Error Handling for Protocol Data – NAS

NAS Error Handling
Protocol Data Error

AMF Handling

N1 message is too short to contain a complete message type information element.

Ignore the message.

N1 message with message type not defined or not implemented.

Return a status message with cause #97, message type non-existent or not implemented.

AMF cannot parse N1 message. It is a request message.

AMF formulates a reject message and sends it to UE.

AMF cannot parse N1 message as mandatory IE is missing. It is a response message.

Stop retransmission timer and treat it as transmission failure. Formulate and send 5GMM status message to UE with cause #96, invalid mandatory information.

Limit on repetition of information elements is exceeded.

AMF handles the contents of the information elements appearing first up to the limit of repetitions and ignores all subsequent repetitions of the information element.

N1 message with optional IEs that have incorrect syntax.

AMF ignores optional IEs and accepts rest of the message.

Conditional IE errors.

For Conditional IE handling, AMF sends MM status message with cause #100 CONDITIONAL_IE_ERROR