S1 Handover SGW Relocation to CN-SGW (Multi PDN) Call Flow
This section describes the S1 handover SGW relocation to CN-SGW (Multi PDN) to CN-SGW call flow.

Step |
Description |
---|---|
1, 2 |
GTCP-EP ingress receives Create Session Req for both the PDNs with the following:
Establishes new transaction at GTPC-EP ingress. |
3, 4 |
SGW service POD receives Create Session Req for both the PDNs from GTPC-EP ingress. Collision resolver added Create Session Req for PDN 2 in queue. Create a new transaction S-T1. |
5 |
Validate CSReq. |
6 |
NodeMgr allocates TEID. |
7 |
SGW service reads UPF Cache and performs UPF selection. |
8 |
PFCP-EP receives Sx Session Establishment Req from SGW service POD for PDN 1 with the following:
|
9 |
PFCP-EP forwards Sx Session Establishment Req for PDN 1 to UPF. |
10 |
PFCP-PE receives Sx Session Establishment Response for PDN 1 from UPF with Created CTEs. |
11 |
SGW service POD receives Sx Session Establishment Response for PDN 1 from PFCP-EP. |
12 |
SGW service POD forwards Create Session Response for PDN 1 to GTPC-EP ingress. |
13 |
Session updated at CDL. Transaction S-T1 completed. Collision resolver scheduled Create Session Req for PDN 2 from queue. |
14 |
GTPC-EP ingress forwards Create Session Response for PDN 1 to MME. |
15–21 |
Repeat steps 11–14 for PDN2(S-T2). |
22, 23 |
GTPC-EP ingress receives Modify Bearer Req for both the PDNs with updated eNodB FTEID from MME. |
24, 25 |
GTPC-EP ingress forwards Modify Bearer Req to both PDNs to SGW service POD. Collision resolver added Modify Bearer Req for PDN 2 in the queue. Create a new transaction S-T3. |
26 |
PFCP-EP receives Sx Session Modification Req for PDN 1 from SGW service POD with the updated downlink FAR and uplink PDR. |
27 |
PFCP-EP forwards Sx Session Modification Req for PDN 1 to UPF. |
28 |
UPF sends Sx Session Modification Response for PDN 1 to PFCP-EP. |
29 |
SGW service POD receives Sx Modify Response for PDN 1 from PFCP-EP. |
30 |
GTPC-EP receives Modify Bearer Req for PDN 1 from SGW service POD with the following:
|
31 |
GTPC-EP forwards Modify Bearer Req for PDN 1 to PGW. |
32 |
GTPC-EP receives Modify Bearer Response for PDN 1 from PGW. |
33 |
GTPC-EP forwards Modify Bearer Response for PDN 1 to SGW service POD. |
34 |
SGW service POD forwards Modify Bearer Response for PDN 1 to GTPC-EP ingress. |
35 |
Session updated at CDL. |
36 |
GTPC-EP ingress forwards Modify Bearer Response for PDN 1 to MME. |
37 |
SGW service POD sends Modify Bearer Req for PDN 2 to PFCP-EP. Transaction S-T3 completed. Collision resolver schedules Modify Bearer Req to PDN 2. |
38–40 |
Repeat steps 27,28, 29 for PDN 2. |
41 |
SGW service POD sends Modify Bearer request for PDN 2 to GTPC-EP. |
42–47 |
Repeat steps 31–36 for PDN 2. |
48, 49 |
MME sends Delete Session Request for both the PDNs with SI=1 sent to old SGW. |
50 |
MME receives Delete Session Response. Call cleared in old SGW. |