5.4.7.2.4 Abnormal cases in the UE

The following abnormal cases can be identified:

• Transmission failure of the NETWORK SLICE-SPECIFIC AUTHENTICATION COMPLETE message with change in the current TAI

If the current TAI is not in the TAI list, the network slice-specific authentication and authorization procedure shall be aborted and:

• if the UE is in 5GMM-REGISTERED state, a registration procedure for mobility and periodic registration update indicating "mobility registration updating" in the 5GS registration type IE of the REGISTRATION REQUEST message shall be initiated; and

otherwise a registration procedure for initial registration shall be initiated.

• Transmission failure of NETWORK SLICE-SPECIFIC AUTHENTICATION COMPLETE message indication without change in the current TAI

It is up to the UE implementation how to re-run the ongoing procedure that triggered the network slice-specific authentication and authorization procedure.

• Network slice-specific authentication and authorization procedure and de-registration procedure collision

If the UE receives NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message after sending a DEREGISTRATION REQUEST message and the access type included in the DEREGISTRATION REQUEST message is the same as the access in which the NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message is received, then the UE shall ignore the NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message and proceed with the de-registration procedure. Otherwise, the UE shall proceed with both procedures.

• Network slice-specific authentication and authorization procedure and service request procedure collision

If the SERVICE REQUEST message or the CONTROL PLANE SERVICE REQUEST message includes the UE request type IE with the Request type value set to "NAS signalling connection release" and the UE receives a NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message before the ongoing service request procedure has been completed, the UE shall ignore the NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message and proceed with the service request procedure.

If the SERVICE REQUEST message or the CONTROL PLANE SERVICE REQUEST message does not include the UE request type IE with the Request type value set to "NAS signalling connection release" and the UE receives a NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message before the ongoing service request procedure has been completed, the UE shall proceed with both procedures.

• Network slice-specific authentication and authorization procedure and registration procedure for mobility and periodic registration update collision

If the REGISTRATION REQUEST message includes the Unavailability information IE without start of the unavailability period and the UE receives a NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message before the ongoing registration procedure for mobility and periodic registration update has been completed, the UE shall ignore the NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message and proceed with the registration procedure for mobility and periodic registration update procedure.

If the REGISTRATION REQUEST message does not include the Unavailability information IE and the UE receives a NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message before the ongoing registration procedure for mobility and periodic registration update has been completed, the UE shall proceed with both procedures.

If the REGISTRATION REQUEST message includes the Unavailability information IE with the start of the unavailability period and the UE receives a NETWORK SLICE-SPECIFIC AUTHENTICATION COMMAND message before the ongoing registration procedure for mobility and periodic registration update has been completed, the UE shall proceed with both the procedures.