Intra S-GW Handover with Collapsed UPF

The following illustration describes the intra-SGW handover call flow with collapsed UPF.

Intra S-GW Handover with Collapsed UPF Call Flow Description
Step Description
1

As part of UE initial attach, N4 and Sxa session is already established with SMF and UPF. At UPF, N4+Sxa session exists and are interconnected.

The MME sends Modify Bearer Request to the SGW-C/cnSGW.

The SGW-C/cnSGW updates eNodeB F-TEID in FAR.

2

The SGW-C/cnSGW sends Sx Modify Request (Sxa) to the UPF. The UPF:

  • Updates eNodeB F-TEID for downlink data

  • Updates TEP entries at VPP with new Remove TEID

3 The UPF sends Sx Modify Response (Sxa) to the SGW-C/cnSGW.
4 The SGW-C/cnSGW sends Modify Bearer Response to the MME.