to UDM and releases all the AMF and AN resources related to the UE.
19. If PCC is deployed, the PCF may decide to provide the previously removed PCC rules to the SMF+PGW-C again thus triggering the SMF+PGW-C to initiate dedicated bearer activation procedure. This procedure is specified in clause 5.4.1 of TS 23.401 [13] with modification captured in clause 4.11.1.5.4. This step is applicable for PDN Type IP or Ethernet, but not for non-IP PDN Type.
20. Step 21 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13].
21. In the case of home routed roaming, at the expiry of the timer at V-SMF started at step 12e, the V-SMF locally releases the SM context and the UP resource for the PDU Session including the resources used for indirect forwarding tunnel(s) that were allocated at step 10.
In non-roaming or local breakout roaming, if SMF+PGW-C has started a timer in step 16, at the expiry of the timer, the SMF+PGW-C sends N4 Session Modification Request to PGW-U+UPF to release the resources used for the indirect forwarding tunnel(s) that were allocated at step 10.
When the timer set in step 12d expires, AMF also sends a UE Context Release Command message to the source NG RAN. The source NG RAN releases its resources related to the UE and responds with a UE Context Release Complete message. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.2.2 EPS to 5GS handover using N26 interface | 4.11.1.2.2.1 General
N26 interface is used to provide seamless session continuity for single registration mode.
The procedure involves a handover to 5GS and setup of QoS Flows in 5GS.
In the home routed roaming case, the PGW-C+ SMF in the HPLMN always receives the PDU Session ID from UE and provides PDN Connection associated 5G QoS parameter(s) and S-NSSAI to the UE. This also applies in the case that the HPLMN operates the interworking procedure without N26.
In the case of handover to a shared 5GS network, the source E-UTRAN determines a PLMN to be used in the target network as specified by clause 5.2a of TS 23.251 [35] for eNodeB functions. A supporting MME may provide the AMF via N26 with an indication that source EPS PLMN is a preferred PLMN when that PLMN is available at later change of the UE to an EPS shared network.
NOTE 1: If the UE has active EPS bearer for normal voice or IMS emergency voice, the source E-UTRAN can be configured to not trigger any handover to 5GS.
If the PDN Type of a PDN Connection in EPS is non-IP and is locally associated in UE and SMF to PDU Session Type Ethernet or Unstructured, the PDU Session Type in 5GS shall be set to Ethernet or Unstructured respectively.
NOTE 2: If the non-IP PDN Type is locally associated in UE and SMF to PDU Session Type Ethernet, it means that Ethernet PDN Type is not supported in EPS.
NOTE 3: The IP address continuity can't be supported, if SMF+PGW-C in the HPLMN doesn't provide the mapped QoS parameters.
In order to support the E-UTRAN NTN enhancements defined in TS 36.300 [46], for handover from EPS to 5GS, the following applies related to handling of UE's radio capabilities:
- If the target NG-RAN node knows (e.g. by configuration) that the UE's E-UTRA radio capabilities applicable to the target NG-RAN node may be different to the E-UTRA radio capabilities stored in the source eNodeB (e.g. for handover from an eNodeB that supports the NTN enhancements as defined in TS 36.300 [46]), then the target NG-RAN node shall trigger retrieval of the E-UTRA radio capability information again from the UE.
In order to support the E-UTRAN NTN enhancements defined in TS 36.300 [46], for handover from 5GS to EPS, the following applies related to handling of UE's radio capabilities:
- If the target eNodeB node knows (e.g. by configuration) that the UE's E-UTRA radio capabilities applicable to the target eNodeB may be different to the E-UTRA radio capabilities stored in the source NG-RAN node (e.g. for handover to eNodeB that supports the NTN enhancements as defined in TS 36.300 [46]), then the target eNodeB shall trigger retrieval of the E-UTRA radio capability information again from the UE.
4.11.1.2.2.2 Preparation phase
Figure 4.11.1.2.2.2-1 shows the preparation phase of the Single Registration-based Interworking from EPS to 5GS procedure.
Figure 4.11.1.2.2.2-1: EPS to 5GS handover using N26 interface, preparation phase
This procedure applies to the Non-Roaming (TS 23.501 [2] Figure 4.3.1-1), Home-routed roaming (TS 23.501 [2] Figure 4.3.2-1) and Local Breakout roaming Local Breakout (TS 23.501 [2] Figure 4.3.2-2) cases.
- For non-roaming scenario, V-SMF, v-UPF and v-PCF are not present
- For home-routed roaming scenario, the SMF+PGW-C and UPF+PGW-U are in the HPLMN. v-PCF are not present
- For local breakout roaming scenario, V-SMF and v-UPF are not present. SMF+PGW-C and UPF+PGW-U are in the VPLMN.
In local-breakout roaming case, the v-PCF interacts wit the SMF+PGW-C.
1 - 2. Step 1 - 2 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13].
3. Step 3 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13] with the following modifications:
An additional optional parameter Return preferred. Return preferred is an optional indication provided by the MME to indicate a preferred return of the UE to the last used EPS PLMN at a later access change to an EPS shared network. Based on the Return Preferred indication, the initial AMF may store the last used EPS PLMN ID in the UE Context.
The initial AMF converts the received EPS MM Context into the 5GS MM Context. This includes converting the EPS security context into a mapped 5G security context as described in TS 33.501 [15]. The MME UE context includes IMSI, ME Identity, UE security context, UE Network Capability and EPS Bearer context(s) and may also include LTE-M Indication. The MME EPS Bearer context(s) include for each EPS PDN connection the IP address and FQDN for the S5/S8 interface of the SMF+PGW-C and APN and for each EPS bearer the IP address and CN Tunnel Info at the UPF+PGW-U for uplink traffic. If the AMF received the LTE-M indication in the EPS MM Context, then it considers that the RAT Type is LTE-M.
The initial AMF queries the (PLMN level) NRF in serving PLMN by issuing the Nnrf_NFDiscovery_Request including the FQDN for the S5/S8 interface of the SMF+PGW-C and the NRF provides the IP address or FQDN of the N11/N16 interface of the SMF+PGW-C.
If the initial AMF cannot retrieve the address of the corresponding SMF for a PDN connection, it will not move the PDN connection to 5GS.
NOTE 1: If the initial AMF holds a native 5G security context for the UE, the initial AMF may activate this native 5G security context by initiating a NAS SMC upon completing the handover procedure.
4. The initial AMF invokes the Nsmf_PDUSession_CreateSMContext service operation (UE EPS PDN Connection, initial AMF ID, data Forwarding information, Target ID) on the SMF identified by the SMF+PGW-C address and indicates HO Preparation Indication (to avoid switching the UP path). The initial AMF ID uniquely identifies the initial AMF serving the UE. This step is performed for each PDN Connection and the corresponding SMF+PGW-C address/ID in the UE context the initial AMF received in step 3. The SMF finds the corresponding PDU Session based on EPS Bearer Context(s).
Based on configuration and the Direct Forwarding Flag received from the MME, the initial AMF determines the applicability of data forwarding and indicates to the SMF whether the direct data forwarding or indirect data forwarding is applicable.
Target ID corresponds to Target ID provided by the MME in step 3.
For home-routed roaming scenario, the initial AMF selects a default V-SMF per PDU Session and invokes the Nsmf_PDUSession_CreateSMContext service operation (UE PDN Connection Contexts, initial AMF ID, SMF + PGW-C address, S-NSSAI). The S-NSSAI is the S-NSSAI configured in initial AMF for interworking, which is associated with default V-SMF.
The default V-SMF selects the SMF+PGW-C using the received H-SMF address as received from the initial AMF and initiates a Nsmf_PDUSession_Create service operation with the SMF+PGW-C and indicates HO Preparation Indication. The V-SMF provides the QoS constraints of the VPLMN to the H-SMF.
Step 5 and step 6 are skipped if the SMF+PGW-C (H-SMF+PGW-C in the case of home-routed scenario) determines that session continuity from EPS to 5GS is not supported for the PDU Session (e.g. PDU Session ID was not received for the PDN connection in EPS, or PDU Session ID was received but mapped 5GS parameters were not provided to the UE due to 5GC interworking restricted).
5. If dynamic PCC is deployed, the SMF+ PGW-C (H-SMF for home-routed scenario) may initiate SMF initiated SM Policy Modification towards the PCF.
6. The SMF+PGW-C requests the PGW-U+UPF to allocate the CN Tunnel Info for PDU Session. The SMF+PGW-C send N4 Session modification to PGW-U+UPF to establish the CN tunnel for PDU Session at PGW-U+UPF. The PGW-U+UPF is ready to receive the uplink packets from NG-RAN. The PGW-U+UPF allocates the PGW-U CN Tunnel Info for PDU Session and sends it to the SMF+PGW-C. This step is performed at all SMF+PGW-Cs allocated to the UE for each PDU Session of the UE.
7. The SMF+PGW-C (default V-SMF in the case of home-routed roaming scenario only) sends a Nsmf_PDUSession_CreateSMContext Response (PDU Session ID, S-NSSAI, allocated EBIs, N2 SM Information (QoS Profile(s), EPS Bearer Setup List, Mapping between EBI(s) and QFI(s), CN Tunnel-Info, cause code)) to the initial AMF.
For home-routed roaming scenario the step 8 need be executed first. The CN Tunnel-Info provided to the initial AMF in N2 SM Information is the V-CN Tunnel-Info.
The SMF includes mapping between EBI(s) and QFI(s) as part of N2 SM Information container. If the P-GW-C+SMF (H-SMF in the case of home-routed scenario) determines that seamless session continuity from EPS to 5GS is not supported for the PDU Session (e.g. PDU Session ID was not received for the PDN connection in EPS), then it does not provide SM information for the corresponding PDU Session but includes the appropriate cause code for rejecting the PDU Session transfer within the N2 SM Information and release the PDN connection locally in the SMF+PGW-C. If neither indirect forwarding nor direct forwarding is applicable, the SMF shall further include a "Data forwarding not possible" indication in the N2 SM information container. If SMF is indicated that Direct Forwarding is applicable in step 4, the SMF shall further include a "Direct Forwarding Path Availability" indication in the N2 SM information container. In home routed roaming case, the S-NSSAI included in N2 SM Information container is the S-NSSAI received in step 4.
The initial AMF stores an association of the PDU Session ID, S-NSSAI and the SMF ID. The AMF stores also the allocated EBI(s) associated to the PDU Session ID.
If the PDN Type of a PDN Connection in EPS is non-IP and is locally associated in SMF to PDU Session Type Ethernet, the PDU Session Type in 5GS shall be set to Ethernet. If the PDN type of a PDN Connection in EPS is non-IP and is locally associated in UE and SMF to PDU Session Type Unstructured, the PDU Session Type in 5GS shall be set to Unstructured.
NOTE 2: If the non-IP PDN Type is locally associated in SMF to PDU Session Type Ethernet, it means that Ethernet PDN Type is not supported in EPS.
In the case of PDU Session Type Ethernet, that was using PDN type non-IP in EPS, the SMF creates QoS rules and QoS Flow level QoS parameters for the QoS Flow(s) associated with the QoS rule(s) based on the PCC Rules received from PCF.
In the case of home-routed roaming scenario, the V-SMF may apply VPLMN policies as described in TS 23.501 [2], clause 5.17.1.3.
The SMF includes the User Plane Security Policy as part of N2 SM Information container. The SMF determines the User Plane Security Policy as described in clause 5.10.3 of TS 23.501 [2].
8. For home-routed roaming scenario only: The default V-SMF selects a default v-UPF and initiates an N4 Session Establishment procedure with the selected default v-UPF. The default V-SMF provides the default v-UPF with packet detection, enforcement and reporting rules to be installed on the UPF for this PDU Session, including H-CN Tunnel Info.
The default v-UPF acknowledges by sending an N4 Session Establishment Response message. The V-CN Tunnel Info is allocated by the v-UPF and provided to the default V-SMF in this step.
8a. Based on the received S-NSSAI from the SMF+PGW-C, the Initial AMF may reselect a target AMF as described in clause 5.15.5.2.1 of TS 23.501 [2] and invokes Namf_Communication_RelocateUEContext request (SUPI, Target 5GAN Node ID, PDU session ID and the S-NSSAI associated with N2 SM Information received in step 7, Source to Target Transparent Container, 5GS MM Context, MME Tunnel Endpoint Identifier for Control Plane, MME Address for Control plane, 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), SMF+PGW-C ID of each PDU Session, default V-SMF ID and SM Context ID of each PDU Session, allocated EBIs of each PDU Session, Allowed NSSAI received from NSSF) to the selected target AMF.
NOTE 3: When there is no need of AMF reallocation, then the target AMF in following steps is the same as the initial AMF.
NOTE 4: In the case of Home routed PDU Session the S-NSSAI associated with N2 SM information used in steps 8, 8a and 9 is the S-NSSAI configured for interworking in the initial AMF. Otherwise the S-NSSAI received from the SMF in step 7 can be used in steps 8, 8a and 9 for the S-NSSAI associated with N2 SM information.
9. The target AMF sends a Handover Request (Source to Target Transparent Container, Allowed NSSAI, PDU session ID and the S-NSSAI received from Source AMF associated with the corresponding N2 SM Information (QFI(s), QoS Profile(s), EPS Bearer Setup List, V-CN Tunnel Info, Mapping between EBI(s) and QFI(s)), Mobility Restriction List, UE Radio Capability ID) message to the NG-RAN.
If available, the target AMF provides NG-RAN with a PLMN list in the Mobility Restriction List containing at least the serving PLMN, which may also include the last used EPS PLMN ID if it is the preferred PLMN for subsequent mobility to EPS. See TS 38.413 [10], clause 9.3.1.85 for details about the Mobility Restriction List.
NG-RAN can use the source to target transparent container and N2 SM Information container to determine which QoS flows have been proposed for forwarding and decide for which of those QoS flows it accepts the data forwarding or not.
The target AMF provides the UE Radio Capability ID to NG-RAN if RACS is supported. If the UE Radio Capability ID is included in the Handover Request message, when there is no corresponding UE radio capabilities set for UE Radio Capability ID at NG-RAN and no UE radio access capabilities are provided in the Source to Target transparent container, NG-RAN shall request the T-AMF to provide the UE radio capabilities set corresponding to UE Radio Capability ID to the NG-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 access radio 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.
10. The NG-RAN sends a Handover Request Acknowledge (Target to Source Transparent Container, List of PDU Sessions to Hand-over with N2 SM response (PDU Session ID, list of accepted QFI(s), AN Tunnel Info, Data Forwarding Tunnel Info), 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) message to the target AMF.
If indirect data forwarding is applied, the NG-RAN includes one assigned TEID/TNL address per PDU Session (for which there is at least one QoS flow for which it has accepted the forwarding) within the SM Info container. It also includes the list of QoS flows for which it has accepted the forwarding. According to the mapping between EBI(s) and QFI(s), if one EPS bearer in EPS is mapped to multiple QoS flows in 5GS, all such QoS flows need to be accepted to support indirect data forwarding during EPS to 5GS mobility. Otherwise, the NG RAN rejects the indirect data forwarding for the QoS flows which are mapped to the EPS bearer.
If direct data forwarding is applied, the NG-RAN includes one assigned TEID/TNL per E-RAB accepted for direct data forwarding.
When the target NG-RAN rejects the handover with a Handover Failure, steps 11-13 and step 16 are not executed.
The NG-RAN includes the PDU Set Based Handling Support Indication in N2 SM information as described in clause 5.37.5.3 of TS 23.501 [2].
11. The target AMF sends an Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID, N2 SM response received from NG-RAN in step 10) message to the SMF for updating N3 tunnel information. In home routed roaming case, the Data Forwarding Tunnel Info is handled by the default V-SMF and will not be sent to the SMF+PGW-C.
12. SMF+PGW-C (default V-SMF in home-routed roaming scenario) performs preparations for N2 Handover by indicating N3 UP address and Tunnel ID of NG-RAN to the UPF if N2 Handover is accepted by NG-RAN. If indirect data forwarding is applied, SMF+PGW-C indicates the mapping between the TEID where the UPF receives data forwarded by the source SGW and the QFI(s) and N3 Tunnel Info for data forwarding where the UPF is selected to forward such data (e.g. an intermediate UPF). If the EPS bearer is mapped to multiple QoS flows and an intermediate UPF is selected for data forwarding, only one QFI is selected by the SMF+PGW-C from QFIs corresponding to the QoS flows.
If indirect data forwarding is applied in home routed roaming case, the default V-SMF sends a default V-UPF for data forwarding the mapping between the TEID where the UPF receives data forwarded by the source SGW and the QFI and N3 Tunnel Info for data forwarding. If the EPS bearer is mapped to multiple QoS flows and an intermediate UPF is selected for data forwarding, only one QFI is selected by the SMF+PGW-C from QFIs corresponding to the QoS flows.
If N2 Handover is not accepted by NG-RAN, SMF+PGW-C deallocates N3 UP address and Tunnel ID of the selected UPF.
The EPS Bearer Setup list is a list of EPS bearer Identifiers successfully handover to 5GC, which is generated based on the list of accepted QFI(s).
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.
13. SMF+PGW-C (default V-SMF in home-routed roaming scenario) to target AMF: Nsmf_PDUSession_UpdateSMContext Response (PDU Session ID, EPS Bearer Setup List). The data forwarding information is included in the EPS Bearer Setup List. In home routed roaming case, the default V-SMF provides the tunnel information for data forwarding.
This message is sent for each received Nsmf_PDUSession_UpdateSMContext_Request message.
14. The target AMF sends the message Forward Relocation Response (Cause, Target to Source Transparent Container, Serving GW change indication, EPS Bearer Setup List, target AMF Tunnel Endpoint Identifier for Control Plane, Addresses and TEIDs) to MME. The EPS Bearer Setup list is the combination of EPS Bearer Setup list from different SMF+PGW-C(s).
In the case of Handover Failure in step 10, the target AMF provides to the MME the failure related information such as the Target RAN to Source RAN Failure Information.
15. The target AMF invokes Namf_Communication_RelocateUEContext response (Cause) to the initial AMF if step 8a had been performed. The target AMF 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 Namf_Communication_RelocateUEContext response indicates a failure due to RAN rejection. Then the initial AMF invokes the Nsmf_PDUSession_UpdateSMContext request towards the SMF+PGW-C(s) contacted at step 4 indicating . The Nsmf_PDUSession_UpdateSMContext request contains an indication that this is due to a handover rejected by the target RAN.
16. Step 8 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13] is executed if the source MME determines that indirect data forwarding applies.
Upon completion of the handover procedure, based on the PDU Set Based Handling Support Indication received in step 10 as described in clause 5.37.5.3 of TS 23.501 [2], the SMF may initiate the PDU Session modification procedure to provide PDU Set QoS parameters to NG-RAN and configure the PSA UPF to activate/deactivate the PDU Set identification and marking for DL.
4.11.1.2.2.3 Execution phase
Figure 4.11.1.2.2.3-1 shows the Single Registration-based Interworking from EPS to 5GS procedure.
Figure 4.11.1.2.2.3-1: EPS to 5GS handover using N26 interface, execution phase
NOTE: Step 6 P-GW-C+SMF Registration in the UDM is not shown in the figure for simplicity.
1 - 2. Step 9 - 11 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13]. Different from step 9a of clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13], upon reception of Handover Command, the UE will keep the QoS Flow context for which it did not receive the corresponding radio resources in the NG-RAN until the QoS Flow is released by the network using PDU Session Modification procedure in clause 4.3.3. If the QoS Flow with a default QoS Rule of a PDU Session does not have the corresponding radio resources in the NG-RAN, UE considers that the user plane of this PDU Session is deactivated.
3. Handover Confirm: the UE confirms handover to the NG-RAN.
The UE moves from the E-UTRAN and synchronizes with the target NG-RAN. The UE may resume the uplink transmission of user plane data only for those QFIs and Session IDs for which there are radio resources allocated in the NG-RAN.
The E-UTRAN sends DL data to the Data Forwarding address received in step 1. If the indirect data forwarding is applied, the E-UTRAN forward the DL data to NG-RAN via the SGW and the v-UPF. The v-UPF forwards the data packets to the NG-RAN using the N3 Tunnel Info for data forwarding, adding the QFI information. The target NG-RAN prioritizes the forwarded packets over the fresh packets for those QoS flows for which it had accepted data forwarding.
If Direct data forwarding is applied, the E-UTRAN forwards the DL data packets to the NG-RAN via the direct data forwarding tunnel.
4. Handover Notify: the NG-RAN notifies to the target AMF that the UE is handed over to the NG-RAN.
5. Then the target AMF knows that the UE has arrived to the target side and informs the MME by sending a Forward Relocation Complete Notification message.
6. Step 14 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13].
7. Target AMF to SMF +PGW-C (V-SMF in the case of roaming and Home-routed case): Nsmf_PDUSession_UpdateSMContext Request (Handover Complete Indication for PDU Session ID). In the Home-routed roaming case, the V-SMF invokes Nsmf_PDUSession_Update Request (V-CN Tunnel Info, Handover Complete Indication) to SMF+PGW-C.
Handover Complete Indication is sent per each PDU Session to the corresponding SMF +PGW-C (sent by V-SMF in the roaming and Home-routed case) to indicate the success of the N2 Handover.
If indirect forwarding is used, a timer in SMF+PGW-C (V-SMF in the case of roaming and Home-routed case) is started to supervise when resources in UPF (for indirect data forwarding) shall be released.
8. The SMF + PGW-C updates the UPF + PGW-U with the V-CN Tunnel Info, indicating that downlink User Plane for the indicated PDU Session is switched to NG-RAN or V-UPF in the case of roaming in Home-routed case and the CN tunnels for EPS bearers corresponding to the PDU session can be released.
For each EPS Bearer one or more "end marker" is sent to Serving GW by the UPF+PGW-U immediately after switching the path. The UPF + PGW-U starts sending downlink packets to the V-UPF.
9. If PCC infrastructure is used, the SMF + PGW-C informs the PCF about the change of, for example, the RAT type and UE location.
10. SMF +PGW-C to target AMF: Nsmf_PDUSession_UpdateSMContext Response (PDU Session ID).
SMF +PGW-C confirms reception of Handover Complete.
- If the SMF has not yet registered for this PDU Session ID, then the SMF registers with the UDM using Nudm_UECM_Registration (SUPI, DNN, PDU Session ID) for a given PDU Session as in step 4 of PDU Session Establishment Procedure in clause 4.3.2.
11. For home-routed roaming scenario: The V-SMF provides to the v-UPF with the N3 DL AN Tunnel Info. This step is executed after step 7.
12. The UE performs the EPS to 5GS Mobility Registration Procedure from step 2 in clause 4.11.1.3.3. The UE includes the UE Policy Container containing the list of PSIs, indication of UE support for ANDSP and OSId if available. If the UE holds a native 5G-GUTI it also includes the native 5G-GUTI as an additional GUTI in the Registration Request. The UE shall select the 5G-GUTI for the additional GUTI as follows, listed in decreasing order of preference:
- a native 5G-GUTI assigned by the PLMN to which the UE is attempting to register, if available;
- a native 5G-GUTI assigned by an equivalent PLMN to the PLMN to which the UE is attempting to register, if available;
- a native 5G-GUTI assigned by any other PLMN, if available.
The additional GUTI enables the target AMF to find the UE's 5G security context (if available). The target AMF provides NG-RAN with a PLMN list in the Handover Restriction List containing at least the serving PLMN, taking into account of the last used EPS PLMN ID and Return preferred indication as part of the Registration procedure execution and target AMF signalling to NG-RAN. The Handover Restriction List contains a list of PLMN IDs as specified by TS 23.501 [2].
13. Step 19 from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13]. Step 20a - 20b from clause 5.5.1.2.2 (S1-based handover, normal) in TS 23.401 [13], with the following modification:
For the PDN connections that are not possible to be transferred to 5GS (e.g. PDN connections are anchored in a standalone PGW), the MME initiates PDN connection release procedure as specified in TS 23.401 [13].
14. If indirect forwarding was used, then the expiry of the timer started at step 7 triggers the SMF+PGW-C (V-SMF in the case of roaming and Home-routed case) to release temporary resources used for indirect forwarding that were allocated at steps 11 to 13 in clause 4.11.1.2.2.2. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.2.3 Handover Cancel | Instead of completing the handover procedure, the source RAN node (NG-RAN, E-UTRAN) may at any time, during the handover procedure, up to the time when a handover command message is sent to the UE, cancel the handover. The reason for cancelling may be e.g. due to a timer expiration or due to other events within the source RAN node and is initiated by sending a handover cancel message to the source CN node (AMF or MME).
A handover cancel message shall also be sent by the source RAN node after a handover command message is sent to the UE for the case where the handover fails and the UE returns to the old cell or radio contact with the UE is lost. This is done in order to release the resources reserved for the handover in the target system.
During EPS to 5GS handover when the initial AMF has invoked a target AMF (as described in step 8a in clause 4.11.1.2.2),
- when the source MME has received a N26 Forward Relocation Response from the target AMF, the MME sends N26 Cancel Relocation Request directly to the target AMF and the initial AMF is not involved at all in the Cancel Relocation procedure.
- When the source MME has not received a response from the target AMF, the MME sends N26 Cancel Relocation Request to the initial AMF:
- if the initial AMF has already invoked the target AMF, the initial AMF indicates the Cancel Relocation to the target AMF and the target AMF becomes responsible of the Handover Cancellation (e.g. the target AMF initiates Nsmf_PDUSession_UpdateSMContext request indicating Handover Cancel towards the SMF+PGW-C(s) unless the target AMF has already indicated a Handover failure due to prior target NG RAN rejection of the Handover);
- otherwise the initial AMF handles the relocation cancellation.
Figure 4.11.1.2.3-1: Handover Cancel procedure
1. When the source RAN (NG-RAN, E-UTRAN) decides to cancel the handover to the target system, the source RAN initiates handover cancel message to the source CN node (AMF or MME).
2. After receiving the handover cancel message from the source RAN, if the source CN node or the target CN node is MME, it sends a Relocation Cancel Request message to the target CN node (MME or AMF). If both the source CN node and target CN node are AMF, the source AMF invokes (via initial AMF if AMF re-allocation is performed during preparation phase) the Namf_Communication_ReleaseUEContext Request (UE Context ID) toward the target AMF. During EPS to 5GS handover with AMF reallocation if the initial AMF has invoked a target AMF, the initial AMF invokes the Namf_Communication_CancelRelocateUEContext Request (UE Context ID) toward the target AMF.
3. The target CN node (MME or AMF) triggers release of resources towards target RAN node. The target RAN node releases the AN resources allocated for the handover.
4. If the target CN node is MME, the MME sends the Delete Session Request to the SGW/SGW-C (see clause 5.5.2.5.2 of TS 23.401 [13]).
4a. [Conditional] The SGW-C releases the corresponding resource in the SGW-U if allocated during the handover preparation.
4b. If the target CN node is AMF, the AMF invokes the Nsmf_PDUSession_UpdateSMContext request (Relocation Cancel Indication) toward the SMF in non-roaming and local breakout roaming scenarios.
For home-routed roaming scenario, AMF invokes the Nsmf_PDUSession_UpdateSMContext request (Relocation Cancel Indication) toward the (target) V-SMF and the V-SMF invokes the Nsmf_PDUSession_Update Request (Relocation Cancel Indication) towards the H-SMF.
Based on the Relocation Cancel Indication, the SMF(s) deletes the session resources established during handover preparation phase in SMF(s) and UPF(s).
4c. [Conditional] The (target) V-SMF releases the corresponding resource in the (target) V-UPF if allocated during the handover preparation.
4d. [Conditional] The (H-)SMF+PGW-C releases the corresponding resource in the (H-)UPF+PGW-U if allocated during the handover preparation.
5. The target CN node (MME or AMF) sends Relocation Cancel Response towards the source CN node (AMF or MME).
6. The source CN node (AMF or MME) responds with handover cancel ACK towards the source RAN.
7. [Conditional] If target CN node is AMF and the source CN is MME, then cancellation of handover triggers the MME to release the temporary resources used for indirect forwarding.
7b. [Conditional] If the source CN is AMF and the target CN node is MME and if indirect forwarding tunnel had been setup during handover preparation phase, then cancellation of handover triggers the AMF to release the session resources established during handover preparation phase in SMF(s) and UPF(s).
- The AMF invokes the Nsmf_PDUSession_UpdateSMContext request (Relocation Cancel Indication) toward the SMF in non-roaming and local breakout roaming scenarios.
- For home-routed roaming scenario, the AMF invokes the Nsmf_PDUSession_UpdateSMContext request (Relocation Cancel Indication) toward the V-SMF.
Based on the Relocation Cancel Indication, the SMF deletes the session resources (e.g. CN tunnel information for EPS bearer) established during handover preparation phase in SMF UPF and stops any timer that may have been started to monitor the handover in case of non-roaming and local breakout roaming scenarios. The V-SMF deletes the prepared session resources e.g. established for indirect forwarding tunnel in case of home-routed roaming scenario.
7c. [Conditional] In home routed roaming case, the V-SMF releases the corresponding resource in the target V-UPF if allocated during the handover preparation.
7d. [Conditional] In non-roaming or LBO case, the SMF+PGW-C releases the corresponding resource in the UPF+PGW-U if allocated during the handover preparation.
8. [Conditional] If target CN node is MME and indirect forwarding tunnel is setup during handover preparation phase then cancellation of handover triggers the target MME to release the temporary resources used for indirect forwarding.
8a. [Conditional] The SGW-C releases the resources for indirect forwarding in the SGW-U if allocated during the handover preparation. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.3 Idle Mode Mobility procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.3.1 General | When a UE moves from EPC to 5GC, the UE always performs Registration procedure.
When a UE moves from 5GC to EPC, the UE performs either Tracking Area Update or Initial Attach.
The UE performs Tracking Area Update procedure if
- Both the UE and the EPC support "attach without PDN connectivity", or
- The UE has at least one PDU Session for which Session Continuity is supported during interworking, i.e. the UE has EPS Bearer ID and mapped EPS QoS parameters received as described in clause 4.11.1.1.
The UE performs an initial attach procedure if
- The UE is registered without PDU Session in 5GC or the UE is registered only with PDU Session for which Session Continuity is not supported during interworking to EPC; and
- Either the UE or the EPC does not support attach without PDN connectivity. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.3.2 5GS to EPS Idle mode mobility using N26 interface | In the case of network sharing the UE selects the target PLMN ID according to clause 5.18.3 of TS 23.501 [2].
Clause 4.11.1.3.2 covers the case of idle mode mobility from 5GC to EPC. UE performs Tracking Area Update procedure in E-UTRA/EPS when it moves from NG-RAN/5GS to E-UTRA/EPS coverage area.
The procedure involves a Tracking Area Update to EPC and setup of default EPS bearer and dedicated bearers in EPC in steps 1-11 and re-activation, if required.
Figure 4.11.1.3.2-1: 5GS to EPS Idle mode mobility using N26 interface
The TAU procedure in TS 23.401 [13] is used with the following 5GS interaction:
1. Step 1 from clause 5.3.3.1 (Tracking Area Update procedure with Serving GW change) in TS 23.401 [13].
2. Step 2 from clause 5.3.3.1 (Tracking Area Update procedure with Serving GW change) in TS 23.401 [13] with the modification captured in clause 4.11.1.5.3.
3-4. Steps 3-4 from clause 5.3.3.1 (Tracking Area Update procedure with Serving GW change) in TS 23.401 [13].
5a. The AMF verifies the integrity of the TAU request message:
The AMF determines for a PDU Session whether to retrieve context including mapped UE EPS connection from V-SMF (in the case of HR roaming) or from the SMF+PGW-C (in the case of non roaming or LBO roaming) as follows:
- If the AMF determines that one or more of the EBI(s) can be transferred, the AMF sends Nsmf_PDUSession_ContextRequest to the V-SMF or SMF+PGW-C and includes in the message EBI value(s) if any that cannot be transferred.
- The EBI values(s) that cannot be transferred is determined by the AMF if the target MME does not support 15 EPS bearers, i.e. the AMF determines the EBI values in range 1-4 as not to be transferred to EPS and if there are still more than 8 EBI values associated with PDU Sessions, the AMF then determines EBI value(s) not to be transferred to EPS based on S-NSSAI and ARP as specified in clause 5.17.2.2.1 of TS 23.501 [2].
- The AMF does not retrieve the context for a PDU Session that cannot be transferred to EPS due to no EBI allocated, or allocated EBIs not transferrable, or combination of the two.
In non-roaming or LBO roaming, the AMF retrieves context that includes the mapped EPS Bearer Contexts.
- The AMF provides in Nsmf_PDUSession_ContextRequest the target MME capability to the PGW C+SMF in the request to allow the SMF+PGW-C to determine whether to include EPS Bearer context for Ethernet PDN type or non-IP PDN Type or not.
- If the AMF includes in Nsmf_PDUSession_ContextRequest EBI list not to be transferred and if the EBI value of the QoS Flow associated with the default QoS Rule is included in that list, the SMF+PGW-C shall not return the PDN Connection context (which implies the whole PDU Session is not transferred to EPS), otherwise if the EBI value of the QoS Flow associated with the default QoS Rule is not included in the EBI list not to be transferred, the V-SMF or SMF+PGW-C shall not provide the EPS bearer context(s) mapped from QoS Flow(s) associated with that list.
- When the AMF sends Nsmf_PDUSession_ContextRequest to the V-SMF or the SMF+PGW-C, the AMF indicates whether the target MME supports User Plane Integrity Protection with EPS.
The above steps are performed with all the SMF+PGW-Cs corresponding to PDU Sessions of the UE which are associated with 3GPP access and have EBI(s) allocated to them.
In Home Routed roaming, the AMF requests the V-SMF to provide SMF Context by using Nsmf_PDUSession_ContextRequest.
NOTE 1: The AMF knows the MME capability to support 15 EPS bearers, support User Plane Integrity Protection with EPS, Ethernet PDN Type and/or non-IP PDN type or not through local configuration.
5b. For Non-roaming or roaming with local breakout scenario, if the CN Tunnel Info for EPS bearer(s) have not been allocated before, the SMF sends N4 Session Modification Request to PGW-U+UPF to establish the tunnel for each EPS bearers and PGW-U+UPF provides the PGW-U Tunnel Info for each EPS bearers to SMF+PGW-C.
NOTE 2: In home routed roaming case, the CN Tunnel Info for each EPS bearer has been prepared by the SMF+PGW-C and provided to the V-SMF as specified in clause 4.11.1.4.1.
5c. For PDU Sessions that are anchored a UPF, in non-roaming or roaming with local breakout, the SMF+PGW-C returns mapped EPS bearer contexts, which includes PGW-C control plane tunnel information of the PDN connection corresponding to the PDU session, EBI for each EPS bearer, PGW-U tunnel information for each EPS bearer and EPS QoS parameters for each EPS bearer. For PDU Sessions with PDU Session Type Ethernet, if the UE and target MME supports Ethernet PDN type, the SMF+PGW-C provides SM Context for Ethernet PDN Type, otherwise if the UE or target MME does not support Ethernet Type but support non-IP Type, the SMF+PGW-C provides SM Context for non-IP PDN Type. For PDU Sessions with PDU Session Type Unstructured, the SMF provides SM Context for non-IP PDN Type. In home routed roaming, V-SMF provides the SM Context.
If the UP integrity protection policy for the EPS bearer context is set to "Required", the V-SMF or the PGW C+SMF shall not provide the EPS bearer context unless the MME supports User Plane Integrity Protection with EPS and the UE supports User Plane Integrity Protection with EPS.
For PDU Sessions that are anchored at an NEF, the SMF returns an SCEF+NEF ID and an EBI for each PDN connection corresponding to a PDU Session.
If the SMF+PGW-C has marked that the status of one or more QoS Flows are deleted in the 5GC but not synchronized with the UE yet according to clause 4.3.3.2, the SMF+PGW-C does not return to the AMF the EPS context(s) if all its associated QoS Flows are marked as deleted, that is, the SMF+PGW-C returns to the AMF the EPS bearer contexts mapped from QoS Flows where at least one of the QoS Flow for the EPS bearer is not marked as deleted.
6. The AMF responds with a Context Response message as in step 5 in clause 5.3.3.1 of TS 23.401 [13] carrying mapped MM context (including mapped security context), Return preferred and SM EPS UE Context (default and dedicated GBR bearers) to the MME. If the verification of the integrity protection fails, the AMF returns an appropriate error cause. Return preferred is an optional indication by the AMF of a preferred return of the UE to the 5GS PLMN at a later access change to a 5GS shared network. The AMF may start an implementation specific (guard) timer for the UE context.
From the received context and the Tracking Area indicated by the RAN, the MME can determine whether the UE is performing Inter-RAT mobility to or from NB-IoT.
7 - 14. Steps 6-12 from clause 5.3.3.1 (Tracking Area Update procedure with Serving GW change) in TS 23.401 [13] are performed with following addition and modification:
In the step 10, if the PDU Session (PDN connection) has QoS Flows that do not have EPS bearer ID(s) assigned, the SMF+PGW-C deletes the PCC rule(s) associated with those QoS Flows and informs the PCF about the removed PCC rule(s). If there are QoS Flow(s) with PCC rule(s) that do not have allocated TFT packet filters (due to number exceeding limit), the SMF+PGW-C deletes those PCC rule(s) and informs the PCF about the removed PCC rule(s).
In the step 10, if the MME does not indicate support of User Plane integrity protection, or the new eNB does not support User Plane integrity protection, or the UE does not support User Plane Integrity Protection with EPS and the UP integrity protection policy is set to "Required" then the SMF+PGW-C releases the bearers associated with the PDN CONNECTION.
In the step 11, the SMF+PGW-C requests the PGW-U+UPF to establish the tunnel for each EPS bearer by providing SGW-U Tunnel Info.
In step 10, the SMF+PGW-C 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. If the mapped EPS bearers are not included in Modify Bearer Request, the SMF+PGW-C deletes the PCC rule(s) associated with the QoS Flows corresponding to those mapped EPS bearers.
Step 9a from clause 5.3.3.1 (Tracking Area Update procedure with Serving GW change) in TS 23.401 [13] with the modification captured in clause 4.11.1.5.3
If the SCEF connection is to be established, the steps 9-13 are replaced with the steps 2-3 from clause 5.13.1.2 of TS 23.682 [23]. The SCEF+NEF ID and the EBI received from the AMF are included in the Create SCEF Connection Request.
15-15c. The HSS+UDM invokes Nudm_UECM_DeregistrationNotification to notify the AMF associated with 3GPP access with reason as 5GS to EPS Mobility. If the timer started in step 6 is not running, the old AMF removes the UE context. Otherwise, the AMF may remove UE context when the timer expires.
The AMF requests the release of the PDU Session(s) which is associated with 3GPP access and not expected to be transferred to EPC, i.e. AMF requests the release of:
- PDU Session(s) whose corresponding SMF+PGW-C(s) are not contacted by AMF for SM context because the AMF determines that none of EBI(s) for the PDU Session can be transferred to EPS at step 5a; and
- PDU Session(s) for which the SM context retrieval failed at step 5c.
The AMF requests the release of the SM context in the V-SMF only and the V-SMF releases resource in the V-UPF, for Home Routed PDU Session with EBIs allocated. The 5GC may also keep UE context to allow the use of native security parameters when UE moves back from EPS to 5GS later.
If PCC is enabled, the AMF initiates AM Policy Association Termination procedure as defined in clause 4.16.3.2 and UE Policy Association Termination procedure as defined in clause 4.16.13.1.
Registration associated with the non-3GPP access in the AMF is not removed (i.e. an AMF that was serving the UE over both 3GPP and non-3GPP accesses does not consider the UE as deregistered over non 3GPP access and will remain registered and subscribed to subscription data updates in UDM).
When the UE decides to deregister over non-3GPP access or the old AMF decides not to maintain a UE registration for non-3GPP access anymore, the old AMF then deregisters from UDM by sending a Nudm_UECM_Deregistration service operation, unsubscribes from Subscription Data updates by sending an Nudm_SDM_Unsubscribe service operation to UDM and releases all the AMF and AN resources related to the UE.
16 - 18. Steps 17-21 from clause 5.3.3.1 (Tracking Area Update procedure with Serving GW change) in TS 23.401 [13] with the following modification:
- The MME may provide the eNodeB with a PLMN list in the Handover Restriction List taking into account the last used 5GS PLMN ID and the Return preferred indication. The Handover Restriction List contains a list of PLMN IDs as specified by clause 5.2a of TS 23.251 [35] for eNodeB functions.
- The MME may not release the signalling connection with the UE based on the indication received in the step 1 that the UE is moving from 5GC.
19. [conditional] Step 19 from clause 4.11.1.2.1 applies.
If some of the QoS Flow(s) for an EPS bearer were marked as deleted, the SMF+PGW-C may initiate bearer modification as specified in clause 5.4.3 of TS 23.401 [13] to remove the TFT filter(s) corresponding to the Packet Filter Set(s) in the QoS rules.
4.11.1.3.2A 5GS to EPS Idle mode mobility using N26 interface with data forwarding
Figure 4.11.1.3.2A-1 describes the idle mode mobility registration procedure from 5GS to EPS when N26 is supported with data forwarding.
Figure 4.11.1.3.2A-1: 5GS to EPS Idle mode mobility using N26 interface with data forwarding
1. Steps 1-7 from clause 4.11.1.3.2 with the following enhancements:
- The (V-)SMF includes the Buffered DL Data Waiting indication in the Nsmf_PDUSession_Response in step 5c of figure 4.11.1.3.2-1, if the Extended buffering timer is running in (V-)SMF.
- The AMF forwards the Buffered DL Data Waiting indication to MME in step 6 of figure 4.11.1.3.2-1, if it's received from SMF above.
2. Steps 7-9 from clause 5.3.3.1A of TS 23.401 [13].
3. Steps 14, 15, 15a and 16 from clause 4.11.1.3.2.
4. Steps 10-14 from clause 5.3.3.1A of TS 23.401 [13].
5. Steps 10a, b, c from clause 4.11.1.2.1 with the following enhancements:
- If data forwarding tunnel information (i.e. Forwarding F-TEID) is received from MME in step 14 of figure 5.3.3.1A-1 of TS 23.401 [13] in step 4 above, the AMF provides the data forwarding tunnel info to (V-)SMF in Nsmf_PDUSession_UpdateSMContext Request. The (V-)SMF provides the data forwarding tunnel info to (V-)UPF if data is buffered in (V-)UPF.
- The (V-)SMF and (V-)UPF forwards data using the provided SGW forwarding tunnel above. The (V-)SMF also initiates a timer to release the SM context or data forwarding tunnel of the PDU session.
The data received by the Serving GW on the forwarding tunnel is forwarded on the (newly) established tunnel to eNB.
6. Step 15b from clause 4.11.1.3.2 with following enhancements:
The (V-)SMF initiates the release of data forwarding tunnel after the timer in step 5 above is expired. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.3.3 EPS to 5GS Mobility Registration Procedure (Idle and Connected State) using N26 interface | Figure 4.11.1.3.3-1 describes the mobility registration procedure from EPS to 5GS when N26 is supported for idle and connected states.
Figure 4.11.1.3.3-1: EPS to 5GS mobility for single-registration mode with N26 interface
1. The Registration procedure is triggered, e.g. the UE moves into NG-RAN coverage. Step 2 to 9 except step 5, 6 and 8 follow the Registration procedure in clause 4.2.2 with following enhancement.
2. The UE sends Registration Request with registration type set to "Mobility Registration Update".
The UE includes 5G-GUTI mapped from EPS GUTI as the old GUTI, the native 5G-GUTI (if available) as additional GUTI and indicating that the UE is moving from EPC. The UE includes the UE Policy Container containing the list of PSIs, indication of UE support for ANDSP and OSId if available.
When the Registration Request is triggered due to UE mobility from EPS to 5GS, if the UE has locally deleted the EPS bearer which has allocated 5GS parameters and the EPS bearer status has not been synchronized with the network, the UE shall include the EPS bearer status in the Registration Request. If the UE has not received mapped 5GS QoS parameters from the network for PDN connection(s), the UE locally releases those PDN connection(s).
The Additional GUTI is provided both in Idle state and Connected state, if available. The Additional 5G-GUTI enables the AMF to retrieve the UE's MM context from the old AMF (if available). The UE includes the S-NSSAIs associated with the established PDN connections in the Requested NSSAI in RRC and NAS (as described in clause 5.15.7 of TS 23.501 [2]). In the case of Configured NSSAI applicable to this PLMN or an Allowed NSSAI are not present in the UE, the associated HPLMN S-NSSAI(s) shall be provided in the mapping of Requested NSSAI in the NAS as described in clause 5.15.5.2.1 TS 23.501 [2].
In the case of idle mode mobility the UE additionally includes a TAU request message integrity protected using the EPS security context (for further security verification by the MME) in the Registration Request. If the UE holds a native 5G-GUTI for this PLMN then the UE also includes the GUAMI part of the native 5G-GUTI in RRC to enable the NG-RAN to route the Registration Request to the same AMF (if available) and otherwise the UE provides in RRC signalling a GUAMI mapped from the EPS GUTI and indicates it as "Mapped from EPS".
The UE integrity protects the Registration Request message using a 5G security context (if available).
3-4. Steps 2-3 of clause 4.2.2.2.2 are performed.
In the case of idle mode mobility, the AMF derives S-NSSAIs values for the Serving PLMN based on the S-NSSAIs values for the HPLMN, received in NAS Registration Request, associated with the established PDN connections, the AMF may send the S-NSSAIs values for the HPLMN to NSSF by invoking Nnssf_NSSelection_Get service operation and NSSF provides corresponding S-NSSAIs values for VPLMN to AMF.
NOTE 1: In connected mode mobility, the AMF devices S-NSSAIs values during the handover procedure.
Steps 5 and 8 are not performed when this procedure is part of EPS to 5GS handover.
5a. [Conditional] This step is only performed for IDLE mode mobility. The AMF derives the MME address and 4G GUTI from the old 5G-GUTI and sends Context Request to MME including EPS GUTI mapped from 5G-GUTI and the TAU request message according to TS 23.401 [13]. The MME validates the TAU message.
5b. [Conditional] If step 5a is performed, step 5 from clause 5.3.3.1 (Tracking Area Update procedure with Serving GW change) in TS 23.401 [13] is performed with the modification captured in clause 4.11.1.5.3.
The AMF converts the received EPS MM Context into the 5GS MM Context. The received EPS UE context includes IMSI, ME Identity, UE EPS security context, UE Network Capability and EPS Bearer context(s) and may also include LTE-M Indication. The MME EPS Bearer context includes for each EPS PDN connection the IP address and FQDN for the S5/S8 interface of the SMF+PGW-C and APN. If the SCEF connection is invoked, the MME EPS Bearer context includes the SCEF+NEF ID of the PDN connection, EBI, APN, User Identity. The AMF disregards any LTE-M Indication received in the EPS UE context and instead takes into account the LTE M Indication received from NG-RAN, at step 1.
The AMF can determine the whether the UE is performing Inter-RAT mobility to or from NB-IoT based on the received "TAI of last TAU" in the EPC MM Context and the RAT Type used for the Registration Request.
If the Context Response includes the FQDN for the S5/S8 interface of the SMF+PGW-C, the AMF queries the NRF in serving PLMN by issuing the Nnrf_NFDiscovery_Request including the FQDN for the S5/S8 interface of the SMF+PGW-C and the NRF provides the IP address or FQDN of the N11/N16 interface of the SMF+PGW-C.
If the Context Response includes an SCEF+NEF ID, the AMF performs the SMF selection.
The Context Response may include new information Return Preferred. Return Preferred is an indication by the MME of a preferred return of the UE to the last used EPS PLMN at a later access change to an EPS shared network. Based on the Return Preferred indication, the AMF may store the last used EPS PLMN ID in UE Context.
If the AMF cannot retrieve the address of the corresponding SMF for a PDN connection, it will not move the PDN connection to 5GS.
Step 6 is performed only if the AMF is different from the old AMF and the old AMF is in the same PLMN as the AMF.
6a. [Conditional] If the UE includes the 5G-GUTI as Additional GUTI in the Registration Request message, the AMF sends message to the old AMF. The old AMF validates the Registration request message.
The AMF retrieves UE's SUPI and MM Context, event subscription information by each consumer NF and the list of SM PDU Session ID/associated SMF ID for the UE using one of the following three options:
- AMF may invoke the Namf_Communication_UEContextTransfer to the old AMF identified by the additional 5G-GUTI; or
- if the old AMF and the AMF are in the same AMF Set and UDSF is deployed, AMF may invoke Nudsf_UnstructuredDataManagement_Query service operation for the UE identified by the additional 5G-GUTI from the UDSF; or
- if the old AMF and the AMF are in the same AMF Set, AMF may use implementation specific means to share UE context.
6b. [Conditional] If step 6a is performed, the response is performed as described in step 5 in clause 4.2.2.2.2. If a native 5G security context for 3GPP access is available in the AMF (or has been retrieved in step 6a), the AMF may continue to use this security context. Otherwise, the AMF shall either derive a mapped security context from the EPS security context obtained from the MME or initiate an authentication procedure to the UE.
If the new AMF determines that the UE has emergency PDU Session and the AMF is configured to allow emergency services for unauthenticated UE, the new AMF behaves as follows:
- If the UE has only an emergency PDU Session, the AMF either skips the authentication and security procedure in step 7 or accepts that the authentication may fail and continues the Mobility Registration Update procedure; or
- If the UE has both emergency and non emergency PDU Sessions and authentication fails, the AMF continues the Mobility Registration Update procedure and deactivates all the non-emergency PDU Sessions as specified in clause 4.3.4.2.
NOTE 2: The new AMF can determine if a PDU Session is used for emergency service by checking whether the DNN matches the emergency DNN.
7. [Conditional] If the AMF determines to initiate the authentication procedure to the UE in step 6b (e.g. the AMF can not obtain the UE MM context from AMF or other reasons), steps 8-9 of clause 4.2.2.2.2 are optionally performed.
7a. In the case of idle mode mobility, the AMF decide whether a new AMF needs to be selected. If a new AMF is to be selected, the AMF reroute the Registration request to the new AMF as described in clause 4.11.1.3.4, where the initial AMF refers to the AMF.
8. [Conditional] If step 5b is performed and the AMF accepts to serve the UE, the AMF sends Context Acknowledge (Serving GW change indication) to MME according to TS 23.401 [13].
9. Steps 11-12 of clause 4.2.2.2.2 are optionally performed.
10. Void.
11. Steps 13-14e of clause 4.2.2.2.2 are performed: This includes that if an MM context is retrieved from the old AMF in step 6 (i.e. corresponding to an existing UE registration for non-3GPP access in 5GC), then the AMF indicates to the UDM that the AMF identity to be registered in the UDM applies to both 3GPP and non-3GPP accesses by sending separate/independent Nudm_UECM_Registration service operations for "3GPP Access" and "non-3GPP Access".
12. Void.
13. Void.
14-14f. Step 16 of clause 4.2.2.2.2 (AM Policy Association Establishment) is optionally performed.
In the home-routed roaming case and connected state mobility, based on the S-NSSAI value for the Serving PLMN of the PDU Session(s), the AMF decides whether V-SMF change is needed or not.
- If the V-SMF reallocation is not needed and if the two values (i.e. the S-NSSAI value configured in AMF for interworking and S-NSSAI value for the Serving PLMN) are different, the AMF invokes Nsmf_PDUSession_UpdateSMContext (PDU Session ID, S-NSSAI value for the Serving PLMN).
- If V-UPF is not changed, the V-SMF updates 5G AN with the new S-NSSAI of VPLMN by sending a N2 SM message to 5G AN via AMF.
- If V-UPF is changed, the V-SMF performs procedure as specified in clause 4.23.4.2 with the difference that I-SMF/I-UPF in clause 4.23.4.2 is replaced by V-SMF/V-UPF and with the following modification:
- In step 11 of clause 4.2.3.2 referenced by clause 4.23.4.2, the V-SMF includes in N2 SM information with the new S-NSSAI of the VPLMN.
- If the V-SMF change is needed, the AMF performs as the case of I-SMF change defined in clause 4.23.4.3 with the difference that I-SMF in clause 4.23.4.3 is replaced by V-SMF and with following modifications:
- In step 3 of clause 4.23.4.3, the AMF sends indication of no NG-RAN change to the new V-SMF.
- In step 4a of clause 4.23.4.3, when the new V-SMF retrieves SM context from the old V-SMF, the new V-SMF sends indication of no NG-RAN change as it is received in step 3.
- In step 4b of clause 4.23.4.3, as the old V-SMF receives the indication of no NG-RAN change, the old V-SMF returns additional N3 tunnel information of NG-RAN.
- In step 6 of clause 4.23.4.3, the new I-SMF should reuse the N3 tunnel information of NG-RAN received from old I-SMF/SMF.
- In step 9 of clause 4.23.4.3, when the new V-SMF sends a Nsmf_PDUSession_CreateSMContext Response, the new V-SMF includes PDU Session Resource Modify in N2 SM information.
In the home-routed roaming case and idle state mobility, the AMF selects a default V-SMF per PDU Session and invokes Nsmf_PDUSession_CreateSMContext service operation of the V-SMF to create an association with the AMF. It includes UE EPS PDN Connection, MSISDN as a GPSI if received from MME, H-SMF ID, S-NSSAI and indicates all the PDU Session(s) to be re-activated as received in the Registration request message along with List Of PDU Sessions To Be Activated. The S-NSSAI is the S-NSSAI configured in AMF for interworking, which is associated with default V-SMF. The V-SMF creates the association and based on the received SMF ID, the V-SMF invokes Nsmf_PDUSession_Create request service operation of the H-SMF and provides the information received from the AMF. Before invoking Nsmf_PDUSession_Create service operation, the V-SMF request the V-UPF to provide the CN tunnel info.
In the home-routed roaming case and idle state mobility, the V-SMF provides the QoS constraints of the VPLMN to the H-SMF.
The subsequent handling is performed as follows:
- The H-SMF finds the corresponding PDU Session based on the PDN Connection Context in the request. The H-SMF initiates N4 Session modification procedure to establish the CN tunnel for the PDU Session. The tunnel info for PDU Session is allocated by PGW-U+UPF and provided to the SMF+PGW-C. The H-SMF responds V-SMF with the PDU Session ID corresponding to the PDN Connection Context in the request, the allocated EBI(s) information, the S-NSSAI of the PDU Session, S-NSSAI of HPLMN, UE EPS PDN connection(s) and other PDU session parameters, such as PDU Session Type, Session AMBR in the Nsmf_PDUSession_Create response.
- The V-SMF updates its SM contexts and returns a Nsmf_PDU_Session_CreateSMContextResponse message including the information received from the H-SMF. The V-SMF updates the V-UPF of the CN tunnel info of SMF+PGW-C. The V-SMF also includes the N2 SM Context in the response message sent to the AMF if the corresponding PDU Session is in the received List Of PDU Sessions To Be Activated. The V-SMF stores an association of the PDU Session ID and the H-SMF ID. The AMF stores the V-SMF ID and it also stores S-NSSAI and the allocated EBI(s) associated to the PDU Session ID. Based on the S-NSSAI value for the Serving PLMN of the PDU Session(s) the AMF decides whether V-SMF relocation is needed or not.
- If V-SMF relocation is not needed and if the two values (i.e. the S-NSSAI value configured in AMF for interworking and S-NSSAI value for the Serving PLMN) are different, the AMF sends the S-NSSAI value for the Serving PLMN to V-SMF by invoking Nsmf_PDUSession_UpdateSMContext service operation. If V-UPF change is not needed, the V-SMF updates NG RAN with the S-NSSAI value for the Serving PLMN via N2 SM message. If V-UPF change is needed, the V-SMF performs procedure as specified in clause 4.23.4.2 with the difference that I-SMF/I-UPF is replaced with V-SMF/V-UPF and with the following modification:
- In step 11 of clause 4.2.3.2 referenced by clause 4.23.4.2, the V-SMF includes in N2 SM information with the new S-NSSAI of the VPLMN.
- If V-SMF relocation is needed, the AMF performs V-SMF relocation as defined in clause 4.23.4.3.
In the case of home-routed roaming scenario, the V-SMF may apply VPLMN policies as described in TS 23.501 [2], clause 5.17.1.3.
In non-roaming and LBO cases and idle state mobility, AMF invokes Nsmf_PDUSession_CreateSMContext Request (UE EPS PDN Connection) service operation of the SMF+PGW-C and indicates all the PDU Session(s) to be re-activated as received in the Registration request message along with List Of PDU Sessions To Be Activated. This step is performed for each PDN Connection and the corresponding SMF+PGW-C address/ID in the UE context the AMF received in Step 6.
The SMF+PGW-C finds the corresponding PDU Session based on the PDN Connection Context in the request.
If the P-GW-C+SMF (H-SMF in the case of home-routed roaming case) determines that seamless session continuity from EPS to 5GS is not supported for the PDU Session, (e.g. if PDU Session ID was not received by the SMF+PGW-C for the PDN connection or PDU Session ID was received but mapped 5GS parameters were not provided to the UE due to 5GS interworking not supported), then it does not provide SM information for the corresponding PDU Session but includes the appropriate cause code for rejecting the PDU Session transfer within the N2 SM Information. The PDN connection(s) not further transferred to 5GC are locally released at the SMF+PGW-C.
Otherwise, if session continuity from EPS to 5GS is supported for the PDU Session, the SMF+PGW-C finds the corresponding PDU Session based on the PDN Connection Context in the request. The SMF+PGW-C initiates N4 Session modification procedure to establish the CN tunnel for the PDU Session. If the SMF+PGW-C has not yet registered for this PDU Session ID, the SMF+PGW-C registers with the UDM using Nudm_UECM_Registration (SUPI, DNN, PDU Session ID) for a given PDU Session as in step 4 of PDU Session Establishment Procedure in clause 4.3.2. The tunnel info for PDU Session is allocated by PGW-U+UPF and provided to the SMF+PGW-C. The SMF+PGW-C updates its SM contexts and returns the AMF a Nsmf_PDUSession_CreateSMContext Response message including the PDU Session ID corresponding to the PDN Connection Context in the request, the allocated EBI(s) information, the S-NSSAI of the PDU Session and the N2 SM Context if the corresponding PDU Session is in the received List Of PDU Sessions To Be Activated. The AMF stores an association of the PDU Session ID and the SMF ID, S-NSSAI and the allocated EBI(s) associated to the PDU Session ID. Based on the allocated EBI(s) information received from all the related SMF+PGW-C for this UE, an EPS bearer status, which reflects all existing EPS bearer, is generated by the AMF.
NOTE 3: For Connected State mobility registration, the release of CN tunnels for EPS bearers and UDM registration for the session corresponding to the PDU session is performed in the handover execution phase.
If the PDN Type of a PDN Connection in EPS is non-IP and it was originally established as Ethernet PDU Session when UE was camping in 5GS (known based on local context information that was set to PDU Session Type Ethernet in UE and SMF), the PDU Session Type in 5GS shall be set to Ethernet by the SMF and UE. If the PDN type of a PDN Connection in EPS is non-IP and is locally associated in UE and SMF to PDU Session Type Unstructured, the PDU Session Type in 5GS shall be set to Unstructured by the SMF and UE.
NOTE 4: If the non-IP PDN Type is originally established as Ethernet PDU Session, it means that Ethernet PDN Type is not supported in EPS.
If the AMF has received the EPS Bearer Status in the Registration Request from UE, the AMF shall send the EPS Bearer Status to all corresponding SMF+PGW-Cs. If the SMF+PGW-C receives the EPS Bearer Status from AMF, the SMF+PGW-C shall check whether the EPS bearer(s) has been deleted by UE but not notified to network. If yes, the SMF+PGW-C shall release those EPS bearer(s), the corresponding 5G QoS Rule(s) and the QoS Flow level QoS parameters locally.
If the SCEF+NEF ID is provided to the SMF, the SMF establishes the SMF-NEF connection as described in steps 2-3 from clause 4.25.2, the SMF provides the SCEF+NEF ID, EBI, APN, User Identity to the SCEF+NEF and the SCEF+NEF updates the SM contexts and returns the NEF ID, PDU Session ID, DNN and User Identity to the SMF.
If the UE is performing Inter-RAT mobility to or from NB-IoT, the (H-)SMF will maintain, reconnect, release or leave PDU Session handling to the local VPLMN policy in the case of roaming for each PDU session according to the "PDU Session continuity at inter RAT mobility" subscription information. If the (H-)SMF does not have "PDU Session continuity at inter RAT mobility" for a PDU session, the (H-)SMF retrieves it from the UDM before determining any action. The SMF may use local policy to determine the handling a PDU Session if "PDU Session continuity at inter RAT mobility" cannot be retrieved from the UDM.
After the step 14a, the SMF+PGW-C receives the SM context create request from AMF and the SMF+PGW-C awares that the UE returns back from EPS. When the SMF+PGW-C notifies the PCF for the PDU session of changing RAT from EPS to 5GS, the PCF for the PDU session checks if there exists a UE policy association in EPS for the UE and in that case, request the termination of such UE Policy Association to the PCF for the UE.
15 - 16a. HSS+UDM cancels the location of the UE in the MME as defined in steps 13 - 14 from clause 5.3.3.1 (Tracking Area Update procedure with Serving GW change) in TS 23.401 [13]. Subsequently, the steps 18 - 19 from clause 5.3.3.1 (Tracking Area Update procedure with Serving GW change) in TS 23.401 [13] are also executed with the following modification:
According to configuration, for the PDN connections which are anchored in a standalone PGW, the MME initiates PDN connection release procedure as specified in TS 23.401 [13].
17-18. These steps follow the steps 21, 21b and 22 of Registration procedure in clause 4.2.2.2.2.
The Registration Accept message shall include the updated 5G-GUTI to be used by the UE in that PLMN over any access. If the active flag was included in the Registration request, The AMF may provide NG-RAN with a Mobility Restriction List taking into account the last used EPS PLMN ID and the Return preferred indication. The Mobility Restriction List contains a list of PLMN IDs as specified by TS 23.501 [2]. The Allowed NSSAI in the Registration Accept message shall contain at least the S-NSSAIs corresponding to the active PDN Connection(s) and the corresponding mapping to the HPLMN S-NSSAIs.
The AMF shall include the EPS bearer status, which is generated at step 14, in the Registration Accept message. Based on the received EPS bearer status information, the UE shall check whether there are QoS Flow(s) existing locally but no associated EPS bearer(s) in the received EPS bearer status. The UE shall locally delete the 5G QoS Rule(s) and QoS Flow level QoS parameters of the QoS Flow(s) if the associated EPS bearer(s) do not exist in the received EPS bearer status.
4.11.1.3.3A EPS to 5GS Idle mode mobility using N26 interface with data forwarding
Figure 4.11.1.3.3A-1 describes the idle mode mobility registration procedure from EPS to 5GS when N26 is supported with data forwarding.
Figure 4.11.1.3.3A-1: EPS to 5GS Idle mode mobility using N26 interface with data forwarding
1. Step 1-7 from clause 4.11.1.3.3 with the following enhancements:
- In step 5b of the figure 4.11.1.3.3-1, if the old MME indicates Buffered DL Data Waiting in the Context Response (as specified in step 5 of clause 5.3.3.1A in TS 23.401 [13]).
- For Control Plane CIoT EPS Optimisation, when the DL data is buffered in old MME and the DL Data Expiration Time has not expired, the old MME shall discard the buffered DL data (as specified in step of clause 5.3.3.1A in TS 23.401 [13]).
2. Steps 9-18 from clause 4.11.1.3.3 with following enhancements:
In step 14a of the figure 4.11.1.3.3-1, the AMF forwards the Buffered DL Data Waiting indication from above to (V-)SMF in Nsmf_PDUSession_CreateSMContext service operation.
If the Buffered DL Data Waiting indication is provided by AMF, the (V-)SMF and (V-)UPF shall allocate the user plane resource and include the N2 SM information (i.e. the V-CN Tunnel-Info) in the Nsmf_PDUSession_CreateSMContext Response towards the AMF in step 14d of the figure 4.11.1.3.3-1 to trigger the user plane setup in NG-RAN.
NOTE: AMF may send NAS message Registration Accept in step 17 of figure 4.11-1.3.3-1 as part of the N2 message in step 3 below.
3. AMF to NG-RAN: N2 message (N2 MM information, N2 SM information list).
If N2 SM information is received from SMF in step 2 above, the AMF sends a N2 request message to setup the user plane resource.
NG-RAN performs RRC connection Reconfiguration with the UE to setup the user plane resource and response to AMF with N2 response message with N2 SM information.
4. Steps 11-13 from clause 4.11.1.2.2.2 with the following enhancement:
Based on Buffered DL Data Waiting indication received in step 2 above, the (V-)SMF and (V-)UPF allocate data forwarding tunnel resource and provide the CN tunnel information for data forwarding from EPS (i.e. Forwarding F TEID) in Nsmf_PDUSession_UpdateSMContext Response to AMF in step 13 of figure 4.11.1.2.2.2-1. The (V-) SMF also starts a timer for release of resources for data forwarding.
The (V-) SMF may select a different UPF from the serving (V-)UPF for data forwarding.
The (V-)SMF shall not provide Charging Enforcement Rules and QoS Enforcement Rules to the (V-)UPF for DL packets that were received via the forwarding tunnel.
5. Steps 14-18 from clause 5.3.3.1A in TS 23.401 [13] with following changes.
The AMF sends the Context Acknowledge message to MME as in step 14 of figure 5.3.3.1A-1 in TS 23.401 [13], including the CN tunnel information (i.e. Forwarding F TEID) for data forwarding from EPS received from (V-)SMF in step 4 above.
The Serving GW forwards the buffered DL data to the (V-)UPF based on the Forwarding F-TEID received from MME. The data received by the (V-)UPF on the forwarding F-TEID is forwarded by the (V-)UPF on the (newly) established N3 tunnel to the NG-RAN.
6. SMF to UPF: N4 Session Termination/Modification.
At the expiration of the timer started in step 4 above, the (V-) SMF starts the release of resource established in step 4 for data forwarding and informs the (V-)UPF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.3.4 EPS to 5GS Mobility Registration Procedure (Idle) using N26 interface with AMF reallocation | During Idle state mobility registration procedure from EPS to 5GS, the initial AMF may select a new AMF based on S-NSSAIs associated with the established PDU Session, received in NAS Registration Request.
Figure 4.11.1.3.4-1: EPS to 5GS mobility with AMF re-allocation for single-registration mode and N26 interface configuration
1. Step 1 to 7 of clause 4.11.1.3.3 in EPS to 5GS mobility using N26 interface is performed.
2. Step 3 to 4 of clause 4.2.2.2.3 in Registration with AMF reallocation procedure is performed with the difference that before the Network Slice selection the AMF needs to derive the S-NSSAI for the serving PLMN as described in clause 5.15.5.2.1 of TS 23.501 [2].
3. [Conditional] Initial AMF to MME: Context Acknowledge (failure cause) to MME according to TS 23.401 [13].
The initial AMF decides a new AMF needs to be reselected. The initial AMF sends a Context Acknowledge message with cause code indicating that the procedure is not successful. The MME shall continue as if Context Request was never received.
4. Step 6 to 7 of clause 4.2.2.2.3 in Registration with AMF reallocation procedure are performed.
5. After receiving the Registration Request message, the new AMF continues the registration from step 5 until step 18 of figure 4.11.1.3.3 (EPS to 5GS mobility using N26 procedure), which includes the UE context retrieved from old AMF. If the 5G security context is received from the initial AMF, the new AMF continues using that one instead of the mapped 5G security context retrieved from MME. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.4 Procedures for EPS bearer ID allocation | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.4.1 EPS bearer ID allocation | Following procedures are updated to allocate EPS bearer ID(s) towards EPS bearer(s) mapped from QoS flow(s) and provide the EPS bearer ID(s) to the NG-RAN:
- UE requested PDU Session Establishment (Non-roaming and Roaming with Local Breakout (clause 4.3.2.2.1) including Request Types "Initial Request", "Existing PDU Session", "Initial emergency request" and "Existing emergency PDU session".
- UE requested PDU Session Establishment (Home-routed Roaming (clause 4.3.2.2.2) including Request Types "Initial Request" and "Existing PDU Session".
- UE or network requested PDU Session Modification (non-roaming and roaming with local breakout) (clause 4.3.3.2).
- UE or network requested PDU Session Modification (home-routed roaming) (clause 4.3.3.3).
- UE Triggered Service Request (clause 4.2.3.2) to move PDU Session(s) from non-3GPP access to 3GPP access
EBI allocation shall apply to PDU Session via 3GPP access using SSC mode 1 and supporting EPS interworking with N26. EBI allocation shall not apply to PDU Session via 3GPP access supporting EPS interworking without N26 and shall not apply to PDU Session via non-3GPP access supporting EPS interworking. EBI allocation shall also not apply to PDU Session using SSC mode 2 or SSC mode 3.
Figure 4.11.1.4.1-1: Procedures for EPS bearer ID allocation
1. Procedure as listed in this step is initiated as specified in the relevant clauses of this specification. The relevant steps of the procedure as specified in the figure above are executed.
2. If the SMF+PGW-C (or H-SMF in the case of home routed case), determines, based on the indication of EPS interworking support with N26 as defined in clauses 4.11.5.2, 4.11.5.3 and 4.11.5.4 and operator policies e.g. User Plane Security Enforcement information, Access Type, that EPS bearer ID(s) needs to be assigned to the QoS flow(s) in the PDU Session, SMF+PGW-C invokes Namf_Communication_EBIAssignment Request (PDU Session ID, ARP list) (via V-SMF Nsmf_PDUSession_Update in the case of home routed case). When V-SMF receives Nsmf_PDUSession_Update request from H-SMF for EPS bearer ID allocation request, V-SMF needs to invoke Namf_Communication_EBIAssignment Request (PDU Session ID, ARP list). If the SMF+PGW-C (or H-SMF in the case of home-routed roaming) serves multiple PDU sessions for the same DNN but different S-NSSAIs for a UE, then the SMF shall only request EBIs for PDU sessions served by a common UPF (PSA). If different UPF (PSA) are serving those PDU sessions, then the SMF chooses one of the UPF (PSA) for this determination based on operator policy. When the PDU session is established via non-3GPP access, the SMF+PGW-C shall not trigger EBI allocation procedure.
Steps 3 to 6 apply only when AMF needs to revoke EBI previously allocated for an UE in order to serve a new SMF request of EBI for the same UE.
3. [Conditional] If the AMF has no available EBIs, the AMF may revoke an EBI that was assigned to QoS flow(s) based on the ARP(s) and S-NSSAI stored during PDU Session establishment, EBIs information in the UE context and local policies. If an assigned EBI is to be revoked, the AMF takes the ARP pre-emption vulnerability and the ARP priority level into consideration and revokes EBIs with a higher value of the ARP priority level first. The AMF invokes Nsmf_PDUSession_UpdateSMContext (EBI(s) to be revoked) to request the related SMF (called "SMF serving the released resources") to release the mapped EPS QoS parameters corresponding to the EBI to be revoked. The AMF stores the association of the assigned EBI, ARP pair to the corresponding PDU Session ID and SMF address.
4. The "SMF serving the released resources" that receives the request in step 3 shall evaluate if any of the revoked EBI(s) corresponds to the QoS Flow associated with the default QoS rule. If the revoked EBI corresponds to the QoS Flow associated with the default QoS rule, the SMF shall release the EBI(s) corresponding to all other QoS Flows of the PDU Session and update the AMF of this release by sending Namf_Communication_EBIAssignment Request (PDU Session ID, Released EBI List). Next, the SMF shall invoke Namf_Communication_N1N2Message Transfer (N2 SM information (PDU Session ID, EBI(s) to be revoked), N1 SM container (PDU Session Modification Command (PDU Session ID, EBI(s) to be revoked))) to inform the (R)AN and the UE to remove the mapped EPS QoS parameters corresponding to the EBI(s) to be revoked. In home routed roaming scenario, the H-SMF includes EBI(s) to be revoked to V-SMF to inform V-SMF to remove the mapped EPS bearer context corresponding to the EBI(s) to be revoked.
NOTE 1: The SMF can also decide to remove the QoS flow if it is not acceptable to continue the service when no corresponding EPS QoS parameters can be assigned.
For home routed roaming scenario, the "SMF serving the released resources" sends an N4 Session Modification Request to request the PGW-U+UPF to release N4 Session corresponding to the revoked EBI(s).
In home routed roaming case, the V-SMF starts a VPLMN initiated QoS modification for the PDU Session and the Namf_Communication_N1N2Message Transfer is invoked by the V-SMF based on the corresponding QoS modification message received from H-SMF.
5. If the UE is in CM-CONNECTED state, the AMF sends N2 PDU Session Resource Modify Request (N2 SM information received from SMF, NAS message (PDU Session ID, N1 SM container (PDU Session Modification Command))) Message to the (R)AN.
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 step 5-6 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.
6. The rest steps of the procedure are executed as specified in the figure above.
7 If the AMF successfully assigns EBI(s), it responds with the assigned EBI(s). Otherwise, it responds with a cause indicating EBI assignment failure. If the PDU Session is associated to an S-NSSAI subject for Network Slice-Specific Authentication and Authorization the AMF should indicate EBI assignment failure.
If a PDU Session from another SMF already exists towards the same DNN, the AMF either rejects the EBI assignment request, or revokes the EBI(s) from the existing PDU Session(s) to the same DNN but different SMFs if the AMF makes the decision based on the operator policy, that the existing PDU Session cannot support EPS interworking N26.
The AMF stores the DNN and SMF+PGW-C in which the PDU Session(s) support EPS interworking to UDM in clause 4.11.1.6.
NOTE 2: The above applies only when the S-NSSAI(s) for the PDU Sessions are different, otherwise the same SMF is selected for PDU Sessions to the same DNN.
8. The SMF+PGW-C sends an N4 Session Establishment/Modification Request to the PGW-U+UPF.
For home routed roaming scenario, if the EBI is assigned successfully, the SMF+PGW-C prepares the CN Tunnel Info for each EPS bearer. For non roaming and LBO scenario, if the EBI is assigned successfully, the SMF+PGW-C may prepare the CN Tunnel Info for each EPS bearer.
The PGW-U+UPF allocates the PGW-U tunnel info for the EPS bearer and sends it to the SMF+PGW-C. The PGW-U+UPF is ready to receive uplink packets from E-UTRAN.
NOTE 3: In the home routed roaming scenario the SMF+PGW-C prepares the CN Tunnel Info for each EPS bearer and provide it to V-SMF. Thus when the UE move to EPC network, the V-SMF does not need interact with the SMF+PGW-C to get the EPS bearer context(s).
9. If the SMF+PGW-C receives any EBI(s) from the AMF, it adds the received EBI(s) into the mapped EPS bearer context(s).
In home routed roaming scenario, the SMF+PGW-C generates EPS bearer context which includes per EPS bearer PGW-U tunnel information. In addition, if the default EPS bearer is generated for the corresponding PDN Connection of PDU Session (i.e. during the PDU Session establishment procedure), the SMF+PGW-C generates the PGW-C tunnel information of the PDN connection and include it in UE EPS PDN connection.
9a. [Conditional] In non-roaming or LBO scenario, the SMF+PGW-C includes the mapped EPS bearer context(s) and the corresponding QoS Flow(s) to be sent to the UE in the N1 SM container. SMF+PGW-C also indicates the mapping between the QoS Flow(s) and mapped EPS bearer context(s) in the N1 SM container. SMF+PGW-C also includes the mapping between the received EBI(s) and QFI(s) into the N2 SM information to be sent to the NG-RAN. The SMF+PGW-C sends the N1 SM container and N2 SM information to AMF via the Nsmf_PDUSession_UpdateSMContext Response in the case of the PDU Session Modification procedure triggered by UE or AN, or UE Triggered Service Request procedure that results in session transfer from N3GPP to 3GPP, otherwise, via the Namf_Communication_N1N2MessageTransfer.
9b [Conditional] In home routed roaming scenario, the SMF+PGW-C sends mapped EPS bearer context(s), the mapping between the received EBI(s) and QFI(s), linked EBI and EPS bearer context(s) to V-SMF via Nsmf_PDUSession_Create Response in the case of PDU Session Establishment, or via Nsmf_PDUSession_Update Request in the case of PDU Session Modification. The V-SMF stores the EPS bearer context(s) and generates N1 SM container and N2 SM information and forwards them to AMF via the Nsmf_PDUSession_UpdateSMContext Response in the case of the PDU Session Modification procedure triggered by UE or AN, or UE Triggered Service Request procedure that results in session transfer from N3GPP to 3GPP, otherwise, via the Namf_Communication_N1N2MessageTransfer.
10. The N1 SM container and N2 SM information are sent to the UE and NG-RAN respectively. The relevant steps of the procedure as specified in the figure above are executed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.4.2 EPS bearer ID transfer | Following procedures are updated to transfer EPS bearer ID(s) allocation information to target AMF.
- step 14d in figure 4.11.1.3.3-1 in EPS to 5GS Idle mode mobility with N26 (clause 4.11.1.3.3).
- step 7 in figure 4.11.1.2.2.2-1 in EPS to 5GS handover using N26 interface prepare phase (clause 4.11.1.2.2.2).
Figure 4.11.1.4.2-1: Procedures for EPS bearer IDs transfer
1. The AMF sends an Nsmf_PDUSession_CreateSMContext Request message to the SMF in above case;
2. The SMF+PGW-C to AMF: Nsmf_PDUSession_CreateSMContext Response with the allocated EBI information. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.4.3 EPS bearer ID revocation | Following procedures are updated to revoke the EPS bearer ID(s) assigned to the QoS flow(s):
- UE or network requested PDU Session Release for Non-roaming and Roaming with Local Breakout (clause 4.3.4.2).
- UE or network requested PDU Session Release for Home-routed Roaming (clause 4.3.4.3).
- UE or network requested PDU Session Modification (non-roaming and roaming with local breakout) (clause 4.3.3.2).
- UE or network requested PDU Session Modification (home-routed roaming) (clause 4.3.3.3).
- 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)
- Handover of a PDU Session procedure from 3GPP to untrusted non-3GPP access (home routed roaming) (clause 4.9.2.4
When the PDU Session is released as described in clauses 4.3.4.2 or 4.3.4.3, 4.9.2.2, or 4.9.2.4 and the SMF invokes Nsmf_PDUSession_StatusNotify to notify AMF that the SM context for this PDU Session is released, the AMF releases the association between the SMF ID and the PDU Session ID and releases the EBIs assigned for this PDU Session. When all the PDU sessions which are allocated with EBIs are released in the same SMF, the AMF may revoke DNN and SMF+PGW-C FQDN for S5/S8 interface in the UDM using Nudm_UECM_Update service operation.
NOTE 1: If the SMF+PGW-C in which the PDU sessions support EPS interworking is changed for the same DNN, the AMF can update the DNN and new SMF+PGW-C FQDN for S5/S8 interface in the UDM using Nudm_UECM_Update service operation.
When the UE initiates a PDU Session Modification as described in clauses 4.3.3.2 or 4.3.3.3 and the SMF needs to release the assigned EBI from a QoS flow (e.g. when the QoS flow is released), the SMF can indicate the Released EBI list in the Nsmf_PDUSession_UpdateSMContext Response to the AMF. The AMF releases the corresponding EBI allocation for this PDU Session.
When the AMF decides to revoke some EBI(s), e.g. when the AMF receives a new EBI allocation request but there is no EBI available, the AMF may decide to revoke EBI(s) for another PDU Session, the AMF initiates a PDU Session Modification as described in clauses 4.3.3.2 or 4.3.3.3 and includes EBI list to be revoked in the Nsmf_PDUSession_UpdateSMContext Request. The SMF releases the indicated EBI(s) for the PDU Session.
When the AMF initiates a PDU Session Modification as described in clauses 4.3.3.2 or 4.3.3.3 to change the status of EPS interworking with N26 to "not supported", the AMF releases the EBIs assigned for this PDU Session and SMF release the assigned EBIs from the QoS Flows belonging to this PDU Session.
When the SMF initiates a PDU Session Modification as described in clauses 4.3.3.2 or 4.3.3.3 and the SMF needs to release the assigned EBI from a QoS flow (e.g. when the QoS flow is released), the SMF invokes Namf_Communication_EBIAssignment and indicates the Released EBI list to the AMF. The AMF releases the corresponding EBI allocation for this PDU Session.
When the handover of a PDU Session procedure from 3GPP to untrusted non-3GPP access is performed in clause 4.9.2.2 or clause 4.9.2.4.1, the AMF, the SMF and the UE releases locally the EBI(s) allocated for this PDU Session.
When the handover of a PDU Session procedure from 3GPP to untrusted non-3GPP access is performed in clause 4.9.2.4.2, the H-SMF invokes Nsmf_PDUSession_StatusNotify to notify V-AMF to release the association between the SMF ID and the PDU Session ID and as a result, the EBI(s) assigned for this PDU Session are released. The UE releases locally the EBI(s) allocated for this PDU Session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.5 Impacts to EPS Procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.5.1 General | This clause captures changes to procedures in TS 23.401 [13] due to interworking with 5GS based on N26. The handover procedures between EPS and 5GS captured in clause 4.11.1.2 capture impacts to clause 5.5.1.2.2 of TS 23.401 [13] (S1-based handover, normal). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.5.2 E-UTRAN Initial Attach | The E-UTRAN Initial Attach Procedure specified in clause 5.3.2.1 of TS 23.401 [13] is impacted as shown in Figure 4.11.1.5.2-1 when interworking with 5GS using N26 interface is supported.
Figure 4.11.1.5.2-1: Impacts to E-UTRAN Initial Attach procedure
1. The UE sends an Attach Request message as specified in TS 23.401 [13] with the following modifications:
- If the UE was previously registered in 5GS, the UE provides in Access Stratum signalling a GUMMEI mapped from the 5G-GUTI and indicates it as a native GUMMEI and should in addition indicate it as "Mapped from 5G-GUTI".
- If the UE was previously registered in 5GS, the UE provides, in the Attach Request message, an EPS GUTI mapped from 5G-GUTI sent as old Native GUTI and indicates that it is moving from 5GC. The UE integrity protects the Attach Request message using the 5G security context.
- A UE that supports 5GC NAS procedures shall indicate its support of 5G NAS as part of its UE Core Network Capability IE.
- If the UE includes ESM message container for PDN Connection Establishment and the Request type is "initial request", the UE shall allocate a PDU Session ID and include it in the PCO. The PDU Session ID shall be unique across all other PDN connections of the UE.
- MME may steer the UE from EPC by rejecting the Attach request with an appropriate cause value. If the UE supports any of the CIoT 5GS Optimisations included in 5GC Preferred Network Behaviour, then the UE shall include its 5GC Preferred Network Behaviour if it included its EPC Preferred Network Behaviour in the Attach request. The MME should take into account availability of 5GC to the UE and the Preferred and Supported Network Behaviour (see clause 5.31.2 of TS 23.501 [2]) before steering the UE from EPC.
2. The relevant steps of the procedure as specified in the figure above are executed with the following modification:
- The HSS/UDM on receiving Update Location Request from MME, de-register any old AMF by sending an Nudm_UECM_DeregistrationNotification service operation to the registered AMF for 3GPP access.
- Step 7 and step 10 as specified in clause 5.3.2.1 of TS 23.401 [13] (i.e. IP-CAN Session Termination) is replaced by SM Policy Association Termination procedure as specified in clause 4.16.6.
- Step 14 as specified in clause 5.3.2.1 of TS 23.401 [13] (i.e. IP-CAN Session Establishment/Modification) are replaced by SM Policy Association Establishment/Modification procedure as specified in clause 4.16.4 and clause 4.16.5.
3. Step 15 as specified in clause 5.3.2.1 of TS 23.401 [13] with the following modification:
- The SMF+PGW-C allocates 5G QoS parameters corresponding to PDN connection, e.g. Session AMBR, QoS rules and QoS Flow level QoS parameters if needed for the QoS Flow associated with the QoS rule(s) and then includes them in PCO.
4. The relevant steps of the procedure as specified in the figure above are executed.
5. Step 18 as specified in clause 5.3.2.1 of TS 23.401 [13] with the following modification:
- The 5G QoS parameters for the PDU session and for the QoS Flow associated with the default QoS rule are stored in the UE.
6. The relevant steps of the procedure as specified in the figure above are executed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.5.3 Tracking Area Update | The following changes are applied to clause 5.3.3.1 (Tracking area update procedure with Serving GW change) in TS 23.401 [13]:
- Step 2: The UE shall in Access Stratum signalling include GUMMEI that is mapped from 5G-GUTI following the mapping rules specified in TS 23.501 [2] and the UE indicates it as a native GUMMEI and should in addition indicate it as "Mapped from 5G-GUTI". The UE shall, in the TAU request message, include EPS GUTI that is mapped from 5G-GUTI following the mapping rules specified in TS 23.501 [2]. The UE indicates that it is moving from 5GC. The UE integrity protects the TAU request message using the 5G security context. If the UE supports any of the CIoT 5GS Optimisations included in 5GC Preferred Network Behaviour, then the UE shall include its 5GC Preferred Network Behaviour if it included its EPC Preferred Network Behaviour in the TAU request.
MME may steer the UE from EPC by rejecting the TAU request with an appropriate cause value. The MME should take into account availability of 5GC to the UE and the Preferred and Supported Network Behaviour (see clause 5.31.2 of TS 23.501 [2]) before steering the UE from EPC.
- Step 5 and message Context Response may include new information Return preferred.
Return preferred is an indication by the AMF of a preferred return of the UE to the last used 5GS PLMN at a later access change to a 5GS shared network.
RFSP Index in Use Validity Time is provided by the AMF to the MME if the AMF selects the RFSP Index in use identical to the authorized RFSP Index as specified in clause 5.4.3.4 of TS 23.501 [2] and validity time is received from PCF as specified in clause 4.16.2.2 and in clause 6.1.2.1 of TS 23.503 [20]. The MME handles RFSP Index as specified in clause 4.11.1.5.8.
The MME may store the last used 5GS PLMN ID in UE's MM Context.
The MME may provide E-UTRAN with a Handover Restriction List taking into account the last used 5GS PLMN ID and the Return Preferred indication. The Handover Restriction List contains a list of PLMN IDs as specified by TS 23.251 [35].
- Step 9a IP‑CAN Session Modification procedure:
It is replaced by SM Policy Association Modification as specified in clause 4.16.5.
- Step 13 and HSS use of Cancel Location
The HSS/UDM de-registers any old AMF node by sending an Nudm_UECM_DeregistrationNotification service operation to the registered AMF for 3GPP access. The registered AMF for 3GPP access initiates AM Policy Association Termination procedure as defined in clause 4.16.3.2 and UE Policy Association Termination procedure as defined in clause 4.16.13.1.
- Step 17: If the DNN and SMF+PGW-C FQDN for S5/S8 interface association exist, the HSS/UDM sends APN mapped form DNN and SMF+PGW-C FQDN for S5/S8 to UE.
- Step 20 and MME processing of the partial Tracking Area Update (TAU) procedure.
The MME may use an indication Return preferred from Context Response at step 6 when deciding the PLMN list content.
The MME may provide the eNodeB with a PLMN list. The Handover Restriction List contains a list of PLMN IDs as specified by TS 23.501 [2]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.5.4 Session Management | 4.11.1.5.4.1 PDN Connection Request
The UE Requested PDN Connectivity Procedure specified in clause 5.10.2 of TS 23.401 [13] is impacted as shown in in Figure 4.11.1.5.4.1-1 when interworking with 5GS is supported.
Figure 4.11.1.5.4.1-1: Impacts to UE Requested PDN Connectivity Procedure
1. UE sends a PDN connectivity Request to the MME as specified in Step 1 in clause 5.10.2 of TS 23.401 [13] with the following modification:
- If the UE is 5G NAS capable and the Request type is "initial request", the UE shall allocate a PDU Session ID and include it in the PCO. The PDU Session ID shall be unique across all other PDN connections of the UE.
2. The relevant steps of the procedure as specified in the figure above are executed. In step 4 of TS 23.401 [13], IP Session Establishment/Modification procedure is replaced by SM Policy Association Establishment/Modification procedure as specified in clauses 4.16.4 and 4.16.5.
3. Step 6 as specified in clause 5.10.2 of TS 23.401 [13] is executed with the following modification:
- If the SMF+PGW-C accepts to provide interworking of the PDN connection with 5GC, the SMF+PGW-C shall allocate 5G QoS parameters corresponding to PDN connection, e.g. Session AMBR, QoS rules and QoS Flow level QoS parameters if needed for the QoS Flow(s) associated with the QoS rule(s) and then include them in PCO.
- If the SMF+PGW-C accepts to provide interworking of the PDN connection with 5GC, the SMF+PGW-C shall determine the S-NSSAI associated with the PDN connection based on the operator policy and send the S-NSSAI together with the PLMN ID to the UE in the PCO.
- If the SMF+PGW-C accepts to provide interworking of the PDN connection with 5GC the SMF+PGW-C, if Small Data Rate Control is used, provides the Small Data Rate Control parameters to the UE in the PCO.
4. The relevant steps of the procedure as specified in the figure above are executed.
5. Step 8 as specified in clause 5.10.2 of TS 23.401 [13] with the following modification:
- If 5G QoS parameters are included in the PCO, the UE shall store them. If 5G QoS parameters are not included in the PCO, the UE shall note that session continuity for this PDN connection on mobility to 5G is not provided by the network.
- If the S-NSSAI and the PLMN ID associated with the PDN connection are included in the PCO, the UE shall store them.
- If the Small Data Rate Control parameters are included in the PCO, the UE shall store them.
6. The relevant steps of the procedure as specified in the figure above are executed.
4.11.1.5.4.2 UE or MME Requested PDN Disconnection
The procedure as specified in clause 5.10.3 of TS 23.401 [13] applies with the following modification:
Step 8. (RRC Connection Reconfiguration): On receiving the NAS Deactivate EPS Bearer Context Request(LBI) message, if the UE has mapped 5G parameters for the PDU session, the UE deletes the corresponding mapped 5GS PDU session.
In addition if the SMF+PGW-C has registered to HSS+UDM for this PDN connection before, the SMF+PGW-C invokes the Nudm_UECM_Deregistration service operation to notify the UDM to remove the association between the SMF+PGW-C identity and the associated DNN and PDU Session ID as described in the step 12 of clause 4.3.4.2. If there is no PDN connection for the associated (DNN, S-NSSAI) handled by the SMF+PGW-C, the SMF+PGW-C unsubscribes from Session Management Subscription data changes notification with the HSS+UDM by means of the Nudm_SDM_Unsubscribe (SUPI, DNN, S-NSSAI) service operation as described in step 12 of clause 4.3.4.2.
4.11.1.5.4.3 Dedicated Bearer Activation, Bearer Modification and Bearer Deactivation
The procedures specified in clauses 5.4.1 through 5.4.5 of TS 23.401 [13] apply with the following modifications:
- PCRF initiated IP-CAN Modification in TS 23.401 [13] is replaced with PCF initiated SM Policy Association Modification as specified in clause 4.16.5.2. PCEF initiated IP-CAN Session Modification/Termination TS 23.401 [13] is replaced with SM Policy Association Modification/Termination as specified in clauses 4.16.5 and 4.16.6.
- In the step where the PDN-GW sends a Create Bearer Request, i.e.:
- Step 2 in clause 5.4.1 of TS 23.401 [13] (Dedicated Bearer Activation).
the PCO includes mapped 5GS QoS parameters for the EPS bearer being created.
- In the step where the PDN-GW sends an Update Bearer Request, i.e.:
- Step 2 in clause 5.4.2.1 of TS 23.401 [13] (PDN GW initiated bearer modification with bearer QoS update).
- Step 5 in clause 5.4.2.2 of TS 23.401 [13] (HSS Initiated Subscribed QoS Modification).
- Step 2 in clause 5.4.3 of TS 23.401 [13] (PDN GW initiated bearer modification without bearer QoS update) if TFT or APN-AMBR is being modified.
the PCO includes the modification to the mapped 5GS QoS parameters, if impacted by the modification, corresponding to the EPS bearer being modified.
- In the step where the UE receives the NAS Session Management message from the MME which contains the PCO relayed via the MME, i.e.:
- Step 5 in clause 5.4.1 of TS 23.401 [13] (Dedicated Bearer Activation).
- Step 5 in clause 5.4.2.1 of TS 23.401 [13] (PDN GW initiated bearer modification with bearer QoS update).
- Step 5 in clause 5.4.3 of TS 23.401 [13] (PDN GW initiated bearer modification without bearer QoS update) if TFT or APN-AMBR is being modified.
the UE updates the mapped 5G QoS parameters as included in the PCO from the PDN-GW.
- In the step where the UE receives EPS bearer request message, i.e.:
- Step 5 in clause 5.4.4.1 of TS 23.401 [13] (PDN GW initiated bearer deactivation).
the UE also deletes the mapped 5GS QoS flow and its associated parameter. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.5.5 5GS to EPS handover using N26 interface | In step 3 of clause 4.11.1.2.1, the Forward Relocation Request may include new information Return Preferred.
Return Preferred is an indication by the AMF of a preferred return of the UE to the last used 5GS PLMN at a later access change to a 5GS shared network.
RFSP Index in Use Validity Time is provided by the AMF to the MME if the AMF selects the RFSP Index in use identical to the authorized RFSP Index as specified in clause 5.4.3.4 of TS 23.501 [2] and validity time is received from PCF as specified in clause 4.16.2.2 and in clause 6.1.2.1 of TS 23.503 [20]. The MME handles RFSP Index as specified in clause 4.11.1.5.8.
The MME may store the last used 5GS PLMN ID in UE's MM Context.
The MME may provide E-UTRAN with a Handover Restriction List taking into account the last used 5GS PLMN ID and the Return Preferred indication. The Handover Restriction List contains a list of PLMN IDs as specified by TS 23.251 [35]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.5.6 UE triggered Service Request | The following changes are applied to clause 5.3.4.1 (UE triggered Service Request) in TS 23.401 [13]:
- Step 4: MME may steer the UE from EPC by rejecting the service request with an appropriate cause value. The MME should take into account availability of 5GC to the UE and the Preferred and Supported Network Behaviour (see clause 5.31.2 of TS 23.501 [2]) before steering the UE from EPC. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.5.7 Establishment of S1-U bearer during Data Transport in Control Plane CIoT EPS Optimisation | The following changes are applied to clause 5.3.4B.4 (Establishment of S1-U bearer during Data Transport in Control Plane CIoT EPS Optimisation) in TS 23.401 [13]:
- Step 3: MME may steer the UE from EPC by rejecting the Control Plane Service Request with an appropriate cause value. The MME should take into account availability of 5GC to the UE and the Preferred and Supported Network Behaviour (see clause 5.31.2 of TS 23.501 [2]) before steering the UE from EPC. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.5.8 Radio Resource Management functions and Information Storage | The following changes are applied to clause 4.3.6 (Radio Resource Management functions) in TS 23.401 [13]:
- At 5GS to EPS mobility or during inter-MME mobility, if RFSP Index in Use Validity Time is received from the AMF or the old MME, the new MME uses the received RFSP Index in use by the time indicated in RFSP Index in Use Validity Time. Only when RFSP Index in Use Validity Time expires, the MME re-evaluates the RFSP Index in use as in clause 4.3.6 of TS 23.401 [13].
NOTE: RFSP Index in Use Validity Time is the validity time that is sent by the AMF to the MME as specified in clause 5.17.2.2 of TS 23.501 [2].
The following new parameter is to be added in Table 5.7.2-1 of TS 23.401 [13]:
Table 5.7.2-1: MME MM and EPS bearer Contexts
Field
Description
RFSP Index in Use Validity Time
Defines the validity period of RFSP Index in Use. The MME shall not re-evaluate the RFSP Index in Use before RFSP Index in Use Validity Time expires. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.1.6 EPS interworking information storing Procedure | Depending on the operator's configuration, the AMF serving the 3GPP access store DNN and SMF+PGW-C FQDN for S5/S8 interface in the UDM using Nudm_UECM_Update service operation when N26 is deployed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.2 Interworking procedures without N26 interface | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.2.1 General | Clause 4.11.2 defines the procedures to support interworking between 5GS and EPS without any N26 interface between AMF and MME.
Interworking between EPS and 5GS is supported with IP address preservation by assuming SSC mode 1. The UE shall not request handover to EPS of a PDU session with SSC mode 2 or SSC mode 3.
During interworking from EPS to 5GS, as the SMF+PGW-C may have different IP addresses when being accessed over S5/S8 and N11/N16 respectively, the AMF shall discover the SMF instance by an NF/NF service discovery procedure using the FQDN for the S5/S8 interface received from the UDM as a query parameter.
This is required for both non-roaming and roaming with local breakout, as well as for home routed roaming.
NOTE: As the AMF is not aware of the S-NSSAI assigned for the PDN Connection, the NF/NF service discovery used to find the SMF instance can use PLMN level NRF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.2.2 5GS to EPS Mobility | The following procedure is used by UEs in single-registration or dual registration mode on mobility from 5GS to EPS.
In the case of network sharing the UE selects the target PLMN ID according to clause 5.18.3 of TS 23.501 [2].
Figure 4.11.2.2-1: Mobility procedure from 5GS to EPS without N26 interface
The UE operating in single-registration mode can start the procedure from Step 1 or Step 5. The UE operating in dual-registration mode starts the procedure from Step 5.
NOTE 1: The network has indicated the " Interworking without N26" to the UE. To support IP address preservation, the UE in single-registration mode starts the procedure from Step 5. If the UE in single-registration mode starts the procedure from Step 1, the IP address preservation is not provided.
0. UE is registered in 5GS and established PDU sessions. The FQDN for the S5/S8 interface of the SMF+PGW-C is also stored in the UDM by the SMF+PGW-C during PDU Session setup in addition to what is specified in clause 4.3.2.2.1 and clause 4.3.2.2.2.
NOTE 2: At 5GS to EPS mobility, the MME use the FQDN for the S5/S8 interface of the SMF+PGW-C to find the SMF+PGW-C and when UE moves back from EPS to 5GS, the AMF uses FQDN for the S5/S8 interface of the SMF+PGW-C to find the SMF+PGW-C.
1. Step 1 as in clause 5.3.3.1 (Tracking Area Update) in TS 23.401 [13].
2. Step 2 as in clause 5.3.3.1 (Tracking Area Update) in TS 23.401 [13] with the following modifications:
The UE shall provide a EPS-GUTI that is mapped from the 5G-GUTI following the mapping rules specified in TS 23.501 [2]. The UE indicates that it is moving from 5GC.
3. Step 3 as in clause 5.3.3.1 (Tracking Area Update) in TS 23.401 [13].
4. If the MME determined that the old node is an AMF based on UE's GUTI mapped from 5G-GUTI and the MME is configured to support 5GS-EPS interworking without N26 procedure, the MME sends a TAU Reject to the UE.
5. Step 1 as in clause 5.3.2.1 (E-UTRAN Initial Attach) in TS 23.401 [13] with the modifications captured in clause 4.11.2.4.1.
6. Step 2 as in clause 5.3.2.1 (E-UTRAN Initial Attach) in TS 23.401 [13].
7. Steps 4-7 as in clause 5.3.2.1 (E-UTRAN Initial Attach) in TS 23.401 [13], with the modifications captured in clause 4.11.2.4.1.
8. Step 8 as in clause 5.3.2.1 (E-UTRAN Initial Attach) in TS 23.401 [13], with the modifications captured in clause 4.11.2.4.1.
9. Step 11 as in clause 5.3.2.1 (E-UTRAN Initial Attach) in TS 23.401 [13], with the following modifications:
The subscription profile the MME receives from HSS+UDM includes per DNN/APN at most one SMF+PGW-C FQDN as described in in clause 5.17.2.1 of TS 23.501 [2].
10. Steps 12-24 as in clause 5.3.2.1 (E-UTRAN Initial Attach) in TS 23.401 [13], with the modifications as described in clause 4.11.2.4.1.
11. Step 25 as in clause 5.3.2.1 (E-UTRAN Initial Attach) in TS 23.401 [13].
12. Step 26 as in clause 5.3.2.1 (E-UTRAN Initial Attach) in TS 23.401 [13].
13. If the UE has remaining PDU Sessions in 5GS which it wants to transfer to EPS and maintain the same IP address/prefix, the UE performs the UE requested PDN Connectivity Procedure as specified in clause 5.10.2 of TS 23.401 [13] and sets the Request Type to "handover" or "handover of emergency bearer services" in Step 1 of the procedure with modification captured in clause 4.11.2.4.2. UE provides an APN and the PDU Session ID corresponding to the PDU Session it wants to transfer to EPS. The UE provides the PDU Session ID in PCO as described in clause 4.11.1.1.
UEs in single-registration mode performs this step for each PDU Session immediately after completing the E-UTRAN Initial Attach procedure. UEs in dual-registration mode may perform this step any time after the completing of E-UTRAN Initial Attach procedure. Also, UEs in dual-registration mode may perform this step only for a subset of PDU Sessions.
The MME determines the SMF+PGW-C address for the Create Session Request based on the APN if received from the UE, local Emergency Configuration Data (as in clause 4.11.0a.4) and the subscription profile which may include the Emergency Information received from the HSS+UDM in Step 9 or when the HSS+UDM notifies the MME for the new SMF+PGW-C ID in the updated subscription profile.
The SMF+PGW-C uses the PDU Session ID to correlate the transferred PDN connection with the PDU Session in 5GC.
As a result of the procedure the PGW-U+UPF starts routing DL data packets to the Serving GW for the default and any dedicated EPS bearers established for this PDN connection.
14. For Non-Roaming case and Roaming with Local Breakout, the SMF+PGW-C initiates release of the PDU Session(s) in 5GS transferred to EPS as specified in clause 4.3.4.2 with the following clarification:
- In step 2, the SMF+PGW-C shall not release IP address/prefix(es) allocated for the PDU Session;
- If UP connection of the PDU Session is not active, step 3b is not executed, thus the steps triggered by step 3b are not executed;
If UP connection of the PDU Session is active, the SMF invokes the Namf_Communication_N1N2MessageTransfer service operation in step 3b without including N1 SM container (PDU Session Release Command);
- In step 11, Nsmf_PDUSession_SMContexStatusNotify service operation invoked by the SMF to notify AMF that the SM context for this PDU Session is released due to handover to EPS.
For Home Routed roaming, the SMF+PGW-C initiates release of the PDU Session(s) in 5GS transferred to EPS as specified in clause 4.3.4.3 with the following clarification:
- In step 3a, the H-SMF invokes the Nsmf_PDUSession_Update service operation without including N1 SM container (PDU Session Release Command);
- In step 16a, Nsmf_PDUSession_StatusNotify operation invoked by H-SMF to notify the V-SMF that the PDU session context is released due to handover to EPS;
- In step 16b, Nsmf_PDUSession_SMContexStatusNotify service operation invoked by the V-SMF to notify AMF that the SM context for this PDU Session is released due to handover to EPS. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.2.3 EPS to 5GS Mobility | The following procedure is used by UEs in single-registration mode on mobility from EPS to 5GS.
In the case of network sharing the UE selects the target PLMN ID according to clause 5.18.3 of TS 23.501 [2].
This procedure is also used by UEs in dual-registration mode to perform registration in 5GS when the UE is also registered in EPC. The procedure is the General Registration procedure as captured in clause 4.2.2. Difference from that procedure are captured below.
The UE has one or more ongoing PDN connections including one or more EPS bearers. During the PDN connection establishment, the UE allocates the PDU Session ID and sends it to the SMF+PGW-C via PCO, as described in clause 4.11.1.1.
Figure 4.11.2.3-1: Mobility procedure from EPS to 5GS without N26 interface
0. The UE is attached in EPC as specified in clause 4.11.2.4.1.
1. Step 1 in clause 4.2.2.2.2 (General Registration) with the following clarifications:
The UE indicates that it is moving from EPC. The UE in single registration mode provides the Registration type set to "mobility registration update", a 5G-GUTI mapped from the 4G-GUTI and a native 5G-GUTI (if available) as an Additional GUTI. The UE includes the UE Policy Container containing the list of PSIs, indication of UE support for ANDSP and OSId if available. The UE shall select the 5G-GUTI for the additional GUTI as follows, listed in decreasing order of preference:
- a native 5G-GUTI assigned by the PLMN to which the UE is attempting to register, if available;
- a native 5G-GUTI assigned by an equivalent PLMN to the PLMN to which the UE is attempting to register, if available;
- a native 5G-GUTI assigned by any other PLMN, if available.
The UE in dual registration mode provides the Registration type set to "initial registration" and a native 5G-GUTI or SUCI. In single registration mode, the UE also includes at least the S-NSSAIs (with values for the Serving PLMN) associated with the established PDN connections in the Requested NSSAI in RRC Connection Establishment.
2. Step 2 as in clause 4.2.2.2.
3. Step 3 as in clause 4.2.2.2.2 (General Registration), with the following modifications:
If the Registration type is "mobility registration update" and the UE indicates that it is moving from EPC in step 1 and the AMF is configured to support 5GS-EPS interworking procedure without N26 interface, the AMF treats this registration request as "initial Registration" and the AMF skips the PDU Session status synchronization.
NOTE 1: The UE operating in single registration mode includes the PDU Session IDs corresponding to the PDN connections to the PDU Session status.
If the UE has provided a 5G-GUTI mapped from 4G-GUTI in step 1 and the AMF is configured to support 5GS-EPS interworking procedure without N26 interface, the AMF does not perform steps 4 and 5 in clause 4.2.2.2 (UE context transfer from the MME).
4. Steps 4-13 as in clause 4.2.2.2.2 (General Registration), with the following modifications:
If the UE has included an additional GUTI in the Registration Request, then the new AMF attempts to retrieve the UE's security context from the old AMF in steps 4 and 5.
If the UE's security context is not available in the old AMF or if the UE has not provided an additional GUTI then the AMF retrieves the SUCI from the UE in steps 6 and 7.
5. Step 14 as in clause 4.2.2.2.2 (General Registration), with the following modifications:
If the UE indicates that it is moving from EPC and the Registration type is set to "initial registration" or "mobility registration update" in step 1 and AMF is configured to support 5GS-EPS interworking without N26 procedure, the AMF sends an Nudm_UECM_Registration Request message to the HSS+UDM indicating that registration of an MME at the HSS+UDM, if any, shall not be cancelled. The HSS+UDM does not send cancel location to the old MME.
NOTE 2: If the UE does not maintain registration in EPC, upon reachability time-out, the MME can implicitly detach the UE and release the possible remaining PDN connections in EPC.
The subscription profile the AMF receives from HSS+UDM includes the DNN/APN and SMF+PGW-C FQDN for S5/S8 interface for each PDN connection established in EPC. For emergency PDU Session, the AMF receives Emergency Information containing SMF+PGW-C FQDN from HSS+UDM.
6. Steps 15-19c as in clause 4.2.2.2.2 (General Registration).
7. Step 21 as in clause 4.2.2.2.2 (General Registration) with the following modifications:
The AMF includes an "Interworking without N26" indicator to the UE.
If the UE had provided PDU Session Status information in step 1, the AMF Sets the PDU Session Status to not synchronized.
8. Step 22 as in clause 4.2.2.2.2 (General Registration)
9. UE requested PDU Session Establishment procedure as in clause 4.3.2.2.1.
If the UE had setup PDN Connections in EPC which it wants to transfer to 5GS and maintain the same IP address/prefix and the UE received "Interworking without N26" indicator in step 7, the UE performs the UE requested PDU Session Establishment Procedure as in clause 4.3.2.2 and sets the Request Type to "Existing PDU Session" or "Existing Emergency PDU Session" in step 1 of the procedure. The UE provides a DNN for non-emergency PDU Session, the PDU Session ID and S-NSSAI corresponding to the existing PDN connection it wants to transfer from EPS to 5GS. The S-NSSAI is set as described in clause 5.15.7.2 of TS 23.501 [2].
If the Request Type indicates "Existing Emergency PDU Session", the AMF shall use the Emergency Information received from the HSS+UDM which contains SMF+PGW-C FQDN for S5/S8 interface for the emergency PDN connection established in EPS and the AMF shall use the S-NSSAI locally configured in Emergency Configuration Data.
UEs in single-registration mode performs this step for each PDN connection immediately after the step 8. UEs in dual-registration mode may perform this step any time after step 8. Also, UEs in dual-registration mode may perform this step only for a subset of PDU Sessions. The AMF determines the S5/S8 interface of the SMF+PGW-C for the PDU Session based on the DNN received from the UE and the SMF+PGW-C ID in the subscription profile received from the HSS+UDM in step 5 or when the HSS+UDM notifies the AMF for the new SMF+PGW-C ID in the updated subscription profile. The AMF queries the NRF in serving PLMN by issuing the Nnrf_NFDiscovery_Request including the FQDN for the S5/S8 interface of the SMF+PGW-C and the NRF provides the IP address or FQDN of the N11/N16 interface of the SMF+PGW-C. The AMF invokes the Nsmf_PDUSession_CreateSMContext service with the SMF address provided by the NRF. The AMF includes the PDU Session ID to the request sent to the SMF+PGW-C.
The SMF+PGW-C uses the PDU Session ID to determine the correct PDU Session.
After step 16a of Figure 4.3.2.2.1-1 in clause 4.3.2.2.1, user plane is switched from EPS to 5GS.
As specified clause 4.3.2.2, if the SMF has not yet registered for the PDU Session ID, then the SMF registers with the UDM using Nudm_UECM_Registration (SUPI, DNN, PDU Session ID) and if Session Management Subscription data for corresponding SUPI, DNN and S-NSSAI is not available, then SMF retrieves the Session Management Subscription data using Nudm_SDM_Get (SUPI, Session Management Subscription data, DNN, S-NSSAI) and subscribes to be notified when this subscription data is modified using Nudm_SDM_Subscribe (SUPI, Session Management Subscription data, DNN, S-NSSAI).
NOTE 3: 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.
10. The SMF+PGW-C performs release of the resources in EPC for the PDN connections(s) transferred to 5GS by performing the PDN GW initiated bearer deactivation procedure as defined in clause 5.4.4.1 of TS 23.401 [13], except the steps 4-7. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.2.4 Impacts to EPS Procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.2.4.1 E-UTRAN Attach | Impact on clause 5.3.2.1 of TS 23.401 [13] from adding support for the optional network functionality dual registration mode:
- Step 1:
The UE constructs the Attach Request message according to the following principles:
- If UE operates in single-registration mode, the UE indicates that it is moving from 5GC and provides a native 4G-GUTI or a 4G-GUTI mapped from 5G GUTI (indicated as native GUTI), if available, otherwise the IMSI, or
- If the UE operates in dual-registration mode, the UE indicates that it is moving from 5GC and provides native 4G-GUTI, or
- If the UE sent a TAU in step 2 and it was rejected because the MME could not derive the UE identity, the UE provides IMSI.
If the UE wants to transfer a PDU Session to EPC as part of the Attach procedure, it includes a PDN CONNECTIVITY Request message in the Attach Request and provides a Request type "Handover", DNN/APN and PDU Session ID of the PDU Session (clause 5.3.2.1 of TS 23.401 [13]). The UE provides the PDU Session ID in PCO as described in clause 4.11.1.1. For PDU Session of Ethernet Type, if the UE and the network support Ethernet PDN Type in EPS which is negotiated during PDU Session Establishment as described in clause 4.11.5, the UE includes PDN Type Ethernet in PDN CONNECTIVITY Request message.
If the UE supports URSP provisioning in EPS, the UE also includes the "Indication of URSP Provisioning Support in EPS" in the PCO or in the ePCO in the first PDN CONNECTIVITY Request or during Initial Attach procedure. The PDN CONNECTIVITY Request is sent together with Initial Attach request as described in clause 5.17.8 of TS 23.501 [2].
If the TAU was rejected in step 2 the IP address preservation is not provided. In this case the UE provides IMSI in the Attach Request and does not provide a Request Type "Handover" in the PDN CONNECTIVITY Request if included in the Attach Request.
The UE provides an EPS bearer ID for all mapped EPS bearers in the EPS bearer status. For the initial Attach Request the EPS bearer status is empty.
NOTE 1: The UE is aware the network is configured to support 5GS-EPS interworking without N26 procedure. The UE does not include the EPS bearer IDs corresponding to the 5G QoS flows to the EPS bearer status.
If the UE supports 5GC NAS procedures (see clause 5.17.2 of TS 23.501 [2]), then the UE shall indicate its support of 5G NAS in a NAS indicator.
- Step 3:
If the UE provided a 4G-GUTI mapped from 5G-GUTI and the MME is configured to support 5GS-EPS interworking without N26 procedure, the MME does not perform step 3, Identification Request to old MME/SGSN/AMF in clause 5.3.2.1 of TS 23.401 [13].
NOTE 2: As the 4G-GUTI mapped from 5G-GUTI is unknown identity to the MME, the MME sends an Identity Request to the UE to request the IMSI. The UE responds with Identity Response (IMSI).
- Step 8:
If the UE indicates that it is moving from 5GC (Attach Request) and the MME is configured to support 5GS-EPS interworking without N26 procedure, the MME sends an Update Location Request message to the HSS+UDM indicating that registration of an AMF at the HSS+UDM, if any, shall not be cancelled. The HSS+UDM does not send Nudm_UECM_DeregistrationNotification to the old AMF.
NOTE 3: If the UE does not maintain registration in 5GC, upon reachability time-out, the AMF can implicitly detach the UE and release the possible remaining PDU Sessions in 5GC.
- Step 11:
The HSS+UDM selects one of the SMF+PGW-C FQDN for one APN based on operator's policy. The HSS+UDM sends selected SMF+PGW-C FQDN along with APN to the MME for the UE.
- Step 12:
The MME determines the SMF+PGW-C address for the Create Session Request based on the APN received from the UE and the subscription profile received from the HSS+UDM.
- Step 13:
The SMF+PGW-C uses the PDU Session ID received from the UE in PCO to correlate the transferred PDN connection with the PDU Session in 5GC.
In this release, if the Handover Indication is present in the Create Session Request and the SMF+PGW-C detects it corresponds to a PDU Session for a LADN in 5GC, the SMF+PGW-C rejects the request.
- Step 14:
IP-CAN Session Modification procedure is replaced by SM Policy Association Modification Procedure as described in clause 4.16.5.
- Step 17:
If the UE indicated support for 5GC NAS procedures (see clause 5.11.3) and the MME supports procedures for interworking with 5GC without N26, the MME may indicate in the Attach Accept, that interworking without N26 is supported. UE handling of this indicator is defined in TS 23.501 [2].
- Step 23a:
As a result of the procedure the PGW-U+UPF starts routing DL data packets to the Serving GW for the default and any dedicated EPS bearers established for this PDN connection.
- Step 25:
Notify Request is sent to HSS/UDM if the network supports the procedures for 5GC interworking without N26 and that the UE is allowed to access 5GC (condition that is identified based on the subscription data). For emergency attach, Notify Request is sent to HSS/UDM if the network supports the procedures for 5GC interworking without N26 and operator policy allows handover of emergency session to 5GS. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.2.4.2 Session Management | 4.11.2.4.2.1 PDN Connection Request
Same procedure as specified in clause 4.11.1.5.4.1 is used with the following clarification:
Step 6. The relevant steps of the procedure as specified in the figure above are executed with the following modification:
- Additional condition to trigger Notify Request to HSS in step 15 of Figure 5.10.2-1 in TS 23.401 [13] is that the network supports the procedures for 5GC interworking without N26 and that the UE is allowed to use 5GS in the subscription data. If the Request Type of the UE requested connectivity procedure indicates "Emergency", MME triggers Notify Request to HSS if the network supports the procedures for 5GC interworking without N26 and operator policy allows handover of emergency session to 5GS.
For an unauthenticated or roaming UE, if the Request Type of the UE requested connectivity procedure indicates "Emergency", the MME shall not send any Notify Request to an HSS. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.2.4.3 Void | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.3 Handover procedures between EPS and 5GC-N3IWF | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.3.1 Handover from EPS to 5GC-N3IWF | Figure 4.11.3.1-1: Handover from EPS to 5GC-N3IWF
0. Initial status: one or more PDN connections have been established in EPC between the 5G capable UE and the PGW via E-UTRAN.
1. The UE initiates Registration procedure on untrusted non-3GPP access via N3IWF (with 5G-GUTI is available or SUCI if not) per clause 4.12.2.
2. The UE initiates a UE requested PDU Session Establishment with Existing PDU Session indication in 5GC via Untrusted non-3GPP Access via N3IWF per clause 4.12.5.
If the Request Type indicates "Existing Emergency PDU Session", the AMF shall use the Emergency Information received from the HSS+UDM which contains SMF+PGW-C FQDN for S5/S8 interface for the emergency PDN connection established in EPS and the AMF shall use the S-NSSAI locally configured in Emergency Configuration Data.
The combined PGW+SMF/UPF initiates a PDN GW initiated bearer deactivation as described in clause 5.4.4.1 of TS 23.401 [13] to release the EPC and E-UTRAN resources. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.3.2 Handover from 5GC-N3IWF to EPS | Figure 4.11.3.2-1: Handover from 5GC-N3IWF to EPS
0. Initial status: one or more PDU Sessions have been established in 5GC between the UE and the SMF/UPF via untrusted non-3GPP access and N3IWF. During PDU Session setup and in addition to what is specified in clause 4.3.2.2.1 and clause 4.3.2.2.2, the AMF includes an indication that EPS interworking is supported to the SMF+PGW-C as specified in clause 4.11.5.3 and the SMF+PGW-C sends the FQDN related to the S5/S8 interface to the HSS+UDM which stores it as described in clause 4.11.5.
1. For the UE to move PDU session(s) from 5GC/N3IWF to EPC/E-UTRAN, the UE's behaviour is as follows:
- If the UE is operating in single-registration mode (as described in clause 5.17.2.1 of TS 23.501 [2]) and the UE is registered via 3GPP access to 5GC;
- the UE behaves as specified in clause 4.11.1 or 4.11.2 and moves its PDU session from 5GC/N3IWF to EPC/E-UTRAN using the PDN connection establishment with "Handover" indication procedure as described in TS 23.401 [13].
- otherwise, i.e. either the UE is operating in single registration mode and is not registered via 3GPP access to 5GC, or the UE is operating in dual registration mode; and
- if the UE is not attached to EPC/E-UTRAN, the UE initiates Handover Attach procedure in E-UTRAN as described in TS 23.401 [13] for a non-3GPP to EPS handover with "Handover" indication, except note 17.
- otherwise (i.e. the UE is attached to EPC/E-UTRAN), the UE initiates the PDN Connection establishment with "Handover" indication procedure as described in TS 23.401 [13].
2. The combined PGW+SMF/UPF initiates a network requested PDU Session Release via untrusted non-3GPP access and N3IWF according to Figure 4.12.7-1 steps 3 to 12 to release the 5GC and N3IWF resources with the following exception:
- the H-SMF indicates in the Nsmf_PDUSession_Update Request that the UE shall not be notified. This shall result in the V-SMF not sending the N1 SM Container (PDU Session Release Command) to the UE.
- Nsmf_PDUSession_StatusNotify service operation invoked by H-SMF to V-SMF indicates the PDU Session is moved to a different system;
- Nsmf_PDUSession_SMContexStatusNotify service operation invoked by the (V-)SMF indicates the PDU Session is moved to another system.
- The Npcf_SMPolicyControl_Delete service operation to PCF shall not be performed.
4.11.3a Handover procedures between EPS and 5GC-TNGF
4.11.3a.1 Handover from EPS to 5GC-TNGF
The handover procedure from EPS to 5GC-TNGF is supported as specified in clause 4.11.3.1 for handover procedure from EPS to 5GC-N3IWF with the following differences:
- The untrusted non-3GPP access is substituted by trusted non-3GPP access point (TNAP).
- The N3IWF is substituted by TNGF.
- The registration procedure via trusted non-3GPP access as specified in clause 4.12a.2 shall be performed in step 1.
- The UE requested PDU Session Establishment with Existing PDU Session indication in 5GC via trusted non-3GPP access is performed in step 2 as specified clause 4.12a.5.
4.11.3a.2 Handover from 5GC-TNGF to EPS
The handover procedure from 5GC-TNGF to EPS is supported as specified in clause 4.11.3.2 for handover procedure from 5GC-N3IWF to EPS with the following differences:
- The untrusted non-3GPP access is substituted by trusted non-3GPP access point (TNAP).
- The N3IWF is substituted by TNGF.
- The network requested PDU Session Release via TNAP and TNGF shall be initiated as specified in clause 4.12a.7 from steps 3 to 12. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4 Handover procedures between EPC/ePDG and 5GS | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.1 Handover from EPC/ePDG to 5GS | Figure 4.11.4.1-1: Handover from EPC/ePDG to 5GS
0. Initial status: one or more PDN Connections have been established between the UE and the EPC/ePDG via untrusted non-3GPP access as specified in clauses 7.2.4 and 7.6.3 of TS 23.402 [26] with modification described in clauses 4.11.4.3.3 and 4.11.4.3.5.
1. For the UE to move its PDU session(s) from EPC/ePDG to 5GC/3GPP access, the UE's behaviour is as follows:
- If the UE is operating in single-registration mode (as described in clause 5.17.2.1 of TS 23.501 [2]) and the UE is attached to EPC/E-UTRAN:
- the UE behaves as specified in clause 4.11.1 or clause 4.11.2 and gets registered to 5GC via 3GPP access.
- otherwise i.e. either the UE is operating in single registration mode and is not attached to EPC/E-UTRAN, or the UE is operating in dual registration mode; and
- if the UE is already registered in 5GS via 3GPP access, the UE skips to step 2.
- otherwise (i.e. UE is not registered in 5GS via 3GPP access), the UE performs Registration procedure of type initial registration in 5GS via 3GPP access as described in clause 4.2.2.2.
2. The UE initiates a UE requested PDU Session Establishment via 3GPP Access according to clause 4.3.2.2 and includes the "Existing PDU Session" indication or "Existing Emergency PDU Session" and the PDU Session ID.
For Request Type "Existing PDU Session", the UE provides a DNN, the PDU Session ID and S-NSSAI corresponding to the existing PDN connection it wants to transfer from EPC/ePDG to 5GS. The S-NSSAI and PLMN ID sent to the UE are set in the same way as for EPS to 5GS mobility as specified in clause 5.15.7.1 of TS 23.501 [2].
If the Request Type indicates "Existing Emergency PDU Session", the AMF shall use the Emergency Information containing SMF+PGW-C FQDN for the S2b interface it has received from the HSS+UDM. The SMF+PGW-C FQDN was sent by PGW-C when the Emergency PDN connection was established in EPC via ePDG and the AMF shall use the S-NSSAI locally configured in Emergency Configuration Data.
3. The combined PGW+SMF/UPF initiates a PDN GW initiated Resource Allocation Deactivation with GTP on S2b as described in clause 7.9.2 of TS 23.402 [26] to release the EPC and ePDG resources when S6b is used. When S6b is not used between SMF+PGW-C and AAA, impacts to step 5 of TS 23.402 [26] Figure 7.9.2-1 are captured in clause 4.11.4.3.6. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.2 Handover from 5GS to EPC/ePDG | Figure 4.11.4.2-1 describes the procedure for handing over a PDU Session from 5GS to EPC/ePDG. The UE shall not request a handover of a PDU session with SSC mode 2 or SSC mode 3 to EPC/ePDG.
Figure 4.11.4.2-1: Handover from 5GS to EPC/ePDG
NOTE: In step 2, the UE can also trigger this procedure when 5G NAS (i.e. N1 mode) capability is disabled while the UE is in 5GS.
0. Initial status: one or more PDU Sessions have been established between the UE and the SMF/UPF via NG-RAN.
1. The UE connects to an untrusted non-3GPP access and the N3IWF-ePDG selection process results in selecting an ePDG.
2. The UE initiates a Handover procedure as described in clause 8.6.2.1 of TS 23.402 [26], except step 11 of referenced figure 8.2.3-1 that corresponds to the release of resources in source system.
3. The combined PGW+SMF/UPF initiates a network requested PDU Session Release via 3GPP access according to Figure 4.3.4.2-1 steps 3b to 7b, step 11 or Figure 4.3.4.3-1 steps 3a-16b to release the 5GC and NG-RAN resources with the following exception:
- For non-roaming or local breakout in clause 4.3.4.2, the SMF does not include N1 SM Container in Namf_Communication_N1N2MessageTransfer service operation.
- For home routing roaming in clause 4.3.4.3, the H-SMF indicates in the Nsmf_PDUSession_Update Request that the UE shall not be notified. This shall result in the V-SMF not sending the N1 SM Container (PDU Session Release Command) to the UE.
- Nsmf_PDUSession_StatusNotify service operation invoked by H-SMF to V-SMF and Nsmf_PDUSession_SMContexStatusNotify service operation invoked by the (V-)SMF to the AMF indicate that the PDU Session is moved to a different system.
- The Npcf_SMPolicyControl_Delete service operation to PCF shall not be performed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.3 Impacts to EPC/ePDG Procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.3.1 General | This clause captures enhancements to procedures in TS 23.402 [26] to support interworking with 5GS. The architecture for interworking is shown in clause 4.3.4 of TS 23.501 [2]. with the ePDG connected to SMF+PGW-C and UPF+PGW-U using GTP based S2b. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.3.2 ePDG FQDN construction | Clause 4.5.4.2 of TS 23.402 [26] applies with the following modification:
- Tracking/Location Area Identity FQDN: When the 5GC NAS capable UE uses the Tracking Area of the NG-RAN when the UE is registered with the 5GC when constructing the Tracking Area Identity FQDN. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.3.3 Initial Attach with GTP on S2b | The procedure in clause 7.2.4 of TS 23.402 [26] applies with the following modifications:
- In Step A.1 IKEv2 tunnel establishment procedure, the 5GC NAS capable UE shall indicate its support of 5GC NAS in IKEv2. The UE allocates a PDU Session ID and also includes it in IKEv2 signalling sent to the ePDG. For 5GC NAS capable UE even if the NAS capability is currently disabled (i.e. N1 mode is disabled), the UE may also allocate a PDU Session ID and include it in IKEv2 signalling sent to the ePDG.
- In Step A.1, UE's mobility restriction parameters related to 5GS or indication of support for interworking with 5GS for this APN or both as defined for MME in clause 4.11.0a.3 apply to the ePDG and are obtained by the ePDG as part of the reply from the HSS via the 3GPP AAA Server. These parameters and the 5G NAS support indicator from the UE, may be used by the ePDG to determine if a combined SMF+PGW-C or a standalone PGW should be selected.
- In Step B.1, if the PDN connection is not restricted to interworking with 5GS by user subscription and if PDU Session ID is received from the UE, the ePDG shall send the 5GC Not Restricted Indication, 5GS Interworking Indication and the PDU Session ID to the SMF+PGW-C.
- In Step B.1, if the SMF+PGW-C supports more than one S-NSSAI and the APN is valid for more than one S-NSSAI, the SMF+PGW-C selects S-NSSAI as specified in clause 4.11.0a.5.
- In Step D.1 (Create Session Response), if the PDU Session ID is present and 5GC Not Restricted Indication is set, the SMF+PGW-C assigns a S-NSSAI to be associated with the PDN connection as specified in clause 5.15.7.1 of TS 23.501 [2]. The SMF+PGW-C sends the S-NSSAI to the ePDG together with a PLMN ID that the S-NSSAI relates to.
- In Steps B.1 and D.1, if the UE does not support 5GC NAS but has 5GS subscription and a SMF+PGW-C is selected and interaction with UDM, PCF and UPF is required, the SMF+PGW-C assigns PDU Session ID as specified in clause 4.11.0a.5. The SMF+PGW-C shall not provide any 5GS related parameters to the UE.
- In the IKEv2 Authentication Response message, the ePDG sends S-NSSAI and the PLMN ID that the S-NSSAI relates to, to the UE. The UE associates the received S-NSSAI and the PLMN ID that the S-NSSAI relates to, with the PDN Connection.
- After step D.1, the SMF+PGW-C provides the PCF ID selected for the PDN connection in the UDM using the Nudm_UECM_Registration service operation.
4.11.4.3.3a Initial Attach for emergency session (GTP on S2b)
The procedure in clause 7.2.5 of TS 23.402 [26] applies with the following modification:
- Step 3 (Create Session Request): ePDG determines if interworking with 5GC is supported based on UE's 5G NAS capability and local configuration. In SMF+PGW-C, only one S-NSSAI is configured for the emergency APN. An emergency SMF+PGW-C identity should be configured as part of the Emergency Configuration Data specified in clause 13.5 of TS 23.402 [26].
- Step 6 (Create Session Response), compared to step D.1 of clause 4.11.4.3.3, SMF+PGW-C does not include S-NSSAI in PCO for emergency PDN connection. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.3.4 Interaction with PCC | When interworking with 5GS is supported and a SMF+PGW-C is selected by the ePDG, policy interactions between PDN GW and PCRF specified in TS 23.402 [26] are replaced by equivalent interactions between SMF+PGW-C and PCF as captured in clause 4.11.0a.2.
If SMF+PGW-C is selected and interaction with PCF is required for a UE that does not support 5GC NAS, the SMF+PGW-C determines the PDU Session ID and S-NSSAI in the same way as for PDN connection via MME as specified in clause 4.11.0a.5. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.3.5 UE initiated Connectivity to Additional PDN with GTP on S2b | The procedure in clause 7.6.3 of TS 23.402 [26] references the Initial Attach procedure with GTP on S2b. Impacts to the initial attach procedure with GTP on S2b are captured in clause 4.11.4.3.3 above. If the additional PDN connection is for emergency service, impact as captured in clause 4.11.4.3.3a applies. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.3.6 Use of N10 interface instead of S6b | This clause applies to scenarios when ePDG is connected to SMF+PGW-C and S6b in not used. It is applicable for procedures specified in TS 23.402 [26] including mobility between EPC/ePDG and EPC/EUTRAN and also for mobility between EPC/ePDG and 5GS.
When S6b, as specified in TS 23.402 [26], is not deployed between SMF+PGW-C and AAA and the UE creates and deletes a PDN connection via ePDG connected to SMF+PGW-C, the registration and de-registration of PDN GW is performed on the N10 interface instead of the S6b interface.
If SMF+PGW-C is selected for a UE that does not support 5GC NAS, the SMF+PGW-C determines the PDU Session ID and S-NSSAI in the same way as for PDN connection via EPC/EUTRAN as specified in clause 4.11.0a.5.
For roaming scenario with local-breakout (TS 23.501 [2], Figure 4.3.4.2.1), the use of N10 interface instead of S6b interface may be based on support of this feature from HSS+UDM to SMF+PGW-C on N10 interface.
The specific impacts to procedures in clauses 7 and 8 of TS 23.402 [26] are as follows:
7.2.4 Initial Attach with GTP on S2b
- Instead of Step C.1 in Figure 7.2.4-1 of TS 23.402 [26], step 16c (Nudm_UECM_Registration with an optional indication that access is from ePDG) from Figure 4.3.2.2.1-1 are performed between the SMF+PGW-C and HSS+UDM. Based on this indication, the HSS+UDM does not send notification of PGW-C assignment on SWx to AAA.
7.2.5 Initial Attach for emergency session (GTP on S2b)
- Instead of step 5 in Figure 7.2.5-1 of TS 23.402 [26], step 16c (Nudm_UECM_Registration with an optional indication that access is from ePDG) from Figure 4.3.2.2.1-1 are performed between the SMF+PGW-C and HSS+UDM. Based on this indication, the HSS+UDM does not send notification of PGW-C assignment on SWx to AAA.
The indication of access from ePDG is forwarded on the interface between UDM and HSS.
7.4.3 UE/ePDG-initiated Detach Procedure and UE-Requested PDN Disconnection with GTP on S2b
7.4.3.1 Non-Roaming, Home Routed Roaming and Local Breakout Case
- Instead of Step A.2 in Figure 7.4.3-1 of TS 23.402 [26], step 12 (Nudm_UECM_Deregistration) from Figure 4.3.4.2-1 is performed between the SMF+PGW-C and HSS+UDM.
7.4.4 HSS/AAA-initiated Detach Procedure with GTP on S2b
7.4.4.1 Non-Roaming, Home Routed Roaming and Local Breakout Case
- Instead of step 3 in Figure 7.4.1-1 of TS 23.402 [26] (referenced by Figure 7.4.4-1 of TS 23.402 [26]), Step 12 (Nudm_UECM_Deregistration) from Figure 4.3.4.2-1 is performed between the SMF+PGW-C and HSS+UDM
7.9.2 PDN GW initiated Resource Allocation Deactivation with GTP on S2b
- Instead of step 5 in Figure 7.9.2-1 of TS 23.402 [26], Step 12 (Nudm_UECM_Deregistration) from Figure 4.3.4.2-1 is performed between the SMF+PGW-C and HSS+UDM.
8.6.1.1 General Procedure for GTP based S5/S8 for E-UTRAN Access
- Step 18 of clause 8.6.1.1 of TS 23.402 [26] refers to clause 7.9.2 of TS 23.402 [26]. The Nudm_UECM_Deregistration in the impacted referenced clause 7.9.2 above is not performed as resources in the SMF+PGW-C are not released.
8.6.2.1 3GPP Access to Untrusted Non-3GPP IP Access Handover with GTP on S2b
- In Step B.2 of clause 8.6.2.1 of TS 23.402 [26], if the registration of the SMF+PGW-C in the HSS+UDM is not already done, step 16c (Nudm_UECM_Registration with an optional indication that access is from ePDG) from Figure 4.3.2.2.1-1 is performed between the SMF+PGW-C and HSS+UDM.
The impacts to procedure in clause 4.11.4.1 (Handover from EPC/ePDG to 5GS) are as follows:
- For step 0, the impacts to clause 7.2.4 of TS 23.402 [26] are captured above.
- In step 2, if the Request Type indicates "Existing Emergency PDU Session", the AMF shall use the Emergency Information containing SMF+PGW-C FQDN for the S2b interface and the S NSSAI locally configured in Emergency Configuration Data.
- In step 3, the impacts to clause 7.9.2 of TS 23.402 [26] are captured above. Nudm_UECM_Deregistration is not performed by SMF+PGW-C, as resources in the SMF+PGW-C are not released.
The impacts to procedures in clause 4.11.4.2 (Handover from 5GS to EPC/ePDG) are as follows:
- For step 2, impacts to clause 8.6.2.1 (3GPP Access to Untrusted Non-3GPP IP Access Handover with GTP on S2b) of TS 23.402 [26] are captured above and Step 16c of Figure 4.3.2.2.1-1 is not performed as SMF+PGW-C already registered in the HSS+UDM when the UE is in 5GS. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.4.3.7 5GC NAS capability (re-)enabled and disabled | When 5G NAS (i.e. N1 mode) capability is (re-)enabled, the UE does not report the UE capability change to ePDG.
NOTE: The ePDG is not aware of the N1 mode Enabled / Disabled status at the UE. If a standalone PGW was previously selected, the ePDG is not able to initiate PDN disconnection with reactivation required for the purpose of re-selecting an SMF+PGW-C.
When N1 is re-enabled, how to handle PDN connection(s) established over EPC/ePDG and without a mapped S-NSSAI is defined in TS 24.501 [25]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5 Impacts to 5GC Procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.1 General | This clause captures impacts to 5GC procedures in other clauses of this specification to support interworking with EPS. These impacts are applicable to interworking based on N26 and interworking without N26 for PDU Session via 3GPP access and for PDU Session via non-3GPP access.
This clause also captures the impact to 5GC if the UE was previously in GERAN/UTRAN as specified in clause 5.17.2.4 of TS 23.501 [2]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.2 Registration procedure | The following impacts are applicable to clause 4.2.2.2 (Registration procedure):
- Step 1: If the Registration type is set to "Initial Registration", the UE is not registered in EPS and the UE provides the 5G-GUTI mapped from EPS GUTI as the old GUTI, then the UE includes complete EPS Attach Request in the Registration request message.
- Step 4: If the Registration type is "Initial Registration" as in step 1 of the Registration Procedure captured in clause 4.2.2.2.2, the target AMF may perform Identification Request towards MME along with complete EPS Attach Request message for MME to verify it as in step 3 as specified in clause 5.3.2.1 of TS 23.401 [13].
NOTE 1: The steps above apply to interworking with N26.
- Step 14a:
- If the AMF does not have event subscription information from the UDM, the AMF indicates it in Nudm_UECM_Registration. The UDM then provides event subscriptions (possibly retrieved from UDR) if any.
- If mobility between GERAN/UTRAN and 5GS is required (as specified in clause 5.17.2.4 of TS 23.501 [2]), at Initial Registration, the AMF serving 3GPP access shall also register with the Nudm_UECM_Registration even if the AMF has a valid context.
- Step 14d: If mobility between GERAN/UTRAN and 5GS is required (as specified in clause 5.17.2.4 of TS 23.501 [2]), when the UDM stores the associated 3GPP Access Type together with the serving AMF as indicated in step 14a, it will also cause cancellation of any other previously registered serving node (e.g. MME if AMF does not indicate not to cancel or SGSN) via HSS/HLR.
NOTE 2: Upon mobility from GERAN/UTRAN to 5GS as specified in clause 5.17.2.4 of TS 23.501 [2], the previously registered SGSN needs to be cancelled from HSS/HLR, otherwise the incoming session can fail.
- At the end of registration procedure, the AMF may initiate synchronization of event subscriptions with the UDM if the AMF does not indicate unavailability of event subscription in step 14a.
NOTE 3: The details how synchronization can be done is left to stage 3.
For PDU Session via 3GPP access the following impacts are applicable to clause 4.2.2.2 (Registration procedure) when the UE has established PDU Session(s):
In clause 4.3.2.2.1 Non-roaming and Roaming with Local Breakout:
- Step 17: Additional trigger for step 17 Nsmf_PDUSession_UpdateSMContext are:
- If status of interworking with EPS for a PDU session changes, e.g. due to change of 5GMM capability (e.g. "S1 mode supported"), the UE subscription data change (e.g. Core Network Type Restriction to EPC), the AMF invokes Nsmf_PDUSession_UpdateSMContext (EPS Interworking Indication with N26 or without N26) to SMF. The SMF determines whether the PDU session supports interworking with EPS need be changed. If it needs to be changed, the SMF invokes Nudm_UECM_Update service operation to add or remove the PGW-C FQDN for S5/S8 interface from the UE context in SMF data stored at the UDM.
For interworking with the N26 interface, if status of interworking with EPS for a PDU session is changed at SMF+PGW-C, the SMF+PGW-C invokes EBI allocation or revocation as described in clause 4.11.1.4.1 and clause 4.11.1.4.2 respectively.
For PDU Session via non-3GPP access, the AMF determines if EPS interworking is supported and sends the indication to the SMF in the same way as for PDU Session via 3GPP access. The SMF makes the final decision on the EPS interworking in the same way as for PDU Session via 3GPP access with the following modification:
If the SMF does not receive the interworking indication, the SMF makes its decision based on subscription. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.3 UE Requested PDU Session Establishment procedure | For PDU Session via 3GPP, the following impacts are applicable to clause 4.3.2.2 (UE Requested PDU Session Establishment procedure) to support interworking with EPS:
In clause 4.3.2.2.1 Non-roaming and Roaming with local breakout:
- Step 1: In PDU Session Establishment Request message, the UE includes also the UE capability of Ethernet PDN type support in EPS to the SMF (or H-SMF in home routing roaming);
- Step 3: The AMF determines that a PDU Session supports EPS interworking with N26 or without N26, based on e.g. 5GMM capability (e.g. "S1 mode supported"), UE subscription data (e.g. Core Network Type Restriction to EPS, EPC interworking support per (S-NSSAI, subscribed DNN)) and network configuration if EPS interworking with N26 or without N26 is supported. The AMF then includes in the Nsmf_PDUSession_CreateSMContext an indication whether the PDU Session supports EPS Interworking and whether EPS Interworking is done with N26 or without N26.
For PDU Session with Request Type "initial emergency request", the AMF decides the EPS interworking with N26 or without N26 based on 5GMM capability and local configuration.
For PDU Session with Request Type "Existing Emergency PDU Session", the AMF shall use Emergency Information received from HSS+UDM and the S-NSSAI locally configured in Emergency Configuration Data.
If the Request Type indicates "Existing PDU Session" the AMF selects the SMF based on SMF-ID or SMF+PGW-C FQDN received from UDM during the Registration or Subscription Profile Update Notification procedure. The case where the AMF does not recognize the PDU Session ID or the subscription context that the AMF received from UDM neither contains an SMF ID nor a SMF+PGW-C FQDN corresponding to the PDU Session ID constitutes as an error case.
NOTE 1: If the AMF receives from the UDM, for a PDU Session, both a SMF ID and a SMF+PGW-C FQDN, the SMF ID takes precedence.
If the AMF has stored APN Rate Control Status and the PDU Session is considered a new first PDU Session to a DNN that is the same as the APN in stored APN Rate Control Status and interworking with EPC is enabled for this PDU Session, then the AMF sends the APN Rate Control Status to the SMF.
The AMF indicates to the SMF whether the UE support User Plane Integrity Protection with EPS and whether the AMF has associated functionality.
- Step 4: If the EPS Interworking indication received from AMF indicates that the UE supports EPS interworking and the SMF determines, based on the EPS interworking support indication from the AMF and additional UE subscription data (e.g. whether UP integrity protection of UP Security Enforcement Information is not set to required, EPS interworking is allowed for this DNN and S-NSSAI), that the PDU Session supports EPS interworking and the PDU Session is using SSC mode 1, the SMF+PGW-C FQDN for S5/S8/S2b interface is included in the Nudm_UECM_Registration Request. The SMF+PGW-C also includes the SMF+PGW-C FQDN for S5/S8/S2b interface if the PDU Session is using SSC mode 1 and mobility to ePDG/EPC is allowed based on operator's policy.
- Step 10a: If APN Rate Control Status is received from the AMF then the SMF provides the configured APN Rate Control Status to the PGW-U+UPF.
- Step 11: if the SMF+PGW-C supports URSP delivery in EPS and ePCO it provides the Indication of URSP Provisioning Support in EPS in the PDU Session Establishment Accept (see clause 5.17.8 of TS 23.501 [2]).
- Step 13: In PDU Session Establishment Accept message, the SMF also includes indication of Ethernet PDN type supported if the Ethernet PDN type is supported by both the UE and the SMF+PGW-C. The SMF and the UE stores the information if Ethernet PDN type is supported for later use when UE moves from 5GS to EPS.
- Step 16c: For PDU Session establishment with Request Type "initial PDU Session", if the SMF+PGW-C selects the same PCF as the PCF ID received from AMF as specified in clause 4.3.2.2.1 and if the PDU Session supports EPC interworking, the SMF provide the selected PCF ID in the UDM using the Nudm_UECM_Registration service operation.
NOTE 2: The subscription data "EPS interworking support indication" is used by AMF when determining the EPS interworking support for the PDU Session. Therefore, when the UE establishes the PDU Session via the 3GPP access, the SMF does not need to consider the same subscription data "EPS interworking support indication" again.
In clause 4.3.2.2.2 Home-routed Roaming:
- Step 3a: Same impact as for step 3 for the non-roaming and roaming with local breakout case above.
- Step 5: Same impact as for step 10a for the Non-roaming and Roaming with Local Breakout case above.
- Step 6: The V-SMF pass the EPS interworking support indication received from the AMF to the H-SMF in Nsmf_PDUSession_Create.
- Step 7: If the EPS interworking indication received from V-SMF indicates that the PDU Session supports EPS interworking and the H-SMF determines, based on the EPS interworking support indication from the AMF and additional information such as UP integrity protection of UP Security Enforcement Information as described in clause 4.11.1.1, that the PDU Session supports EPS interworking, the SMF+PGW-C FQDN for S5/S8 interface is included in the Nudm_UECM_Registration Request.
- Step 15: Same impact as in step 13 for the non-roaming and roaming with local breakout case above with the difference that it's the home SMF+PGW-C that includes the indication of Ethernet PDN type supported.
For interworking with the N26 interface, if the PDU Session supports interworking with EPS, the SMF+PGW-C invokes EBI allocation as described in clause 4.11.1.4.1.
For non-emergency PDU Session via non-3GPP, the AMF determines if EPS interworking is supported and sends the indication to the SMF in the same way as for PDU Session via 3GPP. The SMF makes the final decision on the EPS interworking in the same way as for PDU Session via 3GPP with the following modification:
- If the SMF does not receive the interworking indication, the SMF makes its decision based on subscription.
For emergency PDU Session via non-3GPP, the AMF determines if EPS interworking is supported and sends the indication to the SMF in the same way as for emergency PDU Session via 3GPP supporting EPS interworking. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.4 UE or Network Requested PDU Session Modification procedure | For PDU Session via 3GPP, the following impacts are applicable to clause 4.3.3.2 (UE or network requested PDU Session Modification (non-roaming and roaming with local breakout)) to support interworking with EPS:
- Step 1: In addition to the triggers listed in step 1 of clause 4.3.3.2, the procedure may be also triggered by the following event:
- AMF initiated modification: If the support of EPS Interworking for this PDU Session has changed, e.g. the change of the UE's subscription data (e.g. Core Network Type Restriction to EPS), or change of 5GMM capability (e.g. "S1 mode supported"), the AMF invokes Nsmf_PDUSession_UpdateSMContext update the status of EPS interworking support in the to SMF.
- Step 3a: This step also applies to AMF initiated modification. For AMF initiated modification, the SMF may determines whether the PDU session supports EPS interworking need be changed. If it need be changed, the SMF invokes Nudm_UECM_Update service operation to add or remove the PGW-C FQDN for S5/S8 interface from the UE context in SMF data stored at the UDM,
For PDU Session via 3GPP, the following impacts are applicable to clause 4.3.3.3 (UE or network requested PDU Session Modification (home-routed roaming)) to support interworking with EPS:
- Step 1a (AMF to V-SMF): Same impact as for step 1 of clause 4.3.3.2 above.
- Step 1a (V-SMF to H-SMF): The V-SMF pass the status of EPS interworking support to the H-SMF.
- Step 1a (H-SMF to V-SMF): Same impact as for clause 3a of 4.3.3.2 above.
For interworking with the N26 interface, if status of interworking with EPS for a PDU session is changed at SMF+PGW-C, the SMF+PGW-C invokes EBI allocation or revocation as described in clause 4.11.1.4.1 and clause 4.11.1.4.2 respectively.
For PDU Session via non-3GPP access, the AMF determines if EPS interworking is supported and sends the indication to the SMF in the same way as for PDU Session via 3GPP access. The SMF makes the final decision on the EPS interworking in the same way as for PDU Session via 3GPP access with the following modification:
If the SMF does not receive the interworking indication, the SMF makes its decision based on subscription. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.5 Xn based inter NG-RAN handover | The following impacts are applicable to clause 4.9.1.2.1 (General) to support interworking with EPS:
- If there is Mapping between EBI(s) and QFI(s) for the UE in the source NG-RAN, the source NG-RAN sends the Mapping to target NG-RAN during handover. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.6 Inter NG-RAN node N2 based handover | The following impacts are applicable to clause 4.9.1.3.2 (Preparation phase) to support interworking with EPS:
- Step 7: If the PDU session supports EPS interworking, the N2 SM information contains the Mapping between EBI(s) and QFI(s). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.7 UE or Network Requested PDU Session Release procedure | The following impacts are applicable to clause 4.3.4.2 (UE or network requested PDU Session Release for Non-Roaming and Roaming with Local Breakout) to support interworking with EPS:
- Step 2b: If the released PDU Session used APN Rate Control in EPC then the PGW-U+UPF provides the APN Rate Control Status to the SMF if the released PDU Session supported interworking with EPC and it is the last PDU Session to the DNN that is the same as the APN identified in the APN Rate Control Status.
- Step 3: If the PGW-U+UPF provided APN Rate Control Status to the SMF then the SMF provides the APN Rate Control Status to the AMF.
The following impacts are applicable to clause 4.3.4.3 (UE or network requested PDU Session Release for Home-routed Roaming) to support interworking with EPS:
- Step 2b: Same impact as for step 2b for the Non-roaming and Roaming with Local Breakout case above.
- Step 3: Same impact as for step 3 for the Non-roaming and Roaming with Local Breakout case above. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.8 Network Configuration | To avoid the need for identifier coordination between AMFs and MMEs, the AMF provides to the NG-RAN its served GUAMIs by separating the values between native AMF values and the values mapped from MME. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.9 Network Slice Admission Control | Support of NSAC in conjunction with interworking with EPC is described in clause 5.15.11.5 of TS 23.501 [2].
If EPS counting is required for a network slice, the SMF+PGW-C performs NSACF discovery that supports controlling the maximum number of PDU sessions per network slice as described in clause 6.3.22 of TS 23.501 [2] and in clause 5.2.7.3.2.
If non-Hierarchical NSAC or Centralized NSAC architecture is deployed at the network, the following impacts are applicable to clause 4.2.11.4 (Number of PDU Sessions per network slice availability check and update procedure):
- The SMF+PGW-C invokes this procedure to perform network slice availability check on the number of PDU Sessions and update for S-NSSAI associated with the PDN connection during PDN connection establishment and PDN connection release. In this case the SMF in figure 4.2.11.4-1 is replaced with SMF+PGW-C.
- Step 3: The NSACF determines whether or not to accept the request as described in clause 5.15.11.5 of TS 23.501 [2].
If Hierarchical NSAC architecture is deployed at the network, the following impacts are applicable to clause 4.2.11.4a:
- The SMF+PGW-C invokes this procedure to perform network slice availability check on the number of PDU Sessions and update for S-NSSAI associated with the PDN connection during PDN connection establishment. In this case the SMF in figure 4.2.11.4a-1 is replaced with SMF+PGW-C.
- Step 8: The NSACF determines whether or not to accept the request as described in clause 5.15.11.5 of TS 23.501 [2]. When the local maximum number is reached, the NSACF may interact with the Primary NSACF before it returns the response back to the SMF+PGW-C as defined in clause 4.2.11.4a.
The SMF+PGW-C performs NSACF discovery that supports controlling the maximum number of UEs per network slice as described in clause 6.3.22 of TS 23.501 [2] and in clause 5.2.7.3.2.
If non-Hierarchical NSAC or Centralized NSAC architecture is deployed at the network, the following impacts are applicable to clause 4.2.11.2 (Number of UEs per network slice availability check and update procedure):
- The SMF+PGW-C invokes this procedure to perform network slice availability check on the number of UEs and update for S-NSSAI associated with the PDN connection during PDN connection establishment. In this case the AMF in figure 4.2.11.2-1 is replaced with SMF+PGW-C.
- Step 2: The SMF+PGW-C includes in the message the S-NSSAI, identity of SMF+PGW-C, UE ID and update flag. In a centralized NSAC architecture, the SMF+PGW-C additionally includes the NSAC service area if available.
- Step 3: The AMF ID is replaced by the SMF + PGW-C ID.
- Step 3: The NSACF determines whether or not to accept the request as described in clause 5.15.11.5 of TS 23.501 [2].
If Hierarchical NSAC architecture is deployed at the network, the following impacts are applicable to clause 4.2.11.2a:
- The SMF+PGW-C invokes perform network slice availability check on the number of UEs and update for S-NSSAI associated with the PDN connection during PDN connection establishment. In this case the AMF in figure 4.2.11.2a-1 is replaced with SMF+PGW-C.
- Step 2: The SMF+PGW-C includes in the message the S-NSSAI, identity of SMF+PGW-C, UE ID and update flag.
- Step 3: The AMF ID is replaced by the SMF + PGW-C ID.
- Step 8: The NSACF determines whether or not to accept the request as described in clause 5.15.11.5 of TS 23.501 [2]. When the local maximum number is reached the NSACF may interact with the Primary NSACF before it returns the response back to the SMF+PGW-C as defined in clause 4.2.11.2a.
The SMF+PGW-C shall continue the PDN Connection Establishment procedure only when the Network Slice subject to NSAC is available based on both numbers of PDU Sessions and number of UEs.
4.11.5.9a Network Slice Admission Control in 5GS for maximum number of UE with at least one PDU session and one PDN connection
Support of NSAC in conjunction with interworking with EPC for maximum number of UE with at least one PDU session/PDN connection is described in clause 5.15.11.5a of TS 23.501 [2].
For option 1, the same mechanisms in clause 4.2.11.2 (Number of UEs per network slice availability check and update procedure) is used with the following additions:
- The SMF+PGW-C invokes this procedure per Access Type when the UE establishes the first PDU Session/PDN Connection in one Access Type and when the last PDU Session/PDN Connection associated with the network slice in the same Access Type is released. In this case, the AMF in figure 4.2.11.2-1 is replaced with SMF+PGW-C.
- Step 2: The SMF+PGW-C includes in the message the S-NSSAI, identity of SMF+PGW-C, UE ID and update flag. The update flag may include either 'increase', 'decrease' or 'update' values.
- Step 2: The AMF ID is replaced by the SMF+PGW-C ID.
- Step 3: The 'update' value indicates that for existing UE registration the Access Type is to be replaced with a new Access Type during inter access mobility. If the update flag parameter from the SMF+PGW-C indicates update value, i.e. during inter access mobility, the NSACF locates the existing entry with UE ID and NF ID and replaces the Access Type in the existing entry. The NSACF may take the Access Type into account for UE counting based on local policy. The followings applies:
- If the new Access Type is taken into account and if there was one UE ID entry in the new Access Type with same NF ID then NSACF shall not increase the count again.
- If the new Access Type is taken into account and if there was one UE ID entry in the new Access Type with different NF ID then NSACF may add this new NF ID in the UE entry and shall not increase the count.
- If the new Access Type is taken into account and if there are no entries for the UE, then the entry is added and the count for the new Access Type shall be increased.
- If the old Access Type is taken into account and if there was only one UE ID entry with same NF ID in the old Access Type then NSACF removes the UE ID entry and decrease the count if there was no other NF ID in this UE ID entry. If there is other NF ID in this UE ID entry then NSAC removes the NF ID from the UE ID entry and shall not change the count.
- The NSACF determines whether or not to accept the request as described in clause 5.15.11.5a of TS 23.501 [2]
NOTE 1: EAC mode is not applicable here.
For option 2, the same mechanisms in clause 4.2.11.4 (Number of PDU Sessions per network slice availability check and update procedure) are used with the following additions:
- The NSACF also counts the maximum number UE with at least one PDU session/PDN connection based on the value in update flag received from SMF+PGW-C.
- The behaviour for an update flag parameter is identical to the case for option 1.
- The NSACF determines whether to accept the request as described in clause 5.15.11.5a of TS 23.501 [2].
- The NSACF performs other actions in addition to the above to keep track of the last PDU Session/Connection released so as to decrease the count for the number of Registered UEs with at least one PDU Session/one PDN Connection.
NOTE 2: EAC mode is not applicable here.
If Hierarchical NSAC architecture is deployed in the network, there are the following additional enhancements:
- For option 2, the NSAC for the number of UEs with at least one PDU session/PDN connections and the NSAC for the number of PDU sessions shall be handled within the same NSACF.
- For both options, when the local maximum number of UEs with at least one PDU Session/PDN Connection or local threshold is reached, the NSACF may interact with the Primary NSACF before it returns the response back to the SMF+PGW-C. During this interaction procedure, for option 2, when the NSACF identifies that either the number of UEs or the number of PDUs for the S-NSSAI is exceeded then the NSACF shall may also provide the corresponding indication in of NSAC for maximum number of UEs or NSAC for maximum number of PDUs in Nnsacf_NSAC_NumOfPDUsUpdate message to Primary NSACF. Based on the received indication, the Primary NSACF either delegates the NSAC update request to the NSACF (i.e. adjusts the local maximum number related to corresponding indication) or reject the request. For more details on handling between the NSACF and Primary NSACF see clause 4.2.11.2a.
NOTE 3: For both options, given that the SMF+PGW-C can not provide the UE already registered indication to NSACF, hence when the NSACF interacts with Primary NSACF, the Primary NSACF either delegate the NSAC update request to the NSACF or reject the NSAC update request from the NSACF.
- For NSAC for number of PDU Sessions, when the local maximum number is reached, the NSACF may interact with the Primary NSACF before it returns the response back to the SMF+PGW-C. For more details on handling between the NSACF and Primary NSACF see clause 4.2.11.4a. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.10 UE Policy Association control | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.5.10.1 UE Policy Association Establishment for URSP delivery in EPS | The following impacts are applicable to clause 4.16.11 (UE Policy Association Establishment procedure) during initial registration or during UE registration with 5GS when the UE moves from EPS to 5GS:
In addition to step 3 in clause 4.16.11, if the indication about the support of provisioning of URSP rules in EPS is received in step 2 within Npcf_UEPolicyControl_Create Request, that indication is added in the list of parameters to be stored in UDR using Nudr_DM_Create. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.6 Interworking for common network exposure | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.6.1 Subscription and Notification of availability or expected level of support of a service API | Figure 4.11.6.1 1 represent the information flow subscribing and notifying the availability or expected level of support of a service API.
For the subscription to Nnef_APISupportCapability service, the subscription request may include the Duration of Reporting. If the Duration of Reporting is expired, the SCEF+NEF deletes the subscription without any explicit signalling interaction.
For the CN type Change Event subscription to the HSS+UDM, the subscription request may include the Duration of Reporting. If the Duration of Reporting is expired, the HSS+UDM locally unsubscribe the CN Type Change Event without any explicit signalling interaction.
The SCEF+NEF informs the AF of the API Indication which indicates list of available north-bound API(s).
Figure 4.11.6.1-1: Subscription and Notification of availability or expected level of support of a service API
1. The AF subscribes to Nnef_APISupportCapability service for a UE or a group of UEs by sending Nnef_APISupportCapability_Subscribe Request (UE ID or External Group ID, Report Type, callback URI, Duration of Reporting) message.
The callback URI parameter is optional and is used in step 6 if provided.
The Report Type can be either One-time report or Continuous report. If this is a subscription for Continuous report type, then the Duration of Reporting may be included. The Duration of Reporting is optional and is used to indicate when the subscription is invalid. If the SCEF+NEF has established direct connection with MME or AMF or SMF, steps 2 - 3 and step 5 are omitted. If this is a subscription for One-time report type and if the Freshness Timer of last One-time report type subscribe request is not expired or a direct connection has been set up with MME or AMF or SMF, the SCEF+NEF determines the CN type locally, steps 2 - 3 are omitted.
2. SCEF+NEF subscribes the CN Type Change Event to HSS+UDM by sending Nudm_EventExposure_Subscribe Request (CN Type Change, Report Type, UE ID or External Group ID, Duration of Reporting) message.
If Duration of Reporting is received at step 1, it shall include Duration of Reporting in this message.
3. The HSS+UDM determines the CN type that is serving the indicated UE or the indicated group of UEs based on the registered MME or AMF. The HSS+UDM informs SCEF+NEF of the CN type by sending Nudm_EventExposure_Subscribe Response (CN Type) message. If the Report Type indicates One-time report, the HSS+UDM delete the CN Type Change Event subscription after sending the response with CN Type. The Freshness Timer is set in SCEF+NEF per operator's policy, e.g. based on the statistics of UE activities. If the Report Type indicates Continuous report, HSS+UDM stores the CN Type Change Event subscription.
4. According to the CN type received or local stored, the SCEF+NEF determines the availability or expected level of support of common north-bound APIs for the indicated UE or the indicated group of UEs. SCEF+NEF responds to AF by sending Nnef_APISupportCapability_Subscribe Response (API Indication).
If the subscription is for One-time report type, then steps 5 - 6 are omitted.
5. When HSS+UDM detects that the indicated UE is switching between EPC and 5GC the HSS+UDM determines the CN type that is serving the indicated UE or the indicated group of UEs. The HSS+UDM informs SCEF+NEF of the CN type by sending Nudm_EventExposure_Notify (CN type).
The CN type denotes the 5GC or EPC or 5GC+EPC serving the UE or the group of UEs.
6. According to the CN type received and local detected, the SCEF+NEF node determines the availability or expected level of support of common north-bound APIs for the indicated UE or the indicated group of UEs. SCEF+NEF inform AF of such API information by sending Nnef_APISupportCapability_Notify (API Indication) message.
If callback URI is provided at step 1, then SCEF+NEF will send the Nnef_APISupportCapability_Notify (API Indication) message to the node addressed by callback URI.
Upon reception of API Indication in step 4 or step 6, the AF obtains the availability or expected level of support of a given service for the indicated UE or the indicated group of UEs. If required, the AF can select the valid north-bound API based on such API information. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.6.2 Unsubscribing to N11otification of availability or expected level of support of a service API | Figure 4.11.6.2 1 represent the information flow unsubscribing to Continuous report type subscription of the availability or expected level of support of a service API.
If the AF invokes Nnef_APISupportCapability_Subscribe service to SCEF+NEF node with the Duration of Reporting parameter for Continuous report type, the subscription on the SCEF+NEF and HSS+UDM are implicitly unsubscribed if the Duration of Reporting timer expires, i.e. the explicit unsubscribe service operation is not needed.
If the explicit unsubscribe operation is needed, the information flow is as follows.
Figure 4.11.6.2 1: Unsubscribing to notification of the availability or expected level of support of a service API
1. The AF unsubscribes to Nnef_APISupportCapability service for a UE or a group of UEs by sending APISupportCapability_Unsubscribe Request (UE ID or External Group ID) message.
2. If SCEF+NEF has subscribed to CN Type Change Event for the indicated UE or the indicated group of UEs, SCEF+NEF unsubscribes the CN Type Change Event by sending Ndum_EventExposure_Unsubscribe Request (CN Type Change, UE ID or External Group ID) message to HSS+UDM.
3. HSS+UDM deletes the CN Type Change Event subscription for the indicated UE or the indicated group of UEs, HSS+UDM responses to the SCEF+NEF by sending Ndum_EventExposure_Unsubscribe Response (Operation execution result indication) message.
4. If result indication indicates the operation is successful, the SCEF+NEF deletes the subscription to Nnef_APISupportCapability service. SCEF+NEF acknowledges the operation result by sending Nnef_APISupportCapability_Unsubscribe Response (Operation execution result indication) to AF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.11.6.3 Configuration of monitoring events for common network exposure | Figure 4.11.6.3-1 represent the information flow to configure monitoring events applicable to both EPC and 5GC using 5GC procedures towards UDM in scenarios where interworking between 5GS and EPC is possible.
Figure 4.11.6.3-1: Configuration of monitoring events for common network exposure
1. The AF configures a monitoring event via the SCEF+NEF using the Nnef_EventExposure_Subscribe service operation.
2. SCEF+NEF configures the monitoring event in the UDM+HSS using the Nudm_EventExposure_Subscribe service operation.
The combined SCEF+NEF indicates that the monitoring event is also applicable to EPC (i.e. the event must be reported both by 5GC and EPC). Depending on the type of event, the SCEF+NEF may include a SCEF address (i.e. if the event needs to be configured in the MME and the corresponding notification needs to be sent directly to the SCEF).
3. The HSS+UDM configures the monitoring event. For events that need to be reported from a serving node (e.g. location change) the HSS+UDM requests the configuration of the monitoring event to the corresponding serving node in the 5GC and EPC. The HSS+UDM uses the corresponding Event Exposure Subscribe service operation to configure monitoring events in 5GC serving NFs (e.g. Namf_EventExposure_Subscribe or Nsmf_EventExposure_Subscribe). The HSS+UDM uses the procedures defined in TS 23.682 [23] to configure monitoring events in MME. The HSS+UDM provides the MME with the SCEF address during the configuration of the monitoring event in EPC. If the HSS and UDM are deployed as separate network entities, UDM shall use HSS services to configure the monitoring event in EPC as defined in TS 23.632 [68].
4. The HSS+UDM replies the SCEF+NEF with the indication that the monitoring event was successfully configured in 5GC and EPC by sending the Nudm_EventExposure_Subscribe Response.
5. The SCEF+NEF responds to AF by sending Nnef_EventExposure_Subscribe Response.
6. The SCEF+NEF is notified when HSS+UDM or the serving node at the 5GC or EPC detects the corresponding event. The HSS+UDM notifies the SCEF+NEF using the Nudm_EventExposure_Notify service operation. A serving NF in the 5GC notifies the SCEF+NEF using the corresponding Event Exposure Notify service operation (e.g. Namf_EventExposure_Notify or Nsmf_EventExposure_Notify). The MME notifies the SCEF+NEF using the procedures defined in TS 23.682 [23] using the SCEF address provided by the HSS+UDM in step 3.
7. The SCEF+NEF notifies the AF using the Nnef_EventExposure_Notify service operation. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12 Procedures for Untrusted non-3GPP access | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.1 General | Clause 4.12 defines the procedures to support Untrusted non-3GPP access by describing the differences compared to the defined procedures in other clauses. The procedures for Untrusted non-3GPP access are also used by a UE that accesses SNPN services via a PLMN over 3GPP access. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.2 Registration via Untrusted non-3GPP Access | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.2.1 General | Clause 4.12.2 specifies how a UE can register to 5GC via an untrusted non-3GPP Access Network. It is based on the Registration procedure specified in clause 4.2.2.2.2 and it uses a vendor-specific EAP method called "EAP-5G". The EAP-5G packets utilize the "Expanded" EAP type and the existing 3GPP Vendor-Id registered with IANA under the SMI Private Enterprise Code registry. The "EAP-5G" method is used between the UE and the N3IWF and is utilized only for encapsulating NAS messages (not for authentication). If the UE needs to be authenticated, mutual authentication is executed between the UE and AUSF. The details of the authentication procedure are specified in TS 33.501 [15].
In Registration and subsequent Registration procedures via untrusted non-3GPP access, the NAS messages are always exchanged between the UE and the AMF. When possible, the UE can be authenticated by reusing the existing UE security context in AMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.2.2 Registration procedure for untrusted non-3GPP access | The signalling flow in Figure 4.12.2.2-1 does not show all the details of a registration procedure via untrusted non-3GPP access. It shows primarily the steps executed between the UE and N3IWF. All the details of a registration procedure, including interactions with UDM, etc. are specified in clause 4.2.2.2.2.
Figure 4.12.2.2-1: Registration via untrusted non-3GPP access
1. The UE connects to an untrusted non-3GPP Access Network with any appropriate authentication procedure and it is assigned an IP address. For example, a non-3GPP authentication method can be used, e.g. no authentication (in the case of a free WLAN), EAP with pre-shared key, username/password, etc. When the UE decides to attach to 5GC network, the UE not operating in SNPN access mode for NWu interface selects an N3IWF in a 5G PLMN, as described in clause 6.3.6 of TS 23.501 [2]. When the UE decides to attach to 5GC network, the UE operating in SNPN access mode for NWu interface selects an N3IWF in an SNPN, as described in clause 6.3.6.2a of TS 23.501 [2].
NOTE 1: The UE Selection of a N3IWF that supports the S-NSSAIs needed by the UE is enabled based on ANDSP configuration defined in TS 23.501 [2]. The N3IWF selection based on this information is documented in TS 23.501 [2].
2. The UE proceeds with the establishment of an IPsec Security Association (SA) with the selected N3IWF by initiating an IKE initial exchange according to RFC 7296 [3]. After step 2, all subsequent IKE messages are encrypted and integrity protected by using the IKE SA established in this step.
3. The UE shall initiate an IKE_AUTH exchange by sending an IKE_AUTH request message. The AUTH payload is not included in the IKE_AUTH request message, which indicates that the IKE_AUTH exchange shall use EAP signalling (in this case EAP-5G signalling). If the UE supports MOBIKE, it shall include a Notify payload in the IKE_AUTH request, as specified in RFC 4555 [40], indicating that MOBIKE is supported. In addition, as specified in TS 33.501 [15], if the UE is provisioned with the N3IWF root certificate, it shall include the CERTREQ payload within the IKE_AUTH request message to request the N3IWF's certificate. In the case of WLAN access, if the UE has an MPS subscription, the UE shall include a Notify payload in the IKE_AUTH request indicating its MPS subscription.
NOTE 2: Based on operator policy, the N3IWF can use the MPS subscription indication at this time to handle this UE with priority.
4. The N3IWF responds with an IKE_AUTH response message, which includes an EAP-Request/5G-Start packet. The EAP-Request/5G-Start packet informs the UE to initiate an EAP-5G session, i.e. to start sending NAS messages encapsulated within EAP-5G packets. If the N3IWF has received a CERTREQ payload from the UE, the N3IWF shall include the CERT payload in the IKE_AUTH response message containing the N3IWF's certificate. How the UE uses the N3IWF's certificate is specified in TS 33.501 [15].
5. The UE shall send an IKE_AUTH request, which includes an EAP-Response/5G-NAS packet that contains the Access Network parameters (AN parameters) and a Registration Request message. The AN parameters contain information that is used by the N3IWF for selecting an AMF in the 5G core network. This information includes e.g. the GUAMI, the Selected PLMN ID (or PLMN ID and NID, see clause 5.30 of TS 23.501 [2]), the Requested NSSAI and the Establishment cause. The Establishment cause provides the reason for requesting a signalling connection with 5GC and the N3IWF may use the Establishment cause to determine the DSCP value on N2.. Whether and how the UE includes the Requested NSSAI as part of the AN parameters is dependent on the value of the Access Stratum Connection Establishment NSSAI Inclusion Mode parameter, as specified in clause 5.15.9 of TS 23.501 [2]. The registration request may contain an indication that the UE supports N3IWF selection based on the slices the UE wishes to use over untrusted non-3GPP access (i.e. that the UE supports Extended Home N3IWF identifier configuration and Slice-specific N3IWF prefix configuration). If at step 1 the UE selects the N3IWF based on Tracking/Location Area of same PLMN as described in clause 6.3.6 of TS 23.501 [2], the UE may include this TA in the last visited TAI in registration request in order to help the AMF to determine the target N3IWF as described in step 17. If the UE in SNPN access mode for NWu interface performs the Registration procedure for UE onboarding, the UE shall include an indication in the AN parameters that the connection request is for onboarding. The Registration Type "SNPN Onboarding" indicates that the UE wants to perform SNPN Onboarding Registration.
NOTE 3: The N3IWF does not send an EAP-Identity request because the UE includes its identity in the first IKE_AUTH. This is in line with RFC 7296 [3] clause 3.16.
6. The N3IWF shall select an AMF based on the received AN parameters and local policy, as specified in clause 6.3.5 of TS 23.501 [2]. The N3IWF shall then forward the Registration Request received from the UE to the selected AMF within an N2 message. This message contains N2 parameters that include the Selected PLMN ID and optionally the Selected NID and the Establishment cause.
NOTE 4: The Selected NID is present when the UE connects to an SNPN via Untrusted non-3GPP access.
7. The selected AMF may decide to request the SUCI by sending a NAS Identity Request message to UE. This NAS message and all subsequent NAS messages are sent to UE encapsulated within EAP/5G-NAS packets. The AMF may use the Establishment cause to determine the Message Priority header and then the DSCP value for subsequent signalling according to TS 29.500 [17].
8. The AMF may decide to authenticate the UE by invoking an AUSF. In this case, the AMF shall select an AUSF as specified in clause 6.3.4 of TS 23.501 [2] based on SUPI or SUCI.
The AUSF executes the authentication of the UE as specified in TS 33.501 [15]. The AUSF selects a UDM as described in clause 6.3.8 of TS 23.501 [2] and gets the authentication data from UDM. The authentication packets are encapsulated within NAS authentication messages and the NAS authentication messages are encapsulated within EAP/5G-NAS packets. After the successful authentication:
- In step 8h, the AUSF shall send the anchor key (SEAF key) to AMF which is used by AMF to derive NAS security keys and a security key for N3IWF (N3IWF key). The UE also derives the anchor key (SEAF key) and from that key it derives the NAS security keys and the security key for N3IWF (N3IWF key). The N3IWF key is used by the UE and N3IWF for establishing the IPsec Security Association (in step 11).
- In step 8h, the AUSF shall also include the SUPI, if in step 8a the AMF provided to AUSF a SUCI.
NOTE 5: EAP-AKA' or 5G-AKA are allowed for the authentication of UE via non-3GPP access, as specified in TS 33.501 [15]. Figure 4.12.2.2-1 only shows authentication flow using EAP-AKA'. Authentication methods other than EAP-AKA' or 5G-AKA are also allowed for UE accessing SNPN services via a PLMN, as specified in TS 33.501 [15], Annex I, as well as for UE accessing SNPN services directly via Untrusted non-3GPP access.
If the UE in SNPN access mode for NWu interface performs the Registration procedure for UE onboarding, the interaction between AMF and AUSF (step 8a, 8b, 8g and 8h in Figure 4.12.2.2-1) is replaced with step 9-1 or step 9-2 or step 9-3 in Figure 4.2.2.2.4-1, depending on the 5GC architecture that is used for UE onboarding.
9a. The AMF shall send a NAS Security Mode Command to UE in order to activate NAS security. If an EAP-AKA' authentication was successfully executed in step 8, the AMF shall encapsulate the EAP-Success received from AUSF within the NAS Security Mode Command message.
9b. The N3IWF shall forward the NAS Security Mode Command message to UE within an EAP/5G-NAS packet.
9c. The UE completes the EAP-AKA' authentication (if initiated in step 8), creates a NAS security context and an N3IWF key and sends the NAS Security Mode Complete message within an EAP/5G-NAS packet.
9d. The N3IWF relays the NAS Security Mode Complete message to the AMF.
10a. Upon receiving NAS Security Mode Complete, the AMF shall send an NGAP Initial Context Setup Request message that includes the N3IWF key.
10b. This triggers the N3IWF to send an EAP-Success to UE, which completes the EAP-5G session. No further EAP-5G packets are exchanged.
11. The IPsec SA is established between the UE and N3IWF by using the common N3IWF key that was created in the UE in step 9c and received by the N3IWF in step 10a. This IPsec SA is referred to as the "signalling IPsec SA". After the establishment of the signalling IPsec SA, the N3IWF notifies the AMF that the UE context (including AN security) was created by sending a NGAP Initial Context Setup Response. The signalling IPsec SA shall be configured to operate in tunnel mode and the N3IWF shall assign to UE:
a) an "inner" IP address; and
b) a NAS_IP_ADDRESS and a TCP port number.
The N3IWF may apply a DSCP value to this signalling IPsec SA, in which case all IP packets exchanged between the UE and N3IWF via the "signalling IPsec SA" shall be marked with this DSCP value. If the N3IWF has received an indication that the UE supports MOBIKE (see step 3), then the N3IWF shall include a Notify payload in the IKE_AUTH response message sent in step 11a, indicating that MOBIKE shall be supported, as specified in RFC 4555 [40].
NOTE 6: The DSCP value is determined by operator policy, and may e.g. be based on the DSCP value on N2.
All subsequent NAS messages exchanged between the UE and N3IWF shall be sent via the signalling IPsec SA and shall be carried over TCP/IP. The UE shall send NAS messages within TCP/IP packets with source address the "inner" IP address of the UE and destination address the NAS_IP_ADDRESS that is received in step 11a. The N3IWF shall send NAS messages within TCP/IP packets with source address the NAS_IP_ADDRESS and destination address the "inner" IP address of the UE. The TCP connection used for reliable NAS transport between the UE and N3IWF shall be initiated by the UE right after the signalling IPsec SA is established in step 11a. The UE shall send the TCP connection request to the NAS_IP_ADDRESS and to the TCP port number specified in TS 24.502 [41].
12. The AMF determines the allowed subset of the Requested NSSAI that is allowed by the Subscribed S-NSSAI(s); the AMF may detect that the N3IWF used by the UE is not compatible with this allowed subset and based on operator's policy configured in the AMF, the AMF determines whether a different N3IWF should be used. If the UE supports slice-based N3IWF selection and the AMF determines to use a different N3IWF, then the AMF proceeds with steps 15-19. Otherwise, i.e. if the AMF determines to use the selected N3IWF that supports part of the allowed subset, the AMF proceeds with steps 13 and 14. In this case, steps 15-19 are skipped.
NOTE 7: The AMF considers the subscribed S-NSSAI(s) before determining to trigger the UE PCF to avoid triggering the UE PCF to update the UE policies for Requested S-NSSAIs that the UE is not subscribed for.
13. The AMF sends the NAS Registration Accept message in an N2 message sent to the N3IWF. The N2 Message includes the Allowed NSSAI for the access type for the UE. The Allowed NSSAI is a subset of the slices supported by the selected N3IWF.
14. The N3IWF forwards the NAS Registration Accept message to UE via the established signalling IPsec SA. If the NAS Registration Accept message is received by the N3IWF before the IPsec SA is established, the N3IWF shall store it and forward it to the UE only after the establishment of the signalling IPsec SA.
14b. The AMF may trigger a UE policy association as described in clause 4.2.2.2.2 if a UE policy association does not exist yet. If the UE Registration Request contains an indication that the UE supports N3IWF selection based on the slices the UE wishes to use over untrusted non-3GPP access the AMF indicates to the PCF that the UE supports N3IWF selection based on the slices the UE wishes to use over untrusted non-3GPP access.
Steps 15 to 19 correspond to the case where the AMF has detected that the N3IWF used by the UE is not compatible with the subset of the requested NSSAI that is allowed by the subscribed S-NSSAI(s).
15. If the AMF is able to select a UE PCF that supports UE policies for slice specific N3IWF selection, the AMF may trigger UE policy association establishment if a suitable UE policy association does not exist yet. The AMF indicates to the PCF that the UE supports N3IWF selection based on the slices the UE wishes to use over untrusted non-3GPP access.
The AMF triggers the UE PCF to update the UE policies for slice specific N3IWF selection.
The AMF requests the PCF to receive a notification when the PCF has completed the update of these UE policies.
16. The PCF updates the UE policies for slice specific N3IWF selection per the procedure defined in figure 4.2.4.3-1. When the update of these UE policies is completed, the PCF notifies the AMF by invoking Npcf_UEPolicyControl_UpdateNotify.
17. The AMF sends via the N3IWF a UE Registration Reject indicating that the UE selected N3IWF was not appropriate for the requested slices that the UE is allowed to access to. The AMF optionally may provide target N3IWF information (FQDN and/or IP address) to the UE within the Registration Reject message.
NOTE 8: The AMF uses locally configured N3IWF information to provide target N3IWF information.
NOTE 9: The AMF may determine a target N3IWF that supports the subset of the requested NSSAI that is allowed by the subscribed S-NSSAI(s) based on the list of supported TAs and the corresponding list of supported slices for each TA obtained in N2 interface management procedures as specified in TS 38.413 [10]. To determine the target N3IWF, the AMF may take into account UE location corresponding to last visited TAI included in Registration Request as described at step 5 when the UE selects N3IWF based on Tracking/Location Area of same PLMN.
18. If supported by the UE and if the UE received target N3IWF information in step 17, the UE connects to the target N3IWF, otherwise the UE may perform N3IWF selection again using the updated N3IWF selection information received in step 16. The UE uses the target N3IWF information in the Registration Reject only for the N3IWF selection directly following the rejected registration and UE shall not store for future use.
The AMF provides the Access Type set to "Non-3GPP access" to the UDM when it registers with the UDM and the RAT type determined as specified in clause 5.3.2.3 of TS 23.501 [2].
NOTE 10: The Access Type and the RAT type are is set to "Untrusted Non-3GPP access" even when the UE accesses SNPN services via PLMN over 3GPP access. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.2.3 Emergency Registration for untrusted non-3GPP Access | Emergency Registration procedure is used by UEs requiring to perform emergency services but cannot gain normal services from the network. These UEs are in limited service state as defined in TS 23.122 [22].
The regular registration procedure described in clause 4.12.2 applies with the following differences:
- If the UE has no SUPI and no valid 5G-GUTI, PEI shall be included instead of its encrypted Permanent User ID (SUCI) in the NAS message.
- NSSAI shall not be included by the UE. The AMF shall not send the Allowed NSSAI in the Registration Accept message.
- If the AMF is not configured to support Emergency Registration, the AMF shall reject any Registration Request that indicates Registration type "Emergency Registration".
- If the AMF is configured to support Emergency Registration for unauthenticated UEs and the UE indicated Registration Type "Emergency Registration", the AMF skips the authentication and security setup or the AMF accepts that the authentication may fail and continues the Emergency Registration procedure.
- If the authentication is performed successfully, the NAS messages will be protected by the NAS security functions (integrity and ciphering). The AMF shall derive the N3IWF key, per TS 33.501 [15] and shall provide it to the N3IWF after the authentication completion using an NGAP Initial Context Setup Request message as in the regular registration procedure.
- If the authentication is skipped or authentication fails, the NAS messages will not be protected by the NAS security functions (integrity and ciphering). However, the AMF shall create an N3IWF key and shall provide it to the N3IWF after the authentication completion (whenever authentication has failed or has been skipped) using an NGAP Initial Context Setup Request message. The N3IWF shall use it to complete IKE SA establishment and shall acknowledge the AMF by sending an NGAP Initial Context Setup Response message.
NOTE: According to TS 33.501 [15], the UE and the AMF independently generate the KAMF (and derived keys) in an implementation defined way and populate the 5G NAS security context with this KAMF to be used when activating a 5G NAS security context."
- As in step 14 of figure 4.2.2.2.2-1 for Emergency Registration, if the UE was not successfully authenticated, the AMF shall not update the UDM. Also for an Emergency Registration, the AMF shall not check for access restrictions, regional restrictions or subscription restrictions.
- Steps 16 and 21b of figure 4.2.2.2.2-1 are not performed since AM and UE policy for the UE are not required for Emergency Registration. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.3 Deregistration procedure for untrusted non-3gpp access | Figure 4.12.3-1: Deregistration procedure for untrusted non-3gpp access
1. The Deregistration procedure is triggered by one of the events:
1a. For UE-initiated Deregistration as in steps from 1 to 7 of Figures 4.2.2.3.2-1.
1b. For network initiated deregistration as in steps from 1 to 6 of Figure 4.2.2.3.3-1.
If the UE is in CM-CONNECTED state either in 3GPP access, non-3GPP access or both,
- the AMF may explicitly deregister the UE by sending a Deregistration request message ( Deregistration type, access type set to non-3GPP) to the UE as in step 2 of Figure 4.2.2.3.3-1.
- the UDM may want to request the deletion of the subscribers RM contexts and PDU Sessions with the reason for removal set to subscription withdrawn to the registered AMF as in step 1 of Figure 4.2.2.3.3-1.
2. AMF to N3IWF: The AMF sends a N2 Context UE Release Command message to the N3IWF with the cause set to Deregistration to release N2 signalling as defined in step 4 of clause 4.12.4.2.
3. N3IWF to UE: The N3IWF sends INFORMATIONAL Request (Delete payload) message to the UE. The Delete payload is included to indicate the release of the IKE SA.
4. UE to N3IWF: The UE sends an empty INFORMATIONAL Response message to acknowledge the release of the IKE SA as described in RFC 7296 [3]. Non-3GPP access specific resources are released including the IKEv2 tunnel (and the associated IPsec resources) and the local UE contexts in N3IWF (N3 tunnel Id).
5. N3IWF to AMF: The N3IWF acknowledges the N2 UE Context Release Command message by sending N2 UE Context Release Complete message to the AMF as defined in step 7 of clause 4.12.4.2. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.4 N2 procedures via Untrusted non-3GPP Access | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.4.1 Service Request procedures via Untrusted non-3GPP Access | The Service Request procedure via Untrusted non-3GPP Access shall be used by a UE in CM-IDLE state over non-3GPP access to request the re-establishment of the NAS signalling connection and the re-establishment of the user plane for all or some of the PDU Sessions which are associated to non-3GPP access.
The Service Request procedure via Untrusted non-3GPP Access shall be used by a UE in CM-CONNECTED state over non-3GPP access to request the re-establishment of the user plane for one or more PDU Sessions which are associated to non-3GPP access.
When the UE is in CM-IDLE state over non-3GPP access, the Service Request procedure via Untrusted non-3GPP Access is as described in clause 4.2.3.2 (UE Triggered Service Request) with the following exceptions:
- The Service Request procedure is never a response to a Paging, i.e. there is no Network Triggered Service Request procedure via Untrusted non-3GPP Access.
- The (R)AN corresponds to an N3IWF.
- The UE establishes a "signalling IPsec SA" with the N3IWF by using the procedure specified in clause 4.12.2 for the registration via untrusted non-3GPP access. In particular, the UE includes the Service Request and the AN parameters in an EAP-5G packet, which is further encapsulated in an IKE_AUTH request.
- The AN parameters include the Selected PLMN ID (or PLMN ID and NID, see clause 5.30 of TS 23.501 [2]) and Establishment cause. The Establishment cause provides the reason for requesting a signalling connection with the 5GC. The UE includes GUAMI information in the AN parameters. The N3IWF selects the AMF according to GUAMI information.
- The N2 parameters sent from N3IWF to AMF include the Establishment cause.
- The user plane between the UE and N3IWF is established not with RRC signalling but with IKEv2 signalling, as specified in clause 4.12.5 (i.e. by using an IKEv2 Create_Child_SA exchange). The IKEv2 Create Child SA Request may include the Additional QoS Information to reserve non-3GPP specific QoS resources as defined in clause 4.12a.5. The user plane of each PDU Session consists of one or more Child SAs.
When the UE is in CM-CONNECTED state over non-3GPP access, the Service Request procedure via Untrusted non-3GPP Access is as described in clause 4.2.3.2 (UE Triggered Service Request) with the following exceptions:
- All NAS signalling exchanged between the UE and network is transferred within the established "signalling IPsec SA".
- The (R)AN corresponds to an N3IWF.
- The user plane between the UE and N3IWF is established not with RRC signalling but with IKEv2 signalling, as specified in clause 4.12.5 (i.e. by using an IKEv2 Create_Child_SA exchange). The user plane of each PDU Session consists of one or more Child SAs.
When the UE is in CM-CONNECTED state over non-3GPP access and the network receives downlink data for a PDU Session over non-3GPP access that has no user plane, the steps 1-4a in clause 4.2.3.3 (Network Triggered Service Request) shall be performed with the following exceptions:
- The (R)AN corresponds to an N3IWF.
- The user plane between the UE and N3IWF is established (in step 4a) with IKEv2 signalling, as specified in clause 4.12.5 (i.e. by using an IKEv2 Create_Child_SA exchange). The user plane of each PDU Session consists of one or more Child SAs. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.4.2 Procedure for the UE context release in the N3IWF | This procedure is used to release the N2 signalling connection and the N3 User Plane connection. If the procedure is initiated by the AMF the IKEv2 SA for a UE is being released. The procedure will move the UE from CM-CONNECTED to CM-IDLE in AMF and all UE related context information is deleted in the N3IWF.
Both N3IWF-initiated and AMF-initiated UE context release in the N3IWF procedures are shown in Figure 4.12.4.2-1.
Figure 4.12.4.2-1: Procedure for the UE context release in the N3IWF
1. The UE has already registered in the 5GC and may have established one or multiple PDU Sessions.
2. The N3IWF detects that the UE is not reachable.
3. The N3IWF sends a N2 UE Context Release Request message to the AMF This step is equivalent to step 1b of Figure 4.2.6-1.
NOTE: AN Release procedure can also be triggered by an AMF internal event and in that case step 2 and step 3 do not take place.
4. AMF to N3IWF: If the AMF receives the N2 UE Context Release Request from N3IWF or if due to an internal AMF event the AMF wants to release N2 signalling, the AMF sends an N2 UE Context Release Command (Cause) to the N3IWF. The cause indicated is cause from step 3 or a cause due to internal AMF event. This step is equivalent to step 2 of Figure 4.2.6-1.
5. If the IKEv2 tunnel has not been released yet, the N3IWF performs the release of the IPsec tunnel as defined in RFC 7296 [3] indicating to release the IKE SA and any Child IPsec SA if existing. The N3IWF sends to the UE the indication of the release reason if received in step 4.
6. The UE sends an empty INFORMATIONAL Response message to acknowledge the release of the IKE SA as described in RFC 7296 [3]. The N3IWF deletes the UE's context after receiving the empty INFORMATIONAL Response message.
7. N3IWF to AMF: The N3IWF confirms the release of the UE-associated N2-logical connection by returning N2 UE Release Complete (list of PDU Session ID(s) with active N3 user plane) to the AMF as in step 4 defined in clause 4.2.6. The AMF marks the UE as CM-IDLE state in untrusted non-3GPP access.
8. For each of the PDU Sessions in the N2 UE Context Release Complete, the steps 5 to 7 in clause 4.2.6 are performed (PDU Session Update SM Context). After the AMF receives the Nsmf_PDUSession_UpdateSMContext Response as in step 7 of clause 4.2.6, the AMF considers the N3 connection as released. If list of PDU Session ID(s) with active N3 user plane is included in step 3, then this step is performed before step 4. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.4.3 CN-initiated selective deactivation of UP connection of an existing PDU Session associated with Untrusted non-3GPP Access | The procedure described in clause 4.3.7 (CN-initiated selective deactivation of UP connection of an existing PDU Session) is used for CN-initiated selective deactivation of UP connection for an established PDU Session associated with non-3GPP Access of a UE in CM-CONNECTED state, with the following exceptions:
- The NG-RAN corresponds to an N3IWF.
- The user plane between the UE and N3IWF, i.e. Child SA(s) for the PDU Session, is released not with RRC signalling but with IKEv2 signalling, as specified in clause 4.12.7. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.5 UE Requested PDU Session Establishment via Untrusted non-3GPP Access | Clause 4.12.5 specifies how a UE can establish a PDU Session via an untrusted non-3GPP Access Network as well as to hand over an existing PDU Session between 3GPP access and non-3GPP access. The procedure applies in non-roaming, roaming with LBO as well as in home-routed roaming scenarios.
For non-roaming and LBO scenarios, if the UE is simultaneously registered to a 3GPP access in a PLMN different from the PLMN of the N3IWF, the functional entities in the following procedures are located in the PLMN of the N3IWF. For home-routed roaming scenarios, the AMF, V-SMF and associated UPF in VPLMN in the following procedure is located in the PLMN of the N3IWF.
The procedure below is based on the PDU Session Establishment procedure specified in clause 4.3.2.2.1 (for non-roaming and roaming with LBO) and the PDU Session Establishment procedure specified in clause 4.3.2.2.2 (for home-routed roaming).
Figure 4.12.5-1: PDU Session establishment via untrusted non-3GPP access
1. The UE shall send a PDU Session Establishment Request message to AMF as specified in step 1 of clause 4.3.2.2.1. This message shall be sent to N3IWF via the IPsec SA for NAS signalling (established as specified in clause 4.12.2) and the N3IWF shall transparently forward it to AMF in the 5GC.
2a. In the case of non-roaming or roaming with Local Breakout, steps 2-11 specified in clause 4.3.2.2.1are executed according to the PDU Session Establishment procedure over 3GPP access. In the case of home-routed roaming, steps 2-14 specified in clause 4.3.2.2.2 are executed according to the PDU Session Establishment procedure over 3GPP access.
2b. As described in step 12 of clause 4.3.2.2.1, the AMF shall send a N2 PDU Session Request message to N3IWF to establish the access resources for this PDU Session.
If L4S in untrusted non-3GPP access is supported and if applicable as per clause 5.37.3 of TS 23.501 [2], for a QoS flow.
NOTE: The SMF is assumed to have corresponding PCC rule(s) for the specific DNN and NSSAI associated with the L4S QoS flow for which ECN marking is expected.
3. Based on its own policies and configuration and based on the QoS profiles received in the previous step, the N3IWF shall determine the number of IPsec Child SAs to establish and the QoS profiles associated with each IPsec Child SA. For example, the N3IWF may decide to establish one IPsec Child SA and associate all QoS profiles with this IPsec Child SA. In this case, all QoS Flows of the PDU Session would be transferred over one IPsec Child SA. The N3IWF may bind the QoS Flow associated with PDU Set QoS parameters to an IPsec Child SA and no other QoS Flow is bound to this IPsec Child SA.
4a. The N3IWF shall send to UE an IKE Create_Child_SA request according to the IKEv2 specification in RFC 7296 [3] to establish the first IPsec Child SA for the PDU Session. The IKE Create_Child_SA request indicates that the requested IPsec Child SA shall operate in tunnel mode. This request shall include a 3GPP-specific Notify payload which contains (a) the QFI(s) associated with the Child SA, (b) the identity of the PDU Session associated with this Child SA, (c) optionally, a DSCP value associated with the Child SA, (d) optionally a Default Child SA indication and (e) optionally, the Additional QoS Information specified in clause 4.12a.5
The IKE Create_Child_SA request shall also include another 3GPP-specific Notify payload, which contains the UP_IP_ADDRESS that is specified in step 8 below.
If a DSCP value is included, then the UE and the N3IWF shall mark all IP packets sent over this Child SA with this DSCP value. There shall be one and only one Default Child SA per PDU session. The UE shall send all QoS Flows to this Child SA for which there is no mapping information to a specific Child SA. The IKE Create_Child_SA request also contains other information (according to RFC 7296 [3]) such as the SA payload, the Traffic Selectors (TS) for the N3IWF and the UE, etc.
After receiving the IKE Create_Child_SA request, if the Additional QoS Information is received, the UE may reserve non-3GPP Access Network resources according to the Additional QoS Information.
4b. If the UE accepts the new IPsec Child SA, the UE shall send an IKE Create_Child_SA response according to the IKEv2 specification in RFC 7296 [3]. During the IPsec Child SA establishment the UE shall not be assigned an IP address.
4c-4d. If in step 3 the N3IWF determined to establish multiple IPsec Child SAs for the PDU Session, then additional IPsec Child SAs shall be established, each one associated with one or more QFI(s), optionally with a DSCP value, with a UP_IP_ADDRESS and optionally with the Additional QoS Information specified in clause 4.12a.5. For each IPsec Child SA, if the Additional QoS Information is received, the UE may reserve non-3GPP Access Network resources according to the Additional QoS Information for the IPsec Child SA.
5. After all IPsec Child SAs are established, the N3IWF shall forward to UE via the signalling IPsec SA (see clause 4.12.2.2) the PDU Session Establishment Accept message received in step 2b.
6. The N3IWF shall send to AMF an N2 PDU Session Response.
7. In the case of non-roaming or roaming with Local Breakout, all steps specified in clause 4.3.2.2.1 after step 14 are executed according to the PDU Session Establishment procedure over 3GPP access. In the case of home-routed roaming, all steps specified in clause 4.3.2.2.2 after step 18 are executed according to the PDU Session Establishment procedure over 3GPP access.
8. On the user-plane:
- When the UE has to transmit an UL PDU, the UE shall determine the QFI associated with the UL PDU (by using the QoS rules of the PDU Session), it shall encapsulate the UL PDU inside a GRE packet and shall forward the GRE packet to N3IWF via the IPsec Child SA associated with this QFI. The header of the GRE packet carries the QFI associated with the UL PDU. The UE shall encapsulate the GRE packet into an IP packet with source address the "inner" IP address of the UE and destination address the UP_IP_ADDRESS associated with the Child SA.
- When the N3IWF receives a DL PDU via N3, the N3IWF uses the QFI and the identity of the PDU Session in order to determine the IPsec Child SA to use for sending the DL PDU over NWu. The N3IWF encapsulates the DL PDU inside a GRE packet and copies the QFI in the header of the GRE packet. The N3IWF may include also in the GRE header a Reflective QoS Indicator (RQI), which shall be used by the UE to enable reflective QoS. The N3IWF shall encapsulate the GRE packet into an IP packet with source address the UP_IP_ADDRESS associated with the Child SA and destination address the "inner" IP address of the UE. For QoS Flows that are configured for PDU Set handling, the N3IWF may, based on operator local configurations, use the PDU Set Importance received in the GTP-U header to determine the DSCP value for the DL packets.
NOTE: It is recommended that the used PDU Set Importance based transport level packet marking values only vary the drop precedence between PDUs in the transport network nodes (e.g. IP routers) on the NWu/NWt interfaces. This is needed to avoid causing packet reordering in the transport network when different DSCP marking values are used for a single QoS Flow.
- PDUs belonging to L4S-enabled QoS flow(s) may be transferred over dedicated IPsec Child SA(s). If a DSCP value is included, then the UE and the N3IWF shall mark all IP packets sent over this IPsec Child SA with this DSCP value. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.6 UE or Network Requested PDU Session Modification via Untrusted non-3GPP access | The UE or network requested PDU Session Modification procedure via untrusted non-3GPP access is depicted in figure 4.12.6-1. The procedure applies in non-roaming, roaming with LBO as well as in home-routed roaming scenarios.
For non-roaming and LBO scenarios, the functional entities in the following procedures are located in the PLMN of the N3IWF.
The procedure below is based on the PDU Session Modification procedure specified in clause 4.3.3.2 (for non-roaming and roaming with LBO) and on the PDU Session Modification procedure specified in clause 4.3.3.3 (for home-routed roaming).
Figure 4.12.6-1: UE or Network Requested PDU Session Modification via untrusted non-3GPP access
1. If the PDU Session Modification procedure is initiated by the UE, the UE shall send a PDU Session Modification Request message to AMF as specified in step 1 of clause 4.3.2.2. The message shall be sent to N3IWF via the established IPsec SA for NAS signalling. The N3IWF shall transparently forward the PDU Session Modification Request to AMF/SMF.
2. In the case of non-roaming or LBO, the steps 1a (from AMF) to 1e and steps 2-3 as per the PDU Session Modification procedure in clause 4.3.3.2 are executed.
In the case of home-routed, the steps 1a (from AMF) to 1d and steps 2-3 as per the PDU Session Modification procedure in clause 4.3.3.3 are executed.
3. The AMF sends N2 PDU Session Resource Modify Request (N2 SM information received from SMF, NAS message) message to the N3IWF. This step is the same as step 4 in clause 4.3.3.2 (for non-roaming and roaming with Local Breakout) and step 5 in clause 4.3.3.3 (for home-routed roaming).
If L4S in untrusted non-3GPP access is supported and if applicable as in clause 5.37.3 of TS 23.501 [2], for a QoS flow.
4. The N3IWF may issue IKEv2 signalling exchange with the UE that is related with the information received from SMF according to the IKEv2 specification in RFC 7296 [3]. Based on the N2 SM information received from the SMF, the N3IWF may perform one of the following:
4a. The N3IWF may decide to create a new Child SA for the new QoS Flow(s). The N3IWF may bind the QoS Flow associated with the PDU Set QoS parameters to an IPsec Child SA and no other QoS Flow is bound to this IPsec Child SA. In this case, the N3IWF establishes a new Child SA by sending an IKE_CREATE_CHILD_SA request message, which includes the SA, the PDU Session ID, the QFI(s), optionally a DSCP value and optionally the Additional QoS Information specified in clause 4.12a.5. If the Additional QoS Information is received, the UE may reserve non-3GPP Access Network resources according to the Additional QoS Information.
For each L4S-enabled QoS Flow, the N3IWF may establish a dedicated IPsec Child SA. If a DSCP value is included, then the UE and the N3IWF shall mark all IP packets sent over this IPsec Child SA with this DSCP value.
4b. The N3IWF may decide to add or remove QoS Flow(s) to/from an existing Child SA. In this case, the N3WIF updates the QoS Flow and Child SA mapping information by sending an INFORMATIONAL request message, which includes the QFI(s) associated with the Child SA and optionally the Additional QoS Information specified in clause 4.12a.6, which contains the new QoS information that should be associated with the existing Child SA. If the Additional QoS Information is received, the UE may update the reserved non-3GPP Access Network resources for the existing Child SA according to the Additional QoS Information.
4c. The N3IWF may decide to delete an existing Child SA, e.g. when there is no QoS Flow mapped to this Child SA. In this case, the N3IWF deletes the existing Child SA by sending INFORMATIONAL request message, which includes a Delete payload.
NOTE: If the N3IWF has included the Default Child SA indication during the establishment of one of the Child SAs of the PDU Session, the N3IWF may not update the mapping between QoS Flows Child SAs.
5. The N3IWF acknowledges N2 PDU Session Request by sending a N2 PDU Session Response Message to the AMF to acknowledge the success or failure of the request.
6. In the case of non-roaming or LBO, step 7 as per the PDU Session Modification procedure in clause 4.3.3.2 is executed. In the case of home-routed, the steps 8-10 as per the PDU Session Modification procedure in clause 4.3.3.3 are executed.
7. The N3IWF sends the PDU Session Modification Command to UE (if received in step 3) and receives the response message from UE.
Steps 4a/4c and step 7 may happen consecutively. Steps 7b map happen before step 4b/4d.
8. The N3IWF forwards the NAS message to the AMF.
9. For non-roaming and roaming with LBO, all the steps after step 10 in clause 4.3.3.2 are executed according to the general PDU Session Modification procedure. For home-routed roaming, all steps after step 13 in clause 4.3.3.3 are executed according to the general PDU Session Modification procedure. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.7 UE or network Requested PDU Session Release via Untrusted non-3GPP access | Clause 4.12.7 specifies how a UE or network can release a PDU Session via an untrusted non-3GPP Access Network. The UE requested PDU Session Release procedure via Untrusted non-3GPP access applies in non-roaming, roaming with LBO as well as in home-routed roaming scenarios.
For non-roaming and LBO scenarios, if the UE is simultaneously registered to a 3GPP access in a PLMN different from the PLMN of the N3IWF, the functional entities in the following procedures are located in the PLMN of the N3IWF. For home-routed roaming scenarios, the AMF, V-SMF and associated UPF in VPLMN in the following procedure is located in the PLMN of the N3IWF.
NOTE: If the UE is simultaneously registered to 3GPP access in the same PLMN as non-3GPP access, when non-3GPP access is not available to the UE (e.g. due to out of non-3GPP access coverage) or UE is in CM-IDLE for non-3GPP access, the UE may perform the PDU Session Release procedure via 3GPP access as described in clause 4.3.4.
Figure 4.12.7-1: UE Requested PDU Session Release via Untrusted non-3GPP access
1. One or more PDU Sessions are already established for the UE using the procedure described in clause 4.12.2.
2. The UE sends a NAS message (N1 SM container (PDU Session Release Request), PDU Session ID) to the AMF via the N3IWF as defined in clause 4.3.4.
3. For non-roaming and roaming with LBO, the steps 1a (from AMF) to 4 according to the PDU Session Release procedure defined in clause 4.3.4.2 are executed. For home-routed roaming, the steps 1a (from AMF) to step 7 according to the PDU Session Release procedure defined in clause 4.3.4.3 are executed.
4. This step is the same as step 4 in clause 4.3.4.2 (non-roaming and LBO) and step 6 in clause 4.3.4.3 (home-routed roaming).
If the message received from the SMF does not include N2 SM Resource Release request, the AMF sends N2 Downlink NAS transport (N1 SM container (PDU Session Release Command), PDU Session ID, Cause) message to the N3IWF and steps 5 to 8 are skipped.
5. Upon receiving AN session release request message from the AMF, the N3IWF triggers the release of the corresponding Child SA by sending INFORMATIONAL EXCHANGE (Delete Payload) to the UE. Delete payload is included in the message listing the SPIs of the Child SAs to be deleted to this PDU Session as described in RFC 7296 [3].
6. The UE responds with INFORMATIONAL EXCHANGE (Delete Payload) message. Delete payload is included for the paired SAs going in the other direction as described in RFC 7296 [3].
7. This step is the same as step 6 in 4.3.4.2 (non-roaming and LBO) and step 8 in clause 4.3.4.3 (home-routed roaming).
8. For non-roaming and roaming with LBO, steps 7 according to the PDU Session Release procedure defined in clause 4.3.4.2 are executed. For home-routed roaming, step 9-10 according to the PDU Session Release procedure defined in clause 4.3.4.3 are executed.
9. The N3IWF delivers the NAS message (N1 SM container (PDU Session Release Command), PDU Session ID, Cause) to the UE.
10. The UE sends a NAS message (N1 SM container (PDU Session Release Ack), PDU Session ID) to the N3IWF.
11. This step is the same as step 9 in 4.3.4.2 (non-roaming and LBO) and step 11 in clause 4.3.4.3 (home-routed roaming).
Steps 5 and 9 may happen consecutively. Step 10 may happen before step 6.
12. For non-roaming and roaming with LBO, all steps after step 10 in the PDU Session Release procedure defined in clause 4.3.4.2 are executed. In the case of home-routed roaming, all steps after step 12 in the PDU Session Release procedure defined in clause 4.3.4.3 are executed.
The network requested PDU Session Release procedure via Untrusted non-3GPP access is the same as the network requested PDU Session Release Procedure specified in clause 4.3.4.2 (for Non-Roaming and Roaming with Local Breakout) with the following differences:
- The (R)AN corresponds to an N3IWF.
- In step 5 the N3IWF upon receiving N2 SM request to release the AN resources associated with the PDU Session from the AMF, the N3IWF triggers the release of the corresponding Child SA to the UE as specified in step 5 and 6, in Figure 4.12.7-1.
- User Location Information is not included in the step 6, 7a, 9, 10a and 12 of the procedure. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.12.8 Mobility from a non-geographically selected AMF to a geographically selected AMF | This procedure describes the AMF change that takes place when an UE initially served via non-3GPP access by an AMF selected based on non-geographical criteria (e.g. because the UE had no 3GPP access coverage or because only non-geographically selectable N3IWF are deployed) gets 3GPP access and is now to be served by an AMF selected in the same PLMN by the NG-RAN based on geographical criteria.
Figure 4.12.8-1: Mobility from a non-geographically selected AMF to a geographically selected AMF
1. The UE registers over non-3GPP access, as described in clause 4.12.2. During this procedure:
a An AMF (source AMF) is selected by the N3IWF in step 6a, based on non-geographical criteria (e.g. because the UE has no 3GPP access coverage or because only non-geographically selectable N3IWF are deployed).
b The UE receives, within the Registration Accept message, a 5G-GUTI containing a GUAMI of the non-geographically selected AMF. The UE also receives an Allowed NSSAI and optionally Mapping Of Allowed NSSAI.
2. The UE may activate PDU Sessions over non-3GPP access, as described in clause 4.12.5.
3. The UE gets 3GPP access and issues a Registration Request over 3GPP access as defined in step 1 of Figure 4.2.2.2.2-1, providing its 5G-GUTI.
If the 5G-GUTI does not indicate an AMF of the same Region ID as that of the NG-RAN, the NG-RAN selects an AMF Set and an AMF in the AMF Set as described in clause 6.3.5 of TS 23.501 [2].
Steps 3 to 22 of Figure 4.2.2.2.2-1 take place including following aspects:
- step 4 of Figure 4.2.2.2.2-1 takes place i.e. the new AMF invokes the Namf_Communication_UEContextTransfer service operation on the old AMF to request the UE's SUPI and MM Context.
- in step 5 of Figure 4.2.2.2.2-1, the old AMF includes information about active NGAP association to N3IWF.
- in step 18 of Figure 4.2.2.2.2-1, the new AMF modifies the NGAP association toward N3IWF.
- in step 21 of Figure 4.2.2.2.2-1, the Registration Accept message shall include the updated 5G-GUTI that the UE will use to update its 3GPP and non-3GPP registration contexts.
4.12a Procedures for Trusted non-3GPP access
4.12a.1 General
Clause 4.12a defines the procedures to support trusted non-3GPP access by describing the differences compared to the defined procedures in other clauses.
4.12a.2 Registration via Trusted non-3GPP Access
4.12a.2.1 General
Clause 4.12a.2 specifies how a UE can register to 5GC via a trusted non-3GPP Access Network. The utilized procedure is very similar with the 5GC registration procedure over untrusted non-3GPP access in clause 4.12.2.2 and it is based on the Registration procedure specified in clause 4.2.2.2.2. It uses the same vendor-specific EAP method (called "EAP-5G") as the one specified in clause 4.12.2.1. In this case, the "EAP-5G" method is used between the UE and the TNGF and is utilized for encapsulating NAS messages.
In Registration and subsequent Registration procedures via trusted non-3GPP access, the NAS messages are always exchanged between the UE and the AMF. When possible, the UE can be authenticated by reusing the existing UE security context in AMF.
4.12a.2.2 Registration procedure for trusted non-3GPP access
The UE connects to a trusted non-3GPP Access Network (TNAN) and it also registers to 5GC over via this TNAN, by using the EAP-based procedure shown in the figure 4.12a.2.2. This procedure is very similar with the 5GC registration procedure over untrusted non-3GPP access in clause 4.12.2.2. The link between the UE and the TNAN can be any data link (L2) that supports EAP encapsulation, e.g. PPP, PANA, Ethernet, IEEE 802.3, IEEE 802.11, etc. The interface between the TNAP and TNGF is an AAA interface.
Figure 4.12a.2.2-1: Registration via trusted non-3GPP access
0. The UE which is not operating in SNPN access mode for Yt interface selects a PLMN and a TNAN for connecting to this PLMN by using the Trusted Non-3GPP Access Network selection procedure specified in clause 6.3.12 of TS 23.501 [2]. During this procedure, the UE discovers the PLMNs with which the TNAN supports trusted connectivity (e.g. "5G connectivity").
The UE operating in SNPN access mode for Yt interface selects an SNPN and a TNAN for connecting to this SNPN by using the Trusted Non-3GPP Access Network selection procedure specified in clause 5.30.2.13 of TS 23.501 [2]. During this procedure, the UE discovers the SNPNs with which the TNAN supports trusted connectivity (e.g. "5G connectivity").
NOTE 1: In this Release, it is assumed that when the trusted non-3GPP access is a trusted WLAN access, the UE is configured (e.g. with the WLANSP rules defined in TS 23.503 [20]) to select an TNAN(SSID and TNGF) associated with a non-3GPP Tracking Area, which supports one or more of the UE's subscribed S-NSSAIs.
1. A layer-2 connection is established between the UE and the TNAP. In the case of IEEE Std 802.11 [48], this step corresponds to an 802.11 Association. In the case of PPP, this step corresponds to a PPP LCP negotiation. In other types of non-3GPP access (e.g. Ethernet), this step may not be required.
2-3. An EAP procedure is initiated. EAP messages are encapsulated into layer-2 packets, e.g. into IEEE 802.3/802.1x packets, into IEEE 802.11/802.1x packets, into PPP packets, etc. The NAI provided by the UE not operating in SNPN access mode for Yt interface indicates that the UE requests "5G connectivity" to a specific PLMN and is defined in clause 28.7.6 of TS 23.003 [33]. In the case of WLAN access, if the UE has an MPS subscription, the UE shall also include an indication of its MPS subscription in the username part of the NAI as per TS 23.003 [33]. The NAI provided by the UE operating in SNPN access mode for Yt interface indicates that the UE request "5G connectivity" to a specific SNPN and is defined in clause 28.7.6 of TS 23.003 [33]. If the WLANSP rule contains information including TNGF ID to use for specific slices and the UE supports such information, the UE builds the realm of NAI taking the TNGF ID into account. This NAI is defined in clause 28.7.6 of TS 23.003 [33] and triggers the TNAP to send an AAA request to a TNGF, which operates as an AAA proxy.
Between the TNAP and TNGF the EAP packets are encapsulated into AAA messages. The AAA request also include the TNAP identifier, which can be treated as the User Location Information defined in clause 5.6.2 of TS 23.501 [2]. In order to support usage of the TNAP identifier defined in TS 23.316 [53], when a 5G-RG acts as a TNAP , the W-5GAN may, as defined in clause 5.6.2 of TS 23.501 [2], provide the 5G RG civic address information in the TNAP identifier.
NOTE 2: In this Release, it is assumed that when the trusted non-3GPP access is a trusted WLAN access, the TNAP selects a TNGF based on the realm (e.g. MCC, MNC and TNGF ID) provided by the UE and also based on the SSID selected by the UE. In a deployment a TNGF may be reached over different SSID(s) where the TNGF supports a Tracking Area and be associated with a set of slices, or an SSID may provide access to one or more TNGF(s), where each of these TNGF(s) can support a different Tracking Area and a different set of slices.
NOTE 3: Based on operator policy, after receiving the indication of MPS subscription from the UE, the TNAN can treat this UE with priority.
4-10. An EAP-5G procedure is executed as the one specified in clause 4.12.2.2 for the untrusted non-3GPP access with the following modifications:
- The registration request may contain an indication that the UE supports TNGF selection based on the slices the UE wishes to use over trusted non-3GPP access (i.e. that the UE supports Extended WLANSP rule).
- A TNGF key (instead of an N3IWF key) is created in the UE and in the AMF after the successful authentication. The TNGF key is transferred from the AMF to TNGF in step 10a (within the N2 Initial Context Setup Request). The TNGF derives a TNAP key, which is provided to the TNAP. The TNAP key depends on the non-3GPP access technology (e.g. it is a Pairwise Master Key in the case of IEEE Std 802.11 [48]). How these security keys are created, it is specified in TS 33.501 [15].
- In step 5 the UE shall include the Requested NSSAI in the AN parameters only if allowed, according to the conditions defined in clause 5.15.9 of TS 23.501 [2], for the trusted non-3GPP access. The UE shall also include a UE Id in the AN parameters, e.g. a 5G-GUTI if available from a prior registration to the same PLMN or SNPN. If the UE in SNPN access mode for Yt interface performs the Registration procedure for UE onboarding, the UE shall include an indication in the AN parameters that the connection request is for onboarding.
- In the N2 message sent in step 6b, the TNGF includes a UE Location Information (ULI)including the TNAP ID and the UE IP address based on information received in step 3. If the ULI includes the IP address, this is set to a "null" IP address (e.g. 0.0.0.0) because the UE is not yet assigned an IP address. If the TNGF has received the TNAP ID in step 3 over Ta, the TNGF includes the TNAP ID within UE Location Information (ULI) sent to AMF. After the UE is assigned an IP address, the TNGF includes this address in subsequent N2 messages. This N2 message also includes the Selected PLMN ID and optionally the Selected NID and the Establishment cause.
NOTE 4: The Selected NID is present when the UE connects to an SNPN via Trusted non-3GPP access.
- If the UE in SNPN access mode for Yt interface performs the Registration procedure for UE onboarding, the interaction between AMF and AUSF (step 8a and step 8c in Figure 4.12a.2.2-1) is replaced with step 9-1 or step 9-2 or step 9-3 in Figure 4.2.2.2.4-1, depending on the 5GC architecture that is used for UE onboarding.
- After receiving the TNGF key from AMF in step 10a, the TNGF shall send to UE an EAP-Request/5G-Notification packet containing the "TNGF Contact Info", which includes the IP address of TNGF. After receiving an EAP-Response/5G-Notification packet from the UE in step 10c, the TNGF shall send message 10d containing the EAP-Success packet.
11. The TNAP key is used to establish layer-2 security between the UE and TNAP. In the case of IEEE Std 802.11 [48], a 4-way handshake is executed, which establishes a security context between the WLAN AP and the UE that is used to protect unicast and multicast traffic over the air.
12. The UE receives IP configuration from the TNAN, e.g. with DHCP.
13. At this point, the UE has successfully connected to the TNAN and has obtained IP configuration. The UE sets up a secure NWt connection with the TNGF as follows:
The UE initiates an IKE_INIT exchange using the IP address of TNGF received during the EAP-5G signalling, in step 10b. Subsequently, the UE initiates an IKE_AUTH exchange and provides its identity. The identity provided by the UE in the IKEv2 signalling should be the same as the UE Id included in the AN parameters in step 5. This enables the TNGF to locate the TNGF key that was created before for this UE, during the authentication in step 8. The TNGF key is used for mutual authentication. NULL encryption is negotiated between the UE and the TNGF, as specified in RFC 2410 [49].
In step 13c, the TNGF provides to UE (a) an "inner" IP address, (b) a NAS_IP_ADDRESS and a TCP port number and (c) a DSCP value. After this step, an IPsec SA is established between the UE and TNGF. This is referred to as the "signalling IPsec SA" and operates in Tunnel mode. Operation in Tunnel mode enables the use of MOBIKE [40] for re-establishing the IPsec SAs when the IP address of the UE changes during mobility events. All IP packets exchanged between the UE and TNGF via the "signalling IPsec SA" shall be marked with the above DSCP value. The UE and the TNAP may map the DSCP value to a QoS level (e.g. to an EDCA Access Class [48]) supported by the underlying non-3GPP Access Network. The mapping of a DSCP value to a QoS level of the non-3GPP Access Network is outside the scope of 3GPP.
Right after the establishment of the "signalling IPsec SA", the UE shall setup a TCP connection with the TNGF by using the NAS_IP_ADDRESS and the TCP port number received in step 13c. The UE shall send NAS messages within TCP/IP packets with source address the "inner" IP address of the UE and destination address the NAS_IP_ADDRESS. The TNGF shall send NAS messages within TCP/IP packets with source address the NAS_IP_ADDRESS and destination address the "inner" IP address of the UE.
This concludes the setup of the NWt connection between the UE and the TNGF. All subsequent NAS messages between UE and TNGF are carried over this NWt connection (i.e. encapsulated in TCP/IP/ESP).
14. After the NWt connection is successfully established, the TNGF responds to AMF with an N2 Initial Context Setup Response message.
15. The AMF determines the allowed subset of the Requested NSSAI that is allowed by the Subscribed S-NSSAI(s); the AMF may detect that the TNGF used by the UE is not compatible with this allowed subset and based on operator's policy configured in the AMF, the AMF determines whether a different TNGF should be used. If the UE supports slice-based TNGF selection and the AMF determines to use a different TNGF, then the AMF proceeds with steps 17-21. Otherwise, i.e. if the AMF determines to use the selected TNGF that supports part of allowed the subset, the AMF proceeds with step 16. In this case, steps 17-21 are skipped.
NOTE 5: The criteria for the AMF to determine that the TNGF used by the UE is not compatible with the subset of the requested NSSAI that is allowed by the subscribed S-NSSAI(s) is based on local AMF policies. For example the AMF can determine that the TNGF used by the UE is compatible as soon as there is one supported slice in common.
16a-16b. The NAS Registration Accept message is sent by the AMF and is forwarded to UE via the established NWt connection. Now the UE can use the TNAN (a) to transfer non-seamless offload traffic and (b) to establish one or more PDU Sessions.
16c. The AMF may trigger a UE policy association as described in clause 4.2.2.2.2 if a UE policy association does not exist yet. If the UE Registration Request contains an indication that the UE supports TNGF selection based on the slices the UE wishes to use over untrusted non-3GPP access the AMF indicates to the PCF that the UE supports TNGF selection based on the slices the UE wishes to use over trusted non-3GPP access.
Steps 17 to 21 correspond to the case where the AMF has detected that TNGF used by the UE is not compatible with the subset of the requested NSSAI that is allowed by the subscribed S-NSSAI(s).
17. If the AMF is able to select a UE PCF that supports UE policies for slice specific trusted access selection, the AMF may trigger UE policy association establishment if a suitable UE policy association does not exist yet. The AMF indicates to the PCF that the UE supports TNGF selection based on the slices the UE wishes to use over trusted non-3GPP access.
The AMF triggers the UE PCF to update the UE policies for slice specific trusted access selection.
The AMF requests the PCF to receive a notification when the PCF has completed the update of these UE policies.
18. The PCF updates the UE policies for slice specific trusted access selection according to the procedure defined in figure 4.2.4.3-1.
19. When the update of these policies is completed, the PCF notifies the AMF by invoking Npcf_UEPolicyControl_UpdateNotify.
20. The AMF sends via the TNGF a UE Registration Reject indicating that the selected TNGF was not appropriate for the requested slices that the UE is allowed to access to. The AMF may provide target TNAN information (SSID, TNGF ID) to the UE within the Registration Reject message indicating the UE to build the NAI based on the TNGF ID.
NOTE 6: The AMF may determine a target TNGF that supports the subset of the requested NSSAI that is allowed by the subscribed S-NSSAI(s) based on the list of supported TAs and the corresponding list of supported slices for each TA obtained in N2 interface management procedures as specified in TS 38.413 [10] and considering UE location.
21. If supported by the UE and if the UE received target TNAN information in step 20, the UE connects to the target TNAN, otherwise the UE may perform TNAN selection again using the updated WLANSP rule received in step 18. If the target TNAN information includes TNGF ID, the UE shall build the NAI based on TNGF ID. The UE uses the target TNAN information in the Registration Reject only for the TNAN selection directly following the rejected registration and UE shall not store it for future use.
4.12a.2.3 Emergency Registration for trusted non-3GPP Access
Emergency Registration procedure for trusted non-3GPP access shall be supported as specified in clause 4.12.2.3 for untrusted non-3GPP access with the following differences:
- The regular registration shall refer to clause 4.12a.2.
- The N3IWF is substituted by the TNGF.
- The N3IWF key is substituted by the TNGF key.
4.12a.3 Deregistration procedure for Trusted non-3GPP access
The Deregistration procedure via trusted non-3GPP access shall be supported as specified in clause 4.12.3 for the untrusted non-3GPP access with the following modifications:
- The untrusted non-3GPP access is substituted by a trusted non-3GPP access point (TNAP).
- The N3IWF is substituted by the TNGF.
- If the UE has reserved QoS resources over non-3GPP access by using the Additional QoS Information (specified in clause 4.12a.5), then the UE shall release these resources.
4.12a.4 N2 procedures via Trusted non-3GPP Access
4.12a.4.1 Service Request procedures via Trusted non-3GPP Access
The Service Request procedure via trusted non-3GPP access shall be supported as specified in clause 4.12.4.1 for the untrusted non-3GPP access with the following modifications:
- The untrusted non-3GPP access is substituted by a trusted non-3GPP access.
- The N3IWF is substituted by the TNGF.
- The user plane between the UE and TNGF is established with IKEv2 signalling, as specified in clause 4.12a.5 (i.e. by using an IKEv2 Create_Child_SA exchange). The IKEv2 Create Child SA Request shall include the Additional QoS Information to reserve non-3GPP specific QoS resources as defined in clause 4.12a.5.
4.12a.4.2 Procedure for the UE context release in the TNGF
This procedure for releasing the N2 signalling connection and the N3 user plane connection for a UE connected to 5GC via trusted non-3GPP access, shall be the same as the procedure specified in clause 4.12.4.2 for the untrusted non-3GPP access with the following modifications:
- The untrusted non-3GPP access is substituted by a trusted non-3GPP access point (TNAP).
- The N3IWF is substituted by the TNGF.
- If the UE has reserved any non-3GPP specific QoS resources, the UE releases these resources when the IKEv2 Child SA is released.
4.12a.4.3 CN-initiated selective deactivation of UP connection of an existing PDU Session associated with Trusted non-3GPP Access
The procedure described in clause 4.3.7 (CN-initiated selective deactivation of UP connection of an existing PDU Session) is used for CN-initiated selective deactivation of UP connection for an established PDU Session associated with trusted non-3GPP Access for a UE in CM-CONNECTED state, with the following exceptions:
- The NG-RAN corresponds to a TNAN including a TNGF.
- The user plane between the UE and TNGF, i.e. Child SA(s) for the PDU Session, is released not with RRC signalling but with IKEv2 signalling, as specified in clause 4.12a.7.
- If the UE has reserved any non-3GPP specific QoS resources, the UE releases these resources when the IKEv2 Child SA is released.
4.12a.5 UE Requested PDU Session Establishment via Trusted non-3GPP Access
After the UE registers to 5GC via trusted non-3GPP access, the UE may request a PDU Session establishment by using the same procedure as the one specified in clause 4.12.5 for untrusted non-3GPP access, with the following modifications:
- The N3IWF in Figure 4.12.5-1 should be substituted with a TNGF and the Untrusted non-3GPP access should be substituted with a Trusted non-3GPP Access Point (TNAP).
- The TNGF may send a TNGF Identities parameter to AMF inside an N2 Uplink NAS Transport message. The TNGF Identities parameter contains a list of identifiers (i.e. FQDNs or IP addresses) of N3 terminations supported by the TNGF. If received by the AMF, it shall forward it to the SMF, which may use it as input to UPF selection. The AMF provides ULI information received from TNGF to the SMF which then propagates it to the PCF.
- If the L4S in trusted non-3GPP access is supported and if applicable as in clause 5.37.3 of TS 23.501 [2], for a QoS flow.
NOTE 1: The SMF is assumed to have corresponding PCC rule(s) for the specific DNN and S-NSSAI associated with the L4S QoS flow(s) for which ECN marking is expected.
- The IKEv2 Create Child SA Request message that is sent by the TNGF to UE (in steps 4a and 4c), in order to establish a child SA for one or more QoS flows, shall also include Additional QoS Information. The Additional QoS Information shall contain:
a) If the IPsec child SA carries a GBR flow: QoS Characteristics and GBR QoS Flow Information:
- The QoS Characteristics are associated with the 5QI of the GBR flow and are defined in clause 5.7.3 of TS 23.501 [2]. The TNGF either receives the QoS Characteristics via the N2 interface (in the case of a dynamically assigned 5QI), or is pre-configured with the QoS Characteristics (in the case of a standardized 5QI).
- The GBR QoS Flow Information (defined in TS 38.413 [10]) is part of the QoS Profile received via the N2 interface and contains: MFBR, GFBR and optionally Maximum Packet Loss Rate. The Notification Control is not included in the QoS profile.
b) If the IPsec child SA carries a non-GBR flow: QoS Characteristics:
- The QoS Characteristics are defined in bullet a) above.
The TNGF may aggregate multiple GBR flows or multiple non-GBR flows into the same IPsec child SA. In this case, the TNGF derives, in an implementation specific way, the QoS Characteristics of the aggregated flow by considering the QoS Characteristics of the individual flows. Similarly, the TNGF derives, in an implementation specific way, the GBR QoS Flow Information of an aggregated GBR flow by considering the GBR QoS Flow Information of the individual GBR flows.
NOTE 2: The above behaviour of the TNGF does not create any impact on the N2 interface.
- After receiving an IKEv2 Create Child SA Request message, the UE shall use the Additional QoS Information contained in this message to determine what QoS resources to reserve over the non-3GPP access, including e.g. guaranteed bit rates and delay bounds for UL/DL communication. How the UE determines what QoS resources to reserve over the non-3GPP access and how these QoS resources are reserved, is outside the scope of 3GPP specifications.
- For each L4S-enabled QoS Flow, the TNGF may establish a dedicated IPsec Child SA. If a DSCP value is included, then the UE and the TNGF shall mark all IP packets sent over this Child SA with this DSCP value.
- If the UE fails to reserve QoS resources over non-3GPP access for the QoS flows associated with the child SA (e.g. because the non-3GPP Access Network rejects the allocation of the requested bit rates), the UE shall reject the IKEv2 Child SA Request. Based on operator policy, the network may reattempt to establish the Child SA without the Additional QoS Information.
4.12a.6 UE or network Requested PDU Session Modification via Trusted non-3GPP access
The UE or network requested PDU Session Modification procedure via trusted non-3GPP access is the same procedure as the one specified in clause 4.12.6 for untrusted non-3GPP access, with the following modifications:
- The N3IWF in Figure 4.12.6-1 should be substituted with a TNGF and the Untrusted non-3GPP access should be substituted with a Trusted non-3GPP Access Point (TNAP).
If the L4S in trusted non-3GPP access is supported and if applicable as in clause 5.37.3 of TS 23.501 [2], for a QoS flow.
- The IKEv2 Create Child SA Request sent by the TNGF in step 4a, in order to create new QoS flow(s) for the PDU Session, shall include the Additional QoS Information defined in clause 4.12a.5. If the UE decides to reserve QoS resources over non-3GPP access for the QoS flows associated with the Child SA but fails to reserve these resources, the UE shall reject the IKEv2 Child SA Request. Based on operator policy, the network may reattempt to establish the Child SA without the Additional QoS Information.
For each L4S-enabled QoS Flow, the TNGF may establish a dedicated IPsec Child SA. If a DSCP value is included, then the UE and the TNGF shall mark all IP packets sent over this Child SA with this DSCP value.
- The IKEv2 Informational Request sent by the TNGF in step 4b shall include the Additional QoS Information defined in clause 4.12a.5, when the IKEv2 Informational Request is sent to modify one or more existing QoS flows. If the UE decides to reserve QoS resources over non-3GPP access for the QoS flows associated with the Child SA but fails to reserve these resources, the UE shall indicate the failure in the IKEv2 Informational Response. The TNGF includes the list of QoS flows which are failed to setup in step 5. Based on operator policy, the network may reattempt to modify the failed QoS Flows without the Additional QoS Information.
- The IKEv2 Informational Request sent by the TNGF in step 4c to release an existing IKEv2 Child SA shall trigger the UE to release the resources reserved over non-3GPP access for this IKEv2 Child SA.
- If, after the PDU Session establishment, the UE determines that the QoS resources reserved over non-3GPP access for the QoS flows associated with a Child SA are released, then the UE shall initiate an INFORMATIONAL exchange, as specified in RFC 7296 [3], to delete the Child SA. After the Child SA is deleted, the TNGF initiates PDU Session Modification procedure as described in step 1e, in clause 4.3.3.2, including the list of QoS flows, which are released.
4.12a.7 UE or network Requested PDU Session Release via Trusted non-3GPP access
The UE or the network can release a PDU Session via a trusted non-3GPP Access Network as specified in clause 4.12.7 for the untrusted non-3GPP access with the following modifications:
- The untrusted non-3GPP access is substituted by a trusted non-3GPP access point (TNAP).
- The N3IWF is substituted by the TNGF.
- If the UE reserved any non-3GPP specific QoS resources, the UE releases these resources when the IKEv2 Child SA is released.
4.12a.8 Mobility from a non-geographically selected AMF to a geographically selected AMF
The procedure specified in clause 4.12.8 for untrusted non-3GPP access applies also to the trusted non-3GPP access with the following modifications:
- The untrusted non-3GPP access is substituted by a trusted non-3GPP access point (TNAP).
- The N3IWF is substituted by the TNGF.
- The PDU Session is activated in step 2 as specified in clause 4.12a.5.
4.12a.9 Support of mobility from source to target TNAP
If the UE moves from a source TNAP to a target TNAP, the UE shall perform a full authentication via the target TNAP to re-connect to the 5G system unless the UE and the network support the mechanism defined in clause 7A.2.1.2 of TS 33.501 [15].
4.12b Procedures for devices that do not support 5GC NAS over WLAN access
4.12b.1 General
As specified in clause 4.2.8.5 of TS 23.501 [2], devices that do not support 5GC NAS signalling over WLAN access (referred to as "Non-5G-Capable over WLAN" devices, or N5CW devices for short), may access 5GC in a PLMN or an SNPN via a trusted WLAN Access Network that supports a Trusted WLAN Interworking Function (TWIF). The following clause specifies how a N5CW device can be registered to 5GC and how it can send data via a PDU Session.
A N5CW device may be 5G-capable over 3GPP access, in which case it is also a 5G UE over 3GPP access.
4.12b.2 Initial Registration & PDU Session Establishment
Figure 4.12b.2-1 illustrates how the N5CW device can connect to a trusted WLAN Access Network and simultaneously register to a 5G core network. A single EAP-based authentication procedure is executed for connecting the N5CW device to the trusted WLAN Access Network and for registering the N5CW device to the 5G core network.
Figure 4.12b.2-1: Initial registration and PDU session establishment
0. The N5CW device selects a PLMN (or SNPN) and a trusted WLAN that supports "5G connectivity-without-NAS" to this PLMN (or SNPN) by using the procedure specified in clause 6.3.12a and clause 5.30.2.15 of TS 23.501 [2] for access to PLMN and SNPN, respectively.
Steps 1-10: Initial registration to 5GC.
1. The N5CW device associates with the selected trusted WLAN and the EAP authentication procedure is initiated.
2. The N5CW device provides its Network Access Identity (NAI). The Trusted WLAN Access Point (TWAP) selects a Trusted WLAN Interworking Function (TWIF), e.g. based on the received realm and sends an AAA request to the selected TWIF.
If the N5CW device has not registered over 3GPP access to 5GC of the selected PLMN or SNPN when the above procedure is initiated, then the NAI includes the SUCI as specified in clause 28.7.7 of TS 23.003 [33]. For example, when accessing a PLMN the NAI can have the following format: NAI=type1.rid678.schid0.useriduser17@nai.5gc-nn.mnc<MNC>.mcc<MCC>.3gppnetwork.org. If the selected PLMN is VPLMN, the N5CW device should use the decorated NAI format as specified in clause 28.7.9 of TS 23.003 [33] to indicate to TWAN which is the selected VPLMN, for example, NAI=nai.5gc-nn.mnc<MNC_Home>.mcc<MCC_Home>.3gppnetwork.org!type1.rid678.schid0.useriduser17@nai.5gc-nn.mnc<MNC_visited>.mcc<MCC_visited>.3gppnetwork.org.
If the N5CW device has registered to 5GC over 3GPP access to 5GC of the selected PLMN or SNPN (i.e. it is also a 5G UE) when the above procedure is initiated, then the NAI includes the 5G-GUTI assigned to N5CW device over 3GPP access. This enables the TWIF in step 4a below to select the same AMF as the one serving the N5CW device over 3GPP access.
If the N5CW device accesses to SNPN with the credentials owned by Credentials Holder, the decorated NAI as specified in clause 28.7.9 of TS 23.003 [33] should be provided. For example, NAI=nai.5gc-nn.nid<NID_Home>.mnc<MNC_Home>.mcc<MCC_Home>.3gppnetwork.org!type1.rid678.schid0.useriduser17@nai.5gc-nn.nid<NID_visited>.mnc<MNC_visited>.mcc<MCC_visited>.3gppnetwork.org.
The NAI provided by the N5CW device in step 2b indicates that the N5CW device wants "5G connectivity-without-NAS" towards a specific PLMN or SNPN (i.e. the PLMN or SNPN selected in step 0). For example, when accessing a PLMN, the NAI can have the following format: NAI=<5G-GUTI>@nai.5gc-nn.mnc<MNC>.mcc<MCC>.3gppnetwork.org or NAI=nai.5gc-nn.mnc<MNC_Home>.mcc<MCC_Home>.3gppnetwork.org!type1.rid678.schid0.useriduser17@nai.5gc-nn.mnc<MNC_visited>.mcc<MCC_visited>.3gppnetwork.org, the N5CW device indicating that it wants "5G connectivity-without-NAS" (5gc-nn) to the PLMN with MCC=<MCC> and MNC=<MNC> and to the PLMN with MCC=<MCC_visited> and MNC=<MNC_visited>.
3. The TWIF creates a 5GC Registration Request message on behalf of the N5CW device. The TWIF uses default values to populate the parameters in the Registration Request message, which are the same for all N5CW devices. The Registration type indicates "Initial Registration".
If the TWIF receives a Decorated NAI, in Registration Request message the TWIF send the NAI which corresponds to the HPLMN by removing the decoration, for example NAI=type1.rid678.schid0.useriduser17@ nai.5gc-nn.mnc<MNC_Home>.mcc<MCC_Home>.3gppnetwork.org.
4. The TWIF selects an AMF by using the 5G-GUTI in the NAI, or selects the AMF of the VPLMN indicates by the realm of the decoration in the Decorated NAI, for example "mnc<MNC_visited>.mcc<MCC_visited>.3gppnetwork.org" or selects the AMF by using the local configuration. TWIF sends an N2 message to the AMF including the Registration Request, the User Location and an AN Type.
If the N5CW device provides a Decorated NAI to the TWIF, the TWIF shall select the AMF in the visited PLMN/SNPN as per decoration part and remove the decoration part from the Decorated NAI (i.e. change the format to NAI format of SUCI as defined in clause 28.7.7 of TS 23.003 [33]) and provides it to AMF in the Registration Request. For example, if the NAI is "nai.5gc-nn.nid<NID_Home>.mnc<MNC_Home>.mcc<MCC_Home>.3gppnetwork.org!type1.rid678.schid0.useriduser17@nai.5gc-nn.nid<NID_visited>.mnc<MNC_visited>.mcc<MCC_visited>.3gppnetwork.org.", the TWIF selects the AMF in the SNPN corresponding to "nai.5gc-nn.nid<NID_visited>.mnc<MNC_visited>.mcc<MCC_visited>.3gppnetwork.org." and provides the AMF in the Registration Request with the NAI of "type1.rid678.schid0.useriduser17@ nai.5gc-nn.nid<NID_Home>.mnc<MNC_Home>.mcc<MCC_Home>.3gppnetwork.org".
5. The AMF triggers an authentication procedure by sending a request to AUSF indicating the AN type.
6. An EAP authentication procedure takes place between the N5CW device and AUSF. Over the N2 interface, the EAP messages are encapsulated within NAS Authentication messages. The type of EAP authentication procedure is specified in TS 33.501 [15].
NOTE: The SUPI used for authentication does not take the format of Decorated NAI.
7. After a successful authentication, the AUSF sends to AMF the EAP-Success message and the created SEAF key. The AMF derives an AN key from the received SEAF key.
8. The NAS Security Mode Command (SMC) is sent from the AMF to the TWIF. The selected NAS security algorithms of integrity protection and ciphering are set to NULL.
9. The AMF sends an N2 Initial Context Setup Request and provides the AN key to TWIF. In turn, the TWIF derives a Pairwise Master Key (PMK) from the AN key and sends the PMK key and the EAP-Success message to the Trusted WLAN Access Point, which forwards the EAP-Success to the N5CW device. The PMK is the key used to secure the WLAN air-interface communication according to IEEE Std 802.11 [48]. A layer-2 or layer-3 connection is established between the Trusted WLAN Access Point and the TWIF for transporting all user-plane traffic of the N5CW device to TWIF. This connection is later bound to an N3 connection that is created for this N5CW device.
10. Finally, the AMF sends a Registration Accept message to TWIF. At this point, the N5CW device is connected to the WLAN Access Network and is registered to 5GC.
Steps 20-21: PDU Session Establishment.
20. The TWIF creates a PDU Session Establishment Request message on behalf of the N5CW device and sends this message to AMF. This may be triggered by receiving an IP configuration request (e.g. DHCP Offer/Request) from the N5CW device. The TWIF may use default values to populate the parameters in the PDU Session Establishment Request message, but may also skip some PDU session parameters and let the AMF or the SMF determine these parameters based on the N5CW device subscription information received during the registration procedure. This way, default PDU session parameters can be used per N5CW device.
The value of the PDU Session id provided by TWIF in step 20c shall always be the same. It will be a value reserved for the PDU sessions requested by the TWIF and it will be different from the values that can be used by the N5CW device when requesting a PDU session over 3GPP access. This way, the PDU session id provided by the TWIF cannot be the same with the PDU Session ID of any PDU session established by the N5CW device over 3GPP access.
21. The AMF sends upon request of the SMF an N2 PDU Session Request message to TWIF in order to reserve the appropriate Access Network resources. This N2 message includes the PDU Session Establishment Accept message. In step 21b, the TWIF may reserve WLAN access resources for the user-plane communication between the N5CW device and TWIF. If and how this resource reservation is performed is outside the scope of 3GPP.
After the establishment of the PDU session, the TWIF assigns IP configuration data to N5CW device (e.g. with DHCP). The IP address assigned to N5CW device is the IP address allocated to the PDU session.
Step 25: User plane communication.
The TWIF binds the N5CW device-specific L2/L3 connection created in step 9g with the N3 connection created in step 21. All user-plane traffic sent by the N5CW device is forwarded to TWIF via the L2/L3 connection and then to UPF via the N3 connection. The TWIF operates as a Layer-2 relay.
The TWIF may receive URSP rules (see TS 23.503 [20]), which indicate the traffic that should be offloaded locally by TWIF (sent outside the PDU session) and the traffic that should be sent inside the PDU session.
The above procedure supports only one PDU session per N5CW device whose parameters are either configured for all N5CW devices in the TWIF or are derived from default values in the N5CW device subscription.
If the TWIF is co-located with one or more local UPFs then:
- In step 20c (N2 Uplink NAS Transport), the TWIF may send a TWIF Identities parameter to AMF. The TWIF Identities parameter contains a list of identifiers (i.e. FQDNs or IP addresses) of N3 terminations supported by the TWIF.
- If received by the AMF, it shall forward it to the SMF when invoking Nsmf_PDUSessionCreateSMContext i.e. at the establishment of the PDU Session. The SMF may use this information to select a local UPF for the PDU Session.
4.12b.3 Deregistration procedure
The Deregistration procedure for devices (N5CW devices) that do not support 5G NAS signalling over WLAN access shall be supported as specified in clause 4.12a.3 for the trusted non-3GPP access with the following modifications:
- The TNAP is substituted by a trusted WLAN access point (TWAP).
- The TNGF is substituted by the Trusted WLAN Interworking Function (TWIF).
- The TWIF sends and receives NAS deregistration request/accept messages on behalf of N5CW device.
- For both UE/Network-initiated deregistration procedures, the TWIF may initiate the release of Yt' connection between the N5CW device and TWIF.
- UE-initiated deregistration procedure can be initiated by the TWIF, when it has lost connectivity to the N5CW device.
4.12b.4 N2 procedures
4.12b.4.1 Service Request procedures
The Service Request procedure for devices that do not support 5G NAS signalling over WLAN access shall be used by a TWIF when the CM state in TWIF for a N5CW device is CM-IDLE over Trusted WLAN to request the re-establishment of the NAS signalling connection and the re-establishment of the user plane for all or some of the PDU Sessions which are associated to non-3GPP access.
The Service Request procedure for N5CW devices shall be used by a TWIF when the CM state in TWIF for a N5CW device is CM-CONNECTED over trusted WLAN to request the re-establishment of the user plane for one or more PDU Sessions which are associated to non-3GPP access.
This Service Request procedure shall be supported as specified in clause 4.12a.4.1 for the trusted non-3GPP access with the following modifications:
- The trusted non-3GPP access is substituted by a trusted WLAN access point (TWAP).
- The TNGF is substituted by the TWIF.
- The TWIF sends and receives NAS messages on behalf of N5CW device.
- The user plane between the N5CW device and TWIF is established with Yt' connection instead of IKEv2 signalling.
4.12b.4.2 Procedure for the UE context release in the TWIF
This procedure for releasing the N2 signalling connection and the N3 user plane connection for a N5CW device connected to 5GC via trusted WLAN access, shall be the same as the procedure specified in clause 4.12a.4.2 for the trusted non-3GPP access with the following modifications:
- The trusted non-3GPP access is substituted by a TWAP.
- The TNGF is substituted by the TWIF.
- The TWIF may initiate the release of Yt' connection between the N5CW device and TWIF.
4.12b.4.3 CN-initiated selective deactivation of UP connection of an existing PDU Session
The procedure described in clause 4.3.7 (CN-initiated selective deactivation of UP connection of an existing PDU Session) is used for CN-initiated selective deactivation of UP connection for an established PDU Session associated with Trusted WLAN access for a N5CW device in CM-CONNECTED state, with the following exceptions:
- The NG-RAN corresponds to a TNAN including a TWIF.
- The user plane between the N5CW device and TWIF is released without neither RRC signalling nor IKEv2 signalling. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13 Specific services | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.1 General | Clause 4.13 defines the additional procedures or additions to the existing procedures to support specific services such as SMS over NAS. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.2 Application Triggering | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.2.1 General | The AF invokes the Nnef_Trigger service to request that the network send an Application trigger to the UE. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.2.2 The procedure of "Application Triggering" Service | Figure 4.13.2.2-1: Device triggering procedure via Nnef
1. The AF determines the need to trigger the device. If the AF has no contact details for the NEF, it shall discover and select NEF services.
2. The AF invokes the Nnef_Trigger_Delivery request service.
3. The NEF checks that the AF is authorised to send trigger requests and that the AF has not exceeded its quota or rate of trigger submission over Nnef. If this check fails, the NEF sends an Nnef_Trigger_Delivery response with a cause value indicating the reason for the failure condition and the flow stops at this step. Otherwise, the flow continues with step 4.
4. The NEF invokes Nudm_SDM_Get (Identifier Translation, GPSI and AF Identifier) to resolve the GPSI to SUPI when the AF is authorized to trigger the UE.
NOTE 1: Optionally, mapping from GPSI (External Id) to GPSI (MSISDN) is also provided for legacy SMS infrastructure not supporting MSISDN-less SMS.
5. The UDM may invoke the Nudr_DM_Query service to retrieve a list of AF's that are allowed to trigger the UE and determines, based on UDM policy, which identifier (SUPI or MSISDN) should be used to trigger the UE. The UDM provides a Nudm_SDM_Get response (SUPI, optionally MSISDN. If the AF is not allowed to send a trigger message to this UE, or there is no valid subscription information for this user, the NEF sends an Nnef_Trigger_Delivery response with a cause value indicating the reason for the failure condition and the flow stops at this step. Otherwise this flow continues with step 6.
NOTE 2: The presence of an MSISDN in the reply is interpreted as an indication to the NEF that MSISDN is used (instead of IMSI) to identify the UE when sending the SMS to the SMS-SC via T4.
6. The NEF invokes Nudm_UECM_Get (GPSI, SMS) to retrieve the UE SMSF identities.
7. The UDM may invoke the Nudr_DM_Query service to retrieve the UE SMSF identities. The UDM provides a Nudm_UECM_Get response with the corresponding UE SMSF identities. UDM policy (possibly dependent on the VPLMN ID) may influence which serving node identities are returned.
NOTE 3: The NEF can cache serving node information for the UE. However, this can increase the probability of trigger delivery attempt failures when the cached serving node information is stale.
8. The NEF selects a suitable SMS-SC based on configured information. The NEF acts as an MTC-IWF and sends a Submit Trigger (GPSI, SUPI, AF Identifier, trigger reference number, validity period, priority, SMSF serving node ID(s) (if available, are obtained from UDM in step 7), SMS Application port ID, trigger payload, Trigger Indication) message to the SMS-SC.
If the NEF indicates that "Absent subscriber" was received from the UDM, the SMS-SC should not submit the message, but store it directly and send Routing Information for SM to request the UDM to add the SMS-SC address to the Message Waiting List.
9. The SMS-SC sends a Submit Trigger Confirm message to the NEF to confirm that the submission of the SMS has been accepted by the SMS-SC.
10. The NEF sends a Nnef_Trigger_Delivery response to the AF to indicate if the Device Trigger Request has been accepted for delivery to the UE.
11. The SMS_SC performs MT SMS delivery as defined in clause 4.13.3. The SMS-SC may provide the routing information that it received in step 6 to SMS-GMSC to avoid UDM interrogation. The SMS-SC generates the necessary CDR information and includes the AF Identifier. The SMS Application port ID, which is included in the SM User Data Header and the Trigger Indication are included in the CDRs in order to enable differentiated charging. The SMS-SC stores the trigger payload, without routing information. If the message delivery fails and is attempted to be delivered again, UDM interrogation will be performed. If the message delivery fails and the validity period of this trigger message is not set to zero, the SMS-SC shall send a SM Message Delivery Status Report to request the UDM to add the SMS-SC address to the Message Waiting list. When the message delivery is later re-attempted, a new UDM interrogation will be performed by the SMS-GMSC using SUPI or MSISDN. UDM interrogations using SUPI shall not be forwarded or relayed to SMS-Router or IP-SM-GWs. The UDM may include up to four serving node identities (MSC or MME, SGSN, IP-SM-GW, AMF) in the response to SMS-GMSC.
12. If the message delivery fails (either directly or when validity period of the trigger message expires) or when the message delivery succeeds, the SMS-SC shall send a Message Delivery Report (cause code, trigger reference number, AF Identifier) to the NEF.
13. The NEF provides a Nnef_Trigger_DeliveryNotify message to the AF with a Delivery Report indicating the trigger delivery outcome (e.g. succeeded, unknown or failed and the reason for the failure). The NEF generates the necessary CDR information including the GPSI and AF Identifier.
14. In response to the received device trigger, the UE takes specific actions and may take into consideration the content of the trigger payload. This action typically involves initiation of immediate or later communication with the AF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3 SMS over NAS procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3.1 Registration procedures for SMS over NAS | Figure 4.13.3.1-1: Registration procedure supporting SMS over NAS
1. During Registration procedure in 5GS defined in Figure 4.2.2.2.2-1, to enable SMS over NAS transporting, the UE includes an "SMS supported" indication in Registration Request in step 1-3 indicating the UE's capability for SMS over NAS transport. The "SMS supported" indication indicates whether the UE supports SMS delivery over NAS.
2. Step 4 to step 14 of the Registration procedure in Figure 4.2.2.2.2-1 are performed. The AMF may retrieve the SMS Subscription data and UE Context in SMSF data using Nudm_SDM_Get. This requires that UDM may retrieve this information from UDR by Nudr_DM_Query. The UDM includes the SMSF information in the Nudm_SDM_Get response message if the stored SMSF belongs to the same PLMN of the AMF. After a successful response is received and if SMS service is allowed, the AMF subscribes to be notified using Nudm_SDM_Subscribe when the SMS Subscription data is modified and UDM may subscribe to UDR by Nudr_DM_Subscribe. For an MPS-subscribed UE, the subscription data may include the MPS priority for Messaging indication. If the AMF receives the MPS for Messaging indication from UDM, the AMF stores the MPS for Messaging indication in the UE context.
The AMF can also receive UE context information containing SMSF Information from old AMF. When AMF re-allocation happens during the Registration procedure, the old AMF transfers SMSF Information to the new AMF as part of UE context in step 5 of Figure 4.2.2.2.2-1.
NOTE 1: The AMF 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 AMF and the UDM.
3. If the "SMS supported" indication is included in the Registration Request, the AMF checks in the SMS Subscription data that was received in step 2 whether the SMS service is allowed to the UE. If SMS service is allowed and the UE context received in step 2 includes an available SMSF of the serving PLMN, the AMF activates this SMSF Address and continues the registration procedure. If SMS service is allowed but an SMSF of the serving PLMN was not received in step 2, the AMF discovers and selects an SMSF to serve the UE as described in clause 6.3.10 of TS 23.501 [2].
4. Step 15 to step 20 of the Registration procedure in Figure 4.2.2.2.2-1 are performed.
5. The AMF invokes Nsmsf_SMService_Activate service operation from the SMSF. The invocation includes AMF address, Access Type, RAT Type, Trace Requirements, GPSI (if available) and SUPI. AMF uses the SMSF Information derived from step 3. Trace Requirements is provided if it has been received by AMF as part of subscription data. When the AMF determines the UE has the MPS for Messaging indication in UE context as specified in step 2, the AMF includes a Message Priority header with a value appropriate for MPS to indicate priority treatment.
6. The SMSF discovers a UDM as described in clause 6.3.8 of TS 23.501 [2].
7a. If the UE context for the current Access Type already exists in the SMSF, the SMSF shall replace the old AMF address with the new AMF address.
Otherwise, the SMSF considers this a Registration request from a new Access Type and the SMSF registers with the UDM using Nudm_UECM_Registration with Access Type. As a result, the UDM stores the following information: SUPI, SMSF identity, SMSF address, Access Type(s) in UE Context in SMSF data. The UDM may further store SMSF Information in UDR by Nudr_DM_Update (SUPI, Subscription Data, UE Context in SMSF data).
If the Nsmsf_SMService_Activate request contains two Access Types and one of them is already registered in the SMSF, the SMSF shall replace the old AMF address with the new AMF address for that Access Type. The SMSF shall then register the other Access Type with the UDM using Nudm_UECM_Registration request.
7b-7c SMSF retrieves SMS Management Subscription data (e.g. SMS teleservice, SMS barring list) using Nudm_SDM_Get and this requires that UDM may get this information from UDR by Nudr_DM_Query (SUPI, Subscription Data, SMS Management Subscription data). After a successful response is received, the SMSF subscribes to be notified using Nudm_SDM_Subscribe when the SMS Management Subscription data is modified and UDM may subscribe to notifications from UDR by Nudr_DM_Subscribe.
SMSF also creates a UE context to store the SMS subscription information and the AMF address that is serving this UE.
NOTE 2: The SMSF 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 SMSF and the UDM.
8. The SMSF responds back to the AMF with Nsmsf_SMService_Activate service operation response message. The AMF stores the SMSF Information received as part of the UE context.
9. The AMF includes the "SMS allowed" indication to the UE in the Registration Accept message of step 21 of Figure 4.2.2.2.2-1 only after step 8 in which the AMF has received a positive indication from the selected SMSF.
The "SMS allowed" indication in the Registration Accept message indicates to the UE whether the network allows the SMS message delivery over NAS. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3.2 Deregistration procedures for SMS over NAS | If UE indicates to AMF that it no longer wants to send and receive SMS over NAS (e.g. not including "SMS supported" indication in subsequent Registration Request message) or AMF considers that UE is deregistered on specific Access Type(s) or AMF receives Deregistration Notification from UDM for specific Access Type(s) indicating UE Initial Registration, Subscription Withdrawn or 5GS to EPS Mobility as specified in clause 5.2.3.2.2, then:
- AMF may, if the UE is not registered at other Access Type at the AMF any more, unsubscribe from SMS Subscription data changes notification with the UDM by means of the Nudm_SDM_Unsubscribe service operation.
- AMF invokes Nsmsf_SMService_Deactivate service operation to trigger the release of UE Context for SMS on SMSF for the impacted Access Type(s) based on local configurations.
- AMF may, if the UE is not registered at other Access Type at the AMF anymore, delete or deactivate the stored SMSF address in its UE Context.
- The SMSF unsubscribes from SMS Management Subscription data changes notification with the UDM by means of the Nudm_SDM_Unsubscribe service operation if the UE is not registered at other Access Type for SMS over NAS service at the SMSF anymore.
- The SMSF shall invoke Nudm_UECM_Deregistration (SUPI, NF ID, Access Type) service operation from UDM to trigger UDM to delete SMSF address of the UE for the impacted Access Type(s). The SMSF also removes the UE Context for SMS for the impacted Access Type(s), including AMF address.
- The UDM may update UE context in SMSF in UDR by Nudr_DM_Update (SUPI, Subscription Data, SMS Subscription data, SMSF address). The UDM may remove the corresponding subscription of data change notification in UDR by Nudr_DM_Unsubscribe service operation. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3.3 MO SMS over NAS in CM-IDLE (baseline) | Figure 4.13.3.3-1: MO SMS over NAS
1. The UE performs domain selection for UE originating SMS as defined in clause 5.16.3.8 of TS 23.501 [2] if SMS delivery via non 3GPP access is allowed and possible. If an UE under CM-IDLE state is going to send uplink SMS message, then UE and network perform the UE Triggered Service Request procedure firstly as defined in clause 4.2.3.2 to establish a NAS signalling connection to AMF.
2a. The UE builds the SMS message to be sent as defined in TS 23.040 [7] (i.e. the SMS message consists of CP-DATA/RP-DATA/TPDU/SMS-SUBMIT parts). The SMS message is encapsulated in an NAS message with an indication indicating that the NAS message is for SMS transporting. The UE send the NAS message to the AMF.
2b. The AMF forwards the SMS message and SUPI to the SMSF serving the UE over N20 message by invoking Nsmsf_SMService_UplinkSMS service operation. In order to permit the SMSF to create an accurate charging record, the AMF adds the IMEISV, the current UE Location Information (ULI) of the UE as defined in clause 5.6.2 of TS 23.501 [2] and if the UE has sent the SMS via 3GPP access, the local time zone.
When the AMF determines that the UE has the MPS for Messaging indication set (enabled) in the UE context, the AMF includes a Message Priority header to indicate priority information. Other NFs relay the priority information by including the Message Priority header in service-based interfaces, as specified in TS 29.500 [17].
2c. The SMSF invokes Namf_Communication_N1N2MessageTransfer service operation to forward SMS ack message to AMF.
2d. The AMF forwards the SMS ack message from the SMSF to the UE using downlink unit data message.
3-5. The SMSF checks the SMS management subscription data. If SMS delivery is allowed, the procedure defined in TS 23.040 [7] or TS 23.540 [84] applies. If the Message Priority header received in step 2 contains a value that indicates MPS, the SMSF may set the transport priority (e.g. the DRMP) to a value appropriate for MPS.
6a-6b. The SMSF forwards the submit report to AMF by invoking Namf_Communication_N1N2MessageTransfer service operation which is forwarded to UE via Downlink NAS transport. If the SMSF knows the submit report is the last message to be transferred for UE, the SMSF shall include a last message indication in the Namf_Communication_N1N2MessageTransfer service operation so that the AMF knows no more SMS data is to be forwarded to UE.
NOTE: The behaviour of AMF based on the "last message indication" is implementation specific.
If the UE has more than one SMS message to send, the AMF and SMSF forwards SMS /SMS ack/submit report the same way as described in step 2a-6b.
6c-6d. When no more SMS is to be sent, UE returns a CP-ack as defined in TS 23.040 [7] to SMSF. The AMF forwards the SMS ack message by invoking Nsmsf_SMService_UplinkSMS service operation to SMSF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3.4 Void | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3.5 MO SMS over NAS in CM-CONNECTED | MO SMS in CM-CONNECTED State procedure is specified by reusing the MO SMS in CM-IDLE State without the UE Triggered Service Request procedure. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3.6 MT SMS over NAS in CM-IDLE state and RRC_INACTIVE with CN based MT communication state via 3GPP access | Figure 4.13.3.6-1: MT SMS over NAS in CM-IDLE and RRC_INACTIVE state via 3GPP access
1-3 MT SMS interaction between SC/SMS-GMSC/UDM follow the procedure as defined in TS 23.040 [7] or TS 23.540 [84]. If there are two AMFs serving the UE, one is for 3GPP access and another is for non-3GPP access, there are two SMSF addresses stored in UDM/UDR. The UDM shall return both SMSF addresses.
If the MPS for Messaging indication is set for the UE, the UDM may provide the parameter to the SMS-GMSC. If the MPS for Messaging indication from the UDM is set(enabled), or if a priority indication is received with the SMS message from the SC (as in TS 23.272 [61]), the SMS-GMSC shall include a Message Priority header (or DRMP) to indicate priority information towards SMSF.
4. The SMSF checks the SMS management subscription data. If SMS delivery is allowed, SMSF invokes Namf_MT_EnableUEReachability service operation to AMF. AMF pages the UE using the procedure defined in clause 4.2.3.3. The AMF includes Paging Priority if Paging needs to be triggered and the MPS for Messaging indication is stored in the UE context. The UE responds to the page with Service Request procedure.
The AMF shall page with priority:
- if it receives an MT-SMS from the SMSF and has received an indication that MPS for Messaging is enabled for the UE in the UDM.
- if it receives an MT-SMS from the SMSF with a Message Priority header value used for MPS for Messaging.
If the AMF indicates SMSF that UE is not reachable (including the cases that UE applies power saving enhancement as described in clause 5.31.7 of TS 23.501 [2]), the procedure of the unsuccessful Mobile terminating SMS delivery described in clause 4.13.3.9 is performed and the following steps are skipped. In the case of power saving enhancement, the AMF further stores the information received in the Namf_MT_EnableUEReachability request and pages the UE when UE is considered reachable.
If the UE access to the AMF via both 3GPP access and non-3GPP access, the AMF determines the Access Type to transfer the MT-SMS based on operator local policy.
5a-5b. SMSF forward the SMS message to be sent as defined in TS 23.040 [7] (i.e. the SMS message consists of CP‑DATA/RP‑DATA/TPDU/SMS‑DELIVER parts) to AMF by invoking Namf_Communication_N1N2MessageTransfer service operation. The AMF transfers the SMS message to the UE.
5c-5d. The UE acknowledges receipt of the SMS message to the SMSF. For uplink unitdata message toward the SMSF, the AMF invokes Nsmsf_SMService_UplinkSMS service operation to forward the message to SMSF. In order to permit the SMSF to create an accurate charging record, the AMF also includes IMEISV, the current UE Location Information (ULI) of the UE as defined in clause 5.6.2 of TS 23.501 [2] and if the SMS is delivered to the UE via 3GPP access, the local time zone.
6a-6b. The UE returns a delivery report as defined in TS 23.040 [7]. The delivery report is encapsulated in an NAS message and sent to the AMF which is forwarded to SMSF by invoking Nsmsf_SMService_UplinkSMS service operation.
6c-6d. The SMSF acknowledges receipt of the delivery report to the UE. The SMSF uses Namf_Communication_N1N2MessageTransfer service operation to send SMS CP ack message to the AMF. The AMF encapsulates the SMS message via a NAS message to the UE. If SMSF has more than one SMS to send, the SMSF and the AMF forwards subsequent SMS /SMS ack/ delivery report the same way as described in step 4-6c.
If the SMSF knows the SMS CP ack is the last message to be transferred for UE, the SMSF shall include a last message indication in the Namf_Communication_N1N2MessageTransfer service operation so that the AMF knows no more SMS data is to be forwarded to UE.
NOTE: The behaviour of AMF based on the "last message indication" is implementation specific.
7. In parallel to steps 6c and 6d, the SMSF delivers the delivery report to SC as defined in TS 23.040 [7] or TS 23.540 [84]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3.7 MT SMS over NAS in CM-CONNECTED state via 3GPP access | MT SMS in CM-CONNECTED procedure is specified by reusing the MT SMS in CM-IDLE state with the following modification:
- There is no need for the AMF to perform Paging of the UE and can immediate continue with a message to SMSF via N20 to allow the SMSF to start forward the MT SMS.
- When the AMF receives an MT-SMS from the SMSF and has either received an indication that MPS for Messaging is enabled for the UE from the UDM, or has received the MT-SMS with a Message Priority header value used for MPS, the AMF shall include the service priority value (RAN Paging Priority IE as in TS 38.413 [10]) appropriate for MPS for Messaging, in the Downlink NAS Transport message sent to the NG-RAN. NG RAN shall use the RAN Paging Priority received from the AMF to page the UE with priority when the UE is in RRC-INACTIVE state.
- If the delivery of the NAS PDU containing the SMS fails e.g. if the UE is in RRC_INACTIVE and NG-RAN paging was not successful, the NG-RAN initiate the UE context release in the AN procedure and provide notification of non-delivery to the AMF. The AMF provides an indication of non-delivery to the SMSF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3.8 MT SMS over NAS via non-3GPP access | MT SMS procedure via non-3GPP access is specified by reusing the MT SMS via 3GPP access in CM-CONNECTED state with the following modification:
- If the UE access to the network via both 3GPP and non-3GPP accesses and the AMF determines to deliver MT-SMS via non-3GPP access based on operator policy in step 4, the NAS messages is transferred via non-3GPP Access Network. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.3.9 Unsuccessful Mobile terminating SMS delivery re-attempt | The procedure of Unsuccessful Mobile terminating SMS delivery re-attempt is defined as follows:
- For SMS delivery, the SMSF and the UDM support the SMSF and UDM role as specified in TS 23.040 [7].
- If the UE is registered over both 3GPP access and non-3GPP access in the same AMF (i.e. the UE is registered in the same PLMN for both Access Types):
- if the MT-SMS delivery over one Access Type has failed, the AMF, based on operator local policy, may re-attempt the MT-SMS delivery over the other Access Type before indicating failure to SMSF;
- if the MT-SMS delivery on both Access Types has failed, the AMF shall inform the SMSF immediately.
- If the AMF informs the SMSF that it cannot deliver the MT-SMS to the UE (including the cases that UE applies power saving enhancement as described in step 4 of clause 4.13.3.6), the SMSF sends a failure report to the first SMS-GMSC (which can be co-located with IP-SM-GW or SMS Router) as defined in TS 23.040 [7] or TS 23.540 [84]. If the SMS-GMSC has more than one entity for SMS transport towards the UE, then upon receiving MT-SMS failure report, the SMS-GMSC, based on operator local policy, may re-attempt the MT-SMS delivery via the other entity.
- After the first SMS-GMSC informs the UDM/HSS that the UE is not able to receive MT-SMS, the UDM shall set the URRP-AMF flag and store the SC address in the MWD list as defined in TS 23.040 [7] or TS 23.540 [84].
- If the UE is registered in an AMF and the UDM has not subscribed to UE Reachability Notification in the AMF yet, the UDM immediately initiates a subscription procedure as specified in clause 4.2.5.2.
- When the AMF detects UE activities, it notifies UDM with UE Activity Notification as described in clause 4.2.5.3. If the UE is registered in an SMSF, the UDM clears its URRP-AMF flag and the UDM/HSS clears the MWD list and alerts related SCs to retry MT-SMS delivery. Otherwise, if the UE is not registered in an SMSF, the UDM clears its URRP-AMF flag but the UDM/HSS keeps the MWD list to notify the SC upon subsequent SMSF registration for the UE.
- When the SMS-GMSC requests routing information from UDM/HSS for a UE not registered in 5GC, or for a registered UE which has not been yet registered for SMS service, the UDM/HSS responds to the SMS-GMSC that the UE is absent, stores the SC address in the MWD list (if not yet stored) and indicates that to the SC as defined in TS 23.040 [7] or TS 23.540 [84].
When the UDM receives an Nudm_UECM_Registration Request from an SMSF for a UE for which the MWD list is stored and no URRP-AMF flag is set, the UDM/HSS alerts the related SCs to retry the MT-SMS delivery and clears the MWD list.
NOTE: This scenario assumes that the UE is not in 2G/3G/4G coverage. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.13.4 Emergency Services |
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