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.

S1 Handover SGW Relocation to CN-SGW (Multi PDN) Call Flow
S1 Handover SGW Relocation to CN-SGW (Multi PDN) Call Flow Description

Step

Description

1, 2

GTCP-EP ingress receives Create Session Req for both the PDNs with the following:

  • Ol flag unset

  • MME control TEID

  • PGW control TEID

  • PGW Data TEID

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:

  • Uplink and downlink Create PDRs/FARs/CTEs.

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:

  • Updated S5 SGW Control TEID and S5 SGW Data TEID.

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.