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Content for  TS 29.502  Word version:  18.5.0

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5.2.2.3.23  AMF requested PDU Session Release due to V/I-SMF failure |R16|p. 52
The AMF may request PDU Session Release towards an alternative V/I-SMF in the same SMF Set when it detects the V/I-SMF has failed and if the V/I-SMF supports the DLSET feature while the (H-)SMF doesn't support the PSETR feature as specified in clause 6.8.2 of TS 23.527. When the AMF sends an Update SM Context Request, the requirements specified in clause 5.2.2.3.1 shall apply with the following modifications.
Step 1.
Same as step 1 of Figure 5.2.2.3.1-1, with the following modifications.
The POST request shall contain:
  • the release IE set to true;
  • the cause IE set to REL_DUE_TO_SMF_NOT_SUPPORT_PSETR.
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5.2.2.3.24  Connection Inactive procedure with CN based MT communication handling |R18|p. 52
The NF Service Consumer (e.g. AMF) shall request the SMF to apply CN based MT communication handling as specified in clauses 4.8.1.1a and 4.8.2.2b of TS 23.502 when the AMF is notified by the NG-RAN that the NG-RAN has transited the UE using eDRX to RRC_INACTIVE state and the SMF supports the UPCSMT feature (see clause 6.1.8).
Reproduction of 3GPP TS 29.502, Fig. 5.2.2.3.24-1: NG-RAN initiated Connection Inactive procedure
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Step 1.
The NF Service Consumer shall request the SMF to suspend the user plane connection of the PDU session by sending a POST request, as specified in clause 5.2.2.3.1, with the following information:
  • cnBasedMt is set to "true"
  • upCnxState attribute set to SUSPENDED;
  • user location and user location timestamp;
  • N2 SM information received from the 5G-AN, e.g. Secondary RAT Data Usage, if available;
  • other information, if necessary.
Step 2a.
Upon receipt of such a request, the SMF shall keep the NG-RAN N3 DL F-TEID and set the upCnxState attribute to SUSPENDED and return a 200 OK response including the upCnxState attribute set to SUSPENDED. The SMF will request the UPF to buffer any subsequent downlink data and report the receiving DL data to the SMF. Upon receiving DL data report, the SMF will invoke the Namf_MT_EnableUEReachability service operation when the upCnxState of the PDU session is set to SUSPENDED, to trigger a NG-RAN paging.
Step 2b.
Same as step 2b of Figure 5.2.2.3.1-1.
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5.2.2.3.25  UE Triggered Connection Resume in RRC Inactive procedure |R18|p. 53
Upon receiving a notification from NG-RAN that the UE is in RRC_CONNECTED mode or when receiving from NG-RAN a MT Communication Handling request indicating the UE is now reachable for downlink data and/or signalling as specified in clause 4.8.2.2 of TS 23.502, the NF Service Consumer (e.g. AMF) shall request the SMF to resume the User Plane connection of an existing PDU session, i.e. establish the N3 tunnel between the 5G-AN and UPF, as follows.
Reproduction of 3GPP TS 29.502, Fig. 5.2.2.3.25-1: UE Triggered Connection Resume in RRC Inactive
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Step 1.
The NF Service Consumer shall request the SMF to resume the user plane connection of the PDU session by sending a POST request, as specified in clause 5.2.2.3.1, with the following information:
  • the upCnxState attribute set to ACTIVATING;
  • user location and user location timestamp;
  • cause attribute set to "PDU_SESSION_RESUMED";
  • N2 SM information received from the 5G-AN, i.e. the Path Switch Request Transfer including the new transport layer address and tunnel endpoint of the downlink termination point for the user data for this PDU session (i.e. 5G-AN's GTP-U F-TEID for downlink traffic), or the N2 Notification Request Transfer;
  • The N2 message (and its IEs, e.g. N2 Notification Request/Response Transfer) to notify the AMF that UE transits into RRC_CONNECTED when the NG-RAN has the UE context is to be aligned with NGAP specification.
  • additional N2 SM information received from the 5G-AN, if any;
  • other information, if necessary.
Step 2a.
If the SMF can proceed with resuming the user plane connection of the PDU session, i.e. request the UPF to forward any received DL data to the NG-RAN DL F-TEID which is stored in the SMF when the SMF is requested to apply CN based MT handling, the SMF shall return a 200 OK response including the following information:
  • the upCnxState attribute set to ACTIVATED;
  • N2 SM information, i.e. Path Switch Response Transfer including the transport layer address and tunnel endpoint of the uplink termination point for the user data for this PDU session (i.e. UPF's GTP-U F-TEID for uplink traffic), or N2 Notification Response Transfer.
Step 2b.
If the SMF cannot proceed with resuming the user plane connection of the PDU session, the SMF shall return an error response, as specified for step 2b of Figure 5.2.2.3.1-1, including:
  • the upCnxState attribute representing the final state of the user plane connection (e.g. DEACTIVATED);
  • N2 SM information, including the cause of the failure.
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5.2.2.3.26  AMF requested PDU Session Release due to Network Slice instance not available |R18|p. 54
The requirements specified in clause 5.2.2.3.1 shall apply with the following modifications.
Step 1.
Same as step 1 of Figure 5.2.2.3.1-1, with the following modifications.
The POST request shall contain:
  • the release IE set to true;
  • the cause IE set to "REL_DUE_TO_NSI_NOT_AVAILABLE".
5.2.2.3.27  AMF requested PDU Session Release due to MBSR not authorized |R18|p. 54
The requirements specified in clause 5.2.2.3.1 shall apply with the following modifications.
Step 1.
Same as step 1 of Figure 5.2.2.3.1-1, with the following modifications.
The POST request shall contain:
  • the release IE set to true;
  • the cause IE set to "REL_DUE_TO_MBSR_NOT_AUTHORIZED".

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