E-UTRAN PDN Modification with S-GW Change

The following figure shows the call flow for PDN modification with S-GW change.

Call Flow for PDN Modification with S-GW Change
Call Flow Description for PDN Modification with S-GW Change
Step Description
1

As part of the call creation at the new S-GW, the MME sends the Create Session Request to the new S-GW.

2

The new S-GW responds with the Create Session Response to MME.

3

MME sends Modify Bearer Request to new S-GW.

4

The new S-GW forwards Modify Bearer Request to SMF.

5

SMF sends Session Modification Request with Query URR to UPF based on event triggers.

Note

serv-node-change event triggers for S-GW change.

6

UPF responds with the N4: PCRF Session Modification Response with Gy and RADIUS URR to SMF based on the Gy and RADIUS configuration, which can be enabled or disabled.

7

SMF responds with Modify Bearer Response to new S-GW.

8

New S-GW forwards Modify Bearer Response to MME.

9

As part of Call deletion at the old S-GW, MME sends Delete Session Request to the new S-GW.

10

SMF sends CCR-U to OCS and Accounting Request (Interim) to AAA.

11

Old S-GW sends Delete Session Response to MME.

12

OCS and AAA respond to SMF with CCA-U and interim Accounting Response respectively.

13

SMF sends PCRF Session Modification Request with update URR to UPF.

14

UPF responds to SMF with PCRF Session Modification Response.

15

SMF sends CCR-U towards PCRF if event trigger is armed.

Note

AN_GW_CHANGE event triggers for S-GW change.

16

PCRF responds to SMF with CCA-U.

17

SMF sends PCRF Session Modification Request with Update QER to UPF.

18

SMF sends PCRF Session Modification Response to UPF.