Section: 5.6.3.4 Abnormal cases on the network side
Content: The following abnormal cases can be identified: a) Expiry of timer T3565. The network shall, on the first expiry of the timer T3565, retransmit the NOTIFICATION message and shall reset and start timer T3565. This retransmission is repeated four times, i.e. on the fifth expiry of timer T3565, the procedure shall be aborted. In addition, upon the fifth expiry of timer T3565: For case a) in subclause 5.6.3.1, the AMF should notify the SMF that the UE is unreachable. The AMF may enter 5GMM-IDLE mode over 3GPP access. For case b) in subclause 5.6.3.1, the AMF may either: 1) perform the paging procedure over the 3GPP access; or 2) notify the SMF that the UE is unreachable. NOTE: Whether the AMF performs the paging procedure or notifies the SMF is up to operator's policies. b) De-registration procedure collision If the network receives a DEREGISTRATION REQUEST message before it receives a SERVICE REQUEST message or REGISTRATION REQUEST message, the AMF shall stop timer T3565 and proceed de-registration procedure as specified in subclause 5.5.2.