Section: 6.3.4 Abnormal cases in the network
Content: The following abnormal case can be identified: a) Lower layer indication of non-delivered NAS PDU due to handover Unless the procedure descriptions in clause 6.4, 6.5 or 6.6 specify a different behaviour, the following applies: If the downlink ESM NAS message could not be delivered due to an intra MME handover and the target TA is included in the TAI list, then upon successful completion of the intra MME handover the MME shall retransmit the ESM message. If a failure of the handover procedure is reported by the lower layer and the S1 signalling connection exists, the MME shall retransmit the downlink ESM NAS message. b) Lower layer indication of non-delivered NAS PDU due to inter-eNodeB connected mode mobility when the transport of user data via the control plane is used If the downlink ESM NAS message could not be delivered due to inter-eNodeB connected mode mobility and the MME is not changed, then upon successful completion of inter-eNodeB connected mode mobility the MME shall retransmit the ESM message. If a failure of inter-eNodeB connected mode mobility is reported by the lower layer and the S1 signalling connection exists, the MME shall retransmit the downlink ESM NAS message. NOTE: If the downlink ESM NAS message could not be delivered due to inter-eNodeB connected mode mobility and the MME is changed, the retransmission of downlink ESM NAS message is not supported.