SMF Initiated Detach Procedure

SMF receives a request for session release through one of the following methods:

  • Clear Subscriber

  • GTP Path Failure

  • Peer Restart

  • Absolute Session Timeout

  • Cp-idle Timeout

The following call flow illustrates the procedure of an E-UTRAN network (SMF) initiated detach.

Call Flow for SMF-initiated Detach
Call Flow Description for SMF Initiated Detach
Step Description
1

SMF sends N4 PFCP Session Modification Request to UPF with FARs having apply action set to Drop.

2

UPF sends N4 PFCP Session Modification Response to SMF.

3

SMF sends Delete Bearer Request to S-GW.

4

S-GW sends Delete Bearer Request to MME.

5

MME sends Delete Bearer Response to S-GW.

6

S-GW sends Delete Bearer Response to SMF.

7

SMF sends N4 PFCP Session Deletion Request to UPF to release N4 session.

8

UPF sends N4 PFCP Session Deletion Response to SMF.

9

SMF sends Radius Accounting Request Stop to AAA server to release the accounting session.

10

AAA server sends Radius Accounting Response to SMF.

11

SMF sends Gx Credit Control Request Terminate to OCS to release the Gy session.

12

OCS sends Gx Credit Control Answer Terminate to SMF.

13

SMF sends Gx Credit Control Request Terminate to PCRF to release the Gx session.

14

PCRF sends Gx Credit Control Answer Terminate to SMF.