Call Flow
This section describes the call flow for the user plane activation of a PDU session.
The following figure illustrates the UE-initiated user plane activation call flow.

Step | Description |
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1 |
The AMF requests SMF to activate the user plane connection of the PDU session by sending a POST request with the following information:
|
2 |
Upon receipt of the request, the SMF starts activating the N3 tunnel of the PDU session. The SMF returns a 200 OK response with the following information:
|
3 |
Then, the AMF requests the SMF by sending POST request with the N2 SM information. If the 5G-AN succeeded in establishing resources for the PDU sessions, the N2 SM information includes the following information:
|
4 |
The SMF initiates PFCP Session Modification procedure towards UPF with downlink FAR updated with the following options:
|
5 | Upon receipt of successful response from UPF node, the SMF sets the upCnxState attribute to ACTIVATED for the PDU session. |
6 | The SMF initiates 200 OK response including the upCnxState attribute set to ACTIVATED towards AMF. |