5G to EPS Handover Using N26 Interface – cnSGW-C and SMF Separate Node Call Flow
This section describes the 5G to EPS Handover Using N26 Interface – cnSGW-C and SMF Separate Node call flow.

Step |
Description |
---|---|
1 |
cnSGW-C selects associated same UPF. cnSGW-C receives Sx Establishment Request with User-plane ID from UPF/UP. |
2 |
cnSGW-C sends Sx Establishment Response from UPF/UP. |
3 |
UPF/UP sends Sx Association Request with User-plane ID to SMF. |
4 |
SMF sends Sx Association Response to UPF/UP. |
5 |
cnSGW-C sends Relocation Request to MME on interface N26. |
6 |
MME sends Create Session Request to cnSGW-C with SMF and PGW-ctrl-TEID information. |
7 |
cnSGW-C selects associated same UPF. cnSGW-C sends Sx Establishment Req (SXA) to UPF/UP. |
8 |
cnSGW-C receives Sx Establishment Rsp (SXA) from UPF/UP. |
9 |
cnSGW-C sends Create Session response to MME. |
10 |
MME sends Modify Bearer Request to cnSGW-C. |
11 |
cnSGW-C sends Sx Modify Req (SXA) to UPF/UP. |
12 |
cnSGW-C receives Sx Modify Rsp (SXA) from UPF/UP. |
13 |
cnSGW-C sends Modify Bearer Request to SMF. |
14 |
SMF sends Sx Modify Request – N4 to UPF/UP. |
15 |
SMF receives Sx Modify Response from UPF/UP. |
16 |
cnSGW-C receives Modify Bearer Response to SMF. |
17 |
cnSGW-C forwards Modify Bearer Response to MME. |