What is the difference between attach request and rrc connection request?

Question

what is difference between UEID IE of rrc connection request and IMSI ?

Answer 1

1.RRC Connection request is a RRC Protocol message and it is between UE and enodeb runs on radio interface(air)
2.Attach request message is a NAS Layer protocol message it is between UE and MME on transfer on
S1-MME)S1AP protocol.both are signalling messages
3.After receiving RRC Connection Setup message from enodeb,UE send a RRC Connection setup complete message+Attach request to enodeb where NAS is piggybacked on RRC in air interface .

Comments

what is piggybacked?

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carrying something along with you is called piggybacked.
simple way suppose If you are carrying a Collage bag.
In this you is "RRC" and Bag is "NAS" just carrying along with you nothing but piggybacked.