Initial Attach Call Flow

This section describes the Initial Attach call flow.

Initial Attach Call Flow
Initial Attach Call flow Description
Step

Description

1

The MME sends the Create Session Request with TEID value zero to the S11-GTP-EP.

2

Transaction E-T1 is started.

The S11-GTP-EP forwards the Create Session Request to the Service-POD (SGW).

3

Transaction S-T2 is started to validate the Create Session Request.

The Service-POD (SGW) sends the Allocate Id Request to the Node-Mgr.

4

The Node-Mgr sends the Allocate Id Response to the Service-POD (SGW).

5

The Service-POD (SGW) reads the cache to perform the UPF selection.

6

The Service-POD (SGW) sends the Sx Establishment Request to the PFCP-EP.

7

Transaction P-T3 is started.

The PFCP-EP sends the Sx Establishment Response to the Service-POD (SGW).

8

Transaction P-T3 is completed.

The Service-POD (SGW) sends the Create Session Request to the S5-SGW-EGRESS-GTP-EP.

9

Transaction E-T4 is started.

The S5-SGW-EGRESS-GTP-EP sends the Create Session Response to the Service-POD (SGW).

10

Transaction E-T4 is completed.

The Service-POD (SGW) sends the Sx Modification Request to the PFCP-EP.

11

Transaction P-T5 is started.

The PFCP-EP sends the Sx Modification Response to the Service-POD (SGW).

12

Transactions P-T5 and S-T2 are completed.

The Service-POD (SGW) sends the Create Session Response to the S11-GPT-EP.

13

Transaction E-T1 is completed.

The S11-GPT-EP forwards the Create Session Response to the MME.

14

The Service-POD (SGW) sends the Create Session to DB message to the CDL-Endpoint.

15

The MME sends the Modify Bearer Request with TEID to the S11-GTP-EP.

16

Transaction E-T1 is started.

The S11-GTP-EP sends the Modify Bearer Request to the Service-POD (SGW).

17

Transaction S-T2 is started.

The Service-POD (SGW) sends the Sx Modification Request to the PFCP-EP.

18

Transaction P-T3 is started.

The PFCP-EP sends the Sx Modification Response to the Service-POD (SGW).

19

Transaction P-T3 is completed.

The Service-POD (SGW) sends the Modify Bearer Response to the S11-GTP-EP.

20

Transaction S-T2 is completed.

The S11-GPT-EP forwards the Modify Bearer Response to the MME.

21

Transaction E-T1 is completed.

The Service-POD (SGW) sends the Update Session to CDL message to the CDL-Endpoint. The session is updated in CDL.