3GPP 24.501 v20.0.0 — the document's own text
5.6.3.4 Abnormal cases on the network side
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
The following abnormal cases can be identified:
- 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 clause 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 clause 5.6.3.1, the AMF may either:
- perform the paging procedure over the 3GPP access; or
- 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.
- 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 clause 5.5.2.
- Lower layers indication of non-delivered NAS PDU due to handover.
If the NOTIFICATION message could not be delivered due to an intra AMF handover and the target TA is included in the TAI list, then upon successful completion of the intra AMF handover the AMF shall retransmit the NOTIFICATION message. If a failure of handover procedure is reported by the lower layer and the N1 NAS signalling connection exists, the AMF shall retransmit the NOTIFICATION message.