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fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.18.1 General | NOTE: The PFDF service is functionality within the NEF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.18.2 PFD management via NEF (PFDF) | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.18.2.1 PFD management triggered by AF | Figure 4.18.2.1-1: Procedure for PFD management via NEF (PFDF) triggered by AF
1. The AF invokes the Nnef_PFDManagement_Create/Update/Delete service. The Allowed Delay is an optional parameter. If the Allowed Delay is included, it indicates that the list of PFDs in this request should be provisioned within the time interval indicated by the Allowed Delay to the SMF(s) that have subscribed to the PFD management service using Nnef_PFDManagement_Subscribe service operation.
2. NEF (PFDF) checks whether the AF is authorized to perform this request and if the AF is authorised to provision this PFD data based on the operator policies. The NEF (PFDF) may in addition subscribe to the NWDAF to receive PFD Determination analytics (defined in clause 6.16.3 of TS 23.288 [50]) for this Application Identifier.
3. The NEF (PFDF) invokes the corresponding Nudr_DM_Create/Update/Delete (Data Key = Packet Flow Descriptions, Application Identifier, one or more PFDs, Allowed Delay) to the UDR.
4. The UDR creates/updates/deletes the list of PFDs for the Application Identifier.
5. The UDR sends a Nudr_DM_Create/Update/Delete Response to the NEF (PFDF).
6. The NEF (PFDF) sends Nnef_PFDManagement_Create/Update/Delete Response to the Application Function. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.18.2.2 PFD management based on PFD Determination analytics | Figure 4.18.2.2-1 shows the procedure that NEF (PFDF) determines the PFD information for the known Application Identifier(s), based on the PFD Determination analytics information notified/responded from the subscribed/requested NWDAF. The procedure enables the NEF (PFDF) to determine whether to create/update/delete PFD information corresponding to the known Application Identifier(s).
Figure 4.18.2.2-1: Procedure for PFD management based on PFD Determination analytics
1. The NWDAF notifies/responds to PFD Determination analytics to the NEF (PFDF) as Consumer NF with PFD Information defined in clause 6.16.3 of TS 23.288 [50].
2. The NEF (PFDF) fetches the PFD information currently in use from UDR if not available in NEF (PFDF) as described from step 2 to step 3 of clause 4.18.3.1.
3. The NEF (PFDF) compares the PFD information from UDR with PFD information from the NWDAF to determine whether to create/update/delete PFD information corresponding to the Application Identifier.
4. If the NEF (PFDF) has determined in step 3 to create/update/delete PFD information corresponding to the Application Identifier, the NEF (PFDF) invokes the Nudr_DM_Create/Update/Delete (Application Identifier, one or more sets of PFDs) to the UDR to create/update/delete PFD information corresponding to the Application Identifier, i.e. from step 3 to step 5 of clause 4.18.2.1 are executed. The NEF (PFDF) may forward new/updated PFD information to UPF via SMF to detect a known application, as defined in clause 6.1.2.3.1 of TS 23.503 [20]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.18.3 PFD management in the SMF | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.18.3.1 PFD Retrieval by the SMF | This procedure enables the SMF to retrieve PFDs for an Application Identifier from the NEF (PFDF) when a PCC rule with this Application Identifier is provided/activated and PFDs provided by the NEF (PFDF) are not available at the SMF.
In addition, this procedure enables the SMF to retrieve PFDs from the NEF (PFDF)when the caching timer for an Application Identifier elapses and a PCC Rule for this Application Identifier is still active.
The NEF (PFDF) retrieves the PFDs from UDR unless already available in NEF (PFDF).
The SMF may retrieve PFDs for one or more Application Identifiers in the same Request. All PFDs related to an Application Identifier are provided in the response from the UDR to NEF (PFDF).
Figure 4.18.3.1-1 PFD Retrieval by the SMF
1. SMF invokes the Nnef_PFDManagement_Fetch (Application Identifier (s)) to the NEF (PFDF).
2. NEF (PFDF) checks if the PFDs for the Application Identifier (s) are available in the NEF (PFDF), if available, the NEF (PFDF) skips to step 4. If not, the NEF (PFDF) invokes Nudr_DM_Query (Application Identifier (s)) to retrieve the PFD(s) from UDR.
3. The UDR provides a Nudr_DM_Query response (Application Identifier(s), PFD(s)) to the NEF (PFDF).
4. The NEF (PFDF) replies to the SMF with Nnef_PFDManagement_Fetch (Application Identifier(s), PFD(s)). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.18.3.2 Management of PFDs in the SMF | This procedure enables the provisioning, modification or removal of PFDs associated with an application identifier in the SMF. Either the complete list of all PFDs of all application identifiers, the complete list of all PFDs of one or more application identifiers or a subset of PFDs for individual application identifiers may be managed.
Each PFD of an application identifier is associated with a PFD id if a subset of the PFD(s) associated with an application identifier can be provisioned, updated or removed. If always the full set of PFD(s) for an application identifier is managed in each transaction, PFD ids do not need to be provided.
Figure 4.18.3.2-1 Management of PFDs in the SMF
1. As pre-requisite condition to receiving push notifications, the SMF subscribes to PFD notifications from the NEF (PFDF) by sending Nnef_PFDManagement_Subscribe message.
2. The NEF (PFDF) invokes Nnef_PFD_Management_Notify (Application Identifier, PFDs, PFDs operation) to the SMF(s) to which the PFD(s) shall be provided. The NEF (PFDF) may decide to delay the distribution of PFDs to the SMF(s) for some time to optimize the signalling load. If the NEF (PFDF) received an Allowed Delay for a PFD, the NEF (PFDF) shall distribute this PFD within the indicated time interval. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.19 Network Data Analytics | The system procedures for Network Data Analytics are defined in clause 6 of TS 23.288 [50]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.19.1 Void | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.19.2 Void | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.20 UE Parameters Update via UDM Control Plane Procedure | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.20.1 General | The purpose of the control plane solution for update of UE parameters is to allow the HPLMN, SNPN, or CH to update the UE with a specific set of parameters, generated and stored in the UDM, by delivering protected UDM Update Data via NAS signalling. The HPLMN, SNPN, or CH updates such parameters based on the operator policies.
The UDM Update Data that the UDM delivers to the UE may contain:
- one or more UE parameters including:
- the updated Default Configured NSSAI (final consumer of the parameter is the ME);
- the updated Routing Indicator Data (final consumer of the parameter is the USIM when the related credential is stored in the USIM, i.e. for PLMN or SNPN credentials; or final consumer of the parameter is the ME when the related credential is stored in the ME, i.e. for SNPN credentials);
- indication of whether disaster roaming is enabled in the UE if UE MINT support indicator is received or UE is registered for Disaster Roaming service currently; and
- indication of 'applicability of "lists of PLMN(s) to be used in disaster condition" provided by a VPLMN' if UE MINT support indicator is received or UE is registered for Disaster Roaming service currently.
- a "UE acknowledgement requested" indication.
- a "re-registration requested" indication. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.20.2 UE Parameters Update via UDM Control Plane Procedure | Figure 4.20.2-1: UE Parameters Update via UDM Control Plane Procedure
1. UDM decides to perform UE parameter update.
2. From UDM to the AMF: The UDM notifies the changes of the information related to the UE to the affected AMF by the means of invoking Nudm_SDM_Notification service operation. The Nudm_SDM_Notification service operation contains the UDM Update Data that needs to be delivered transparently to the UE over NAS within the Access and Mobility Subscription data. The UDM Update Data includes:
- The updated parameters to be delivered to the UE (see clause 4.20.1 for parameters possible to deliver).
- whether the UE needs to send an ack to the UDM.
- whether the UE needs to re-register after updating the data.
If the UE parameter update is performed due to "Routing Indicator update data" and the updated Routing Indicator value is not supported by the UDM where the AMF is currently registered and/or by the AUSF where the UE was authenticated, the UDM shall request the UE to re-register after updating the data.
3. From AMF to UDM: If AMF determines that the UE is not reachable, then AMF invokes the Nudm_SDM_Info service operation to UDM indicating that the transmission of UE Parameters Update data is not successful. The UDM considers the procedure as UE Parameters Update procedure as pending and subsequent steps from 4-7 are skipped.
4. From AMF to the UE: the AMF sends a DL NAS TRANSPORT message to the served UE. The AMF includes in the DL NAS TRANSPORT message the transparent container received from the UDM.
The UE verifies based on mechanisms defined in TS 33.501 [15] that the UDM Update Data is provided by HPLMN, SNPN, or CH; and:
- If the security check on the UDM Update Data is successful, as defined in TS 33.501 [15] the UE either stores the information and uses those parameters from that point onwards, or forwards the information to the USIM; and
- If the security check on the UDM Update Data fails, the UE discards the contents of the UDM Update Data.
5. The UE to the AMF: If the UE has verified that the UDM Update Data is provided by HPLMN, SNPN, or CH and the UDM has requested the UE to send an ack to the UDM, the UE sends an UL NAS TRANSPORT message to the serving AMF with a transparent container including the UE acknowledgement.
6. The AMF to the UDM: If the AMF receives an UL NAS TRANSPORT message with a transparent container carrying a UE acknowledgement from the UE, the AMF sends a Nudm_SDM_Info request message including the transparent container to the UDM.
6a. If the UE parameter update is performed due to "Routing Indicator update data", the updated Routing Indicator value is also supported by the UDM where the AMF is currently registered and/or by the AUSF where the UE was authenticated and the UDM requests the UE to send an ack but does not request the UE to re-register, then upon reception of the transparent container indicating the acknowledgement of successful reception, the UDM shall trigger a Nudm_SDM_Notification service operation to update the UE Context in the AMF with the updated Routing Indicator Data (e.g. to avoid transmitting an outdated Routing Indicator on UE context transfer to another AMF).
7. If the UDM has requested the UE to re-register, the UE waits until it goes back to RRC_IDLE and initiates a Registration procedure as defined in TS 24.501 [25]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.20.3 Void | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.21 Secondary RAT Usage Data Reporting Procedure | The procedure in Figure 4.21-1 may be used to report Secondary RAT Usage Data from NG-RAN node to the AMF. It is executed by the NG-RAN node to report the Secondary RAT Usage Data information towards AMF which is then reported towards SMF.
The procedure in Figure 4.21-2 may be used to report the Secondary RAT Usage Data from AMF towards the SMF. Optionally, it is used to report the Secondary RAT Usage Data from V-SMF to the H-SMF when the reporting to H-SMF is activated.
Figure 4.21-1: RAN Secondary RAT Usage Data Reporting procedure
1. The NG-RAN, if it supports Dual Connectivity with Secondary RAT (using NR radio, E-UTRA radio, or unlicensed spectrum using NR or E-UTRA radio) and it is configured to report Secondary RAT Usage Data for the UE, depending on certain conditions documented in this specification, it shall send a RAN Usage Data Report message to the AMF including the Secondary RAT Usage Data for the UE. The NG-RAN node will send only one RAN Usage Report for a UE when the UE is subject to handover by RAN. The RAN Usage Data Report includes a Handover Flag to indicate when the message is sent triggered by a handover.
Figure 4.21-2: SMF Secondary RAT Usage Data Reporting procedure
The NG-RAN, if it supports Dual Connectivity with Secondary RAT (using NR radio, E-UTRA radio, or unlicensed spectrum using NR or E-UTRA radio) and it is configured to report Secondary RAT usage data for the UE, it shall include the Secondary RAT usage data for the UE to the AMF in certain messages depending on certain conditions documented elsewhere in this TS.
1. The AMF forwards the N2 SM Information (Secondary RAT Usage Data) to the SMF in a Nsmf_PDUSession_UpdateSMContext Request.
2. The V-SMF sends the Nsmf_PDUSession_Update (Secondary RAT Usage Data) message to the H-SMF.
3. The H-SMF acknowledges receiving the Secondary RAT Usage data for the UE.
4. The V-SMF acknowledges receiving the Secondary RAT Usage data back to the AMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22 ATSSS Procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.1 General | This clause specifies the procedures that enable the support of Access Traffic Steering, Switching and Splitting (ATSSS), as defined in clause 5.32 of TS 23.501 [2]. These procedures can be applied only by ATSSS-capable UEs and 5GC networks.
The key enabler of ATSSS is the Multi Access-PDU (MA PDU) Session. As specified in clause 5.32.1 of TS 23.501 [2], a MA PDU Session is a PDU Session associated with two independent N3/N9 tunnels between the PSA and RAN/AN and with multiple access types, i.e. with one 3GPP access and one non-3GPP access both connected to 5GC. A MA PDU Session may also be a PDU Session associated with one 3GPP access connected to EPC and one non-3GPP access connected to 5GC, or a PDU Session associated with one non-3GPP access connected to EPC and one 3GPP access connected to 5GC. The traffic of a MA PDU Session can be transferred over 3GPP access, or over non-3GPP access, or over both accesses. How the traffic is transferred over the available accesses of a MA PDU Session is governed by the applicable policy created by the 5GC network.
The UE determines whether ATSSS is supported by the network based on the MA PDU Session Support indicator provided by the AMF during the Registration procedures, as specified in clause 4.22.9.1. If the network does not support ATSSS, the UE shall not initiate the following procedures in this network:
- establishment of a MA PDU Session (clause 4.22.2);
- establishment of a PDU Session with "MA PDU Network-Upgrade Allowed" indication (clause 4.22.3);
- addition of user-plane resources over one access for an existing MA PDU Session, which has been established over the other access in a different network (clause 4.22.7); or
- PDU Session Modification with Request Type of "MA PDU request" or with "MA PDU Network-Upgrade Allowed" indication after moving from EPC to 5GC (clause 4.22.6.3). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2 UE Requested MA PDU Session Establishment | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.0 Overview | Clauses 4.22.2.1 and 4.22.2.2 specify the MA PDU Session establishment procedures with both 3GPP access and non-3GPP access connected to 5GC. Clause 4.22.2.3 specifies the MA PDU Session establishment procedure with 3GPP access connected to EPC and non-3GPP access connected to 5GC. Clause 4.22.2.4 specifies the MA PDU Session establishment procedure with non-3GPP access connected to EPC and 3GPP access connected to 5GC. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.1 Non-roaming and Roaming with Local Breakout | The signalling flow for a MA PDU Session establishment when the UE is not roaming, or when the UE is roaming and the PDU Session Anchor (PSA) is located in the VPLMN, is based on the signalling flow in Figure 4.3.2.2.1-1 with the following differences and clarifications:
- The PDU Session Establishment Request message may be sent over the 3GPP access or over the non-3GPP access. In the steps below, it is assumed that it is sent over the 3GPP access, unless otherwise specified.
- In step 1, the UE provides Request Type as "MA PDU Request" in UL NAS Transport message and its ATSSS Capabilities as defined in clause 5.32.2 of TS 23.501 [2] in PDU Session Establishment Request message.
The "MA PDU Request" Request Type in the UL NAS Transport message indicates to the network that this PDU Session Establishment Request is to establish a new MA PDU Session and to apply one or more steering functionalities (defined in TS 23.501 [2], clause 5.32.6) for steering the traffic of this MA PDU session over multiple accesses.
If the UE requests an S-NSSAI and the UE is registered over both accesses, it shall request an S-NSSAI that is allowed on both accesses.
The UE indicates to AMF whether it supports non-3GPP access path switching, i.e. whether the UE can transfer the non-3GPP access path of the MA PDU Session from a source non-3GPP access (N3IWF/TNGF) to a target non-3GPP access (a different N3IWF/TNGF).
- In step 2, if the AMF supports MA PDU sessions, then the AMF selects an SMF, which supports MA PDU sessions. If the AMF supports non-3GPP access path switching and the UE indicated in step 1 that the UE supports non-3GPP access path switching, the AMF selects a SMF that supports non-3GPP access path switching, if such an SMF is available.
- In step 3, the AMF informs the SMF that the request is for a MA PDU Session by including "MA PDU Request" indication and in addition, it indicates to SMF whether the UE is registered over both accesses. If the AMF determines that the UE is registered via both accesses, but the requested S-NSSAI is not allowed on both accesses, then the AMF shall reject the MA PDU session establishment. If the AMF supports non-3GPP access path switching while maintaining two N2 connections for non-3GPP access, the selected SMF supports non-3GPP path switching and UE indicated in step 1 that the UE supports non-3GPP access path switching, the AMF indicates whether the UE supports non-3GPP path switching to the SMF.
The AMF shall reject the PDU Session Establishment request if the request is for a LADN.
- In step 4, the SMF retrieves, via Session Management subscription data, the information whether the MA PDU session is allowed or not.
- In step 7, if dynamic PCC is to be used for the MA PDU Session, the SMF sends an "MA PDU Request" indication to the PCF in the SM Policy Control Create message and the ATSSS Capabilities of the MA PDU session. The SMF provides the currently used Access Type(s) and RAT Type(s) to the PCF. The PCF decides whether the MA PDU session is allowed or not based on operator policy and subscription data.
The PCF provides PCC rules that include MA PDU session control information, as specified in TS 23.503 [20]. From the received PCC rules, the SMF derives (a) ATSSS rules, which will be sent to UE for controlling the traffic steering, switching and splitting in the uplink direction and (b) N4 rules, which will be sent to UPF for controlling the traffic steering, switching and splitting in the downlink direction. If the UE indicates the support of "ATSSS-LL Capability", the SMF may derive the Measurement Assistance Information.
If the SMF receives a UP Security Policy for the PDU Session with Integrity Protection set to "Required" and the MA PDU session is being established over non-3GPP access, the SMF does not verify whether the access can satisfy the UP Security Policy.
- In the remaining steps of Figure 4.3.2.2.1-1, the SMF establishes the user-plane resources over the 3GPP access, i.e. over the access where the PDU Session Establishment Request was sent on:
- In step 10, the N4 rules derived by SMF for the MA PDU session are sent to UPF and two N3 UL CN tunnels info are allocated by the UPF. If the ATSSS LL functionality is supported for MA PDU Session, the SMF may instruct the UPF to initiate performance measurement for this MA PDU Session. If the MPTCP functionality and/or the MPQUIC-UDP and/or MPQUIC-IP functionalities is/are supported for the MA PDU Session with IP PDU Session type, the SMF may instruct the UPF to activate the corresponding functionality/functionalities for this MA PDU Session. If the MPQUIC-E functionality is supported for the MA PDU Session with Ethernet PDU Session type, the SMF may instruct the UPF to activate the MPQUIC-E functionality for this MA PDU Session. In step 10a, the UPF allocates addressing information for the Performance Measurement Function (PMF) in the UPF. If the UPF receives from the SMF a list of QoS flows over which access performance measurements may be performed, the UPF allocates different UDP ports or different MAC addresses per QoS flow per access. In step 10b, the UPF sends the addressing information for the PMF in the UPF to the SMF. If UDP ports or MAC addresses are allocated per QoS flow and per access, the UPF sends the PMF IP address information and UDP ports with the related QFI to the SMF in the case of IP PDU sessions and sends the MAC addresses with the related QFI to the SMF in the case of Ethernet PDU sessions.
In step 10a:
- if the message from the SMF instructs the UPF to activate MPTCP functionality, the UPF allocates the UE "MPTCP link-specific multipath" addresses/prefixes. In step 10b, the UPF sends the "MPTCP link-specific multipath" addresses/prefixes and MPTCP proxy information to the SMF.
- if the message from the SMF instructs the UPF to activate MPQUIC-UDP and/or MPQUIC-IP or MPQUIC-E steering functionality, the UPF allocates the UE "MPQUIC link-specific multipath" addresses/prefixes. In step 10b, the UPF sends the "MPQUIC link-specific multipath" addresses/prefixes and MPQUIC proxy information that corresponds to the activated MPQUIC-based steering functionality/functionalities to the SMF.
The "MPTCP link-specific multipath" addresses/prefixes and the "MPQUIC link-specific multipath" addresses/prefixes may be the same.
NOTE 1: Additional parameters "ipproto" and "target" associated with the MPQUIC CONNECT-ip proxy protocol, which are derived by the UE based on the detected application.
- In step 11, for the MA PDU session, the SMF includes an "MA PDU session Accepted" indication in the Namf_Communication_N1N2MessageTransfer message to the AMF and indicates to AMF that the N2 SM Information included in this message should be sent over 3GPP access. The AMF marks this PDU session as MA PDU session based on the received "MA PDU session Accepted" indication. If the AMF indicated in step 3 that non-3GPP path switching while maintaining two N2 connections for non-3GPP access is supported, the SMF indicates support of non-3GPP path switching in the PDU Session Establishment Accept message.
If the PDU Session Type is "Ethernet", then:
- If the Steering functionality parameter in the MA PDU Session control information of the received PCC rule(s) is set only to MPQUIC-E, then SMF provides the PDU Session type as "IP" in the N2 SM information to NG-RAN,
NOTE 2: When only MPQUIC-E functionality is enabled for an MA PDU Session, the packets exchanged between UE and UPF are IP packets of the "MPQUIC link-specific multipath" addresses/prefixes (i.e. the (R)AN transports IP packets between UE and UPF). PDU Session type IP is provided to the (R)AN so that the NG-RAN can apply ROHC.
- If the Steering functionality parameter in the MA PDU Session control information of the received PCC rule(s) is set only to ATSSS-LL, then SMF behaviour is as in clause 4.3.2.2.1 (i.e. PDU Session type "Ethernet" is provided in the N2 SM information).
NOTE 3: Either ATSSS-LL or MPQUIC-E functionality is enabled for the same Ethernet MA PDU Session.
- In step 13, the UE receives a PDU Session Establishment Accept message, which indicates to UE that the requested MA PDU session was successfully established. This message includes the ATSSS rules for the MA PDU session, which were derived by SMF. If the ATSSS-LL functionality is supported for the PDU Session, the SMF may include the addressing information of PMF in the UPF into the Measurement Assistance Information. If the MPTCP functionality is supported for the MA PDU Session, the SMF shall include the "MPTCP link-specific multipath" addresses/prefixes of the UE and the MPTCP proxy information. If the MPQUIC-IP and/or MPQUIC-UDP or MPQUIC-E functionality/functionalities is supported for the MA PDU Session, the SMF shall include the "MPQUIC link-specific multipath" addresses/prefixes of the UE and the MPQUIC proxy information that corresponds to the activated MPQUIC-based steering functionality/functionalities.
- After step 18 in Figure 4.3.2.2.1-1, if the SMF was informed in step 2 that the UE is registered over both accesses, then the SMF initiates the establishment of user-plane resources over non-3GPP access too. The SMF sends an Namf_Communication_N1N2MessageTransfer to the AMF including N2 SM Information and indicates to AMF that the N2 SM Information should be sent over non-3GPP access. Namf_Communication_N1N2MessageTransfer does not include an N1 SM Container for the UE because this was sent to UE in step 13. After this step, the two N3 tunnels between the PSA and RAN/AN are established.
The last step above is not executed when the UE is registered over one access only, in which case the MA PDU Session is established with user-plane resources over one access only. How user-plane resources can be added over an access of the MA PDU Session is specified in clause 4.22.7. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.2 Home-routed Roaming | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.2.1 Home-routed Roaming - UE registered to the same PLMN | When the UE is registered to the same VPLMN over 3GPP access and non-3GPP access, the MA PDU Session is established as specified in Figure 4.3.2.2.2-1 ("UE-requested PDU Session Establishment for home-routed roaming scenarios") with the differences and clarifications:
- The PDU Session Establishment Request message may be sent over the 3GPP access or over the non-3GPP access.
- In step 1, the UE provides Request Type as "MA PDU Request" in UL NAS Transport message and its ATSSS Capabilities, as defined in clause 5.32.2 of TS 23.501 [2] in PDU Session Establishment Request message. The UE indicates to AMF whether it supports non-3GPP access path switching.
- In step 2, if the AMF supports MA PDU sessions, then the AMF selects a V-SMF and an H-SMF, which supports MA PDU sessions. The V-SMF serves the UE over both accesses. If the AMF supports non-3GPP access path switching and the UE indicated in step 1 that the UE supports non-3GPP access path switching, the AMF selects a V-SMF and H-SMF supporting non-3GPP access path switching, if such a V-SMF and H-SMF are available.
- In step 3, the AMF informs the SMF that the request is for a MA PDU Session by including an "MA PDU Request" indication and in addition, the AMF indicates to V-SMF that the UE is registered over both accesses. If the AMF supports non-3GPP access path switching while maintaining two N2 connections for non-3GPP access, the selected SMFs supports non-3GPP path switching and UE indicated in step 1 that the UE supports non-3GPP access path switching, the AMF indicates whether the UE supports non-3GPP path switching to the V-SMF.
- In step 5, two DL N9 tunnel CN info and two UL N3 tunnel CN info are allocated by the V-SMF or by the V-UPF.
- In step 6, the V-SMF informs the H-SMF that the request is for a MA PDU Session by including an "MA PDU Request" indication and indicates to H-SMF that the UE is registered over both accesses. The V-SMF indicates to H-SMF the relationship between the DL N9 tunnel CN info and the access type. If the single CN Tunnel is established by the H-SMF, the DL N9 tunnel info binding to the access over which the NAS message is received is to be used.
- In step 7, the H-SMF retrieves, via Session Management subscription data, the information whether the MA PDU session is allowed or not.
- In step 9, if dynamic PCC is to be used for the MA PDU Session, the H-SMF sends an "MA PDU Request" indication to H-PCF in the SM Policy Control Create message and the ATSSS Capabilities of the MA PDU session. The H-SMF provides the currently used list of Access Type(s) and RAT Type(s) for the MA-PDU session to the H-PCF. The H-PCF decides whether the MA PDU session is allowed or not based on operator policy and subscription data.
The H-PCF provides the PCC rules containing MA PDU session control information and the H-SMF derives the ATSSS rules for the UE and the N4 rules for the H-UPF.
- In step 12, two UL N9 tunnel CN info are allocated by the H-SMF or by the H-UPF. After this step, the two N9 tunnels between the H-UPF and V-UPF are established.
- In step 13, the H-SMF sends "MA PDU session Accepted" indication to V-SMF in the Nsmf_PDUSession_Create Response message. The H-SMF indicates to V-SMF the relationship between the UL N9 tunnel CN info and the access type.
- In step 14, the V-SMF sends the "MA PDU session Accepted" indication in the Namf_Communication_N1N2MessageTransfer message to the AMF and indicates the AMF to send the N2 SM Information included in this message over the access that the UE sent the PDU Session Establishment Request. The AMF marks this PDU session as MA PDU session based on the received "MA PDU session Accepted" indication.
The V-SMF indicates support of non-3GPP path switching in the PDU Session Establishment Accept message.
If the V-SMF received two UL N9 tunnel CN info from the H-SMF, the V-SMF also initiates the establishment of user-plane resources over the other access. The V-SMF sends an N1N2 Message Transfer to AMF including N2 SM Information and the other access type to indicate to AMF that the N2 SM Information should be sent over the other access. The N1N2 Message Transfer does not include an N1 SM Container for the UE which was sent to UE over the access that the UE sent the PDU Session Establishment Request.
- In step 16, the UE receives a PDU Session Establishment Accept message, which indicates to UE that the requested MA PDU session was successfully established. This message includes the ATSSS rules for the MA PDU session, which were derived by H-SMF and may include Measurement Assistance Information.
- After step 20, if the V-SMF was informed in step 3 that the UE is registered over both accesses, then the V-SMF initiates the establishment of user-plane resources over the other access too. The V-SMF sends an N1N2 Message Transfer to the AMF including N2 SM Information and indicates to the AMF over which access the N2 SM Information should be sent. The N1N2 Message Transfer does not include an N1 SM Container for the UE because this was sent to the UE in step 14. After this step, two N9 tunnels between the H-UPF and the V-UPF as well as two N3 tunnels between the V-UPF and RAN/AN are established, or, if the H-UPF is connected to two different V-UPFs, the H-UPF has one N9 tunnel with each V-UPF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.2.2 Home-routed Roaming - UE registered to different PLMNs | When the UE is registered to different PLMNs over 3GPP access and non-3GPP access, the MA PDU Session is established first over one access as specified in Figure 4.3.2.2.2-1 ("UE-requested PDU Session Establishment for home-routed roaming scenarios") and then over the other access with the following differences and clarifications:
- In step 1, the UE provides Request Type as "MA PDU Request" in UL NAS Transport message and its ATSSS Capabilities, as defined in clause 5.32.2 of TS 23.501 [2]. The UE indicates to AMF whether it supports non-3GPP access path switching. The UE also includes the PDU Session ID of the already established MA PDU Session.
- In step 2, if the AMF supports MA PDU sessions, then the AMF selects a V-SMF, which supports MA PDU sessions. If the AMF supports non-3GPP access path switching and the UE indicated in step 1 that the UE supports non-3GPP access path switching, the AMF may select a V-SMF and H-SMF supporting non-3GPP access path switching. If the UE provides Request Type "MA PDU Request" in step 1 and the UE context in SMF data from UDM includes SMF identity information for that PDU Session ID, the AMF selects the H-SMF indicated by UDM.
- In step 3, the AMF informs the V-SMF that the request is for a MA PDU Session (i.e. it includes an "MA PDU Request" indication). If the AMF supports non-3GPP access path switching while maintaining two N2 connections for non-3GPP access, the selected SMFs supports non-3GPP path switching and UE indicated in step 1 that the UE supports non-3GPP access path switching, the AMF indicates whether the UE supports non-3GPP path switching to the V-SMF.
- In step 6, the V-SMF informs the H-SMF that the request is for a MA PDU Session (i.e. it includes an "MA PDU Request" indication).
- In step 7, the H-SMF retrieves, via Session Management subscription data, the information whether the MA PDU session is allowed or not.
- In step 9, if dynamic PCC is to be used for the MA PDU Session, the H-SMF sends an "MA PDU Request" indication to PCF in the SM Policy Control Create message and the ATSSS Capabilities of the MA PDU session. The H-SMF provides the currently used Access Type(s) and RAT Type(s) for the MA-PDU session to the PCF. The PCF decides whether the MA PDU session is allowed or not based on operator policy and subscription data.
- In step 14, the V-SMF indicates support of non-3GPP path switching in the PDU Session Establishment Accept message.
- In step 16, the UE receives a PDU Session Establishment Accept message, which indicates to UE that the requested MA PDU session was successfully established. This message includes the ATSSS rules for the MA PDU session, which were derived by H-SMF and may include Measurement Assistance Information.
- After the MA PDU Session is successfully established on the first access, the UE shall initiate again the MA PDU Session establishment procedure in Figure 4.3.2.2.2-1 over the other access with the following differences and clarifications:
- In step 1, the UE shall send another PDU Session Establishment Request over the other access containing the same PDU Session ID that was provided over the first access. The UE also provides Request Type as "MA PDU Request" in UL NAS Transport message. The UE indicates to the AMF whether it supports non-3GPP access path switching.
- In step 2, if the AMF supports non-3GPP access path switching while maintaining two N2 connections for non-3GPP access, the may select a V-SMF that support non-3GPP access path switching.
- In step 3, if the AMF supports non-3GPP path switching and the UE indicated in step 1 that the UE supports non-3GPP access path switching, the AMF indicates whether the UE supports non-3GPP path switching to the V-SMF.
- In step 12, new UL N9 tunnel CN info is allocated by the H-SMF or by the H-UPF.
- In step 14, the V-SMF indicates support of non-3GPP path switching in the PDU Session Establishment Accept message.
- In step 16, the UE receives another PDU Session Establishment Accept message, which may contain updated ATSSS rules for the MA PDU session.
- After step 20, two N9 tunnels between the H-UPF and two different V-UPFs as well as two N3 tunnels between different V-UPF and RAN/AN are established, or two N3 tunnels, one is between V-UPF and RAN/AN over 3GPP access and the other is between H-UPF and RAN/AN over non 3GPP access, as well as one N9 tunnel between H-UPF and V-UPF are established. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.3 MA PDU Session establishment with 3GPP access connected to EPC and non-3GPP access connected to 5GC | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.3.1 General | This clause applies to the case where, for a PDU Session, multi-access connectivity via both EPC (over 3GPP access) and 5GC (over non-3GPP access) is supported and allowed in the UE and network. In this case, multi-access connectivity using ATSSS via both 3GPP access to EPC and non-3GPP access to 5GC may be provided as described in this clause.
For this scenario, the general principles for ATSSS as described in clause 5.32 of TS 23.501 [2] apply, with the additions provided in this clause 4.22.2.3.
A Multi-Access PDU Session may be extended with user-plane resources via an associated PDN Connection on 3GPP access in EPC. This enables a scenario where a MA PDU Session can simultaneously be associated with user-plane resources on 3GPP access network connected to EPC and non-3GPP access connected to 5GC. Such a PDN Connection in EPS would thus be associated with multi-access capability in the UE and PGW-C+SMF.
NOTE: To the MME and SGW this is a regular PDN Connection and the support for ATSSS is transparent to MME and SGW.
The UE may operate in either single-registration mode or dual-registration mode in 3GPP access. Irrespective of whether the UE operates in single-registration mode or dual-registration mode in 3GPP access, it is assumed that the UE supports simultaneous registrations for non-3GPP access in 5GC and 3GPP access in EPC.
The ATSSS rules are provided from the PGW-C+SMF to the UE via SM NAS signalling over 5GC, as described in clause 5.32.2 of TS 23.501 [2]. ATSSS rules may be provided via the EPC.
When a UE establishes a MA PDU Session in 5GS, the UE indicates whether it supports 3GPP access leg over EPC. Based on the UE capability, the SMF determines whether the non-3GPP access should be released or not when the MA PDU Session is moved to EPS as described in clause 4.22.6.2.
After the establishment of a MA PDU Session and setting up user-plane resources in 3GPP access in EPC and non-3GPP access in 5GC, the UE distributes the uplink traffic across the two access networks as described in clause 5.32.1 of TS 23.501 [2]. Similarly, the PDU Session Anchor UPF performs distribution of downlink traffic across the two access networks as described in clause 5.32.1 of TS 23.501 [2].
The PMF protocol may be used via any user plane connection, i.e. via 3GPP access in EPC or non-3GPP access in 5GC.
The PCF functionality to support ATSSS, as described in clause 5.32.1 of TS 23.501 [2] and TS 23.503 [20] applies also in the case of interworking with EPC.
When the 3GPP access leg of a MA PDU Session using both 3GPP and non-3GPP access connected to 5GC is transferred to EPC, the PDU Session continues to work as a MA PDU Session using E-UTRAN/EPC and non-3GPP access connected to 5GC, as described in clause 4.22.6. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.3.2 PDN Connections and Multi Access PDU Sessions | When the UE wants to request a new PDN Connection in EPC and wants to use this PDN Connection as user-plane resource associated with a MA PDU Session:
- The UE requests establishment of a new PDN Connection when the UE is registered via 3GPP access in EPS using PDN Connection Establishment procedure. The UE provides via PCO to PGW-C+SMF the following information:
- An indication that the PDN Connection is requested to be associated with a MA PDU Session.
- The UE's ATSSS capabilities as described in clause 5.32.2 of TS 23.501 [2].
- An indication that the UE is capable of supporting the ATSSS rule provisioning via 3GPP Access connected to EPC.
- The MME may select a PGW-C+SMF as described in TS 23.401 [13] and clause 4.11.0a.4.
NOTE 1: The selection of PGW-C+SMF in the correct 5GC slice requires the same mapping between EPC and 5GC slices as required for single-access PDU sessions. In order to select an ATSSS capable PGW-C+SMF it is assumed that the operator deployment ensures that all PGW-C+SMF(s) configured to support the specific APN in this network slice are also capable to support ATSSS. There is however no assumption that all PGW-U+UPFs need to support ATSSS, since PGW-C+SMF can make a selection of PGW-U+UPF taking the multi-access properties into account.
- The PGW-C+SMF determines based its capabilities whether the request can be accepted. The PCF decides whether the multi-access connectivity is allowed or not based on operator policy and subscription data, as described in clause 4.22.2. The PGW-C+SMF provides the following information in the PCO to the UE:
- An indication whether the request for using the PDN Connection for MA-PDU Session is accepted or not.
- If the UE has indicated that it is capable of supporting the MPTCP functionality and/or the MPQUIC-UDP functionality and/or MPQUIC-IP functionality or MPQUIC-E functionality and the PGW-C+SMF accepts to activate the MPTCP functionality and/or the MPQUIC-UDP functionality and/or MPQUIC-IP functionality or MPQUIC-E functionality, then the network provides MPTCP proxy information and/or MPQUIC proxy information corresponding to the activated MPQUIC-based steering functionality/functionalities to the UE, as described in clause 5.32.2 of TS 23.501 [2].
- UE Measurement Assistance Information (as described in clause 5.32.2 of TS 23.501 [2]).
- If the UE has indicated that it is capable of supporting the ATSSS rule provisioning via 3GPP Access connected to EPC, then the network is allowed to provide ATSSS rules via 3GPP Access connected to EPC.
After the PDN Connection establishment:
- If the UE registers to 5GC and wants to add non-3GPP user-plane resources, then the UE shall send a PDU Session Establishment Request over this access containing a "MA PDU Request" indication as described in clause 5.32.2 of TS 23.501 [2].
NOTE 2: Adding the PDU Session connectivity and user plane resources over non-3GPP access in 5GS allows the PGW-C+SMF to provide ATSSS rules to the UE via non-3GPP Access connected to 5GC.
- If the UE registers via non-3GPP access in EPC, the UE shall not trigger PDN Connection establishment to add non-3GPP/EPC access to the MA PDU Session.
When the UE wants to request a new MA PDU Session in 5GC/non-3GPP access, the description in clause 5.32.2 of TS 23.501 [2], applies. After the MA PDU Session establishment in 5GS/non-3GPP access, the description in clause 5.32.2 of TS 23.501 [2], applies with the following additions:
- If the UE is registered to EPC and wants to add user-plane resources on 3GPP access over EPC, then the UE shall send a PDN Connection Establishment Request over this access containing a "handover" indication and include a "MA PDU Request" indication in the PCO as well as the PDU Session ID of the existing MA PDU Session on non-3GPP access over 5GC.
- When the UE deregisters from the EPC access (but remains registered on the 5GC access), the MME will notify the PGW-C+SMF that the PDN Connection is released, as described in TS 23.401 [13]. The SMF can then notify the UPF that the access type has become unavailable.
In order to support EPS interworking when Ethernet type PDN Connection is not supported in EPS, the UE may use non-IP type PDN Connection when the UE establishes a PDN Connection in EPS as an added 3GPP access leg of an Ethernet type MA PDU Session. In this case, the UE and SMF shall locally associate the PDN Connection as an Ethernet type PDU Session as described in TS 23.501 [2]. When Ethernet type PDN Connection is not supported in EPS, the UE does not request to establish a PDN Connection with "MA PDU Request" indication before the UE registers to 5GS and establishes MA PDU Session over non-3GPP access.
A UE that has an established MA-PDU session over non-3GPP access in 5GC and 3GPP access in EPS, may be able to use EN-DC for the 3GPP access leg.
Depending on the RAT types supported by the UE, the PDN connection may also be handed over to 3GPP access in 5GC. For a UE supporting both E-UTRAN/EPC access and NG-RAN/5GC access, the user plane resources for 3GPP access may be moved between E-UTRAN/EPC access and NG-RAN/5GC access as described in clause 5.17.2 of TS 23.501 [2]. The PDU Session and User Plane resources active over non-3GPP/5GC access are not affected by such inter 3GPP access RAT change. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.3.3 QoS Support | The general principles for QoS support with ATSSS as described in clause 5.32.4 of TS 23.501 [2], apply, with the clarifications provided in this clause.
With an MA PDU Session associated to a PDN Connection on EPS there may be separate user-plane tunnels between the AN and the PGW-U+UPF, one associated with 3GPP access in EPC and one associated with non-3GPP access in 5GS.
As described in clause 4.11.1.1, the PGW-C+SMF maps the 5G QoS information received from PCC to EPS QoS parameters. This mapping is e.g. based on operator configuration and may result in that multiple QoS flows are mapped to a single EPS bearer. The PGW-C+SMF applies the appropriate QoS signalling in each access, e.g. to manage dedicated bearers in the access associated with EPC and QoS flows in the access associated with 5GC. The PGW-C+SMF also provides N4 rules to UPF for performing QoS enforcement and for mapping downlink traffic to appropriate GTP-U tunnels.
As described in clause 5.32.4 of TS 23.501 [2], for a GBR QoS flow, the QoS profile is provided to a single access network at a given time. GBR QoS flows (and associated MBR, GBR) are thus only enforced in either the access associated to EPC or the access associated to 5GC. In order to maintain consistency between QoS information received via AS and NAS layers in each system, the PGW-C+SMF only provides the GBR QoS information to the UE for the access where the GBR traffic is enforced.
The UE shall treat the uplink traffic sent via EPC according to the EPS QoS information received in EPC (e.g. UL TFTs) and the uplink traffic sent via 5GC according to the 5G QoS rules received in 5GS. The UE thus need to determine what access to use (3GPP and Non-3GPP) before applying the uplink QoS treatment.
The UPF shall treat the downlink traffic according to the N4 rules (QER, etc.) received from PGW-C+SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.4 MA PDU Session establishment with non-3GPP access connected to EPC and 3GPP access connected to 5GC | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.4.1 General | This clause applies to the case where, for a PDU Session, multi-access connectivity via both EPC (over non-3GPP access) and 5GC (over 3GPP access) is supported and allowed in the UE and network. In this case, multi-access connectivity using ATSSS via both non-3GPP access to EPC and 3GPP access to 5GC may be provided as described in this clause.
For this scenario, the general principles for ATSSS as described in clause 5.32 of TS 23.501 [2] apply, with the additions provided in this clause 4.22.2.4.
A Multi-Access PDU Session may be extended with user-plane resources via an associated PDN Connection on non-3GPP access in EPC. This enables a scenario where a MA PDU Session can simultaneously be associated with user-plane resources on non-3GPP access network connected to EPC and 3GPP access connected to 5GC. Such a PDN Connection in EPS would thus be associated with multi-access capability in the UE and PGW-C+SMF.
The UE may operate in either single-registration mode or dual-registration mode in 3GPP access. Irrespective of whether the UE operates in single-registration mode or dual-registration mode in 3GPP access, it is assumed that the UE supports simultaneous registrations for 3GPP access in 5GC and non-3GPP access in EPC.
The ATSSS rules are provided from the PGW-C+SMF to the UE via SM NAS signalling over 5GC, as described in clause 5.32.2 of TS 23.501 [2]. ATSSS rules may be provided via the EPC.
After the establishment of a MA PDU Session and setting up user-plane resources in non-3GPP access in EPC and 3GPP access in 5GC, the UE distributes the uplink traffic across the two access networks as described in clause 5.32.1 of TS 23.501 [2]. Similarly, the PDU Session Anchor UPF performs distribution of downlink traffic across the two access networks as described in clause 5.32.1 of TS 23.501 [2].
The PMF protocol may be used via any user plane connection, i.e. via non-3GPP access in EPC or 3GPP access in 5GC.
The PCF functionality to support ATSSS, as described in clause 5.32.1 of TS 23.501 [2] and TS 23.503 [20] applies also in the case of interworking with EPC. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.4.2 PDN Connections and Multi Access PDU Sessions | When the UE wants to request a new PDN Connection in EPC and wants to use this PDN Connection as user-plane resource associated with a MA PDU Session:
- The UE requests establishment of a new PDN Connection when the UE is registered via non-3GPP access in EPS using PDN Connection Establishment procedure. The UE provides the following ATSSS information to ePDG via IKE signalling:
- An indication that the PDN Connection is requested to be associated with a MA PDU Session
- The UE's ATSSS capabilities as described in clause 5.32.2 of TS 23.501 [2].
- The ePDG may select a PGW-C+SMF as described in TS 23.402 [26]. The ePDG forwards the ATSSS information to the selected PGW-C+SMF via APCO in Create Session Request message.
NOTE: The selection of PGW-C+SMF in the correct 5GC slice requires the same mapping between EPC and 5GC slices as required for single-access PDU sessions. In order to select an ATSSS capable PGW-C+SMF it is assumed that the operator deployment ensures that all PGW-C+SMF(s) configured to support the specific APN in this network slice are also capable to support ATSSS. There is however no assumption that all PGW-U+UPFs need to support ATSSS, since PGW-C+SMF can make a selection of PGW-U+UPF taking the multi-access properties into account.
- The PGW-C+SMF determines based its capabilities whether the request can be accepted. The PCF decides whether the multi-access connectivity is allowed or not based on operator policy and subscription data, as described in clause 4.22.2. The PGW-C+SMF provides the following information via the APCO in the Create Session Response message to the ePDG:
- An indication whether the request for using the PDN Connection for MA-PDU Session is accepted or not.
- If the UE has indicated that it is capable of supporting the MPTCP functionality and the PGW-C+SMF accepts to activate the MPTCP functionality, then the network provides MPTCP proxy information to the UE, as described in clause 5.32.2 of TS 23.501 [2].
- If the UE has indicated that it is capable of supporting the MPQUIC-UDP functionality and/or MPQUIC-IP functionality or MPQUIC-E functionality and the PGW-C+SMF accepts to activate the MPQUIC-UDP functionality and/or MPQUIC-IP functionality or MPQUIC-E functionality, then the network provides MPQUIC proxy information to the UE, as described in clause 5.32.2 of TS 23.501 [2].
- UE Measurement Assistance Information (as described in clause 5.32.2 of TS 23.501 [2]).
- ATSSS rules
- The ePDG forwards the received above information to the UE via IKE signalling.
After the PDN Connection establishment:
- If the UE registers to 5GC and wants to add 3GPP user-plane resources, then the UE shall send a PDU Session Establishment Request over this access containing a "MA PDU Request" indication as described in clause 5.32.2 of TS 23.501 [2]. The AMF shall select the SMF according to the UE context in SMF data from UDM for the corresponding PDU Session ID.
- If the UE attaches in E-UTRAN/EPC, the UE shall not trigger PDN Connection establishment to add E-UTRAN/EPC access to the MA PDU Session.
When the UE wants to request a new MA PDU Session in 5GC/3GPP access, the description in clause 5.32.2 of TS 23.501 [2], applies. After the MA PDU Session establishment in 5GC/3GPP access, the description in clause 5.32.2 of TS 23.501 [2], applies with the following additions:
- If the UE is registered to EPC and wants to add user-plane resources on non-3GPP access over EPC, then the UE shall send a PDN Connection Establishment Request over this access containing the IP address of the MA PDU Session in CFG_REQUEST Configuration Payload and include a "MA PDU Request" indication and UE's ATSSS capabilities and the PDU Session ID of the existing MA PDU Session on 3GPP access over 5GC. The ePDG shall select the PGW-C/SMF corresponding to the PGW identity provided by the 3GPP AAA server as described in TS 23.402 [26]. The ePDG forwards the ATSSS information via the APCO in the Create Session Request message to the PGW-C/SMF.
- When the UE deregisters from the EPC/non-3GPP access (but remains registered on the 5GC/3GPP access), the ePDG will notify the PGW-C+SMF that the PDN Connection is released, as described in TS 23.402 [26]. The SMF can then notify the UPF that the access type has become unavailable.
A UE that has an established MA-PDU session over 3GPP access in 5GC and non-3GPP access in EPS, may be able to use Dual Connectivity for the 3GPP access leg.
Depending on the RAT types supported by the UE, the PDU Session may also be handed over to 3GPP access in EPC. For a UE supporting both E-UTRAN/EPC access and NG-RAN/5GC access, the user plane resources for 3GPP access may be moved between E-UTRAN/EPC access and NG-RAN/5GC access as described in clause 5.17.2 of TS 23.501 [2]. For the MA PDU session over 3GPP access in 5GC and non-3GPP access in EPS, when a UE moves from NG-RAN/5GC to E-UTRAN/EPC, the SMF+PGW-C may release the user plane resources either over 3GPP access or non-3GPP access based on operator policy. In this case, while the UE remains in EPC in both 3GPP access and non-3GPP access, the UE shall not trigger PDN Connection establishment to add an additional EPC access leg to the MA PDU Session. If the SMF+PGW-C does not release the user plane resources over one of accesses, the UE sends traffic over both accesses based on ATSSS rules. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.2.4.3 QoS Support | The general principles for QoS support with ATSSS as described in clause 4.22.2.3.3 apply, with the clarifications below:
- With an MA PDU Session associated to a PDN Connection on EPS there may be separate user-plane tunnels between the AN and the PGW-U+UPF, one associated with non-3GPP access in EPC and one associated with 3GPP access in 5GS. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.3 UE Requested PDU Session Establishment with Network Modification to MA PDU Session | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.3.1 Overview | When an ATSSS-capable UE requests to establish a single-access PDU Session, but no policy in the UE and no local restrictions mandate a single access, the 5GC network may decide to modify it to a Multi-Access PDU (MA PDU) Session. This decision may be taken when e.g. the SMF wants to offload some traffic of the requested PDU Session to non-3GPP access or when the SMF wants to apply MPTCP and/or MPQUIC-UDP and/or MPQUIC-IP or MPQUIC-E to provide bandwidth aggregation for the requested PDU Session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.3.2 Non-roaming or roaming with local breakout | In the case of non-roaming or roaming with local breakout, the procedure for establishing a MA PDU Session when the UE requests a single-access PDU Session is the same with the procedure specified in clause 4.22.2.1.1, with the following clarifications and modifications:
- In step 1, the UE sets Request Type to initial request and it may include the "MA PDU Network-Upgrade Allowed" indication in UL NAS Transport message and its ATSSS Capabilities in PDU Session Establishment Request message, if the 5GC is ATSSS capable and no policy in the UE (e.g. no URSP rule) and no local restrictions mandate a single access for the requested PDU Session. The "MA PDU Network-Upgrade Allowed" indication indicates that the requested single-access PDU Session may be converted to a MA PDU Session, if the 5GC network wants to.
- In step 2, if the AMF receives the "MA PDU Network-Upgrade Allowed" indication, the AMF may select a SMF that supports MA PDU sessions. The AMF does not send the "MA PDU Request" indication to SMF, but it sends the "MA PDU Network-Upgrade Allowed" indication, if received from the UE. If the AMF determines that the requested S-NSSAI is not allowed on both accesses, the AMF shall not forward "MA PDU Network-Upgrade Allowed" indication to the SMF. If the AMF sends the "MA PDU Network-Upgrade Allowed" indication to SMF, it shall also indicate to SMF whether the UE is registered over both accesses.
If the PDU Session Establishment request is for a LADN, the AMF shall not forward "MA PDU Network-Upgrade Allowed" indication to the SMF.
- After step 6, if SMF receives the "MA PDU Network-Upgrade Allowed" indication, the SMF may decide, if dynamic PCC is not to be used, to convert the single-access PDU Session requested by the UE into a MA PDU Session. The SMF may take this decision based on local operator policy, subscription data indicating whether the MA PDU session is allowed or not and/or other conditions, which are not specified in the present document.
If the SMF receives ATSSS Capabilities from the UE but does not receive "MA PDU Network-Upgrade Allowed" indication from the AMF, the SMF shall not convert the single-access PDU Session requested by the UE into a MA PDU Session.
If the SMF receives a UP Security Policy for the PDU Session with Integrity Protection set to "Required" and the MA PDU session is being established over non-3GPP access, the SMF does not verify whether the access can satisfy the UP Security Policy.
- In step 7, if dynamic PCC is to be used for the PDU Session, the SMF indicates to PCF that the SM policy control information is requested for a MA PDU Session via "MA PDU Network-Upgrade Allowed" indication if the MA PDU session is allowed based on the subscription data. The SMF provides the currently used Access Type(s) and RAT Type(s) for the MA-PDU session to the H-PCF. The SMF also provides the ATSSS Capabilities of the MA PDU session.
- In step 10, the N4 rules derived by SMF for the MA-PDU session are sent to UPF and two N3 UL CN tunnels info are allocated by the UPF.
- In step 11, for the MA PDU Session, the SMF sends an "MA PDU session Accepted" indication in the Namf_Communication_N1N2MessageTransfer message to the AMF. The AMF marks this PDU session as MA PDU session based on the received "MA PDU session Accepted" indication.
- The PDU Session Establishment Accept message includes ATSSS rules which indicate to UE that the requested PDU Session was converted by the network to a MA PDU Session.
- The SMF triggers the establishment of user-plane resources in both accesses, if it was informed in step 2 that the UE is registered over both accesses. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.3.3 Home-routed, the UE registered to the same VPLMN over both access | In the case of home-routed roaming, when the UE is registered to the same VPLMN over 3GPP access and non-3GPP access, the procedure for establishing a MA PDU Session when the VPLMN is ATSSS capable and the UE requests a single-access PDU Session but no policy in the UE and no local restrictions mandate a single access, is the same with the procedure specified in clause 4.22.2.2.1, with the following clarifications and modifications:
- In step 1, the UE sets Request Type to initial request and it may include an "MA PDU Network-Upgrade Allowed" indication in UL NAS Transport message and its ATSSS Capabilities as defined in clause 5.32.2 of TS 23.501 [2] in PDU Session Establishment Request message.
- In step 2, if the AMF receives the "MA PDU Network-Upgrade Allowed" indication, the AMF may select a V-SMF and a H-SMF that support MA PDU sessions. If the AMF determines that the requested S-NSSAI is not allowed on both accesses, the AMF shall not forward "MA PDU Network-Upgrade Allowed" indication to the V-SMF.
- In step 3, the AMF sends the "MA PDU Network-Upgrade Allowed" indication, if received from the UE. If the AMF sends the "MA PDU Network-Upgrade Allowed" indication to V-SMF, it shall also indicate to V-SMF whether the UE is registered over both accesses.
- In step 5, two DL N9 tunnel CN info and two UL N3 tunnel CN info are allocated by the V-SMF or by the V-UPF. Additionally, the V-SMF indicates to H-SMF the relationship between the DL N9 tunnel CN info and the access type. If the single CN Tunnel is established by the H-SMF, the DL N9 tunnel CN info binding to the access over which the NAS message is received is to be used.
- In step 6, the V-SMF provides the "MA PDU Network-Upgrade Allowed" indication, if received from AMF, together with an indication whether the UE is registered over both accesses.
- After step 6, if the H-SMF receives the "MA PDU Network-Upgrade Allowed" indication, the H-SMF may decide to convert the single-access PDU Session requested by the UE into a MA PDU Session, if dynamic PCC is not to be used. The H-SMF may take this decision based on local operator policy, subscription data indicating whether the MA PDU session is allowed or not and/or other conditions, which are not specified in the present document.
If the H-SMF receives ATSSS Capabilities from the UE but does not receive "MA PDU Network-Upgrade Allowed" indication from the AMF, the H-SMF shall not convert the single-access PDU Session requested by the UE into a MA PDU Session.
- In step 9, if dynamic PCC is to be used for the MA PDU Session, the H-SMF sends an "MA PDU Network-Upgrade Allowed" indication instead of "MA PDU Request" indication to H-PCF in the SM Policy Control Create message if the MA PDU session is allowed based on the subscription data. The H-SMF also provides the ATSSS Capabilities of the MA PDU session. The H-PCF decides whether the single-access PDU Session can be converted into an MA PDU session or not based on operator policy and subscription data.
- In step 13, the H-SMF sends "MA PDU session Accepted" indication to V-SMF in the Nsmf_PDUSession_Create Response message.
- In step 14, the V-SMF includes the "MA PDU session Accepted" indication in the Namf_Communication_N1N2MessageTransfer message to the AMF. The AMF mark this PDU session as MA PDU session based on the received "MA PDU session Accepted" indication.
- In step 16, the UE receives a PDU Session Establishment Accept message, which includes ATSSS rules and indicates to UE that the requested single-access PDU session was established as a MA PDU Session.
- After step 18, two N9 tunnels between the H-UPF and the V-UPF as well as two N3 tunnels between the V-UPF and 5G-AN are established, or, if the H-UPF is connected to two different V-UPFs, the H-UPF has one N9 tunnel with each V-UPF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.3.4 Home-routed, the UE registered to different PLMNs over both access | In the case of home-routed roaming, when the UE is registered to different PLMNs over 3GPP access and non-3GPP access, the procedure for establishing a MA PDU Session when the UE requests a single-access PDU Session in an ATSSS capable PLMN but no policy in the UE and no local restrictions mandate a single access, is the same with the procedure specified in clause 4.22.2.2.2, with the following clarifications and modifications:
- In step 1, the UE sets Request Type to initial request and it may include an "MA PDU Network-Upgrade Allowed" indication in UL NAS Transport message and its ATSSS Capabilities as defined in clause 5.32.2 of TS 23.501 [2] in PDU Session Establishment Request message.
- In step 2, if the AMF receives the "MA PDU Network-Upgrade Allowed" indication, the AMF may select a V-SMF that supports MA PDU sessions.
- In step 3, the AMF sends the "MA PDU Network-Upgrade Allowed" indication, if received from the UE.
- In step 6, the V-SMF provides the "MA PDU Network-Upgrade Allowed" indication, if received from AMF.
- After step 6, if the H-SMF receives the "MA PDU Network-Upgrade Allowed" indication, the H-SMF may decide to convert the single-access PDU Session requested by the UE into a MA PDU Session, if dynamic PCC is not to be used. The H-SMF may take this decision based on local operator policy, subscription data indicating whether the MA PDU session is allowed or not and/or other conditions, which are not specified in the present document.
- In step 9, if dynamic PCC is to be used for the MA PDU Session, the H-SMF sends an "MA PDU Network-Upgrade Allowed" indication to H-PCF in the SM Policy Control Create message if the MA PDU session is allowed based on the subscription data. The H-SMF also provides the ATSSS Capabilities of the MA PDU session.
- In step 13, the H-SMF sends "MA PDU session Accepted" indication to V-SMF in the Nsmf_PDUSession_Create Response message.
- In step 14, the V-SMF includes the "MA PDU session Accepted" indication in the Namf_Communication_N1N2MessageTransfer message to the AMF. The AMF mark this PDU session as MA PDU session based on the received "MA PDU session Accepted" indication.
- In step 16, the UE receives a PDU Session Establishment Accept message, which includes ATSSS rules and indicates to UE that the requested single-access PDU session was established as a MA PDU Session.
- After the MA PDU Session is established over one access, the UE shall send another PDU Session Establishment Request over the other access containing the same PDU Session ID that was provided over the first access. The UE also sets Request Type as "MA PDU Request" in UL NAS Transport message. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.4 Access Network Performance Measurements | The PMF of UE side or/and UPF side should be able to correlate the measurement packets with the corresponding access type in order to get the accurate measurement result for each access. The PMF of UE side correlates the sent measurement request and received measurement response messages via the same access type and the PMF of UPF side correlates the sent measurement request and received measurement response messages via the same N3 or N9 Tunnel. The PMF of UPF side shall record the relationship between the RTT measurement result and the N3 or N9 Tunnel.
NOTE: The frequency for RTT measurement for each access is decided by the PMF of the UE and the UPF respectively. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.5 Reporting of Access Availability | After the MA PDU session is established, if Reporting of Access Availability is required by network, the UE performs detection of the unavailability and availability of an access as described in clause 5.32.5.3 of TS 23.501 [2]. To report the availability/unavailability of the access, the UE sends the PMF-Access Report to the UPF via the user plane of any available access of the MA PDU session. The UPF shall use this report to decide which access can be used to deliver the downlink packets.
4.22.5A Suspend and Resume Traffic Duplication
After the MA PDU session is established and the Redundant steering mode is active, the UPF may suspend traffic duplication by sending PMF-Suspend Duplication Request to the UE via the user plane of any available access of the MA PDU session as described in clause 5.32.5.6 of TS 23.501 [2]. The UPF may resume traffic duplication for a UE by sending PMF-Resume Duplication Request via the user plane of any available access of the MA PDU session as described in clause 5.32.5.6 of TS 23.501 [2]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.6 EPS Interworking | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.6.1 General | This clause includes mobility procedures for interworking with EPS. MA PDU Session establishment procedures with user plane resources in EPS are described in clause 4.22.2.3 and clause 4.22.2.4. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.6.2 Impacts to EPS interworking procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.6.2.1 5GS to EPS handover using N26 interface | Based on the signalling flow in Figure 4.11.1.2.1-1, the procedure is performed with the following differences and modifications:
- Step 2 is also performed with all the SMF+PGW-Cs corresponding to MA PDU Sessions with allocated EBI(s).
- In step 12e, the AMF requests the release of the 3GPP access of the MA PDU Session which has resources established for 3GPP access, but not expected to be transferred to EPC, i.e. no EBI(s) allocated to the MA PDU Session by triggering Nsmf_PDUSession_UpdateSMContext service operation.
NOTE: When the SMF received the release request from the AMF, the SMF decides whether the MA PDU Session is completely released or released over a single access based on its local policy.
- In step 16, if the MA PDU Session is established in both 3GPP and non-3GPP accesses and the MA PDU Session is moved to EPS and if the UE or the network does not supports MA PDU Session with 3GPP access connected to EPC, the SMF triggers the MA PDU Session Release procedure over non-3GPP access. If UE and the network support MA PDU Session with 3GPP access connected to EPC, the SMF should keep the user-plane resources over non-3GPP access in 5GC and use the PDN Connection as the 3GPP access leg of the MA PDU Session. If the MA PDU Session is established using one 3GPP access path via 5GC and one non-3GPP access path via ePDG/EPC and the MA PDU Session is moved to EPS and if the UE and network supports MA PDU Session with non-3GPP access connected to EPC, the SMF may keep the MA PDU Session. If MA PDU Sessions with 3GPP access and non-3GPP access user plane resources both connected to EPC is not allowed based on operator policy, the SMF+PGW-C may release the user plane resources either over 3GPP access or non-3GPP access. In this case, while the UE is connected to EPC via both 3GPP access and non-3GPP access, the UE shall not trigger PDN Connection establishment to add an additional EPC access leg to the MA PDU Session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.6.2.2 5GS to EPS idle mode mobility using N26 interface | Based on the signalling flow in Figure 4.11.1.3.2-1, the procedure is performed with the following differences and modifications:
- Step 5a is also performed with all the SMF+PGW-Cs corresponding to the MA PDU Sessions with allocated EBI(s).
- In step 12, if the MA PDU Session is established in both 3GPP and non-3GPP accesses and the MA PDU Session is moved to EPS and if the UE or the network does not support MA PDU Session with 3GPP access connected to EPC, the SMF triggers the MA PDU Session Release procedure over non-3GPP access. If UE and the network support MA PDU Session with 3GPP access connected to EPC, the SMF should keep the user-plane resources over non-3GPP access in 5GC and use the PDN Connection as the 3GPP access leg of the MA PDU Session. If the MA PDU Session is established using one 3GPP access path via 5GC and one non-3GPP access path via ePDG/EPC and the MA PDU Session is moved to EPS and if the UE and network supports MA PDU Session with non-3GPP access connected to EPC, the SMF may keep the MA PDU Session. If MA PDU Sessions with 3GPP access and non-3GPP access user plane resources both connected to EPC is not allowed based on operator policy, the SMF+PGW-C may release the user plane resources either over 3GPP access or non-3GPP access. In this case, while the UE is connected to EPC via both 3GPP access and non-3GPP access, the UE shall not trigger PDN Connection establishment to add an additional EPC access leg to the MA PDU Session.
- In step 15a, the AMF also requests the release of the MA PDU Session which has resources established for 3GPP access, but not expected to be transferred to EPS, i.e. no EBI(s) allocated to the MA PDU Session by triggering Nsmf_PDUSession_UpdateSMContext service operation.
NOTE: When the SMF received the release request from the AMF, the SMF decides whether the MA PDU Session is completely released or released over a single access based on its local policy. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.6.2.3 EPS bearer ID allocation | Based on the signalling flow in Figure 4.11.1.4.1-1, additionally for the MA PDU Session, with the following differences and clarifications:
- In step 1, the following procedures and relevant steps are also initiated during the UE Requested MA PDU Session Establishment, the UE Requested PDU Session Establishment with Network Modification to MA PDU Session and the UE or network requested MA PDU Session Modification procedures.
- In step 2, if the QoS Flow(s) of the MA PDU Session is established and the MA PDU Session is established over 3GPP access and other existing conditions satisfies EPS interworking, the SMF requests EBI allocation for the QoS Flow(s) of the MA PDU Session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.6.2.4 EPS bearer ID revocation | Based on the clause 4.11.1.4.3, additionally the following procedures are updated to revoke the EPS bearer ID(s) assigned to the QoS Flow(s) in the MA PDU Session:
- UE or network requested MA PDU Session Release (non-roaming and roaming with local breakout) in clause 4.22.10.2.
- UE or network requested MA PDU Session Release (home-routed roaming) in clause 4.22.10.3.
- UE or network requested MA PDU Session Modification (non-roaming and roaming with local breakout) in clause 4.22.8.2.
- UE or network requested MA PDU Session Modification (home-routed roaming) in clause 4.22.8.3.
- When the MA PDU Session is released over 3GPP access, the UE and the SMF locally release the EBI(s) for the MA PDU Session. The SMF notifies the AMF of the released EBI(s) by sending Nsmf_PDUSession_SMContextStatusNotify service operation if the MA PDU Session is established in the same PLMN. If the MA PDU Session is established in different PLMNs, the SMF notifies the release of the MA PDU Session and as a result, the AMF removes associated EBI(s). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.6.2.5 5GS to EPS mobility without N26 interface | Based on the signalling flow in Figure 4.11.2.2-1, the procedure is performed with the following differences and modifications:
- In step 10 (and step 13 in clause 4.11.2.4.1), if the MA PDU Session is established in both 3GPP and non-3GPP accesses and the MA PDU Session is moved to EPS and if the UE and the network does not support MA PDU Session with 3GPP access connected to EPC, the PGW-C + SMF triggers the MA PDU Session Release procedure over non-3GPP access. PGW-C + SMF and UE locally release the context related to ATSSS operation, e.g. ATSSS rules and Measurement Assistance Information for the relevant session. If the UE and the network support MA PDU Session with 3GPP access connected to EPC, the UE includes a "MA PDU Request" indication and the PDU Session ID in the PCO, the SMF should keep the user-plane resources over non-3GPP access in 5GC and use the PDN Connection as the 3GPP access leg of the MA PDU Session.
- In step 13, during the additional PDN Connectivity Procedure, if the MA PDU Session is established in both 3GPP and non-3GPP accesses and if the UE and the network support MA PDU Session with 3GPP access connected to EPC, the UE includes a "MA PDU Request" indication and the PDU Session ID in the PCO, the SMF should keep the user-plane resources over non-3GPP access in 5GC and use the PDN Connection as the 3GPP access leg of the MA PDU Session. If the UE and the network does not support MA PDU Session with 3GPP access connected to EPC and the MA PDU Session is moved to EPS, the PGW-C + SMF triggers the MA PDU Session Release procedure over non-3GPP access. PGW-C + SMF and UE locally release the context related to ATSSS operation, e.g. ATSSS rules and Measurement Assistance Information for the relevant session(s).
- Step 14 is also performed for the MA PDU session(s) transferred to EPS. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.6.3 Network Modification to MA PDU Session after a UE moving from EPC | Figure 4.22.6.3-1 describes procedure for Network Modification to MA PDU Session after a UE is moving from EPS.
Figure 4.22.6.3-1: Network Modification to MA PDU Session after a UE moving from EPS
1. When the network supports interworking with N26 interface, a PDN Connection can be moved from EPS to 5GS as described in clause 4.11.1.2.2 and clause 4.11.1.3.3.
2. If the UE requests MA PDU session, or if no policy in the UE (e.g. no URSP rule) and no local restrictions mandate a single access for the PDU Session, the UE requests PDU Session Modification over 3GPP access as described in clause 4.22.8 with following modifications:
- In step 1a, the UE provides Request Type as "MA PDU Request" in UL NAS Transport message, or, if no policy in the UE (e.g. no URSP rule) and no local restrictions mandate a single access for the PDU Session, the UE provides an "MA PDU Network-Upgrade Allowed" indication in UL NAS Transport message. The UE provides its ATSSS Capabilities, as defined in clause 5.32.2 of TS 23.501 [2] in PDU Session Modification Request message. If the AMF receives the "MA PDU Network-Upgrade Allowed" indication from the UE, the AMF may send it to the SMF. If the AMF determines that the UE is registered via both accesses in the same PLMN but the current S-NSSAI is not in the Allowed NSSAI for both accesses, the AMF shall reject the PDU session modification if the UE provides an "MA PDU Request" indication, or the AMF shall not forward "MA PDU Network-Upgrade Allowed" indication to the SMF if received from the UE.
- In step 3a, if the SMF decides to change the PDU Session to MA PDU Session, the SMF includes ATSSS rule(s) in the PDU Session Modification Command message. The SMF may also include Measurement Assistance Information. When the SMF sends Nsmf_PDUSession_UpdateSMContext response, the SMF includes "MA PDU session Accepted" indication. The AMF marks the PDU Session as MA PDU Session based on the indication. If the SMF was informed in step 1a that the UE is registered over both accesses, then the SMF initiates the establishment of user-plane resources over non-3GPP access too.
- In step 5, if the UE receives ATSSS rule(s) in the PDU Session Modification Command message, the UE stores that the PDU Session is MA PDU Session.
3. If the UE is registered to the different PLMN over 3GPP and non-3GPP access or the UE is not registered in non-3GPP access, the UE may trigger the UE requested PDU Session Establishment procedure as described in clause 4.22.7 over non-3GPP access to add second access to the MA PDU Session after the UE is registered in non 3GPP access. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.7 Adding / Re-activating / De-activating User-Plane Resources | If the UE has established a MA PDU Session but the user-plane resources over one access of the MA PDU Session have not been established, then:
- If the UE wants to add user-plane resources over this access, the UE shall initiate the UE Requested PDU Session Establishment procedure over this access, as specified in clause 4.3.2.2. In the UL NAS Transport message, the UE sets Request Type as "MA PDU Request" and the same PDU Session ID of the established MA PDU Session. If only one N9 tunnel is established for the Home Routed roaming case as described in clause 4.22.2.2, additional N9 tunnel is established during this UE Requested PDU Session Establishment procedure. For the roaming with home-routed architecture as defined in TS 23.501 [2] figure 4.2.10-3, an N9 tunnel or an N3 tunnel is established during this PDU Session Establishment procedure, depending on the access for which the UE is requesting user-plane resources.
- The PDU Session Establishment Accept message received by the UE may contain updated ATSSS rules for the MA PDU session.
- If the SMF receives the PDU Session Establishment request message over an access and the SMF already has SM Contexts for the access, the SMF shall not release existing SM Contexts and shall re-activate user plane resources over the access while providing the PDU Session Establishment Accept message to the UE.
If the UE has established a MA PDU Session and the user-plane resources over one access of the MA PDU Session have been established but are currently inactive (e.g. because the UE is CM-IDLE over this access), then:
- If the UE wants to re-activate the user-plane resources over this access, then the UE shall initiate the Registration or UE Triggered Service Request procedure over this access, as specified in clause 4.22.9.2.
- If the network wants to re-activate the user-plane resources over 3GPP access of the MA PDU Session, or over non-3GPP access of the MA PDU Session, the network shall initiate the Network Triggered Service Request procedure, as specified in clause 4.22.9.4.
If the UE has established a MA PDU Session and the user plane resources are activated over either one access or both accesses, then:
- If the network wants to de-activate the user-plane resources over single access, then the network shall initiate the CN-initiated deactivation of UP connection procedure over this access, as specified in clause 4.3.7.
In all cases, if the UP security protection associated with this PDU session indicates that UP security is required, the SMF shall not establish resources over the 3GPP access unless the 3GPP Access Network can enforce the required UP security protection, even if resources were previously established over non-3GPP access. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.8 UE or network requested MA PDU Session Modification | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.8.1 General | This procedure is triggered in the following cases:
- QoS Flow creation / modification (including GBR QoS Flow movement).
- Update of ATSSS rules and/or N4 rules. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.8.2 UE or network requested MA PDU Session Modification (non-roaming and roaming with local breakout) | The signalling flow for a MA PDU Session Modification when the UE is not roaming, or when the UE is roaming and the PDU Session Anchor (PSA) is located in the VPLMN, is based on the signalling flow in Figure 4.3.3.2-1 with the following differences and clarifications:
- In step 1b, the SMF may decide to update ATSSS rules and/or N4 rules based on updated PCC rules.
- In step 1d, if the UPF determines that it cannot send GBR traffic over the current ongoing access e.g. based on the N4 rules and access availability and unavailability report from the UE, the UPF shall send Access Availability report to the SMF. When the SMF receives the Access Availability report, the SMF may decide to move the GBR QoS Flow to the other access as described in clause 5.32.4 of TS 23.501 [2]. If the SMF decides to move the GBR QoS Flow, the SMF triggers this procedure and afterwards moves the GBR QoS Flow to the target access.
- In step 3, if the SMF decides to move the GBR QoS Flow to the other access, the SMF sends N2 SM information to the target AN. The PDU Session Modification Command message is sent to the UE to update ATSSS rule of the UE so that the UE sends uplink GBR traffic over the target access. The SMF releases AN resources of the GBR QoS Flow in the source access.
- In step 3, when the SMF establishes user plane resources for a QoS flows, the SMF provides QoS profile to the AN as follows:
- for Non-GBR QoS Flow, steps 3 to 8 are performed over each access for which the user plane resources are activated.
- for GBR QoS Flow allowed in a single access, steps 3 to 8 are performed in the allowed access.
- for GBR QoS Flow allowed in both accesses, steps 3 to 8 are performed in the access according to the decision by the SMF (as described in clause 5.32.4 of TS 23.501 [2]).
- In step 3, if the SMF wants to update ATSSS rules, the SMF includes updated ATSSS rules in the N1 SM container (PDU Session Modification Command). When the SMF provides N1 SM container and/or N2 SM information, the SMF includes access type in the Namf_Communication_N1N2MessageTransfer to provide routing information to the AMF.
- In step 8, if the SMF decides to moves GBR QoS Flow to the other access, the SMF may send updated N4 rules to the UPF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.8.3 UE or network requested MA PDU Session Modification (home-routed roaming) | The signalling flow for a MA PDU Session Modification when the UE is registered to the same VPLMN over 3GPP access and non-3GPP access and the PDU Session Anchor (PSA) is located in the HPLMN, is based on the signalling flow in Figure 4.3.3.3-1 with the following differences and clarifications:
- In step 1b, the H-SMF may decide to update ATSSS rules and/or N4 rules based on updated PCC rules.
- In step 1d, if the H-UPF determines that it cannot send GBR traffic over the current ongoing access e.g. based on the N4 rules and access availability and unavailability report from the UE, the H-UPF shall send Access Availability report to the H-SMF. When the H-SMF receives the Access Availability report, the H-SMF may decide to move the GBR QoS Flow to the other access as described in clause 5.32.4 of TS 23.501 [2]. If the H-SMF decides to move GBR QoS Flow, the H-SMF triggers this procedure and afterwards moves the GBR QoS flow to the target access.
- In step 3, if the H-SMF decides to move the GBR QoS Flow to the other access, the H-SMF sends updated GBR QoS Flow information contains associated access type and ATSSS rule to the V-SMF. Based on the information the V-SMF establishes AN resources for the GBR QoS Flow to the target access.
- In step 3, when the H-SMF provides GBR QoS Flow information, the H-SMF includes associated access type in Nsmf_PDUSession_Update. When the H-SMF provides non-GBR QoS Flow information, H-SMF provides the information for both accesses in Nsmf_PDUSession_Update.
- In step 3, if the H-SMF wants to update ATSSS rules, the H-SMF triggers Nsmf_PDUSession_Update and includes an updated ATSSS rules.
- In step 4, if the H-SMF decides to move the GBR QoS Flow to the other access, the PDU Session Modification Command message is sent to the UE to update ATSSS rule of the UE so that the UE sends uplink GBR traffic over the target access. The V-SMF releases AN resources of the GBR QoS Flow in the source access.
- In step 4, when the V-SMF establishes user plane resources for a QoS flows, the V-SMF provides QoS profile to the AN as follows:
- for Non-GBR QoS Flow, steps 4 to 9 are performed over each access for which the MA PDU Session is established.
- for GBR QoS Flow allowed in a single access, steps 4 to 9 are performed in the allowed access.
- for GBR QoS Flow allowed in both accesses, steps 4 to 9 are performed in the access according to the decision by the SMF (as described in clause 5.32.4 of TS 23.501 [2]).
- In step 4, if the H-SMF provides updated ATSSS rules, the V-SMF includes the updated ATSSS rules in the N1 SM container (PDU Session Modification Command). When the V-SMF provides N1 SM container and/or N2 SM information, the V-SMF includes access type in the Namf_Communication_N1N2MessageTransfer to provide routing information to the AMF.
The description of signalling flow for a MA PDU Session Modification when the UE is registered to different PLMNs over 3GPP access and non-3GPP access and the PDU Session Anchor (PSA) is located in the HPLMN, is based on above procedure with the following differences and clarifications:
- The description of (V-)SMF providing QoS profile to the AN is not applicable and instead the regular procedures for QoS profile provisioning from (V-)SMF to (R)AN applies. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.9 Connection, Registration and Mobility Management procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.9.1 Registration procedures | Support for using the Registration procedures for non-3GPP access path switching is described in clause 4.22.9.5.
The signalling flow for a Registration is based on the signalling flow in Figure 4.2.2.2.2-1 with the following differences and clarifications:
- In step 1, if the UE wants to re-activate the user plane of the MA PDU Session(s) over the access the Registration message is sent to, the UE indicates PDU Session ID(s) of the MA PDU Session(s) in the List Of PDU Sessions To Be Activated.
If the UE locally releases the MA PDU Session(s) in both accesses, the UE indicates it in the PDU Session Status. If the AMF receives the PDU Session Status and finds mismatch, regardless of roaming mode of the MA PDU Session(s) (i.e. non-roaming, local breakout roaming, home routed roaming in the same PLMN or home routed roaming in different PLMNs), the AMF invokes Nsmf_PDUSession_ReleaseSMContext service towards the SMF(s) in order to release any network resources related to the MA PDU Session(s).
- In step 4, the old AMF determines whether the new AMF support ATSSS or not based on the supported features provided by the new AMF.
- In step 5, if the old AMF determined in step 4 that the new AMF does not support ATSSS, the old AMF does not include the PDU Session context of the MA PDU Session(s) in the UE context transferred to the new AMF.
- If the old AMF has not included MA PDU Session(s) in the UE context in step 5, the old AMF informs the corresponding SMF(s) to release the MA PDU Session(s) by invoking the Nsmf_PDUSession_ReleaseSMContext service operation as described in clause 4.22.10.
- In step 21, the AMF provides an MA PDU Session Support indicator in Registration Accept message to inform the UE whether ATSSS is supported or not. The UE uses this indicator to determine whether an MA PDU session related procedure can be initiated or not, as described in clause 4.22.1.
In step 17, if the UE indicated to re-activate MA PDU Session(s) in the List Of PDU Sessions To Be Activated the AMF includes access type which the Registration Request message is received on when the AMF triggers Nsmf_PDUSession_UpdateSMContext service operation. The SMF only re-activates user plane resources of the access type the Registration Request message is received on.
- In step 21, the AMF indicates to the UE whether it supports non-3GPP access path switching.
- In step 22, if the AMF indicates that the PDU Session(s) has been released in the PDU Session Status to the UE in Registration Accept message, the UE removes locally any internal resources related to the MA PDU Session(s) that are not marked as established. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.9.2 UE Triggered Service Request | The signalling flow for a UE Triggered Service Request is based on the signalling flow in Figure 4.2.3.2-1 with the following differences and clarifications:
- In step 1, if the UE wants to re-activate the user plane of the MA PDU Session(s) over the access the Service Request message is sent to, the UE indicates PDU Session ID(s) of the MA PDU Session(s) in the List Of PDU Sessions To Be Activated.
If the UE locally releases the MA PDU Session(s), the UE indicates it in the PDU Session Status. If the AMF receives the PDU Session Status and finds mismatch, regardless of roaming mode of the MA PDU Session (i.e. non-roaming, local breakout roaming, home routed roaming in the same PLMN or home routed roaming in different PLMNs), the AMF invokes Nsmf_PDUSession_ReleaseSMContext service towards the SMF(s) in order to release any network resources related to the MA PDU Session(s).
In step 4, if the UE indicated to re-activate MA PDU Session(s) in the List Of PDU Sessions To Be Activated the AMF includes access type which the Service Request message is received on when the AMF triggers Nsmf_PDUSession_UpdateSMContext service operation. The SMF only re-activates user plane resources of the access type the Service Request message is received on.
- In step 12, if the AMF indicates that the PDU Session(s) has been released in the PDU Session Status to the UE in Service Accept message, the UE removes locally any internal resources related to the MA PDU Session(s) that are not marked as established.
NOTE: For an MA PDU session established when UE was registered on only one access, during the registration on the second access, the AMF does not notify the SMF (for this MA PDU session) that the UE is now registered on the second access since this will occur later, i.e. when the UE sends the second PDU Session Establishment Request to add user plane resources. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.9.3 N2 based handover | Inter NG-RAN node N2 based handover, as described in clauses 4.9.1.3.2 and 4.9.1.3.3, is supported for the 3GPP access with the differences and clarifications described below.
- In step 2 of clause 4.9.1.3.2, the S-AMF determines whether or not the T-AMF supports ATSSS based on the supported features of the T-AMF provided by NRF or based on local configuration.
- In step 3 of clause 4.9.1.3.2, if the S-AMF determined in step 2 that the T-AMF does not support ATSSS, the S-AMF does not include the PDU Session context of the MA PDU Session(s) in the UE context transferred to the T-AMF.
- After step 6a of clause 4.9.1.3.3, if the S-AMF has not included MA PDU Session(s) in the UE context in step 3 of clause 4.9.1.3.2, the S-AMF informs the corresponding SMF(s) to release the MA PDU Session(s) by invoking the Nsmf_PDUSession_ReleaseSMContext service operation as described in clause 4.22.10. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.9.4 Network Triggered Service Request | The signalling flow for a Network Triggered Service Request is based on the signalling flow in Figure 4.2.3.3-1 with the following differences and clarifications:
- In step 2a, the SMF determines over which access (3GPP access or non-3GPP access or both accesses) the user plane resources need to be activated for the MA PDU Session. The SMF may consider Steering Mode to determine the target access.
- In step 3a, the SMF indicates to the AMF the access type (3GPP access or non-3GPP access) over which the user plane resources are to be activated for the MA PDU Session.
NOTE 1: If the SMF determines to activate both accesses, the SMF performs this step two times, i.e. one for 3GPP access and the other one for non-3GPP access.
In the case of DN-AAA or SMF initiated Secondary re-authentication procedure, when the SMF invokes the Namf_Communication_N1N2MessageTransfer service operation, SMF may indicate the target access type of sending N1 NAS message to the UE.
- In step 4, the AMF considers the MA PDU Session is associated with the access type the SMF has indicated in step 3a.
The AMF determines the access type of which to send the N1 NAS message to the UE based on the target access type value if received from the SMF in step 3a. If the AMF does not receive a target access type value and the UE is CM-CONNECTED in both accesses, the AMF determines the target access type.
- In step 5, if the SMF requested to re-activate user-plane resources over 3GPP access and the AMF has determined the UE is unreachable over 3GPP access (e.g. the AMF receives no response from the UE to the Paging), the AMF shall notify that the UE is unreachable. The (H-) SMF shall indicate the Anchor UPF that the user-plane resources on 3GPP access is unavailable by triggering N4 Session Modification procedure. Further action by the UPF is implementation dependent.
If the SMF requested to re-activate the user-plane resources over non-3GPP access and the AMF has determined the UE is unreachable over non-3GPP access (e.g. the UE is in CM-IDLE on non-3GPP access), the AMF shall reject the request from the SMF. The (H-) SMF shall indicate the Anchor UPF that the user-plane resources on non-3GPP access is unavailable by triggering N4 Session Modification procedure. Further action by the UPF is implementation dependent.
If this procedure is triggered for Secondary Re-authentication and UE and SMF+PGW-C supports for DN authentication and authorization over EPC as described in clause 5.4.4b, SMF+PGW-C selects one access type from non-3GPP access connected to 5GC or 3GPP access connected to EPC in step 3a. If the SMF+PGW-C receives failure indication from the AMF or MME that UE is unreachable then SMF+PGW-C retries by sending it to the other access type. Only when the failure is received from both AMF and MME, then SMF+PGW-C informs the DN-AAA Server that UE is not reachable for re-authentication according to clauses 4.3.2.3 and H.2.1.
NOTE 2: The provision of access availability/unavailability reports via user plane specified in clause 5.32.5.3 is UE implementation dependent. Such reporting by UE to UPF, can assist Anchor UPF to decide on handling DL traffic for the UE. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.9.5 Registration procedures for non-3GPP access path switching | If the UE supports non-3GPP access path switching and the AMF indicates that the network supports non-3GPP access path switching as described in clause 4.22.2, the UE may trigger a Mobility Registration Update via a new non-3GPP access to switch traffic from an old non-3GPP access (i.e. TNGF or N3IWF) to the new non-3GPP access (i.e. TNGF or N3IWF) if the PLMN of the selected new non-3GPP access is the same PLMN of the old non-3GPP access.
The UE may trigger non-3GPP path switching if the AMF indicated support during registration as described in clause 4.22.9.1, even if the SMF did not indicate support to the UE during the MA PDU Session Establishment.
In this case the Registration procedure described in clause 4.22.9.1 applies with the differences and clarifications described in this clause:
Figure 4.22.9.5-1: Mobility Registration procedure for non-3GPP access path switching
1. This is the same as step 1 in clause 4.22.9.1, with the following additions:
- If the UE wants to switch the user plane from an old non-3GPP access to a new non-3GPP access where the Mobility Registration Update is sent, the UE indicates PDU Session ID(s) of the PDU Session(s) in the List Of PDU Sessions To Be Activated. This may include both PDU Session ID(s) corresponding to MA PDU Sessions and single access PDU Sessions.
NOTE 1: The PDU Sessions that are not indicated in the List Of PDU Sessions To Be Activated by the UE are not released but deactivated during the switching procedure. The UE or network can re-activate user plane resources by triggering Service Request procedure after non-3GPP path switching is completed.
The UE may also provide an ("Non-3GPP access path switching while using old AN resources") indication in the Registration Request to indicate that the UP connection(s) via the old non-3GPP access can still be used for the MA PDU Session(s) during the Registration procedure. If the UP connection(s) via the old non-3GPP access cannot be used by the UE during the Registration procedure, the UE shall not provide a "Non-3GPP access path switching while using old AN resources" indication.
The UE shall not perform non-3GPP access path switching if the PLMN of the selected new non-3GPP access is different from the PLMN of the old non-3GPP access.
2. This is the same as step 2 in Figure 4.2.2.2.2-1.
3. This is the same as step 3 in Figure 4.2.2.2.2-1 with the following additions:
- If the UE provided an ("Non-3GPP access path switching while using old AN resources") indication in step 1 and the AMF supports to maintain two N2 connections for non-3GPP access during the Registration procedure and the SMF supports non-3GPP access path switching, the AMF delays the release of the old N2 connection until the UP connection via the new non-3GPP access is established. Otherwise, the AMF may trigger AN release towards the old non-3GPP access before proceeding with the Registration procedure in the new non-3GPP access, as described in clause 4.12.4.2 for untrusted non-3GPP access and clause 4.12a.4.2 for trusted non-3GPP access with the following clarifications:
- During the AN release procedure, the AMF should notify the SMF to release the UP resources for the activated PDU Sessions before sending the N2 UE Context Release Command to the old non-3GPP access.
- Due to pending downlink data in the UPF, the SMF may requests to establish user plane resources before non-3GPP path switching is finished. In this case, the AMF may reject the request with an indication that the Namf_Communication_N1N2MessageTransfer has been temporarily rejected. Upon reception of an Namf_Communication_N1N2MessageTransfer response with an indication that its request has been temporarily rejected, the SMF shall start a locally configured guard timer and wait for any message to come from an AMF. Upon reception of a message from an AMF, the SMF shall re-invoke the Namf_Communication_N1N2MessageTransfer (with N2 SM info and/or N1 SM info) to the AMF.
4. This is the same as steps 4-16 in Figure 4.2.2.2.2-1.
5-11. These steps are the same as step 17 in clause 4.22.9.1, with the following additions:
- If the Registration procedure is triggered to switch traffic from the old non-3GPP access to the new non-3GPP access and the UE provided an ("Non-3GPP access path switching while using old AN resources") indication in step 1, the AMF, if it supports maintaining two N2 connections for non-3GPP access, forwards this indication to the SMF in case the PDU Session is a MA PDU Session. If the SMF receives this indication, the SMF does not trigger release of the UP connection in the old non-3GPP access towards the old N3IWF or TNGF (if any).
- In step 7 and 8, the CN Tunnel Info is sent from SMF to the new non-3GPP AN via AMF. The IPSec child SA(s) between UE and the new non-3GPP AN are established.
- In step 10, the SMF updates the N4 rules by replacing the AN Tunnel Info of the old non-3GPP AN with the AN Tunnel Info of the new non-3GPP AN to instruct the UPF to switch traffic from the old non-3GPP access path to the new non-3GPP access path.
NOTE 2: The resource in the old non-3GPP access, i.e. the old N3IWF or TNGF, will in this case be released by the AMF in step 12.
- After the UP connection via the new non-3GPP access is established, the UE and UPF start to send traffic via the new non-3GPP access.
12. After the UP connection has been established in new non-3GPP access, the AMF also triggers AN release towards the old non-3GPP access (i.e. old N3IWF or TNGF), unless done previously with following clarifications:
- For the PDU Sessions indicated by the old non-3GPP access in the "List of PDU Session ID(s) with active N3 user plane" but not in the List Of PDU Sessions To Be Activated sent by the UE in step 1, the AMF requests the SMF to deactivate the PDU Session(s). For other PDU Sessions, the AMF shall not request the SMF to deactivate the PDU Session(s).
- When the UE receives Registration Accept over the new non-3GPP access, the UE considers that the UE is deregistered from the old non-3GPP access.
NOTE 3: In order to support RAT restrictions for non-3GPP access in the above procedure, it is assumed that UDM has provided restricted non-3GPP RAT types, if any, in the RAT restriction parameter in AM subscription data. In order to ensure that RAT restrictions are not violated in case the PDU Session is established in LBO roaming scenarios, the AMF in VPLMN may be configured to not indicate support for non-3GPP access path switching for inbound roaming UEs during MA PDU Session Establishment towards a SMF in VPLMN, unless it has been agreed in roaming agreements that non-3GPP access path switching can be supported for such UEs. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.10 MA PDU Session Release | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.10.1 General | The MA PDU Session Release procedure is used to release the MA PDU Session, or release the MA PDU Session over a single access. The MA PDU Session Release over a single access may be triggered by the network due to e.g. when the UE is deregistered over an access or when the S-NSSAI of the MA PDU Session is no longer in the Allowed NSSAI over an access. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.10.2 UE or network requested MA PDU Session Release (non-roaming and roaming with local breakout) | The signalling flow for a MA PDU Session Release when the UE is not roaming, or when the UE is roaming and the PDU Session Anchor (PSA) is located in the VPLMN, is based on the signalling flow in Figure 4.3.4.2-1 with the following differences and clarifications:
- In step 1, if the AMF needs to release the MA PDU Session over a single access, the AMF invokes the Nsmf_PDUSession_UpdateSMContext service operation to request the release of the MA PDU Session over a single access. In this case, the AMF includes in which access the MA PDU Session should be released.
NOTE: When the SMF received the release request from the AMF, the SMF decides whether the MA PDU Session is completely released or released over a single access based on its local policy.
- In step 1, if the AMF needs to release the MA PDU Session (e.g. locally released when the UE is CM-IDLE), the AMF invokes the Nsmf_PDUSession_ReleaseSMContext service operation to request the release of the MA PDU Session.
- In step 2a, if the SMF releases the MA PDU Session over a single access, the SMF sends an N4 Session Modification Request (N4 Session ID) message instead of N4 Session Release message to the UPF(s) of the MA PDU session.
- In step 2b, the UPF acknowledges the N4 Session Modification Request by the transmission of an N4 Session Modification Response (N4 Session ID) message to the SMF.
- In step 3, the SMF sends the PDU Session Release Command message to release the MA PDU session over a single access (either 3GPP access or non-3GPP access) or both accesses.
- In step 3, if the SMF releases the MA PDU Session over a single access, the SMF shall not include "skip indicator" in the Namf_Communication_N1N2MessageTransfer service.
- In step 3, if the SMF releases the MA PDU Session over both accesses and user plane resources are established in both accesses, the SMF includes both N1 SM container (PDU Session Release Command) and N2 SM Resource Release request together in the Nsmf_PDUSession_UpdateSMContext or Namf_Communication_N1N2MessageTransfer service so that the UE does not request to activate user plane resources. The SMF releases user plane resources of the other access by including N2 SM Resource Release only in Namf_Communication_N1N2MessageTransfer service.
- In step 3, when the SMF provides N1 SM container and/or N2 SM information, the SMF includes access type in the Namf_Communication_N1N2MessageTransfer to provide routing information to the AMF.
- In step 11, the SMF triggers Nsmf_PDUSession_SMContextStatusNotify service only when the MA PDU Session is released in both accesses. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.22.10.3 UE or network requested MA PDU Session Release (home-routed roaming) | The signalling flow for a MA PDU Session Release when the UE is registered to the same VPLMN over 3GPP access and non-3GPP access and the PDU Session Anchor (PSA) is located in the HPLMN, is based on the signalling flow in Figure 4.3.4.3-1 with the following differences and clarifications:
- In step 1, if the V-AMF needs to release the MA PDU Session over a single access, the V-AMF may invoke the Nsmf_PDUSession_UpdateSMContext service operation to request the release of the MA PDU Session over a single access. In this case, the AMF shall include in which access the MA PDU Session should be released. The V-SMF invokes Nsmf_PDUSession_Update service operation to request the release of the MA PDU Session over a single access. The V-SMF shall include in which access the MA PDU Session should be released.
NOTE: When the H-SMF received the release request from the V-SMF, the H-SMF decides whether the MA PDU Session is released or released over a single access based on its local policy.
- In step 1, if the V-AMF needs to release the MA PDU Session (e.g. locally released when the UE is CM-IDLE), the AMF invokes the Nsmf_PDUSession_ReleaseSMContext service operation to request the release of the MA PDU Session. The V-SMF invokes Nsmf_PDUSession_Release service operation to request the release of the MA PDU Session.
- In steps 2a-2b, if the SMF releases the MA PDU Session over a single access, these steps are the same as steps 2a-2b in clause 4.22.10.2.
- In step 3a, the H-SMF invokes Nsmf_PDUSession_Update service operation towards the V-SMF to release the MA PDU session over a single access (either 3GPP access or non-3GPP access) or both accesses.
- In step 5, the V-SMF sends the PDU Session Release Command message to release the MA PDU session over a single access (either 3GPP access or non-3GPP access) or both accesses.
- In step 5, if the V-SMF releases the MA PDU Session over a single Access Network, the V-SMF shall not include "skip indicator" in the Namf_Communication_N1N2MessageTransfer service.
- In step 5, if the V-SMF releases the MA PDU Session over both accesses and user plane resources are established in both accesses, the V-SMF includes both N1 SM container (PDU Session Release Command) and N2 SM Resource Release request together in the Nsmf_PDUSession_UpdateSMContext or Namf_Communication_N1N2MessageTransfer service so that the UE does not request to activate user plane resources. The V-SMF releases user plane resources of the other access by including N2 SM Resource Release only in Namf_Communication_N1N2MessageTransfer service.
- In step 5, when the V-SMF provides N1 SM container and/or N2 SM information, the V-SMF includes access type in the Namf_Communication_N1N2MessageTransfer to provide routing information to the V-AMF.
- In step 16, the H-SMF triggers Nsmf_PDUSession_StatusNotify service only when the MA PDU Session is released in both accesses. The V-SMF triggers Nsmf_PDUSession_SMContextStatusNotify service only when the MA PDU Session is released in both accesses.
The signalling flow for a MA PDU Session Release when the UE is registered to the different PLMNs over 3GPP access and non-3GPP access and the PDU Session Anchor (PSA) is located in the HPLMN, is based on the above procedure with the following differences and clarifications:
- In step 1a, the (V-)AMF can trigger the MA PDU session release over a single access or over both accesses as described in step 1 of clause 4.22.10.2.
- In step 3a, the H-SMF invokes Nsmf_PDUSession_Update service operation towards the V-SMF to release the MA PDU Session over a single access (either 3GPP access or non-3GPP access) or both accesses.
If the UE is registered to the HPLMN via an access and the H-SMF releases MA PDU Session over the access, the H-SMF invokes Namf_Communication_N1N2MessageTransfer.
- In step 5, the V-SMF releases the MA PDU Session over the access the H-SMF indicated in step 3a. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23 Support of deployments topologies with specific SMF Service Areas | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.1 General | This clause captures changes to 5GC procedures in other clauses of this specification and new procedures to support deployments topologies with specific SMF Service Areas that are defined in clause 5.34 of TS 23.501 [2].
In the case of roaming for a Home Routed PDU Session the following cases may occur:
- A UE moves out of V-SMF serving area in the serving PLMN;
- A UE moves to another (serving) VPLMN;
- A UE moves between HPLMN and a VPLMN.
In the above cases, the procedures in clauses 4.23.2-16 for I-SMF apply for the V-SMF insertion/change/removal by replacing the I-SMF with V-SMF and SMF with H-SMF. When an AMF detects the need to change the V-SMF while the H-SMF does not support V-SMF change, the AMF shall not trigger the V-SMF change but shall trigger the release of the PDU Session.
For an established PDU session an I-SMF is inserted if the UE is not in the SMF Service Area. In this case, when an UE moves from HPLMN to a VPLMN, a V-SMF is inserted and the I-SMF is removed. For mobility from VPLMN to HPLMN, an I-SMF is inserted and the V-SMF is removed. The procedures of this clause apply in this case, i.e. by replacing the target or new I-SMF by a V-SMF for mobility from HPLMN to VPLMN and by replacing the source or old I-SMF by a V-SMF for mobility from VPLMN to HPLMN.
For additional consideration for Home-routed PDU sessions see clause 4.23.17.
NOTE 1: The procedures of mobility registration update and handover specified in the clause 4.23 by replacing the I-SMF with V-SMF and SMF with H-SMF are applicable to the Indirect Network Sharing as specified in clause 5.18 of TS 23.501 [2].
NOTE 2: In the case of Home Routed roaming and Indirect Network Sharing, when the UE moves between different PLMNs, the AMF determines whether the (new) V-SMF needs to be inserted or removed based on, e.g. whether the PLMN changes.
If at UE mobility the service area of the SMF does not include the location where the UE camps and the PDU Session is a MA PDU Session, then the AMF initiates the release of the MA PDU Session over all accesses served by this AMF. This applies to following procedures:
- Registration as defined in clause 4.23.3,
- Service Request as defined in clause 4.23.4,
- Xn Hand-over as defined in clause 4.23.11, or
- N2 Hand-Over as defined in clause 4.23.7.
For an established PDU Session supporting mechanisms for redundant transmission defined in clause 5.33.2 of TS 23.501 [2], or for a PDU Session supporting Time Sensitive Communications as defined in clauses 5.27 and 5.28 of TS 23.501 [2], if the UE moves out of SMF Service Area, the SMF may, based on local policy, release the PDU Session after the mobility procedure. This applies to following procedures: Registration procedure, Service Request procedure, Xn based handover procedure, N2 based handover procedure.
If dynamic CN PDB needs to be configured by the SMF and the I-SMF is involved in the PDU session, the I-SMF receives the Dynamic CN PDB value as part of QoS profile from SMF (over N16a) and forwards it to (R)AN via N2 SM message.
For an established non-roaming PDU session, an I-SMF may be inserted irrespective of whether the current UE location is within the selected SMF service area or not, if Local Offloading Management is allowed and the UE is within Local Offloading Management service area. In this case, when a UE moves out of Local Offloading Management service area, the I-SMF is removed. When a UE moves from one Local Offloading Management service area to another, I-SMF change is triggered. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.2 I-SMF selection | For non-roaming or LBO roaming case, the AMF selects an SMF serving the PDU Session as described in clause 4.3.2.2.3. If the service area of the selected SMF does not control UPF that can serve the UE location, the AMF selects an I-SMF as described in clause 5.34.3 of TS 23.501 [2]. Additionally, if Local Offloading Management is allowed as per the subscription data and the UE is within Local Offloading Management service area, the AMF selects/re-selects an I-SMF as described in clause 6.10 of TS 23.548 [74].
After the PDU Session is established, if the selected SMF cannot serve the target DNAI requested by the PCC rule, the SMF issues Nsmf_PDUSession_SMContextStatusNotify to provide the target DNAI information to the AMF. Then AMF selects an I-SMF that serves this target DNAI as described in clause 5.34.3 of TS 23.501 [2].
For home routed roaming case, the AMF selects V-SMF as described in clause 4.3.2.2.3.2 and reselects V-SMF as described in clause 5.34.3 of TS 23.501 [2].
When the delegated discovery is used, the SCP selects the SMF as described in clause 5.34.3 of TS 23.501 [2] and in Annex E. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.3 Registration procedure | The following impacts are applicable to clause 4.2.2.2 (Registration procedure) when the UE has established PDU Session(s):
- Step 5: The UE context transferred from old AMF includes SMF information. If I-SMF is available for the PDU Session(s), the received SMF information includes I-SMF information and SMF information.
- Step 10: The (target) AMF determines whether I-SMF insertion/change/removal is needed. If the (target) AMF does not have the service area of the SMF(s), the (target) AMF queries the NRF to get service area information of the received SMF(s). The (target) AMF determines on a per PDU Session basis whether a (new) I-SMF needs to be selected based on UE location and service area of the received SMF information. It includes the following cases:
a. if the received SMF information includes only SMF information and service area of SMF includes the area where the UE camps, new I-SMF selection is not needed; or
b. if the received SMF information includes both I-SMF information and SMF information and service area of I-SMF includes the area where the UE camps, the I-SMF can be reused; or
c. if the received SMF information includes both I-SMF information and SMF information and the UE moves into the service area of SMF, the I-SMF removal process is triggered; or
d. if the received SMF information includes only SMF information and the service area of SMF does not include the area where the UE camps, the (target) AMF selects an I-SMF. The I-SMF insertion process is triggered; or
e. if the received SMF information includes both I-SMF and SMF information and the service area of SMF and I-SMF does not include the area where the UE camps, the (target) AMF selects a new I-SMF. The change of I-SMF process is triggered.
- For each PDU Session, if the UE context retrieved from the old AMF includes an I-SMF and the (target) AMF determines the I-SMF needs to be changed or removed, the (target) AMF includes a corresponding indication in Namf_Communication_RegistrationStatusUpdate sent to old AMF
- Step 17: the (target) AMF contacts the SMF/I-SMF ("cases" below are same as for step 10).
For case a), no additional change to step 17 of clause 4.2.2.2.2 is needed for the update of the PDU Session.
For case b), the SMF in step 17 of clause 4.2.2.2.2 is changed to I-SMF and in addition, the reference clause 4.2.3.2 is changed to clause 4.23.4.2. If the AMF has changed, the new AMF invokes Nsmf_PDUSession_UpdateSMContext (SM Context ID at SMF) towards the I-SMF.
For case c) i.e. for I-SMF removal, the (target) AMF invokes Nsmf_PDUSession_CreateSMContext (SM Context ID at SMF) towards the SMF. Steps from step 10 onwards as described in clause 4.23.4.3 are executed.
For cases d) and e), i.e. for I-SMF insertion or change, the (target) AMF invokes Nsmf_PDUSession_CreateSMContext (PDU Session ID, SM Context ID at SMF) towards the new I-SMF. Steps from step 3 onwards as described in clause 4.23.4.3 are executed with the following enhancements:.
- Step 9 (for cases d and e): The N2 SM information is only provided by the I-SMF to the AMF when N3 tunnel needs to be established (i.e. due to buffered DL data in old I-SMF/old-I-UPF or AMF has indicated to I-SMF to active user plane for the PDU session based on List of PDU Sessions To Be Activated received from the UE).
- Step 16 (i.e. case c): The N2 SM information is only provided by the SMF to the AMF when N3 tunnel need to be established (i.e. due to buffered DL data in old I-SMF/old-I-UPF or the AMF has indicated to the SMF to active user plane for the PDU session based on List of PDU Sessions To Be Activated received from the UE).
- Step 17 is executed when N3 tunnel needs to be established. The NAS message Service Accept is replaced with Registration Accept (i.e. step 21 in clause 4.2.2.2).
- Step 17a and 17b is triggered by old AMF towards the old I-SMF based on the I-SMF change or removal indication received from target AMF, when the timer (i.e. started in step 5 of clause 4.2.2.2) in old AMF expires.
NOTE: Step 17a is executed by old AMF together with steps 14d and 14e in clause 4.2.2.2.
- Steps 18 to 21 (i.e. cases d and e) and steps 22 to 25 (i.e. case c): These steps are executed if N2 SM information is provided by the I-SMF/SMF in step 9 or step 16 above.
- Step 21: This step is omitted if step 17 of clause 4.23.4.3 is executed as described above.
4.23.3a Deregistration procedure
The following impacts are applicable to clause 4.2.2.3 (Deregistration procedures) when the UE has established PDU Session(s):
The V-SMF is replaced with I-SMF and the H-SMF is replaced with SMF.
In step 2, if ULCL/BP is included in the data path, the I-SMF releases the local UPF (PSA) and includes N4 information in the Nsmf_PDUSession_Release request. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.4 Service Request procedures | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.4.1 General | The following two scenarios are considered:
- The I-SMF is available for the PDU Session and I-SMF is not changed or removed during the service request procedure. The procedure to support this scenario is described in clause 4.23.4.2.
- The I-SMF is inserted, changed or removed during service request procedure. The procedure to support this scenario is described in clause 4.23.4.3.
When the AMF receives the service request message, for each PDU Session to be activated based on the service area information of SMF and the location where the UE camped the AMF determines which procedure is used. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.4.2 UE Triggered Service Request without I-SMF change/removal | When both I-SMF and SMF are available for a PDU session and no I-SMF change or removal is needed during the service request procedure, the procedure in this clause is used. Compared to the procedure in clause 4.2.3.2, the SMF is replaced with the I-SMF and the impacted intermediate UPF(s) are UPFs that are controlled by I-SMF. Difference are captured below:
- Steps 6a-6b, these steps are not needed as the CN Tunnel Info of UPF (PSA) allocated for N9 is available at the I-SMF when the I-SMF is inserted.
- Step 7a, if a new intermediate UPF is selected, the I-SMF invokes Nsmf_PDUSession_Update Request (DN Tunnel Info of the new intermediate UPF. The I-SMF may also include UE location Information, Time Zone RAT type, Access Type and Operation Type set to "UP Activate", if those information is changed and need to be notified to SMF. If DL Tunnel Info of new intermediate UPF is received, the SMF provides the DL Tunnel Info of new intermediate UPF received from I-SMF to UPF(PSA).
- Step 10, this step does not apply as in this scenario the I-UPF is always needed.
- Step 16, If the I-SMF needs to update SMF with e.g. change of UE location information, change of Time Zone, change of RAT type and/or change of Access type, the I-SMF invokes Nsmf_PDUSession_Update Request to send User Location Information, Time Zone, RAT type and/or Access Type to SMF. If the I-SMF invoked Nsmf_PDUSession_Update Request in step 7a with Operation Type "UP Activate", the I-SMF also includes an Operation Type set to "UP Activated".
If dynamic PCC is deployed and if Policy Control Request Trigger condition(s) have been met (e.g. change of Access Type, change of UE location), the SMF performs SMF initiated SM Policy Modification procedure as defined in clause 4.16.5.1 and may get the updated policy.
- Steps 18a-18b, these steps do not apply as in this scenario the I-UPF is always needed.
- Step 21a, this step does not apply as in this scenario the I-UPF is always needed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.4.3 UE Triggered Service Request with I-SMF insertion/change/removal | When Local Offloading Management specified in TS 23.548 [74] is not applied, as part of a UE Triggered Service Request, I-SMF is to be inserted, changed or removed, the procedure in this clause is used. It includes the following cases:
- the UE moves from SMF service area to new I-SMF service area, a new I-SMF is inserted (i.e. I-SMF insertion); or
- the UE moves from old I-SMF service area to new I-SMF service area, the I-SMF is changed (i.e. I-SMF change); or
- the UE moves from old I-SMF service area to SMF service area, the old I-SMF is removed (i.e. I-SMF removal).
NOTE: The I-SMF insertion/change/removal cases related to Local Offloading Management are described in clause 6.10.2 of TS 23.548 [74].
If the service request is triggered by network due to downlink data and a new I-UPF is selected, forwarding tunnel is established between the old I-UPF(if the old I-UPF is different from PSA) and the new I-UPF to forward buffered data.
For Home Routed Roaming case, the I-SMF (old and new) and I-UPF (old and new) are located in Visited PLMN, while the SMF and UPF(PSA) are located in the Home PLMN. In this HR roaming case only the case of I-SMF change applies (there is always a V-SMF for the PDU Session).
Figure 4.23.4.3-1: UE Triggered Service Request procedure with I-SMF insertion/change/removal
1. Same as the steps 1-3 defined clause 4.2.3.2.
2. The AMF determines whether new I-SMF needs to be selected based on UE location and service area of the SMF, if new I-SMF needs to be selected, the AMF selects a new I-SMF as described in clause 4.23.2.
Case: I-SMF insertion or I-SMF change, steps 3-9 are skipped for I-SMF removal case.
3. If the AMF has selected a new I-SMF, the AMF sends a Nsmf_PDUSession_CreateSMContext Request (PDU Session ID, SM Context ID, UE location info, Access Type, RAT Type, Operation Type) to the new I-SMF. The SM Context ID points to the old I-SMF in the case of I-SMF change or to SMF in the case of I-SMF insertion.
The AMF Set the Operation Type to "UP activate" to indicate establishment of N3 tunnel User Plane resources for the PDU Session(s). The AMF determines Access Type and RAT Type based on the Global RAN Node ID associated with the N2 interface.
If the UE Time Zone has changed compared to the last reported UE Time Zone then the AMF shall include the UE Time Zone IE in this message.
4a. The new I-SMF retrieves SM Context from the old I-SMF (in the case of I-SMF change) or SMF (in the case of I-SMF insertion) by invoking Nsmf_PDUSession_Context Request (SM context type, SM Context ID). The new I-SMF uses SM Context ID received from AMF for this service operation. SM Context ID is used by the recipient of Nsmf_PDUSession_Context Request in order to determine the targeted PDU Session. SM context type indicates that the requested information is all SM context, i.e. PDN Connection Context and 5G SM context.
4b. The old I-SMF in the case of I-SMF change or SMF in the case of I-SMF insertion responds with the SM context of the indicated PDU Session.
If there is Extended Buffering is applied and the Extended Buffering timer is still running in old-SMF or old I-UPF, or the service request is triggered by downlink data, the old I-SMF or SMF includes a forwarding indication in the response to indicate that a forwarding tunnel is needed for sending buffered downlink packets. For I-SMF insertion, if I-UPF controlled by SMF was available for the PDU Session, the SMF includes a forwarding indication.
5. The new I-SMF selects a new I-UPF: Based on the received SM context, e.g. S-NSSAI and UE location information, the new I-SMF selects a new I-UPF as described in clause 6.3.3 of TS 23.501 [2].
6. The new I-SMF initiates a N4 Session Establishment to the new I-UPF. The new I-UPF provide tunnel endpoints to the new I-SMF.
If forwarding indication was received, the new I-SMF also requests the new I-UPF to allocate tunnel endpoints to receive the buffered DL data from the old I-UPF and to indicate end marker reception on this tunnel via usage reporting. In this case, the new I-UPF begins to buffer the downlink packet(s) received from the UPF (PSA).
7a. If the tunnel endpoints for the buffered DL data were allocated, the new I-SMF invokes Nsmf_PDUSession_UpdateSMContext Request (tunnel endpoints for buffered DL data) to the old I-SMF in the case of I-SMF change in order to establish the forwarding tunnel. The new I-SMF uses the SM Context ID received from AMF for this service operation.
7b. The old I-SMF, in the case of I-SMF change initiates a N4 session modification to the old I-UPF to send the tunnel endpoints for buffered DL data to the old I-UPF. After this step, the old I-UPF starts to send buffered DL data to the new I-UPF.
If the old I-UPF receives end marker packets and there is no associated tunnel to forward these packets, the old I-UPF discards the received end marker packets and does not send any Data Notification to SMF.
7c. The old I-SMF, in the case of I-SMF change responds the new I-SMF with Nsmf_PDUSession_UpdateSMContext response.
8a. In the case of I-SMF change, the new I-SMF invokes Nsmf_PDUSession_Update Request (SM Context ID, new I-UPF DL tunnel information, SM Context ID at I-SMF, Access Type, RAT Type, DNAI list supported by the new I-SMF, Operation Type) towards the SMF. The new I-SMF uses the SM Context ID at SMF received from old I-SMF for this service operation.
In the case of I-SMF insertion, the new I-SMF invokes Nsmf_PDUSession_Create Request (new I-UPF DL tunnel information, new I-UPF tunnel endpoint for buffered DL data, SM Context ID at I-SMF, Access Type, RAT type, DNAI list supported by the new I-SMF, Operation Type) towards the SMF.
The SM Context ID at I-SMF is to be used by the SMF for further PDU Session operation, e.g. to notify the new I-SMF of PDU Session Release. If SM Context ID at the I-SMF exists (i.e. in the case of I-SMF change), the SMF shall replace the SM Context ID at I-SMF.
The new I-UPF tunnel endpoint for buffered DL data is used to establish the forwarding tunnel (from old I-UPF controlled by SMF to new I-UPF controlled by new I-SMF).
If the old I-UPF receives end marker packets and there is no associated tunnel to forward these packets, the old I-UPF discards the received end marker packets and does not send any Data Notification to SMF.
The Operation Type is set to "UP activate" to indicate that User Plane resource for the PDU Session is to be established.
8b. The SMF initiates N4 Session Modification toward the PDU Session Anchor UPF. During this step:
- The SMF provides the new I-UPF DL tunnel information.
- If different CN Tunnel Info need be used by PSA UPF, i.e. the CN Tunnel Info at the PSA for N3 and N9 are different, a CN Tunnel Info for the PDU Session Anchor UPF is allocated.
- For I-SMF insertion, if a new I-UPF tunnel endpoint for buffered DL data is received, the SMF triggers the transfer of buffered DL data to the new I-UPF tunnel endpoint for buffered DL data.
If the DL tunnel information has changed, the SMF indicates the UPF (PSA) to send one or more "end marker" packets for each N9 tunnel to the old I-UPF immediately after switching the path to new I-UPF. From now on the PDU Session Anchor UPF begins to send the DL data to the new I-UPF as indicated in the new I-UPF DL tunnel information. The UPF (PSA) sends one or more "end marker" packets for each N9 tunnel to the old I-UPF immediately after switching the path to new I-UPF. If indicated by the new I-SMF in step 6, the new I-UPF reports to SMF when "end marker" has been received. The new SMF initiates N4 Session Modification procedure to indicate the new I-UPF to send the DL packet(s) received from the UPF (PSA).
8c. The SMF responds to the new I-SMF with Nsmf_PDUSession_Update Response (the DNAI(s) of interest for this PDU Session in the case of I-SMF change) or Nsmf_PDUSession_Create Response (the DNAI(s) of interest for this PDU Session, Tunnel Info at UPF(PSA) for UL data in the case of I-SMF insertion if it is allocated in step 8b).
In the case of I-SMF insertion and the PDU session corresponds to a LADN, the SMF shall release the PDU session after the service request procedure is completed.
In the case of I-SMF insertion the SMF starts a timer to release resource, i.e. resource for the indirect data forwarding tunnel.
In the case of I-SMF insertion and the CN Tunnel Info at PSA for N9 is received in the response, I-SMF provides the CN Tunnel Info at the PSA for N9 to I-UPF via N4 Session Modification Request.
9. The new I-SMF sends a Nsmf_PDUSession_CreateSMContext Response (N2 SM information (PDU Session ID, QFI(s), QoS profile(s), CN N3 Tunnel Info, S-NSSAI, User Plane Security Enforcement, UE Integrity Protection Maximum Data Rate), N1 SM Container, Cause)) to the AMF. The CN N3 Tunnel Info is the UL Tunnel Info of the new I-UPF.
If the PDU Session has been assigned any EPS bearer ID, the new I-SMF also includes the mapping between EPS bearer ID(s) and QFI(s) into the N2 SM information to be sent to the NG-RAN.
The new I-SMF starts a timer to release resource, i.e. resource for the indirect data forwarding tunnel.
Case: I-SMF removal: steps 10 to 16 are skipped for I-SMF insertion or I-SMF change cases.
10. If the UE has moved from service area of old I-SMF into the service area of SMF and the Local Offloading Management specified in TS 23.548 [74] is not applied, the AMF sends a Nsmf_PDUSession_CreateSMContext Request (SUPI, PDU Session ID, AMF ID, SM Context ID at I-SMF, UE location info, Access Type, RAT Type) to the SMF.
If the UE Time Zone has changed compared to the last reported UE Time Zone then the AMF shall include the UE Time Zone IE in this message.
The AMF Set the Operation Type to "UP activate" to indicate establishment of User Plane resources for the PDU Session(s). The AMF determines Access Type and RAT Type based, as defined in clause 4.2.3.2.
11a. The SMF retrieves SM Context from the I-SMF by invoking Nsmf_PDUSession_Context Request (SM context type). The SMF uses SM Context ID received from AMF for this service operation. SM context type indicates that the requested SM context is all, i.e. PDN Connection Context and 5G SM context.
11b. The old I-SMF responds with the SM context of the indicated PDU Session. If there is Extended Buffering is applied and the Extended Buffering timer is still running in old-SMF or old I-UPF, or the service request is triggered by downlink data (i.e. the old I-SMF received downlink data notification from old I-UPF), the old I-SMF includes a forwarding indication in the response to indicate that a forwarding tunnel is needed for sending buffered downlink packets from old I-UPF to new I-UPF or PSA (in the case that new I-UPF is not selected).
12. The SMF may select a new I-UPF: If the SMF determines that the service area of the PSA does not cover the UE location, the SMF selects a new I-UPF based on S-NSSAI and UE location information as described in clause 6.3.3 of TS 23.501 [2].
13. If a new I-UPF is selected by SMF, the SMF initiates a N4 Session Establishment to the new I-UPF. The new I-UPF provides tunnel endpoints to the SMF. If forwarding indication was received, the SMF requests the new I-UPF to allocate tunnel endpoints for forwarding data and to indicate end marker reception on this tunnel. In this case, the new I-UPF begins to buffer the downlink packet(s) received from the UPF (PSA).
If the new I-UPF is not selected, i.e. the PSA can serve the UE location, the SMF may initiate N4 Session Modification to the PSA to allocate UL N3 tunnel endpoints Info of PSA. The PSA provides the UL N3 tunnel endpoints to SMF. If the forwarding indication was received, the SMF requests the PSA to allocate the tunnel endpoints for the buffered DL data from the old I-UPF and indicate the PSA via usage reporting rule to report end marker to the SMF. In this case, the UPF (PSA) begins to buffer the DL data it may receive at the same time from the N6 interface. The UPF (PSA) sends one or more "end marker" packets according to the indication from SMF for each N9 tunnel to the old I-UPF immediately after switching the path to (R)AN. If indicated by the SMF, the UPF (PSA) reports to SMF when "end marker" packet is received. Then the SMF initiates N4 Session Modification procedure to indicate the UPF (PSA) to send the DL data received from the N6 interface.
14a. If the tunnel endpoints for the buffered DL data were allocated, the SMF invokes Nsmf_PDUSession_UpdateSMContext Request (tunnel endpoints for buffered DL data) to the old I-SMF in order to establish the forwarding tunnel. The SMF uses the SM Context ID received from AMF for this service operation.
14b. The old I-SMF initiates a N4 session modification to the old I-UPF and sends the tunnel endpoints for buffered DL data to the old I-UPF. After this step, the old I-UPF start to send buffered DL data to the new I-UPF or PSA if new I-UPF is not selected.
If the old I-UPF receives end marker packets and there is no associated tunnel to forward these packets, the old I-UPF discards the received end marker packets and does not send any Data Notification to SMF.
14c. The old I-SMF responds the SMF with Nsmf_PDUSession_UpdateSMContext response.
15. If a new I-UPF was selected by SMF, the SMF initiates N4 Session Modification toward the PDU Session Anchor UPF, providing the new I-UPF DL tunnel information. The PSA begins to send the DL data to the new I-UPF as indicated in the new I-UPF DL tunnel information. If the forwarding indication was received, the SMF indicates the PDU Session Anchor UPF to send one or more "end marker" packets. The UPF (PSA) sends one or more "end marker" packets according to the indication from SMF for each N9 tunnel to the old I-UPF immediately after switching the path to new I-UPF. If indicated by the SMF in step 13, the new I-UPF reports to SMF when "end marker" packet is received. The SMF initiates N4 Session Modification procedure to indicate the new I-UPF to send the DL packet(s) received from the UPF (PSA).
16. The SMF sends a Nsmf_PDUSession_CreateSMContext Response (N2 SM information (PDU Session ID, QFI(s), QoS profile(s), CN N3 Tunnel Info, S-NSSAI), N1 SM Container, Cause)) to the AMF. The CN N3 Tunnel Info is the UL Tunnel Info of the new I-UPF.
If the PDU Session has been assigned any EPS bearer ID, the SMF also includes the mapping between EPS bearer ID(s) and QFI(s) into the N2 SM information to be sent to the NG-RAN.
The SMF starts a timer to release the resource, i.e. resource for indirect data forwarding tunnel.
17. These steps are same as steps 12 to 14 in clause 4.2.3.2. After step 16, the Uplink data is transferred from (R)AN via new I-UPF (if exists) to PSA. If procedure in clause 4.2.3 is triggered together with this procedure, this step can be executed together with the corresponding steps in clause 4.2.3.
17a. If the step 9 or step 16 was successful response, in the case of I-SMF removal or change, the AMF sends Nsmf_PDUSession_ReleaseSMContext Request (I-SMF only indication) to old I-SMF for the release of resources in old I-SMF. The I-SMF only indication indicates to old I-SMF not to invoke resource release in SMF.
The old I-SMF starts a timer to release resources, i.e. resource for indirect data forwarding tunnel.
17b. The old I-SMF responds to AMF with Nsmf_PDUSession_ReleaseSMContext response.
Case: I-SMF insertion or I-SMF change: steps 18 to 21 are skipped for the I-SMF removal case.
18. The AMF sends an Nsmf_PDUSession_UpdateSMContext Request (N2 SM information, RAT type, Access type) to the new I-SMF.
If the AMF received N2 SM information (one or multiple) in step 17, then the AMF shall forward the N2 SM information to the relevant new I-SMF per PDU Session ID.
19. The new I-SMF updates the new I-UPF with the AN Tunnel Info and List of accepted QFI(s). Downlink data is now forwarded from new I-UPF to UE.
20a. The new I-SMF invokes Nsmf_PDUSession_Update request (RAT type, Access type, Operation Type) to SMF. The SMF updates associated access of the PDU Session.
The Operation Type is set to "UP activated" to indicate User Plane resource for the PDU Session has been established.
20b. If dynamic PCC is deployed, SMF may initiate notification about new location information to the PCF (if subscribed) by performing an SMF initiated SM Policy Modification procedure as defined in clause 4.16.5.1. The PCF may provide updated policies. If the PCC rule(s) are updated, the SMF may initiate a N4 Session Modification procedure to UPF (PSA) based on the updated PCC rule(s).
20c. The SMF responds with Nsmf_PDUSession_Update Response.
21. The new I-SMF sends a Nsmf_PDUSession_UpdateSMContext Response to AMF.
Case: I-SMF removal: steps 22 to 25 are skipped for the I-SMF insertion or I-SMF change cases.
22. The AMF sends a Nsmf_PDUSession_UpdateSMContext Request (N2 SM information, RAT Type, Access Type) to the SMF. The AMF determines Access Type and RAT Type based on the Global RAN Node ID associated with the N2 interface.
If the AMF received N2 SM information (one or multiple) in step 17, then the AMF shall forward the N2 SM information to the relevant new I-SMF per PDU Session ID.
23. If dynamic PCC is deployed, SMF may initiate notification about new location information to the PCF by performing an SMF initiated SM Policy Modification procedure as defined in clause 4.16.5.1. The PCF may provide updated policies.
24. If a new I-UPF was selected by the SMF, the SMF updates the new I-UPF with the AN Tunnel Info and List of accepted QFI(s), otherwise, the SMF updates the PSA with the AN Tunnel Info and List of accepted QFI(s).
25. The SMF sends a Nsmf_PDUSession_UpdateSMContext Response to AMF.
26a. In the case of I-SMF insertion or I-SMF change, upon timer set in step 9 expires and the indirect data forwarding tunnel was established before, the new I-SMF sends N4 Session Modification request to new I-UPF to release resources for the forwarding tunnel.
In the case of I-SMF removal, upon timer set in step 16 expires and the indirect data forwarding tunnel was established before, the SMF sends N4 Session Modification request to the new I-UPF or PSA to release the resource for the forwarding tunnel.
26b. In the case of I-SMF removal or change, upon timer set in step 17a expires and the indirect data forwarding tunnel was established before, the old I-SMF sends N4 Session Release request to the old I-UPF to release resources for the PDU Session. The old I-SMF releases the SM Context for the PDU Session. If the old I-UPF acts as UL CL and is not co-located with local PSA, the old I-SMF also sends N4 Session Release request to the local PSA to release resources for the PDU Session.
In the case of I-SMF insertion, upon timer set in step 8c expires and the indirect data forwarding tunnel was established before, the SMF sends N4 Session Release request to the old I-UPF to release the resource for the PDU Session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.4.4 Network Triggered Service Request | For network triggered service request procedure, if the procedure is triggered by downlink packet, the procedure in clause 4.2.3.3 are impacted as following:
- if the I-SMF is available for the PDU Session, the procedure is triggered by I-SMF. Correspondingly, the SMF in that procedure is replaced by the I-SMF.
- The referenced clause 4.4.4 for pause of charging is changed to clause 4.23.14.
- Step 4a:
- If I-SMF is not available for the PDU Session and no I-SMF insertion is needed, no additional change is needed.
- If I-SMF is available for the PDU Session and no I-SMF change or removal is needed, steps 12 to 22 in clause 4.23.4.2 is performed where the SMF in that procedure is replaced by the I-SMF.
- If I-SMF will be inserted, changed or removed, steps 2 to 25 in clause 4.23.4.3 is performed.
- Step 6: If the UE is in CM-IDLE state in 3GPP access, upon reception of paging request for a PDU Session associated to 3GPP access:
- If I-SMF is not available for the PDU Session and no I-SMF insertion is needed, no additional change is needed.
- If I-SMF is available for the PDU Session and no I-SMF change or removal is needed, UE Triggered Service Request procedure as defined in clause 4.23.4.2 is performed.
- If I-SMF will be inserted, changed or removed, UE Triggered Service Request procedure as defined in clause 4.23.4.3 is performed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.5 PDU Session Management procedure | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.5.1 PDU Session establishment procedure | For non roaming or LBO roaming, it includes the following cases:
- If the service area of the selected SMF includes the current UE location and if the Local Offloading Management specified in TS 23.548 [74] is not applied, the UE requested PDU Session Establishment procedure is same as described in clause 4.3.2.2.1.
NOTE 1: Even if the service area of the selected SMF includes the current UE location, the I-SMF can be inserted for Local Offloading Management as specified in TS 23.548 [74]. It does not imply that the Local Offloading Management can be applied only when the UE is inside the SMF service area.
NOTE 2: I-SMF based Local Offloading Management only applies to non-roaming scenario.
- If the service area of the selected SMF does not include the current UE location and the UE does not request for a MA PDU Session, the AMF selects an I-SMF that serves the area where UE camps. The UE requested PDU Session Establishment procedure for Home-routed Roaming defined in clause 4.3.2.2.2 is used to establish the PDU Session. Compared to the procedure defined in clause 4.3.2.2.2, the V-SMF and V-UPF are replaced by I-SMF and I-UPF and H-SMF and H-UPF are replaced by SMF and UPF(PSA) respectively. Also, only the S-NSSAI with the value defined by the serving PLMN is sent to the SMF. The I-SMF provides the DNAI list it supports to SMF and the SMF provides the DNAI(s) of interest for this PDU Session to I-SMF based on the DNAI list information received from I-SMF as defined in Figure 4.23.9.1-1 step 1.
This may happen e.g. at PDU Session mobility from non-3GPP access to 3GPP access as defined in clause 4.23.15.
- If the service area of the selected SMF does not include the current UE location and the UE requests a MA PDU Session, then the AMF rejects the MA PDU Session Establishment procedure.
- When the delegated discovery is used, the SCP selects the SMF as described in Annex E.
- If an I-SMF is selected and the PDU Session supports mechanisms for redundant transmission defined in clause 5.33.2.2 of TS 23.501 [2], the SMF rejects the PDU Session Establishment Request.
- If an I-SMF is selected and the PDU Session supports Time Sensitive Communications (as defined in clauses 5.27 and 5.28 of TS 23.501 [2]), or if the PDU session supports redundant transmission defined in clauses 5.33.2.1 or 5.33.2.3 of TS 23.501 [2], the SMF may, based on local policy, reject the PDU Session Establishment Request.
- If the selected SMF cannot serve the target DNAI requested by the PCC rule, the SMF issues Nsmf_PDUSession_SMContextStatusNotify to provide the target DNAI information to the AMF. The procedure of Home-routed Roaming defined in clause 4.3.2.2.2 is used to establish the PDU Session. Compared to this procedure, the V-SMF and V-UPF are replaced by I-SMF and I-UPF respectively and H-SMF and H-UPF are replaced by SMF and UPF(PSA) respectively. The AMF selects an I-SMF that serves this target DNAI in step 2. Then AMF sends a Nsmf_PDUSession_CreateSMContext Request to the I-SMF as defined in step 3a and the target DNAI received from SMF is included in the message.
- The S-NSSAI registered to UDM by SMF is always the S-NSSAI of HPLMN.
For the Home-Routed roaming case, the UE requested PDU Session Establishment procedure for Home-routed Roaming in clause 4.3.2.2.2 can be reused with the following change.
- If the service area of the selected V-SMF does not include the current UE location and the UE requests a MA PDU Session, then the AMF rejects the MA PDU Session Establishment procedure.
For Local Offloading Management scenario, the details are described in clause 6.10 of TS 23.548 [74]. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.5.2 PDU Session Release procedure | For the non roaming or LBO roaming case, the procedure defined in clause 4.3.4.3 (UE or network requested PDU Session Release for Home-routed Roaming) is used to release the PDU Session, with the V-SMF and V-UPF are replaced by I-SMF and I-UPF and H-SMF and H-UPF are replaced by SMF and UPF(PSA) respectively. Also if the ULCL/BP is included in the data path, in step 1 the I-SMF releases the local UPF (PSA) and includes N4 information in the Nsmf_PDUSession_Release or Nsmf_PDUSession_Update Request respectively.
For AMF triggers PDU Session Release procedure in Registration procedure (see step 17 of clause 4.2.2.2.2) and Deregistration procedure (see step 2 of clause 4.2.2.3.2), if I-SMF is used for the session, the AMF invokes PDU Session Release operation towards the I-SMF, then I-SMF releases the PDU Session towards SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.5.3 PDU Session modification procedure | For the non-roaming or LBO roaming case, the procedure defined in clause 4.3.3.3 (UE or network requested PDU Session Modification for Home-routed Roaming) is used to modify the PDU Session, with the V-SMF and V-UPF are replaced by I-SMF and I-UPF and H-SMF and H-UPF are replaced by SMF and UPF(PSA) respectively.
If the QoS Monitoring as defined in clause 5.33.3 of TS 23.501 [2] is triggered, the following enhancement to clause 4.3.3.3 applies:
- In step 3, if the SMF determines the need for QoS Monitoring for a QoS flow according to the information received from the PCF in step 1b, or based on SMF local policy, SMF includes QoS Monitoring indication and how frequently QoS Monitoring reporting to be performed, in Nsmf_PDUSession_Update Request message.
- In step 3, if, according to the information received from the PCF in step 1b, or based on SMF local policy, the SMF determines the need for GTP-U Path Monitoring as defined in clause 5.33.3.3 of TS 23.501 [2], the SMF includes QoS monitoring policy in Nsmf_PDUSession_Update Request message.
- In step 4b, if in step 3 the I-SMF received QoS Monitoring indication and may receive how frequently QoS Monitoring reporting to be performed in Nsmf_PDUSession_Update Request the I-SMF includes the QoS Monitoring indication and how frequently QoS Monitoring reporting to be performed in N2 SM message sent to the 5G AN.
- In step 4b, if in step 3 the I-SMF received QoS monitoring policy indication and may receive how frequently QoS Monitoring reporting to be performed in Nsmf_PDUSession_Update Request, the I-SMF includes such QoS monitoring policy also to I-UPF for GTP-U path monitoring.
- In step 15, the I-SMF sends Nsmf_PDUSession_Update Response to SMF. The SMF updates N4 session of the UPF PSA as defined for the case where is no I-SMF.
- If later on the RAN provides over N2 the QoS Monitoring Result with UL packet delay information comprising the packet delays of RAN and N3 interface, the I-SMF forwards this information to the SMF in Nsmf_PDUSession_Update Request message.
- I-SMF shall forward monitoring report (for QoS monitoring per GTP-U path) from I-UPF to SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.5.4 SMF triggered I-SMF selection or removal | Figure 4.23.5.4-1: SMF triggered I-SMF selection or removal
1. The PCF sends to the SMF PCC rule(s) which may include DNAI(s) for the PDU sessions by invoking Npcf_SMPolicyControl_UpdateNotify service operation.
Based on the received DNAI(s), the SMF may subscribe to UE mobility event notification from the AMF (e.g. UE moves into or out of Area of Interest corresponding to the received DNAI(s)).
The SMF may determine the target DNAI(s) which are applicable to the current UE location and which can be based on common DNAI (if applicable) as described in TS 23.548 [74]. Then the SMF may decide a target DNAI finally.
NOTE: It is also possible that the SMF determines that there is no any target DNAI can be used based on PCC rule(s), e.g. when the updated PCC rules removes previously provided DNAI(s).
2. The SMF invokes a Nsmf_PDUSession_SMContextStatusNotify service operation (or Nsmf_PDUSession_StatusNotify) in the following cases:
- if the SMF (or the associated old I-SMF) cannot serve the target DNAI, or
- if an I-SMF is used for the PDU Session and the SMF decides that the DNAI currently served by I-SMF is no longer be used for the PDU Session anymore hence the existing I-SMF is not needed, or
- if an I-SMF is used for the PDU Session and the SMF decides that the SMF itself can serve the target DNAI hence the existing I-SMF is not needed.
The content of the message includes the target DNAI information. The target DNAI information which indicates that the I-SMF selection or removal is expected and may include a target DNAI. This is to trigger the AMF to (re)select a suitable I-SMF, or remove the existing I-SMF (if the AMF decides that the SMF can serve the Target DNAI, or the AMF receive a target DNAI information without including target DNAI) for the PDU Session. The target DNAI is used for selecting (I-)SMF, which controls UPF connecting to that DNAI.
If there is an I-SMF serving the PDU session, the SMF invokes Nsmf_PDUSession_StatusNotify and then the I-SMF invokes Nsmf_PDUSession_SMContextStatusNotify message to send the target DNAI information for existing PDU session to AMF.
3. If the I-SMF selection or removal is expected, the AMF selects a new I-SMF which can serve the target DNAI or remove the existing I-SMF (if the AMF decides that the SMF can serve the Target DNAI, or if the AMF receives a target DNAI information without including target DNAI) for the existing PDU Session as described in clause 5.34.3 of TS 23.501 [2].
4. The AMF sends a Nsmf_PDUSession_CreateSMContext Request to the new I-SMF as described in step 3 of clause 4.23.4.3, or to the SMF as described in step 10 of clause 4.23.4.3, with the following enhancement:
The AMF includes target DNAI received from SMF in the message. When the UE is in CONNECTED state the AMF also include indication of no NG-RAN change.
5. The procedure described in clauses 4.23.4.3 (case: I-SMF insertion or I-SMF change) starting from step 4 takes place with the following difference:
In step 4a, the (target) new I-SMF sends the indication of no NG-RAN change to the old I-SMF or SMF as it is received from AMF.
In step 4b, when the old I-SMF or SMF receives indication of no NG-RAN change it include the additional Downlink Tunnel Info of NG-RAN in the SM context of the PDU Session.
In step 5, the I-SMF selects the I-UPF based on target DNAI.
In step 6, the target I-SMF should reuse the downlink Tunnel Info of serving RAN node if received from old I-SMF/SMF as described in clause 4.23.4.3.
In step 9, if the new I-SMF receives the Downlink Tunnel Info of NG-RAN, the N2 SM information includes PDU Session Resource Modification message.
The procedure described in clause 4.23.4.3 (case: I-SMF removal) starting from step 11 takes place with the following difference:
In step 11a, the SMF sends an indication of no NG-RAN change to the old I-SMF as it received from AMF.
In step 11b, when the old I-SMF receives indication of no NG-RAN change it include the additional Downlink Tunnel Info of NG-RAN in the SM context of the PDU Session.
In step 12, the SMF selects a new I-UPF based on target DNAI.
In step 16, if the SMF receives the Downlink Tunnel Info of NG-RAN, the N2 SM information includes PDU Session Resource Modification message.
If the UE is in IDLE state the step 17-21 are skipped. Steps 17a and 17b are still performed to release the old I-SMF.
6. [Conditional] In the case that I-SMF insertion or I-SMF change is performed in step 5, the PSA and UL CL/BP controlled by I-SMF is inserted as described from steps 2 to 11 in figure 4.23.9.1-1 with the following difference:
In step 2, the I-SMF selects a new PDU Session Anchor (PSA2) based on the target DNAI received in step 4.
For the case of I-SMF removal, the PSA and UL CL/BP controlled by SMF is inserted as described from steps 2 to 8 in Figure 4.3.5.4-1 with the following difference:
In step 2, the SMF selects a new PDU Session Anchor (PSA2) based on the target DNAI if received in step 4. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.6 I-SMF Related Procedures with PCF | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.6.1 General | This clause provides PCC related details for scenarios including an I-SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.6.2 Policy Update Procedures with I-SMF | Figure 4.23.6-1 shows procedures related to provisioning of PCC rules containing traffic steering information related to an I-SMF.
Figure 4.23.6-1: Policy Update procedure
In cases where step 1a in figure 4.23.6-1 is triggered in response to PCF receiving AF request, below steps 3 and 4 are applicable, in addition to those steps as explained in clause 4.3.6.1.
Step 3: SMF provides to I-SMF with DNAI(s) of interest for this PDU Session, user plane latency requirement and indication of considering N6 delay for local traffic steering. If PCC rule changes for traffic offloaded via ULCL/BP due to the AF request, the SMF provides the updated N4 information to the I-SMF. For Local Offloading Management scenario, the SMF provides the Local Offloading Management Information to the I-SMF. If PCC rule changes Local Offloading Policy, SMF provides updated Local Offloading Management Information to I-SMF. The Local Offloading Management Information is described in clause 6.10.2.3 of TS 23.548 [74].
Step 4: The procedure described in clauses 4.23.9.1, 4.23.9.2 and 4.23.9.3, from step 2 is executed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.6.3 Reporting UP path change to the AF | Figure 4.23.6.3-1 shows procedures related Reporting UP path change to the AF.
Figure 4.23.6.3-1: Reporting UP path change to the AF
1a. I-SMF indicates that UP path change may occur for the PDU Session via Nsmf_PDUSession_Update Request as described in clause 4.23.9; the SMF responds to the I-SMF.
2. If early notification has been requested by a PCC rule on behalf of AF as described in clause 4.3.6.2, then the SMF notifies the AF accordingly by invoking Nsmf_EventExposure_Notify service operation as described in clause 4.3.6.3. In this case the SMF may wait for further instructions of the AF.
3. SMF initiates Nsmf_PDUSession_Update Request with N4 information to control the local PSA and ULCL/BP as described in clause 4.23.9.
4. I-SMF enforces the change of DNAI or addition, change, or removal of UPF as described in clause 4.23.9.
5 I-SMF answers back to the Nsmf_PDUSession_Update from the SMF.
6. If late notification has been requested by a PCC rule on behalf of AF as described in clause 4.3.6.2, then the SMF notifies the AF accordingly by invoking Nsmf_EventExposure_Notify service operation as described in clause 4.3.6.3. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7 Inter NG-RAN node N2 based handover | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.1 General | The following two scenarios are considered:
- The I-SMF is available for the PDU Session and I-SMF is not changed or removed during the inter NG-RAN node N2 based handover procedure. The procedure to support this scenario is described in clause 4.23.7.2.
- The I-SMF is inserted, changed or removed during inter NG-RAN node N2 based handover procedure. The procedure to support this scenario is described in clause 4.23.7.3. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.2 Inter NG-RAN node N2 based handover without I-SMF change/removal | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.2.1 General | When both I-SMF and SMF are available for a PDU Session and no I-SMF change or removal is needed during inter NG-RAN node N2 handover procedure, the procedure defined in clause 4.9.1.3.2, 4.9.1.3.3 are used with the following differences. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.2.2 Preparation phase | Compared to the procedure in clause 4.9.1.3.2, the SMF interacting with the S-UPF, T-UPF, S-AMF and T-AMF is the I-SMF. The difference is following:
- Step 3: The N14 context exchanged between S-AMF and T-AMF contains the SM Context ID at I-SMF, or SM Context ID at SMF if I-SMF is not applicable before.
- Step 4: The T-AMF determines whether Target I-SMF needs to be selected based on UE location and service area of the SMF. In this case no I-SMF change or removal is needed.
- Step 5: The I-SMF checks whether I-UPF needs to be reallocated, i.e. select a T-UPF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.2.3 Execution phase | Compared to the procedure for execution phase in 4.9.1.3.3, the SMF interacting with the S-UPF, T-UPF, S-AMF and T-AMF is the I-SMF. The difference is as following:
- Step 10a: If I-SMF is available for a PDU Session and the existing intermediate S-UPF is re-allocated, i.e. a new T-UPF is selected, the I-SMF invokes an Nsmf_PDUSession_Update Request (DL CN Tunnel Info of the T-UPF) service operation toward the SMF. The SMF sends N4 Session Modification Request message to PDU Session Anchor UPF, providing DL CN Tunnel Info to the PDU Session Anchor UPF. The PDU Session Anchor sends one or more "end marker" packets for each N3/N9 tunnel on the old path immediately after switching the path, the source NG-RAN shall forward the "end marker" packets to the target NG-RAN.
- Step 10b: The SMF responds with the Nsmf_PDUSession_Update Response service operation to I-SMF once the PDU Session Anchor UPF is updated with the DL Tunnel Info of the T-UPF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.2.4 Handover Cancel | The home routed roaming procedure defined in clause 4.9.1.4 is applied, with V-SMF replaced by I-SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.3 Inter NG-RAN node N2 based handover with I-SMF insertion/change/removal | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.3.1 General | When I-SMF is inserted or changed or removed during inter NG-RAN node N2 handover, the procedures defined in this clause are used.
To support the EAS session continuity upon UL CL relocation, a N9 forwarding tunnel to support the EAS session continuity is established and released between the Source UL CL and Target UL CL as described in clause 4.23.9.4 or clause 4.23.9.5.
NOTE: This allows the UE to go on exchanging with the source EAS despite the fact that a new UL CL has been allocated to the PDU Session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.3.2 Preparation phase | Figure 4.23.7.3.2-1: Inter NG-RAN node N2 based handover, preparation phase, with I-SMF insertion/change/removal
1. Steps 1-3 in clause 4.9.1.3.2 are performed.
2. For PDU sessions in the UE context, the Target AMF determines whether a (new) Target I-SMF needs to be selected based on Target UE location and service area of the SMF or of the old I-SMF. If Target I-SMF needs to be selected, the AMF selects a Target I-SMF as described in clause 5.34.3 of TS 23.501 [2]. If the UE moves from the service area of the I-SMF to the service area of the SMF, the I-SMF will be removed if the Local Offloading Management specified in TS 23.548 [74] is not applied.
The rest of steps are performed for PDU sessions requested to be handed over, i.e. the PDU Sessions with active UP connections.
Case: I-SMF insertion, or I-SMF change, step 3~8 are skipped for I-SMF removal case.
3. T-AMF to Target I-SMF: Nsmf_PDUSession_CreateSMContext (PDU Session ID, Target ID, T-AMF ID, SM Context ID).
The SM Context ID points to the source I-SMF in the case of I-SMF change or to SMF in the case of I-SMF insertion.
Case: I-SMF change, steps 4 are skipped for I-SMF insertion case.
4a. (I-SMF change case) Target I-SMF to Source I-SMF: Target I-SMF retrieves SM Context from the source I-SMF by invoking Nsmf_PDUSession_Context Request (SM context type, SM Context ID).
The Target I-SMF uses SM Context ID received from T-AMF for this service operation. SM context type indicates that the requested information is all SM context, i.e. PDN Connection Context and 5G SM context. The SM Context ID is used by the recipient of Nsmf_PDUSession_Context Request in order to determine the targeted PDU Session.
4b. Source I-SMF to Target I-SMF: Nsmf_PDUSession_Context Response. The source I-SMF responds with the requested SM context.
Case: I-SMF insertion, steps 5 are skipped for I-SMF change case.
5a. Target I-SMF to SMF: Target I-SMF retrieves SM Context from the SMF by invoking Nsmf_PDUSession_Context Request (SM context type, SM Context ID).
The Target I-SMF uses SM Context ID received from T-AMF for this service operation. SM context type indicates that the requested information is all SM context, i.e. PDN Connection Context and 5G SM context. The SM Context ID is used by the recipient of Nsmf_PDUSession_Context Request in order to determine the targeted PDU Session.
5b. Void.
5c. Void.
5d. SMF to Target I-SMF: Nsmf_PDUSession_Context Response. The SMF responds with the requested SM context.
6. The Target I-SMF selects a Target I-UPF: Based on the received SM context, e.g. S-NSSAI and UE location information, the Target I-SMF selects a Target I-UPF as described in clause 6.3.3 of TS 23.501 [2].
7a. The Target I-SMF to Target I-UPF: N4 Session Establishment Request.
An N4 Session Establishment Request message is sent to the Target I-UPF, providing Packet detection, enforcement and reporting rules to be installed on the Target I-UPF. The UL CN Tunnel Info (on N9) of UPF (PSA) for this PDU Session, which is used to setup N9 tunnel, is also provided to the Target I-UPF.
7b. Target I-UPF to Target I-SMF or SMF: N4 Session Establishment Response.
The Target I-UPF sends an N4 Session Establishment Response message to the Target I-SMF with DL CN Tunnel Info (i.e. N9 tunnel info) and UL CN Tunnel Info (i.e. N3 tunnel info).
Case: I-SMF insertion, step 7c~7f are skipped for I-SMF change case.
7c. Target I-SMF to SMF: Nsmf_PDUSession_Create Request (PDU Session ID, HO Preparation Indication).
7d. [Conditional] SMF to UPF (PSA): N4 Session Modification Request.
If different CN Tunnel Info need be used by PSA UPF, i.e. the CN Tunnel Info for N3 and N9 are different, the SMF request CN tunnel information from UPF.
7e. [Conditional] UPF(PSA) to SMF: N4 Session Modification Response.
The UPF (PSA) sends an N4 Session Modification Response message to the SMF with CN Tunnel Info (on N9).
7f. SMF to Target I-SMF: Nsmf_PDUSession_Create Response (PDU Session ID, CN Tunnel Info of UPF(PSA) for N9).
The Target I-SMF provides the CN Tunnel Info of UPF(PSA) for N9 to Target I-UPF via N4 Session Modification.
8. The Target I-SMF to T-AMF: Nsmf_PDUSession_CreateSMContext Response (PDU Session ID, N2 SM Information, Reason for non-acceptance).
If N2 handover for the PDU Session is accepted, the Target I-SMF includes in the Nsmf_PDUSession_CreateSMContext Response the N2 SM Information containing the N3 UP address and the UL CN Tunnel ID of the UPF and the QoS parameters.
Case: I-SMF removal, step 9~13 are skipped for I-SMF insertion, or I-SMF change case.
9. T-AMF to SMF: Nsmf_PDUSession_CreateSMContext (PDU Session ID, Target ID, T-AMF ID, SM Context ID). The SM Context ID points to the source I-SMF.
10. The SMF selects a Target I-UPF if the UE is not in the service area of the PDU Session Anchor UPF. The SMF selects a Target I-UPF as described in clause 6.3.3 of TS 23.501 [2].
11a. [Conditional] SMF to UPF(PSA): N4 Session Modification Request.
If the Target I-UPF was not selected (i.e. the service area of PSA covers UE location) and different CN Tunnel Info (on N3) need to be used by PSA, the SMF sends N4 Session Modification Request to UPF(PSA).
11b. [Conditional] UPF(PSA) to SMF: N4 Session Modification Response. The PSA UPF sends UL CN Tunnel Info (i.e. N3 tunnel info) to SMF.
12a: [Conditional] SMF to Target I-UPF: N4 Session Establishment Request.
If a Target I-UPF is selected by SMF in step 10, the SMF sends N4 Session Establishment Request to Target I-UPF.
An N4 Session Establishment Request message is sent to the Target I-UPF, providing Packet detection, enforcement and reporting rules to be installed on the Target I-UPF. The UL CN Tunnel Info (on N9) of UPF (PSA) for this PDU Session, which is used to setup N9 tunnel, is also provided to the Target I-UPF.
12b. [Conditional]Target I-UPF to SMF: N4 Session Establishment Response. The Target I-UPF sends an N4 Session Establishment Response message to the SMF with DL CN Tunnel Info (i.e. N9 tunnel info) and UL CN Tunnel Info (i.e. N3 tunnel info).
13. SMF to T-AMF: Nsmf_PDUSession_CreateSMContext Response (PDU Session ID, N2 SM Information, Reason for non-acceptance).
If N2 handover for the PDU Session is accepted, the Target I-SMF includes in the Nsmf_PDUSession_CreateSMContext Response the N2 SM Information containing the N3 UP address and the UL CN Tunnel ID of the UPF and the QoS parameters.
14. Same as step 8-10 clause 4.9.1.3.2 are performed.
Case: I-SMF insertion, or I-SMF change, step 15~23 are skipped for I-SMF removal case.
15. T-AMF to Target I-SMF: Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID, N2 SM response received from T-RAN).
The Target I-SMF stores the N3 tunnel info of T-RAN from the N2 SM response if N2 handover is accepted by T-RAN.
16a. [Conditional]Target I-SMF to Target I-UPF: N4 Session modification request (T-RAN SM N3 forwarding Information list, indication to allocate DL forwarding tunnel(s) for indirect forwarding).
Indirect forwarding may be performed via a UPF which is different from the Target I-UPF, in which case the Target I-SMF selects another UPF for indirect forwarding.
16b. [Conditional]Target I-UPF to Target I-SMF: N4 Session Modification Response (Target I-UPF N9 forwarding Information list).
The Target I-UPF allocates Tunnel Info and returns an N4 Session Modification Response message to the Target I-SMF.
The Target I-UPF SM N9 forwarding info list includes Target I-UPF N9 address, Target I-UPF N9 Tunnel identifiers for forwarding data.
Case: I-SMF change, step 17~19 are skipped for I-SMF insertion case.
17. [Conditional]Target I-SMF to Source I-SMF: Nsmf_PDUSession_UpdateSMContext Request.
Target I-SMF invokes Nsmf_PDUSession_UpdateSMContext Request (Target I-UPF SM N9 forwarding Information list, Operation type) to the source I-SMF in order to establish the indirect forwarding tunnel. The Target I-SMF uses the SM Context ID received from Target AMF for this service operation. The Operation type indicates the establishment of forwarding tunnel(s) for indirect forwarding.
18a. [Conditional]The source I-SMF initiates a N4 session modification request (Target I-UPF SM N9 forwarding Information list, indication to allocate DL forwarding tunnel(s) for indirect forwarding) to the source I-UPF to establish indirect forwarding tunnel.
Indirect forwarding may be performed via a UPF which is different from the Source I-UPF.
18b. [Conditional]The source I-UPF to source I-SMF: N4 Session Modification Response (source I-UPF SM N3 forwarding Information list).
19. [Conditional]Source I-SMF to Target I-SMF: Nsmf_PDUSession_UpdateSMContext response (Source I-UPF SM N3 forwarding Information list).
Case: I-SMF insertion, step 20~22 are skipped for I-SMF change case.
20. [Conditional]Target I-SMF to SMF: Nsmf_PDU Session_UpdateSMContext.
The Target I-SMF invokes Nsmf_PDUSession_UpdateSMContext Request (Target I-UPF SM N9 forwarding Information list, Operation type) to the SMF in order to establish the indirect forwarding tunnel. The Target I-SMF uses the SM Context ID received from Target AMF for this service operation. The Operation type indicates the establishment of forwarding tunnel(s) for indirect forwarding.
21a. [Conditional]The SMF initiates a N4 session modification request (UPF SM N9 forwarding Information list, indication to allocate DL forwarding tunnel(s) for indirect forwarding) to the UPF(PSA) to establish indirect forwarding tunnel.
Indirect forwarding may be performed via a UPF which is different from the UPF(PSA).
21b [Conditional] The UPF(PSA) to SMF: N4 Session Modification Response (UPF SM N3 forwarding Information list).
22. [Conditional] The SMF to Target I-SMF: Nsmf_PDUSession_UpdateSMContext response (UPF SM N3 forwarding Information list).
23. Target I-SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response (N2 SM Information).
Target I-SMF creates an N2 SM information containing the DL forwarding Tunnel Info to be sent to the S-RAN by Source AMF via the Target AMF. Target I-SMF includes this information in the Nsmf_PDUSession_UpdateSMContext response. The DL forwarding Tunnel Info can be one of the following information:
- If direct forwarding applies, then Target I-SMF includes the T-RAN N3 forwarding information received in step 15.
- If the indirect forwarding tunnel is setup, then the SMF includes Source I-UPF forwarding information containing the N3 UP address and the Tunnel ID of the Source I-UPF.
Case: I-SMF removal, step 24~30 are skipped for I-SMF insertion, or I-SMF change case.
24. T-AMF to SMF: Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID, N2 SM response received from T-RAN).
The SMF stores the N3 tunnel info of T-RAN from the N2 SM response if N2 handover is accepted by T-RAN.
25a. [Conditional] SMF to UPF (PSA): N4 Session modification Request.
If the Target I-UPF is not selected (i.e. the service area of PSA covers UE location), the SMF sends N4 Session modification request to UPF(PSA) to allocate DL forwarding tunnel(s).
Indirect forwarding may be performed via a UPF which is different from the UPF(PSA), in which case the SMF selects another UPF for indirect forwarding.
25b. [Conditional] UPF (PSA) to SMF: N4 Session Modification Response (UPF N9 forwarding Information list).
26a. [Conditional] SMF to Target I-UPF:
If the Target I-UPF is selected, the SMF sends N4 Session modification request to Target I-UPF to allocate DL forwarding tunnel(s) for indirect forwarding;
Indirect forwarding may be performed via a UPF which is different from the Target I-UPF, in which case the SMF selects another UPF for indirect forwarding.
26b. [Conditional] Target I-UPF to SMF: N4 Session Modification Response (Target I-UPF N9 forwarding Information list).
27. [Conditional] SMF to Source I-SMF: Nsmf_PDUSession_UpdateSMContext.
The SMF invokes Nsmf_PDUSession_UpdateSMContext Request (SM N9 forwarding Information list, Operation type) to the source I-SMF in order to establish the indirect forwarding tunnel. The SMF uses the SM Context ID received from T-AMF for this service operation. The Operation type indicates the establishment of forwarding tunnel(s) for indirect forwarding.
28a. [Conditional] Source I-SMF to Source I-UPF: N4 Session Modification Request.
The source I-SMF initiates a N4 session modification request (Target I-UPF SM N9 forwarding Information list, indication to allocate DL forwarding tunnel(s) for indirect forwarding) to the source I-UPF to establish indirect forwarding tunnel.
Indirect forwarding may be performed via a UPF which is different from the Source I-UPF.
28b. [Conditional]The source I-UPF to source I-SMF: N4 Session Modification Response (source I-UPF SM N3 forwarding Information list).
29. [Conditional]The source I-SMF to SMF: Nsmf_PDUSession_UpdateSMContext response (Source I-UPF SM N3 forwarding Information list).
30. SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response (N2 SM Information).
The SMF creates an N2 SM information containing the DL forwarding Tunnel Info to be sent to the S-RAN by the Source AMF via the Target AMF. The DL forwarding Tunnel Info can be one of the following information:
- If direct forwarding applies, then the SMF includes the T-RAN N3 forwarding information the SMF received in step 24.
- If the indirect forwarding tunnel is setup, then the SMF includes Source I-UPF forwarding information containing the N3 UP address and the Tunnel ID of the Source I-UPF.
31. Same as step 12 in clause 4.9.1.3.2 is performed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.3.3 Execution phase | Figure 4.23.7.3.3-1: Inter NG-RAN node N2 based handover, execution phase, with I-SMF insertion/change/removal
1. Steps 1-6 in clause 4.9.1.3.3 are performed with the following change:
Step 6a: For PDU sessions in the UE context, if the I-SMF is either to be changed, or to be removed, the T-AMF includes an indication in Namf_Communication_N2InfoNotify to indicate the I-SMF change/removal.
Step 6c: The SMF in this step is source I-SMF in the case of I-SMF removal or change, or is SMF in the case of I-SMF insertion.
Case: I-SMF insertion, or I-SMF change, step 2~9 are skipped for I-SMF removal case.
2. T-AMF to Target I-SMF: Nsmf_PDUSession_UpdateSMContext Request (Handover Complete indication, (N2 SM Information (Secondary RAT usage data))).
Handover Complete indication is sent per each PDU Session to the corresponding Target I-SMF to indicate the success of the N2 Handover.
If in step 6b of clause 4.9.1.3.3 the source AMF has provided information for secondary RAT usage reporting the T-AMF propagates this information to the Target I-SMF.
Case: I-SMF change, step 3 is skipped for I-SMF insertion.
3a. S-AMF to Source I-SMF: Nsmf_PDUSession_ReleaseSMContext Request (I-SMF only indication).
After received N2 handover notify from T-AMF, if indication of I-SMF change/removal has been received, the S-AMF invokes Nsmf_PDUSession_ReleaseSMContext Request to inform the Source I-SMF to release the SM context of the PDU Session. The I-SMF only indication is used to inform the Source I-SMF not to invoke resource release in SMF. The Source I-SMF initiates a timer to release the SM Context of the PDU Session if indirect forwarding tunnel(s) were previously established, or if the Source I-SMF has not received request from Target I-SMF to retrieve SM Context. Otherwise, the Source I-SMF immediately releases the SM Context.
3b. Source I-SMF to S-AMF: Nsmf_PDUSession_ReleaseSMContext Response.
4a. Void.
4b. Void.
5a. Target I-SMF to Target I-UPF: N4 Session Modification Request. The N4 Modification Request indicates DL AN Tunnel Info of T-RAN to UPF.
5b. The Target I-UPF to Target I-SMF: N4 Session Modification Response.
6. Target I-SMF to SMF:
In the case of I-SMF change, Nsmf_PDUSession_Update Request (PDU Session ID, DL CN Tunnel Info of Target I-UPF for N9, DNAI(s) supported by the I-SMF, Secondary RAT usage data).
In the case of I-SMF insertion, Nsmf_PDUSession_Update Request (PDU Session ID, DL CN Tunnel Info of Target I-UPF for N9, DNAI(s), Secondary RAT usage data, Handover Complete Indication). The SMF initiates a timer to release the resource, i.e. resource for indirect data forwarding tunnel.
If the T-AMF has provided information for secondary RAT usage reporting in step 2, the Target I-SMF propagates this information to the SMF.
7a. SMF to UPF (PSA): N4 Session Modification Request.
The SMF sends N4 Session Modification Request to UPF PSA, providing the DL CN Tunnel Info of Target I-UPF to the UPF PSA.
7b. UPF (PSA) to SMF: N4 Session Modification Response.
8. SMF to Target I-SMF: In the case of I-SMF change, Nsmf_PDUSession_Update Response. In the case of I-SMF insertion, Nsmf_PDUSession_Create Response. The SMF provides the DNAI(s) of interest for this PDU Session to Target I-SMF.
In the case of I-SMF insertion and the PDU session corresponds to a LADN, the SMF shall release the PDU session after the handover procedure is completed.
9. Target I-SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response.
If indirect data forwarding applies, the Target I-SMF starts an indirect data forwarding timer, to be used to release the resource of indirect data forwarding tunnel.
Case: I-SMF removal, step 10~14 are skipped for I-SMF insertion, or I-SMF change case.
10. T-AMF to SMF: Nsmf_PDUSession_UpdateSMContext Request (Handover Complete indication, (N2 SM Information (Secondary RAT usage data))).
Handover Complete indication is sent per each PDU Session to the corresponding SMF to indicate the success of the N2 Handover.
If in step 6b of clause 4.9.1.3.3 the source AMF has provided information for secondary RAT usage reporting the T-AMF propagates this information to the SMF.
11a. S-AMF to Source I-SMF: Nsmf_PDUSession_ReleaseSMContext Request I-SMF only indication.
After received N2 handover notify from T-AMF, if indication of I-SMF change/removal has been received, the S-AMF invokes Nsmf_PDUSession_ReleaseSMContext Request to inform the Source I-SMF to release the SM context of the PDU Session. I-SMF only indication is used to inform the Source I-SMF not to invoke resource release in SMF. The Source I-SMF initiates a timer to release the SM Context of the PDU Session if indirect forwarding tunnel(s) were previously established, otherwise, the Source I-SMF immediately releases the SM Context.
11b. Source I-SMF to S-AMF: Nsmf_PDUSession_ReleaseSMContext Response.
12a. [Conditional]SMF to Target I-UPF: N4 Session Modification Request.
If the Target I-UPF is selected by SMF, the SMF to Target I-UPF: N4 Session Modification Request. The N4 Modification Request indicates DL AN Tunnel Info of T-RAN to Target I-UPF.
12b. [Conditional] Target I-UPF to SMF: N4 Session Modification Response
13a. SMF to UPF (PSA): N4 Session Modification Request.
The SMF sends N4 Session Modification Request to UPF(PSA). The N4 Modification Request indicates DL AN Tunnel Info of T-RAN to UPF(PSA) if Target I-UPF is not selected by SMF. The N4 Modification Request indicates DL CN Tunnel Info of Target I-UPF if Target I-UPF is selected by SMF.
13b. UPF (PSA) to SMF: N4 Session Modification Response. PDU Session Anchor sends one or more "end marker" packets for each N3/N9 tunnel on the old path immediately after switching the path, the source NG-RAN shall forward the "end marker" packets to the target NG-RAN.
14. SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response (PDU Session ID).
If indirect data forwarding applies, the SMF starts an indirect data forwarding timer, to be used to release the resource of indirect data forwarding tunnel.
15. Steps 12, 14 in clause 4.9.1.3.3 are performed.
During the UE mobility registration procedure, if required, the T-AMF performs I-SMF insertion/change/removal for the PDU session which were not handed over, i.e. the PDU sessions without active UP connections. This takes place as described in clause 4.23.3 with the exception that there is no UE context retrieved from the old AMF and that steps 17a and 17b as described in clause 4.23.4.3 are not applicable.
Case: I-SMF insertion, or I-SMF change, step 16~18 are skipped for I-SMF removal case.
16a. [Conditional]Target I-SMF to Target I-UPF: N4 Session Modification Request.
After indirect data forwarding timer set in step 9 expires, the Target I-SMF sends an N4 Session Modification Request to Target I-UPF to release the indirect data forwarding resource in Target I-UPF.
16b. [Conditional]Target I-UPF to SMF: N4 Session Modification Response.
Case: I-SMF change, step 17 is skipped for I-SMF insertion.
17a. Source I-SMF to Source I-UPF: N4 Session Release Request.
Upon the timer set in step 3 expires, the Source I-SMF sends N4 Session Release Request (Release Cause) to Source I-UPF to release the resources for the PDU Session. This message is also used to release the indirect data forwarding resource in Source I-UPF.
If the Source I-UPF acts as UL CL and is not co-located with local PSA, the Source I-SMF also sends N4 Session Release Request to the local PSA to release the resources for the PDU Session.
17b. Source I-UPF to Source I-SMF: N4 Session Release Response.
The Source I-SMF releases SM Context of the PDU Session.
Case: I-SMF insertion, step 18 is skipped for I-SMF change.
18a. SMF to UPF: N4 Session Modification Request.
Upon the timer set in step 6 expires, if UPF(PSA) is used for indirect forwarding, the SMF sends an N4 Session Modification Request to UPF(PSA) to release the indirect data forwarding resource in UPF(PSA). If the UPF (PSA) uses different Tunnel Info for N3 and N9, this message is also used to release the N3 Tunnel. If I-UPF is used for indirect forwarding, the SMF sends an N4 Session Modification Request to the I-UPF to release the indirect data forwarding resource.
18b. UPF to SMF: N4 Session Modification Response.
If UPF(PSA) is used for indirect forwarding, the UPF (PSA) sends N4 Session Modification Response to SMF.
If I-UPF is used for indirect forwarding, the I-UPF sends N4 Session Modification Response to SMF.
Case: I-SMF removal, step 19~20 are skipped for I-SMF insertion, I-SMF change case.
19a. The Source I-SMF to Source I-UPF: N4 Session Release Request.
Upon the timer set in step 11 expires, the Source I-SMF sends N4 Session Release Request (Release Cause) to Source I-UPF to release the resources for the PDU Session. This message is also used to release the indirect data forwarding resource in Source I-UPF.
19b. Source I-UPF to Source I-SMF: N4 Session Release Response.
The Source I-SMF releases SM Context of the PDU Session.
20a. SMF to UPF: N4 Session Modification Request.
Upon the timer set in step 14 expires, if UPF(PSA) is used for indirect forwarding, the SMF sends an N4 Session Modification Request to UPF (PSA) to release the indirect forwarding resource in UPF (PSA). If the UPF (PSA) uses different Tunnel Info for N3 and N9, this message is also used to release the N3 Tunnel. If I-UPF is used for indirect forwarding, the SMF sends an N4 Session Modification Request to the I-UPF to release the indirect data forwarding resource.
20b. UPF to SMF: N4 Session Modification Response.
If UPF(PSA) is used for indirect forwarding, the UPF (PSA) sends N4 Session Modification Response to SMF.
If I-UPF is used for indirect forwarding, the I-UPF sends N4 Session Modification Response to SMF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.7.3.4 Handover Cancel | Figure 4.23.7.3.4-1: Handover Cancel procedure
1. Step 1~3 in clause 4.11.1.2.3 are performed.
Case: I-SMF Change, step 4~9 are skipped for I-SMF Insertion case and I-SMF Removal case.
4. T-AMF to Target I-SMF: Nsmf_PDUSession_UpdateSMContext Request (Relocation Cancel Indication).
The target AMF invokes Nsmf_PDUSession_UpdateSMContext Request (Relocation Cancel Indication) to the target I-SMF to release the SM Context and all resources allocated on the target I-SMF during preparation phase.
5a. Target I-SMF to Target I-UPF: N4 Session Release Request.
The target I-SMF invokes N4 Session Release Request to target I-UPF, to release all resources allocated for the N4 session.
5b. Target I-UPF to Target I-SMF: N4 Session Release Response.
6. [Conditional] Target I-SMF to Source I-SMF: Nsmf_PDUSession_UpdateSMContext Request (Relocation Cancel Indication).
If indirect forwarding tunnel is setup during preparation phase, the target I-SMF initiates Nsmf_PDUSession_UpdateSMContext Request to the source I-SMF, indicating the source I-SMF to delete the resources temporarily allocated for indirect forwarding tunnel.
7a. [Conditional] Source I-SMF to Source I-UPF: N4 Session Modification Request.
The source I-SMF invokes N4 Session Modification Request to source I-UPF, to delete all resources allocated for indirect forwarding tunnel.
7b. [Conditional] Source I-UPF to Source I-SMF: N4 Session Modification Response.
8. [Conditional] Source I-SMF to Target I-SMF: Nsmf_PDUSession_UpdateSMContext Response.
9. Target I-SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response.
Case: I-SMF Insertion, step 10~18 are skipped for I-SMF Change case and I-SMF Removal case.
10. T-AMF to Target I-SMF: Nsmf_PDUSession_UpdateSMContext Request (Relocation Cancel Indication).
The target AMF invokes Nsmf_PDUSession_UpdateSMContext Request (Relocation Cancel Indication) to the target I-SMF to release the SM Context and all resources allocated on the target I-SMF during preparation phase.
11a. Target I-SMF to Target I-UPF: N4 Session Release Request.
The target I-SMF invokes N4 Session Release Request to target I-UPF, to release all resources allocated for the N4 session.
11b. Target I-UPF to Target I-SMF: N4 Session Release Response.
12. Target I-SMF to SMF: Nsmf_PDUSession_Update Request (PDU Session ID, Relocation Cancel Indication).
The target I-SMF invokes Nsmf_PDUSession_Update Request (PDU Session ID, Relocation Cancel Indication) to the SMF, to release the PDU Session resources allocated during preparation phase, e.g. CN Tunnel for N9.
13a. [Conditional] SMF to UPF (PSA): N4 Session Modification Request.
If CN Tunnel for N9 is allocated during preparation phase, i.e. the CN Tunnel for N3 and N9 are different, the SMF asks UPF (PSA) to release the CN Tunnel on N9.
13b. [Conditional] UPF(PSA) to SMF: N4 Session Modification Response.
14. SMF to Target I-SMF: Nsmf_PDUSession_Update Response.
15. [Conditional] Target I-SMF to SMF: Nsmf_PDUSession_UpdateSMContext Request (Operation Type).
If indirect forwarding tunnel is setup during preparation phase, the target I-SMF initiates Nsmf_PDUSession_UpdateSMContext Request (Operation Type) to the SMF, indicating the SMF to delete the resources temporarily allocated for indirect forwarding tunnel.
16a. [Conditional] SMF to UPF (PSA): N4 Session Modification Request.
The SMF invokes N4 Session Modification Request to UPF (PSA), to delete all resources allocated for indirect forwarding tunnel.
16b. [Conditional] UPF (PSA) to SMF: N4 Session Modification Response.
17. [Conditional] SMF to Target I-SMF: Nsmf_PDUSession_UpdateSMContext Response.
18. Target I-SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response.
Case: I-SMF Removal, step 19~24 are skipped for I-SMF Insertion case and I-SMF Change case.
19. T-AMF to SMF: Nsmf_PDUSession_UpdateSMContext Request (Relocation Cancel Indication).
The target AMF invokes Nsmf_PDUSession_UpdateSMContext Request (Relocation Cancel Indication) to the SMF to release the SM Context and all resources allocated on the SMF during preparation phase.
20a. [Conditional] SMF to UPF (PSA): N4 Session Modification Request.
If CN Tunnel for N3 is allocated during preparation phase, i.e. the CN Tunnel for N3 and N9 are different, the SMF asks UPF (PSA) to release the CN Tunnel on N3.
20b. [Conditional] UPF (PSA) to SMF: N4 Session Modification Response.
21. [Conditional] SMF to Source I-SMF: Nsmf_PDUSession_UpdateSMContext Request (Operation Type).
If indirect forwarding tunnel is setup during preparation phase, the SMF initiates Nsmf_PDUSession_UpdateSMContext Request (Operation Type) to the source I-SMF, indicating the source I-SMF to delete the resources temporarily allocated for indirect forwarding tunnel.
22a. [Conditional] Source I-SMF to Source I-UPF: N4 Session Modification Request.
The source I-SMF invokes N4 Session Modification Request to source I-UPF, to delete all resources allocated for indirect forwarding tunnel.
22. [Conditional] Source I-UPF to SMF: N4 Session Modification Response.
23. [Conditional] Source I-SMF to SMF: Nsmf_PDUSession_UpdateSMContext Response.
24. SMF to T-AMF: Nsmf_PDUSession_UpdateSMContext Response. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.8 AN Release procedure involving I-SMF | For the AN release procedure, if the PDU Session involves an I-SMF, the procedure defined in clause 4.2.6 applies with:
- The SMF and UPF in the procedure replaced by the I-SMF and I-UPF. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.9 Branching Point or UL CL controlled by I-SMF | |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.9.0 Overview | The procedures in this clause describe the Addition, Removal and Change of PDU Session Anchor (PSA2), Branching Point or UL CL controlled by I-SMF. They all rely on following principles:
1. When a (new) I-SMF is inserted (e.g. as described in clause 4.23.7, clause 4.23.11 or clause 6.10 of TS 23.548 [74]), the I-SMF provides the DNAI list it supports to the SMF. This list is assumed to remain constant during the N16a association between the I-SMF and the SMF for a PDU Session.
2. Based on the DNAI list information received from I-SMF, the SMF may then at any time provide or update the list of DNAI(s) of interest for this PDU Session to I-SMF. This may take place e.g. when the I-SMF provides the DNAI list it supports or when new or updated or removed PCC rule(s) is/are received by the SMF as defined in clause 4.23.6. This list of DNAI(s) of interest for this PDU Session indicates to the I-SMF the list of DNAI(s) candidate for local traffic steering within the PDU Session.
An indication of whether Multi-homing is possible is also provided to the I-SMF and the I-SMF uses this information to decide whether multi-homing can be used for the PDU Session.
3. Whenever the I-SMF has inserted or removed or changed a local offload capability the I-SMF invokes a Nsmf_PDUSession_Update Request to indicate to the SMF the list of corresponding DNAI(s). Based on this indication the SMF invokes a Nsmf_PDUSession_Update Request to send the corresponding N4 information to the I-SMF.
4. Then SMF may then at any time invoke a Nsmf_PDUSession_Update Request to send N4 information to the I-SMF.
5. The I-SMF may at any time send a Nsmf_PDUSession_Update Request to forward to the SMF N4 events received from a local UPF; this may e.g. correspond to traffic reporting.
6. When source I-SMF is to be removed from a PDU Session (e.g. at I-SMF change or removal), the SMF issues the N4 information targeting the UL CL/BP (s) and L-PSA(s) controlled by this I-SMF, including requests to release the corresponding N4 Sessions.
If the N9 forwarding tunnel to support the EAS session continuity controlled by I-SMF(s) is not established between the source ULCL and the target UL CL, when the Source I-SMF receives a Nsmf_PDUSession_ReleaseSMContext Request from AMF, it initiates a data forwarding timer (if indirect data forwarding applies) before releasing the resources of the PDU Session. When the Source I-SMF has received N4 release from SMF, it releases the UL CL/BP (s) and L-PSA(s) resources either directly if no data forwarding timer is started, or at the expiry of the data forwarding timer. Otherwise if the N9 forwarding tunnel to support the EAS session continuity controlled by I-SMF(s) is established between the source UL CL and target UL CL, the source I-SMF releases the UL CL/BP (s) and L-PSA(s) after no active traffic over the N9 forwarding tunnel.
When IPv6 multi-homing is used and an I-SMF is removed, the SMF re-configure the UE to not use the original IP prefix @L-PSA(s). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.9.1 Addition of PDU Session Anchor and Branching Point or UL CL controlled by I-SMF | This clause describes a procedure to add a PDU Session Anchor and Branching Point or UL CL controlled by I-SMF.
Figure 4.23.9.1-1: Addition of PDU Session Anchor and Branching Point or UL CL controlled by I-SMF
1. UE has an established PDU Session with a UPF including the PDU Session Anchor 1, which is controlled by SMF. The I-SMF and an I-UPF controlled by I-SMF have already been inserted for the PDU Session. Events described in item 1 and 2 of clause 4.23.9.0 have taken place.
2. At some point, using the list of DNAI(s) of interest for this PDU Session received from the SMF, the I-SMF decides to establish a new PDU Session Anchor e.g. due to UE mobility. The I-SMF selects a UPF and using N4 establishes the new PDU Session Anchor 2 (PSA2) of the PDU Session. During this step:
- (if needed) the PSA2 CN Tunnel Info of the local N9 termination on the PSA2 may be determined,
- In the case of IPv6 multi-homing applies to the PDU Session, a new IPv6 prefix corresponding to PSA2 is allocated by the I-SMF or by the UPF supporting the PSA2.
3. The I-SMF may select a UPF that will be acting as UL CL or Branching Point and replace the current I-UPF.
If a new UPF that will act as UL CL/Branching Point is selected (i.e. the existing I-UPF is replaced), the I-SMF uses N4 establishment to provide the 5G AN Tunnel Info, the PSA1 and (where applicable) PSA2 CN Tunnel Info to the new UPF.
NOTE 1: If the Branching Point or UL CL and the PSA2 are co-located in a single UPF then steps 2 and 3 can be merged.
4. The I-SMF invokes Nsmf_PDUSession_Update Request (Indication of UL CL or Branching Point insertion, IPv6 prefix @PSA2, DNAI(s) supported by PSA2, DL Tunnel Info of the new UL CL/Branching Point, if any) to SMF. Separate N4 contents are exchanged over N16a for the local UL CL/BP(s) and for the local PSA(s) controlled by the I-SMF. Multiple local PSAs (i.e. PSA2) may be inserted at one time, each corresponds to a DNAI and/or an IPv6 prefix in the case of multi-homing.
The I-SMF informs the SMF that a UL CL or Branching Point is inserted, the I-SMF provides DNAI(s) supported by PSA2 to the SMF. The DL Tunnel Info of UL CL/Branching Point is provided to SMF if a new UPF is selected to replace I-UPF in step 3.
In the case of IPv6 multi-homing PDU Session, the IPv6 prefix @PSA2 is also provided to SMF.
The SMF performs the Session Management Policy Modification procedure as defined in clause 4.16.5 to provide the new allocated IPv6 prefix to the PCF. The SMF may also send a notification to the AF, as described in clause 4.3.6.3.
The DNAI(s) supported by PSA2 may be used by the SMF to determine which PCC rules are to be applied at UPF(s) controlled by the I-SMF. The SMF acknowledges the Nsmf_PDUSession_Update from the I‑SMF
5. If a new DL Tunnel Info of UL CL/ Branching Point has been provided in step 4, the SMF updates the PSA1 via N4 with the CN Tunnel Info for the downlink traffic. Now the downlink packets from PSA1 are sent to UE via the new UPF which will act as Branching Point/UL CL. The SMF may also update the forwarding rules in PSA1 if some traffic is to be moved to UPFs controlled by I-SMF.
6. The SMF provides I-SMF with N4 information for the PSA and for the UL CL with a SMF initiated Nsmf_PDUSession_Update Request (set of (N4 information, involved DNAI), Indication of no DNAI change, Indication of no local PSA change)). The SMF generates N4 information for local traffic handling based on PCC rules and CHF requests that will be enforced by UPFs controlled by I-SMF. The N4 information for local traffic handling corresponds to N4 rules (PDR, FAR, URR, QER, etc.) related with the support of a DNAI. This is described in clause 5.34.6 of TS 23.501 [2]. N4 information for local traffic handling may indicate information (as the 5G AN Tunnel Info) that the SMF does not know and that the I-SMF needs to determine itself to build actual rules sent to the UPF(s). If the rule is applied to the local PSA, the N4 information includes the associated DNAI.
If the "Indication of application relocation possibility" or "UE IP address preservation indication" attributes are included in the PCC rule, the SMF includes the corresponding Indication of no DNAI change and Indication no local PSA change respectively.
If the CN Tunnel Info at the PSA1 has changed, the SMF may also provide its new value.
The I-SMF uses N4 information for local traffic handling received from the SMF as well as 5G AN Tunnel Info received from the 5G AN via the AMF and local configuration to determine N4 rules to send to the UPF(s) it is controlling.
7. The I-SMF updates the PSA2 via N4 providing N4 rules determined in step 6. It also provides the Branching Point or UL CL CN Tunnel Info for down-link traffic if the PSA2 and the UL CL/Branching Point are supported by different UPF(s).
8. The I-SMF updates the Branching Point or UL CL via N4 providing N4 rules determined in step 6.
NOTE 2: If the Branching Point or UL CL and the PSA2 are co-located in a single UPF then step 7 and step 8 can be merged.
9. The I-SMF Issues a Nsmf_PDUSession_Update Response to SMF that may include N4 information received from the local UPF(s).
10. Steps 6-8 of clause 4.3.5.4 are performed. In the case of IPv6 multi-homing PDU Session, the SMF notifies the UE of the IPv6 prefix @PSA2 and updates the UE with IPv6 multi-homed routing rule via a PSA controlled by the SMF.
NOTE 3: Step 6 of clause 4.3.5.4 is skipped if the current I-UPF is selected to act as Branching Point or UL CL.
11. If a new UPF is selected to replace I-UPF in step 3, the I-SMF uses N4 Release to remove the I-UPF of the PDU Session. The I-UPF releases resources for the PDU Session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.9.2 Removal of PDU Session Anchor and Branching Point or UL CL controlled by I-SMF | This clause describes a procedure to remove a PDU Session Anchor and Branching Point or UL CL controlled by I-SMF.
Figure 4. 23.9.2-1: Removal of PDU Session Anchor and Branching Point or UL CL controlled by I-SMF
1. UE has an established PDU Session with a UPF including the PDU Session Anchor 1 (controlled by SMF) and the UL-CL/BP and the PDU Session Anchor 2 (controlled by I-SMF). Events described in item 1 and 2 of clause 4.23.9.0 have taken place.
At some point the I-SMF decides to remove the PDU Session Anchor 2 and UL-CL/BP function, e.g. due to UE mobility.
2. The I-SMF may select a new UPF acting as new I-UPF and replace the existing I-UPF which was acting as UL-CL/BP before.
If a new UPF acting as new I-UPF is selected, the I-SMF uses N4 establishment to provide the PSA1 CN Tunnel Info and (R)AN Tunnel Info to the new I-UPF.
3. The I-SMF invokes Nsmf_PDUSession_Update Request (Indication of Removal of traffic offload, Removal of IPv6 prefix @PSA2, DNAI associated with the PSA2, DL Tunnel Info of new I-UPF, if any) to SMF. Multiple local PSAs may be removed, in this case, the I-SMF provides for each local PSA to be removal, the associated DNAI and an IPv6 prefix in the case of multi-homing.
The I-SMF informs the SMF that local traffic offload is removed. In the case of IPv6 multi-homing, the I-SMF also notifies the SMF with the removal of the IPv6 prefix @PSA2.
The SMF issues a SM Policy Association Modification (clause 4.16.5) corresponding to the IP address allocation/release PCRT(Policy Control Request Trigger). The SMF may also send a notification to the AF, as described in clause 4.3.6.3.
4. If a new UPF that replaces existing I-UPF is selected in step 2, the SMF updates the PSA1 via N4. It provides the CN Tunnel Info of the new I-UPF for the downlink traffic. The SMF may update the packet handling rules in PSA1 as now all traffic is to be moved to PSA1.
5. In the case of IPv6 multi-homing, the SMF notifies the UE to stop using the IPv6 prefix corresponding to PSA2. Also the SMF sends IPv6 multi-homed routing rule along with the IPv6 prefix corresponding to PSA1 to the UE. Based on the information provided in the Router Advertisement, the UE starts using the IPv6 prefix (corresponding to PSA1) for corresponding traffic.
7. The SMF provides I-SMF with N4 information for the local UPF(s) with a SMF initiated Nsmf_PDUSession_Update Request; The N4 information indicates the removal of the traffic offload rules.
8. If a new UPF that replaces existing I-UPF is selected in step 2, the I-SMF releases the old I-UPF. Otherwise the I-SMF updates the existing I-UPF with new rules in order to remove the UL-CL/BP functionality from that I-UPF.
If a new UPF that replaces existing I-UPF is selected in step 2, the SMF updates the (R)AN with the new I-UPF CN Tunnel Info.
If the PSA2 is not collocated with UL-CL/BP function, the I-SMF releases it via N4.
9. The I-SMF answers to the SMF with a Nsmf_PDUSession_Update Response SMF that may include N4 information received from the local UPF(s). |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.9.3 Change of PDU Session Anchor for IPv6 multi-homing or UL CL controlled by I-SMF | This clause describes a change of UL-CL/BP function, e.g. addition of a new PDU Session Anchor (i.e. PSA2) and release of the existing additional PDU Session Anchor (i.e. PSA0), via modifying IPv6 multi-homing or UL CL rule in the same Branching Point or UL CL under controlled by the same I-SMF.
Figure 4.23.9.3-1: Change of PDU Session Anchor for Branching Point or UL CL controlled by I-SMF
1. The UE has an established PDU Session with a UPF including the PDU Session Anchor 1(controlled by SMF) and the PDU Session Anchor 0 (PSA0) and an I-UPF acting as UL CL or BP (controlled by I-SMF). Events described in item 1 and 2 of clause 4.23.9.0 have taken place.
2. At some point the I-SMF decides to establish a new PDU Session Anchor and release the existing PDU Session Anchor e.g. due to UE mobility. The I-SMF selects a UPF and using N4 establishes the new PDU Session Anchor 2 of the PDU Session.
In the case of IPv6 multi-homing PDU Session, the I-SMF ensures allocation of a new IPv6 prefix corresponding to PSA2.
3. The I-SMF invokes Nsmf_PDUSession_Update Request (Indication of Change of traffic offload, (new allocated IPv6 prefix @PSA2, DNAI(s) supported by PSA2), (Removal of IPv6 prefix @PSA0, DNAI(s) supported by PSA0)) to SMF.
The I-SMF informs the SMF that a change of traffic offload may occur. Multiple local PSAs may be changed. The I-SMF provides:
- for each local PSA to be added, the DNAI now reachable and in the case of multi-homing: the new allocated IPv6 prefix @PSA2;
- for each local PSA no more reachable, the DNAI no more reachable and in the case of multi-homing, the old IPv6 prefix @PSA0.
4. The SMF may issue a SM Policy Association Modification (clause 4.16.5) corresponding to the IP address allocation/release PCRT. The SMF may also send an "early" notification to the AF, as described in clause 4.23.6.3.
5. The SMF generates the N4 information based on DNAI(s) information received in step 3.The SMF provides I-SMF with N4 information for the PSA and for the UL CL with a SMF initiated Nsmf_PDUSession_Update Request (set of (N4 information, involved DNAI), Indication of no DNAI change, Indication of no local PSA change)). The information includes N4 information to remove the traffic offload related to the DNAI(s) that are no more reachable and to enable the traffic offload related to the DNAI(s) that are now reachable.
6-7. Same as step 7-8 of clause 4.23.9.1
8. The I-SMF releases via N4 the PSA0 if PSA0 is not collocated with UL CL/BP, or updates the UL CL/BP to remove corresponding rules if PSA0 is collocated with UL CL/BP.
9. The I-SMF issues a Nsmf_PDUSession_Update Response to SMF that may include N4 information received from the local UPF(s) including the PSA0.
10. Same as step 7-8 of clause 4.3.5.4 are performed. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.9.4 Simultaneous change of Branching Point or UL CL and additional PSA controlled by I-SMF | This clause describes simultaneous change of UL-CL/BP function and additional PSA, e.g. addition of a new UL CL/BP and PDU Session Anchor (i.e. PSA2) and release of the existing UL CL/BP and additional PDU Session Anchor (i.e. PSA0), with target UPF(s) and source UPF(s) are all controlled by I-SMF.
This procedure may be triggered after N2 handover or Xn based handover procedure.
Figure 4.23.9.4-1: Simultaneous change of Branching Point or UL CL and additional PSA controlled by I-SMF
Comparing to the clause 4.23.9.3, this procedure in addition changes the source UL-CL/BP by a target UL-CL/BP.
1-2. These steps are the same steps 1-2 in clause 4.23.9.3.
3. The I-SMF selects a UPF and using N4 establishes the target UL CL or BP of the PDU Session.
4. The I-SMF invokes Nsmf_PDUSession_Update Request (Indication of Change of traffic offload, (new allocated IPv6 prefix @PSA2, DNAI(s) supported by PSA2), (Removal of IPv6 prefix @PSA0, DNAI(s) supported by PSA0), DL Tunnel Info of the new UL CL/Branching Point) to SMF.
The DL Tunnel Info of target UL CL/Branching Point is provided to SMF.
5. The SMF updates the remote PSA (PSA1) via N4 with the DL Tunnel Info of the Target UL CL/BP for the downlink traffic.
6-8. These steps are the same as steps 4-6 in clause 4.23.9.3.
If EAS session continuity upon UL CL relocation is required, in step 7 the SMF provides the I-SMF additionally with an indication that a N9 forwarding tunnel to support the EAS session continuity is required, UL traffic filter for N9 forwarding by the target UL CL and the value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity. Based on the received information, the I-SMF uses N4 to establish between the source UL CL and target UL CL the N9 forwarding tunnel to support the EAS session continuity. The I-SMF configures the source UL CL to forward traffic received from source L-PSA related to that PDU session toward the target UL CL via the N9 forwarding tunnel.
9. Same as steps 6-8 of clause 4.3.5.4. The I-SMF updates (R)AN for uplink traffic.
10-11. If a N9 forwarding tunnel to support the EAS session continuity is not established between the source UL CL and target UL CL, the I-SMF releases via N4 the source UL-CL/BP as the source UL-CL/BP is replaced by the target UL-CL/BP. The I-SMF also releases via N4 the PSA0 if PSA0 is not collocated with source UL CL/BP ;
12. This step is the same as step 9 in clause 4.23.9.3.
12a. If a N9 forwarding tunnel to support the EAS session continuity is established between the source UL CL and target UL CL, the I-SMF releases the source UL-CL/BP and PSA0 and the N9 forwarding tunnel in target UL CL when detection of no active traffic over the N9 forwarding tunnel takes place per the value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity received from SMF. The detection can be done by Source UL CL, which notifies the I-SMF of no active traffic over the N9 forwarding tunnel.
The I-SMF invokes Nsmf_PDUSession_Update Request to inform the SMF of the release of the resource in UL CL/BP and PSA0 for the PDU Session. |
fe7d56f8e2b5a29b90140ea988c1e8a1 | 23.502 | 4.23.9.5 Simultaneous change of Branching Points or UL CLs controlled by different I-SMFs | This clause describes simultaneous change of UL-CL/BP function and additional PSA, e.g. addition of a new UL CL/BP and PDU Session Anchor (i.e. PSA2) and release of the existing UL CL/BP and PDU Session Anchor (i.e. PSA0), with target UPF(s) and source UPF(s) are all controlled by different I-SMF(s).
This procedure may be triggered after N2 handover or Xn based handover procedure.
Figure 4.23.9.5-1: Simultaneous change of Branching Point or UL CL and additional PSA controlled by different I-SMFs
1. UE has established PDU Session with Source Branching Point or UL CL and Source UPF (PSA0) controlled by source I-SMF and Remote PSA. The UE has mobility with I-SMF change, e.g. handed over from a source RAN to a target RAN. After mobility, the path between Target I-UPF and Remote PSA (PSA1) has been established.
2. This step is the same as steps 2 in clause 4.23.9.3.
3. Same as in step 3 of Figure 4.23.9.4-1.
4. Same as in step 4 of Figure 4.23.9.4-1.
5. Same as in step 5 of Figure 4.23.9.4-1..
6-8. These steps are the same as steps 4-6 in clause 4.23.9.3 with the following enhancement:
In step 7, to support EAS session continuity upon UL CL relocation the SMF provides the target I-SMF with an indication that a N9 forwarding tunnel to support the EAS session continuity is required, UL traffic filter for N9 forwarding by the target UL CL and the value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity. Based on the received information, the target I-SMF installs corresponding N4 rules in the target UL CL for forwarding of uplink traffics via the N9 forwarding tunnel. The time interval for User Plane inactivity report is also provisioned to UL CL per the timer value received from SMF.
9. Same as in step 9 of Figure 4.23.9.4-1.
10. This step is the same as step 9 in clause 4.23.9.3.
The SMF triggers the procedure from step 11 onwards to support EAS session continuity upon UL CL relocation.
11. If N9 forwarding tunnel to support the EAS session continuity is required based on indication received from SMF in step 7, the target I-SMF request target UL CL to allocate N9 forwarding tunnel info via N4 session modification procedure.
12. The target I-SMF invokes Nsmf_PDUSession_UpdateSMContext Request (N9 forwarding tunnel required, target UL CL N9 forwarding tunnel info, value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity) toward the source I-SMF.
13. The source I-SMF triggers N4 modification procedure to request the source UL CL to establish the N9 forwarding tunnel to support the EAS session continuity. The source I-SMF provides the target UL CL N9 forwarding tunnel info to the source UL CL and receives the source UL CL N9 forwarding tunnel info from the source UL CL. The source I-SMF configures the source UL CL to forward traffic received from source L-PSA related to that PDU session toward the target UL CL via the N9 forwarding tunnel.
The source I-SMF configures a time interval for the source ULCL for the detection of no active traffic over the N9 forwarding tunnel, which is based on the value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity as received from target I-SMF.
After this step, the downlink data can be forwarded via N9 forwarding tunnel from the source L-PSA (PSA0).
14. The source I-SMF sends Nsmf_PDUSession_UpdateSMContext Response (source UL CL N9 forwarding to support the EAS session continuity tunnel info).
15. Based on the traffic filter information received from SMF at step 7 and source UL CL N9 forwarding tunnel to support the EAS session continuity info, the target I-SMF request the target UL CL to forward related UL traffic via N9 forwarding tunnel to support the EAS session continuity.
The target I-SMF configures a time interval for the target ULCL for the detection of no active traffic over the N9 forwarding tunnel, which is based on the value of the timer to detect the end of activity on the N9 forwarding tunnel to support the EAS session continuity received from SMF.
After this step, the uplink data can be forwarded via N9 forwarding tunnel toward the source L-PSA (PSA0).
16-17. Upon detection of no active traffic over the N9 forwarding tunnel to support the EAS session continuity, the source I-SMF releases via N4 the source UL-CL/BP The Source I-SMF also releases via N4 the PSA0 if PSA0 is not collocated with source UL CL/BP.
17a. The source I-SMF invokes Nsmf_PDUSession_Update Request to inform the SMF of the release of the resource in the UL CL/BP and the PSA0 for this PDU Session.
18. Upon detection of no active traffic over the N9 forwarding tunnel to support the EAS session continuity, the Target I-SMF releases the N9 forwarding tunnel in Target UL CL and remove the related filter.
4.23.9a Void |
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