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Ti+  for  TS 23.502§4.2.3.2
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5GS-S1. UE‑Triggered Service Request
5 of 38 
Signalling flow for TS 23.502 UE-Triggered Service Request: AMF to SMF: Nsmf_PDUSession_UpdateSMContext Request


Step 4, verbatim
[Conditional] AMF to SMF: Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID(s), Operation Type, UE location information, Access Type, RAT Type, UE presence in LADN service area, Indication of Access Type can be changed).
The Nsmf_PDUSession_UpdateSMContext Request is invoked:
  • If the UE identifies List Of PDU Sessions To Be Activated in the Service Request message;
  • This procedure is triggered by the SMF but the PDU Session(s) identified by the UE correlates to other PDU Session ID(s) than the one triggering the procedure; or
  • If this procedure is triggered by the SMF but the current UE location is outside the "Area of validity for the N2 SM information" provided by the SMF in step 3a of clause 4.2.3.3.
    In this case the AMF shall not send the N2 information provided by the SMF in step 3a of clause 4.2.3.3. If the current UE location is in the "Area of validity for the N2 SM information", steps 4 to 11 are skipped; or
  • In response to paging or NAS notification indicating non-3GPP access and the AMF received N2 SM Information only, or both N1 SM Container and N2 SM Information in step 3a of clause 4.2.3.3.
If the DNN corresponds to an LADN then the "UE presence in LADN service area" indicates if the UE is IN or OUT of the LADN service area. If the AMF does not provide the "UE presence in LADN service area" indication and the SMF determines that the DNN corresponds to a LADN, then the SMF considers that the UE is OUT of the LADN service area.
The AMF determines the PDU Session(s) for which the UP connection(s) shall be activated and sends an Nsmf_PDUSession_UpdateSMContext Request to SMF(s) associated with the PDU Session(s) with Operation Type set to "UP activate" to indicate establishment of 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 procedure was triggered in response to paging or NAS Notification indicating non-3GPP access, the AMF received N2 SM Information in step 3a of clause 4.2.3.3 and the PDU Session for which the UE was paged or notified is not in the List Of Allowed PDU Sessions provided by the UE, the AMF notifies the SMF that the UE is not reachable. For other PDU Sessions in the List Of Allowed PDU Sessions the Service Request Procedure succeeds without re-activating the User Plane of any PDU Sessions, unless they have also been included by the UE in the List Of PDU Sessions To Be Activated.
If the procedure was triggered in response to paging or NAS notification indicating non-3GPP access, and the PDU Session for which the UE was paged or notified is in the List Of Allowed PDU Sessions provided by the UE, and the AMF received N2 SM Information only or N1 SM Container and N2 SM Information from the SMF in step 3a of clause 4.2.3.3, the AMF notifies the SMF that the access type of the PDU session can be changed. The AMF discards any already received N1 SM Container and N2 SM Information.
The AMF may receive a Service Request to establish another NAS signalling connection via a NG-RAN while it has maintained an old NAS signalling connection for UE still via NG-RAN. In this case, AMF shall trigger the AN release procedure toward the old NG-RAN to release the old NAS signalling connection as defined in clause 4.2.6 with following logic:
  • For the PDU Sessions indicated in the List Of PDU Sessions To Be Activated, the AMF requests the SMF to activate the PDU Session(s) immediately by performing this step 4.
  • For the PDU Sessions indicated in the "List of PDU Session ID(s) with active N3 user plane" but not in the List Of PDU Sessions To Be Activated, the AMF requests the SMF to deactivate the PDU Session(s).