IDFT Handling during S1 Handover
The following illustration describes the IDFT handling during S1 handover with collapsed UPF.

Step | Description |
---|---|
1 |
As part of initial attach, N4 and Sxa session is already established with SMF and UPF. S1 handoff is triggered. The MME sends Indirect Tunnel Request Message to the SGW-C/cnSGW. |
2 |
The SGW-C/cnSGW sends Sx Modify Request (Sxa) to the UPF. At UPF:
|
3 | The UPF sends Sx Modify Response (Sxa) to the SGW-C/cnSGW. |
4 | The SGW-C/cnSGW sends Create Indirect Tunnel Response Message to the MME. |
5 | The Source eNodeB sends IDFT data packet to the UPF. If there’s no matching 3 tuple stream at UPF, the packet is forwarded to SessMgr. |
6 | The UPF sends IDFT data packet to the destination eNodeB. |