UPF-initiated Detach Procedure

The following call flow illustrates an E-UTRAN network (UPF) initiated detach.

Call Flow for UPF-initiated Detach
Call Flow Description for UPF-initiated Detach
Step Description
1

UPF sends N4 Session Report Request (ERIR[default bearer]/UPIR) to SMF.

Note

Session Report Request of type ERIR is received when GTP-U Error Indication is received at UPF. Session Report Request of type UPIR is received when the UPF inactivity timer is expired on UPF. Both of these (In case, ERIR is received on default bearer) lead to session termination.

2

SMF sends N4 Session Report Response to UPF.

3

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

4

UPF sends N4 PFCP Session Modification Response to SMF.

5

SMF sends Delete Bearer Request to S-GW.

6

S-GW sends Delete Bearer Request to MME.

7

MME sends Delete Bearer Response to S-GW.

8

S-GW sends Delete Bearer Response to SMF.

9

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

10

UPF sends N4 PFCP Session Deletion Response to SMF.

11

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

12

AAA server sends Radius Accounting Response to SMF.

13

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

14

OCS sends Gy Credit Control Answer Terminate to SMF.

15

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

16

PCRF sends Gx Credit Control Answer Terminate to SMF.