Feature Description

During a session, if the User Plane function (UPF) is in congested state, it rejects the Packet Forwarding Control Protocol (PFCP) establishment messages from SMF with a cause code in the response message. To reduce call loss, the SMF retries to send PFCP establishment messages to a different UPF. Then, SMF selects a UPF based on configured priority value and capacity (that is, load information from UPF).

The SMF provides a failure handling template (FHT) profile for PFCP. This profile is associated with the UPF profile in SMF.

The FHT template provides flexibility for SMF to fine tune its interactions with UPFs for sessions. It enables SMF to handle the error cause codes in response from UPF for both new and existing sessions. Based on the error cause codes in response from UPF, this feature provides the following configurable actions:

  • ignore

  • terminate

  • retry-terminate

This following table describes the configuration options available for N4 Session Establishment Request, N4 Session Modification Request, and N4 Session Report Request messages.

Configuration Matrix
Message type Applicable action Applicable cause code Default behaviour
N4Session EstablishmentReq retry-terminate
  • pfcp-entity-in -congestion

  • system-failure

  • service-not -supported

  • no-resource -available

  • no-response -received

  • reject

terminate

N4Session ModificationReq

terminate

  • mandatory-ie -incorrect

  • session-ctx-not -found

  • no-response -received

  • reject

  • no-resource -available

  • pfcp-entity-in -congestion

continue

N4SessionReportReq

ignore

terminate

2-255

terminate