UE-Initiated PDU Session Release Call Flow

This section describes the UE-Initiated PDU Session Release call flow.

The PDU Session Release procedure is used to release all the resources associated with a PDU session.

UE-Initiated PDU Session Release Call Flow
UE-Initiated PDU Session Release Call Flow Description

Step

Description

1, 2

The UE initiates the UE Requested PDU Session Release procedure by the transmission of an NAS message (N1 SM container (PDU Session Release Request (PDU session ID)), PDU Session ID) message. The NAS message is forwarded by the RAN to the AMF with an indication of User Location Information. This message is relayed to the SMF corresponding to the PDU Session ID through N2 and the AMF.

3

The AMF invokes the Nsmf_PDUSession_UpdateSMContext service operation and provides the N1 SM container to the SMF together with User Location Information (ULI) received from the RAN.

4

The AMF may invoke the Nsmf_PDUSession_ReleaseSMContext service operation to request the release of the PDU session in case of mismatch of PDU session status between UE and AMF.

5

The SMF responds to the AMF with the Nsmf_PDUSession_UpdateSMContext response (N2 SM Resource Release request, N1 SM container (PDU Session Release Command)).

6

If the UP connection of the PDU session is active, the SMF shall also include the N2 Resource Release request (PDU Session ID) in the Namf_Communication_N1N2MessageTransfer, to release the RAN resources associated with the PDU session.

7

The SMF responds to the AMF with the Nsmf_PDUSession_ReleaseSMContext response.

8

The AMF transfers the SM information received from the SMF (N2 SM Resource Release request, N1 SM container) to the RAN.

9

When the RAN has received an N2 SM request to release the AN resources associated with the PDU session, it issues AN specific signaling exchanges with the UE to release the corresponding AN resources.

10

The RAN sends any NAS message (N1 SM container (PDU Session Release Command)) received from the AMF.

11

The AMF invokes the Nsmf_PDUSession_UpdateSMContext (N2 SM Resource Release Ack, User Location Information) to the SMF.

12

The SMF responds to the AMF with an Nsmf_PDUSession_UpdateSMContext response.

13

The UE acknowledges the PDU Session Release Command by sending a NAS message (PDU Session ID, N1 SM container (PDU Session Release Ack)) message over the RAN.

14

The RAN forwards the NAS message from the UE by sending a N2 NAS uplink transport (NAS message (PDU Session ID, N1 SM container (PDU Session Release Ack)), User Location Information) to the AMF.

15

The AMF invokes the Nsmf_PDUSession_UpdateSMContext (N1 SM container (PDU Session Release Ack, User Location Information) to the SMF.

16

The SMF responds to the AMF with an Nsmf_PDUSession_UpdateSMContext response.

17

The SMF invokes Nsmf_PDUSession_SMContextStatusNotify to notify AMF that the SM context for this PDU session is released. The AMF releases the association between the SMF ID and the PDU Session ID, DNN, and S-NSSAI.