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

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

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

Step

Description

1

The AMF sends a POST request for Sm Context Create Service, with the following additional information:

  • UE EPS PDN connection, including the EPS bearer contexts, representing the individual SM context resource to be created. The UE EPS PDN connection may not carry the flows which source does not want to establish in the 5GS network.

  • hoState attribute set to PREPARING

  • targetId identifying the target RAN Node ID and TAI based on the Target ID IE received in the Forward Relocation Request message from the source MME.

2

If the corresponding PDU session is detected based on the EPS bearer contexts and the handover of the PDN connection to 5GS network is possible, then the SMF returns a 201 Created response including the following information:

  • hoState attribute set to PREPARING and N2 SM information to request the target RAN to assign resources to the PDU session, excluding the flows which are not received in the UE EPS PDN connection.

  • PDU Session ID corresponding to the default EPS bearer ID of the EPS PDN connection.

  • allocatedEbiList containing the EBIs allocated to the PDU session.

The POST response includes the Location header and the URI of the created SM context resource.

The AMF stores the association of the PDU Session ID and the SMF ID, and the allocated EBIs associated to the PDU Session ID.