How UE will be authenticated in RRC inactive state?

Question

Assume UE in mobility and RRC inactive sate,once UE wants to make any data connection how UE will be authenticated to make data connection ,because they claim it wont involve any authentication procedure and unnecessary control message then how it will be authenticated?

Answer 1

Authentication is one of the sub procedure of attach procedure and it is done at the NAS level between UE and MME NAS layer. Even after UE moves from RRC connected to RRC idle mode, UE and MME NAS layer maintains context. So next time re-authentication is not required for procedures like TAU and Service Request because UE was already in ECM-REGISTERED state at NAS layer.

Comments

Assume in UE inactive or IDLE  case,if another fake UE comes in middle and sends MAC -CRNTI CE  same as RRC Inactive or IDLE UE then how network will authenticate?

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Hi Jaganathan, I don't have knowledge on 5G RRC but as per LTE RRC understanding, UE context gets deleted from eNodeB when it moves from RRC-Connected to RRC-idle state. So if another fake UE establishes RRC connection  with eNodeB successfully, it will fail at NAS level. There is no relationship of  MAC level C-RNTI with NAS level Authentication procedure for LTE signaling.

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Yeah in case of LTE i got your answer, but in case 5G they claim that INACTIVE state to connected state there wont be any connection establishment procedure because UE context will not be deleted at ENB,then how authentication will happen is my question,