Release Access Bearer (Active to IDLE Transaction) Call Flow
This section describes the Release Access Bearer call flow.

Step |
Description |
---|---|
1 |
MME sends Release Access Bearer (RAB) request to S11-GTP-EP to release all S1-U bearers for the UE. |
2 |
S11-GTP EP decodes the received UDP message and converts it into gRPC. The converted gRPC message then sent to the SGW-Service pod, using the TEID value, which can handle this UE session. SGW-Service pod performs the following activities:
|
3 |
SGW-Service pod sends the Sx Mod request message using the background IPC async call for PDN1 to PFCP-EP. |
4 |
PFCP-EP forwards the Sx Modify Request (PDN1) message to UPF1 through the UDP proxy. UPF1 processes the Sx Modify Request (PDN1) message. |
5 |
SGW-Service pod sends the Sx Modify Request message using the background IPC async call for PDN2. PFCP-EP forwards the Sx Modify Request (PDN2) message to UPF2 through the UDP proxy. |
6 |
UPF2 processes the Sx Modify Request (PDN2) message. |
7 |
UPF1 sends the Sx Modify response (PDN1) message to PFCP-EP. |
8 |
PFCP-EP sends the Async Sx Modify response message to cnSGW-C service for PDN1. SGW-Service pod waits for the PDN2 Sx Modify response message. |
9 |
UPF2 sends the Sx Modify response (PDN2) message to PFCP-EP. |
10 |
PFCP-EP sends the Async Sx Modify response message to cnSGW-C service for PDN2. |
11 |
The SGW-Service pod sends the following, after receiving the PDN (PDN1, PDN2) responses:
|
12 |
SGW-Service pod sends Update Subscriber Context state to CDL, which moves all the bearers to the IDLE state. CDL module updates the information in the database. |
13 |
S11-GTP-EP forwards the RAB response message to MME. MME process the RAB response message. |