Uplink NAS transport message is used between eNodeB and MME to pass NAS messages between UE and MME transparently.
Since eNodeB has already communicated TAI and E-CGI as part of "Initial UE message" and MME knows current serving (cell and tai ) of UE then why both IEs are mandatory in Uplink NAS transport. I think it should be optional and it should be included in the message when there is a change in serving (cell or tai or both).
