Configuring the UPF Failure Handling on N4 Interface

Use the following sample configuration to configure the UPF failure handling on N4 interface.

config 
   profile failure-handling pfcp_name 
      interface pfcp message { N4SessionEstablishmentReq | N4SessionModificationReq } 
      cause-code pfcp-entity-in-congestion 
      action retry-terminate max-retry value 
      end 

NOTES:

  • profile failure-handling : Specify the UPF profile that is associated with FHT.

  • interface pfcp message { N4SessionEstablishmentReq | N4SessionModificationReq } : Specify the failure handling for N4SessionEstablishmentReq (for new sessions) and N4SessionModificationReq messages (for existing sessions).

    Note

    UPF reselection is not applicable for message type N4SessionModificationReq because the session is already active on a UPF.

  • cause-code { pfcp-entity-in-congestion | mandatory-ie-incorrect | mandatory-ie-missing | session-ctx-not-found | system-failure | service-not-supported | no-resource-available | no-response-received | reject } : Specifies the error codes that SMF receives in the failure response message from UPF.

    Note
    • The no-response-received cause code is introduced in this feature to identify the scenarios where SMF does not receive any response from UPF.

    • FHT does not support the following cause codes, which are configured with their default behaviour:

      request-reject-unspecified , cond-ie-missing , invalid-length , invalid-fw-policy , invalid-fteid-alloc-opt , no-established-pfcp-assoc , rule-creation-mod-failure .
    • pfcp-entity-in-congestion : Specify the cause code when UPF is congested.

    • reject : Specify the option to handle the cause codes in the failure response message from UPF, which are not configured by using the CLI commands available for this feature.

  • action { retry-terminate | terminate } : Specify the action to perform based on the error cause code received in the failure response message from UPF.

    • retry-terminate : Specifies a retry attempt to an alternate UPF. If the retry attempt fails, the session is terminated.

      Note

      If all UPFs are in congested state, call fails even if the action is set to continue .

    • max-retry : Specifies the number of retry attempts to reselect an alternate UPF.

      • Default value: 2

      • Maximum value: 5

Verifying the UPF Failure Handling Configuration

Use the show running-config command to view the configuration.

The following is a sample output of the show running-config command.

show running-config
profile network-element upf upf1
pfcp pfcp-failure-profile pfcp1
node-id      n4-peer-upf1
n4-peer-address ipv4 1.1.1.1
n4-peer-port 0000
keepalive    60
 dnn-list     [ uncarrier.5g ]
capacity     10
priority     1
exit
profile failure-handling pfcp1
 interface pfcp message N4SessionEstablishmentReq
  cause-code pfcp-entity-in-congestion
   action retry-terminate max-retry 2
  exit
 exit
interface pfcp message N4SessionModificationReq
  cause-code mandatory-ie-incorrect
   action terminate
  exit
 exit
exit