S-GW Relocation with Same SGW-U
The following illustration describes the S-GW relocation with destination S-GW selecting the same UPF.

Step | Description |
---|---|
1 |
As part of initial attach, N4 and Sxa session is already established with Source SGW-C/cnSGW, SMF/IWF, and UPF. The MME sends Create Session Request to the destination SGW-C/cnSGW. |
2 | The destination SGW-C/cnSGW sends Sx Establishment Request (Sxa) to the UPF. The UPF links new Sxa session with the N4 session for uplink packets (Slowpath). |
3 | The UPF sends Sx Establishment Response (Sxa) to the destination SGW-C/cnSGW. |
4 | The destination SGW-C/cnSGW sends Create Session Response to the MME. |
5 | The MME sends Modify Bearer Request (eNodeB F-TEID) to the destination SGW-C/cnSGW. |
6 | The destination SGW-C/cnSGW sends Sx Modify Request (Sxa) to the UPF. |
7 | The UPF sends Sx Modify Response (Sxa) to the destination SGW-C/cnSGW. |
8 | The destination SGW-C/cnSGW sends Modify Bearer Request to the SMF/IWF. |
9 | The SMF/IWF sends Sx Modify Request (N4) to the UPF. The UPF switches downlink tunnel and links the N4 session with the new Sxa session. |
10 | The UPF sends Sx Modify Response (N4) to the SMF/IWF. |
11 | The SMF/IWF sends Modify Bearer Response to the destination SGW-C/cnSGW. |
12 | The destination SGW-C/cnSGW sends Modify Bearer Response to the MME. |
13 | The MME sends Delete Session Request to the source SGW-C/cnSGW. |
14 | The source SGW-C/cnSGW sends Sx Delete Session Request to the UPF. |
15 | The UPF sends Sx Delete Session Response to the source SGW-C/cnSGW. |
16 | The source SGW-C/cnSGW sends Delete Session Request to the MME. |