UE NAS and MME NAS

Quick thought regarding the NAS layers between UE and MME. Since UE and MME directly cannot talk to each there could be a disconnect between the both. Consider this. When UE goes into idle mode, it is not known to the network until the network receives a TAU. In the mean time imagine that network initiated a bearer deletion procedure. If eNB doesn’t find the UE then bearer is implicitly detached on MME and eNB, but the bearer information is still present with the UE. At this point there could be a disconnect between UE NAS layer and MME NAS layer.

Assume another scenario where handover is in progress. Because of some reason the target eNB has not accepted a particular bearer. The same is conveyed to network in S1AP message and to UE in RRC messages. But NAS layers in MME and UE still have the bearer information. There could be several cases like this where there can be different NAS states in UE and MME. The question here is will RRC and NAS layers in UE be in sync. That is if a Data radio bearer for a particular bearer is not established, will the NAS layer be intimated the same by RRC and UE will delete the bearer from its NAS layer?

Anybody?