Network-initiated Modification Call Flow for Inactive User Plane and UE in CM-Connected State

This section describes the network-initiated modification procedure when the UE is in CM-Connected state and the User Plane (UP) context is deactivated.

  1. The PCF sends a policy update notification to the SMF for a PDU session with rules and QoS change. The SMF handles the updated policy rules when received in a notification from the PCF.

  2. The SMF returns the “200 OK” status code to the PCF.

  3. The SMF sends only N1 message PDU Session Modification Command to the UE with the modified rules and QoS change, using the NAMF Communication N1 N2 Message Transfer service operation towards the AMF.

  4. The AMF sends the NAMF Communication N1 N2 Message Transfer response to the SMF. This response includes the “200 OK” status code and the “N1N2_TRANSFER_INITIATED” cause.

  5. The SMF waits for the Nsmf_PDUSession_UpdateSMContext message from the AMF.

  6. After receiving the response from UE, the SMF updates the subscriber’s session in the UPF with the modified parameter values and the UP context state remains as deactivated.

  7. The SMF sends N4 Session Modification request to the UPF updating the User Plane tunnel modified rules and the QoS details.

  8. The UPF sends the N4 Session Modification response for the PDU session.

  9. The SMF activates the UP connection as a result of the trigger to send downlink or uplink data.