X2 Handover SGW Relocation to CN-SGW (Multi PDN) Call Flow

This section describes the X2 handover SGW relocation to CN-SGW (Multi PDN) to cnSGW-C call flow.

X2 Handover SGW Relocation to CN-SGW (Multi PDN) Call Flow
X2 Handover SGW Relocation to CN-SGW (Multi PDN) Call Flow Description

Step

Description

1, 2

MME sends Create Session Req for both PDNs to GTPC-EP ingress with the following:

  • OI flag set

  • MME Control TEID

  • PGW Control TEID

  • eNodeB Data TEID

  • PGW Data TEID

Establishes new transactions at GTPC-EP ingress.

3, 4

SGW service POD receives Create Session Req for both PDNs from PFCP-EP ingress.

Collision resolver added Create Session Req for PDN 2 in queue.

5

Create a new transaction S-T1 for Create Session Req for PDN1

Validate CSReq.

6

NodeMgr allocates TEID.

7

SGW service POD 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(ApplyAction as Forward)/CTEs.

9

PFCP-EP forwards Sx Session Establishment Req for PDN 1 to UPF.

10

UPF sends Sx Session Establishment Response for PDN 1 to PFCP-EP with Created CTEs.

11

PFCP-EP forwards Sx Session Establishment Response for PDN 1 to SGW service POD.

12

SGW service POD sends Modify Bearer Req for PDN 1 to GTPC-EP with the following:

  • Updated S5 SGW Control TEID

  • S5 SGW Data TEID

13

GTPC-EP forwards Modify Bearer Req for PDN 1 to PGW.

14

PGW sends Modify Bearer Response for PDN 1 to GTPC-EP.

15

GTPC-EP forwards Modify Bearer Response for PDN 1 to SGW service POD.

16

SGW service forwards Create Session Response for PDN 1 to GTPC-EP ingress.

17

Session updated at CDL. Transaction S-T1 completed.

Collision resolver schedules Create Session Req for PDN 2 from queue.

18

GTPC-EP ingress forwards Create Session Response for PDN 1 to MME.

19 - 27

Repeat steps from 8 to 16 for PDN2.

28

Session updated at CDL. Transaction S-T2 completed.

29

GTPC-EP ingress forwards Create Session Response for PDN 2 to MME.

30 - 33

MME sends Delete Session Request for both PDNs with SI=1 to old SGW and receives Delete Session Response. Call cleared in old SGW.