Handling of Flow Failures from Target in EPS to 5GS Handover

The following call flow depicts the handling of flow failure from target RAN in EPS to the 5GS handover.

Flow Failure Handling Call Flow (From Target in EPS to 5GS Handover)
Flow Failure Handling Call Flow Description (From Target in EPS to 5GS Handover)

Step

Description

1

The AMF updates the SM context in the SMF by sending POST request with the following information:

  • hoState attribute set to PREPARED

  • N2 SM information received from the target RAN, including the transport layer address and tunnel endpoint of the downlink termination point for the user data for this PDU session (that is, GTP-U F-TEID of the target RAN for downlink traffic), if the target RAN succeeded in establishing resources for the PDU session; the target RAN may not be able to establish resources for all the flows; the target RAN includes such failed flows information

2

If the target RAN succeeded in establishing resources for the PDU sessions, the SMF sets the hoState attribute to PREPARED and returns a 200 OK response including the following information:

  • hoState attribute set to PREPARED

  • the epsBearerSetup IEs containing the list of EPS bearer contexts successfully handed over to the 5GS and the CN tunnel information for data forwarding, generated based on the list of accepted QFIs received from the RAN; This is the final list of flows handed over to the 5GS network.