How it Works

For this feature, SMF supports the following IE and cause values:

  • Decode "Criticality Diagnostics" IE, which SMF receives as part of the following N2 messages:

    • PDU Session Resource Setup Unsuccessful Transfer

    • PDU Session Resource Modify Unsuccessful Transfer

  • Handle the following N2 cause values in PDU Session Resource Setup Unsuccessful Transfer:

    • Radio Network Layer cause values:

      • Unspecified

      • Multiple PDU Session ID instances

      • NG intra-system handover triggered

      • NG inter-system handover triggered

      • Xn handover triggered

      • UP integrity protection not possible

      • UP confidentiality protection not possible

      • UE maximum integrity protected data rate reason

    • Protocol cause values:

      • Transfer syntax error

      • Abstract syntax error (reject)

      • Abstract syntax error (ignore and notify)

      • Message not compatible with receiver state

      • Semantic error

      • Abstract syntax error (falsely constructed message)

      • Unspecified

    • Miscellaneous cause values:

      • Not enough user plane processing resources

  • Handle the following N2 cause values in PDU Session Resource Modify Unsuccessful Transfer:

    • Radio Network Layer cause values:

      • Unspecified

      • Unknown PDU Session ID

      • Multiple PDU Session ID instances

      • IMS voice EPS fallback or RAT fallback triggered

      • NG intra-system handover triggered

      • NG inter-system handover triggered

      • Xn handover triggered

    • Protocol cause values:

      • Transfer syntax error

      • Abstract syntax error (reject)

      • Abstract syntax error (ignore and notify)

      • Message not compatible with receiver state

      • Semantic error

      • Abstract syntax error (falsely constructed message)

      • Unspecified

    • Miscellaneous cause values:

      • Hardware failure

      • Unknown PLMN

  • Send the following N2 cause values in PDU Session Resource Release Command Transfer:

    • Radio Network Layer cause values:

      • Unspecified

      • Release due to 5GC generated reason

    • NAS cause values:

      • Normal release

      • Authentication failure

      • Deregister

      • Unspecified

  • Handle the following N2 Cause values in Path Switch Request Setup Failed Transfer

    • Radio Network Layer cause values:

      • Unspecified

      • No radio resources available in target cell

      • Radio resources not available

      • Slices not supported

      • Resources not available for the slices

      • UP integrity protection not possible

      • UP confidentiality protection not possible

      • Not supported 5QI value

      • Encryption and/or integrity protection algorithms not supported

      • No radio resources available in target cell

  • Generate an error-level log after SMF receives the N2 cause for a failure cause and debug-level log for a successful cause.

  • Maintain statistics based on N2 cause that SMF receives for PDU Session Resource Setup Unsuccessful Transfer, PDU Session Resource Modify Unsuccessful Transfer, and Path Switch Request Setup Failed Transfer messages.

  • Maintain statistics based on the N2 cause sent in PDU Session Resource Release Command Transfer message.