Network-initiated Idle to Active Transition
The following call flow depicts network initiated idle to active transition.

Step | Description |
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1 |
The UPF sends "PFCP session report request" to the SMF.
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2 | The SMF sends the PFCP session report response. |
3 |
The SMF sends "N1N2MessageTransfer" to AMF with the following attributes:
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4 |
The SMF receives the “N1N2TransferResponse” with the following status codes:
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5 | The AMF sends the N1N2 Transfer failure response. If the UE is not reachable, move to Step 7. |
6 |
Subsequently, the AMF requests the SMF by sending POST request with the following information:
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7 |
The SMF initiates PFCP Session Modification Procedure towards UPF with down link FAR updated with following options:
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8 | Upon receipt of successful response from UPF node, the SMF sets the upCnxState attribute to ACTIVATED for the PDU session. |
9 | The SMF then initiates 200 OK response including the upCnxState attribute set to ACTIVATED towards AMF (Only if Step 6 is completed and response is received from Step 8). |