Is TAU request considered as mo-signalling for establishment cause ?

Question

RRC Connection Request message carries "Initial UE identity" which is just 5 bytes long identifier. Why does so many information elements send within the "Re-establish UE-Identity" like C-RNTI, physcellId etc ?

Answer 1

If UE doesn't have rrc connection with eNodeB and TAU need to be performed then rrc connection request message is sent to eNodeB with establishment cause "Mobile originating signalling".

Comments

Establishment cause = Mobile originating signalling, is for "Attach", "Detach" and "TAU"