LTE: How does an eNodeB validate the rrc connection re-establishment request message that receives from an UE ?

Question

It may be an easy question but still I have some doubt.
How RRC Connection setup procedure gets impacted with the presence of "S-TMSI" as an UE-Identity within the RRC Connection Request message ?
Note: RRC Connection request message can carry either 5 bytes long (S-TMSI) or 5 bytes long random value.

Answer 1

In RRC-Reestablishment Message UE includes the CRNTI and Short MAC-I values. Based on CRNTI value enodeB identifies the UE context and validate the short MAC-I against enodeB calculated MAC-I.