What is the difference between RRCConnectionReconfiguration and RRCre-establishment?

Hi All,
What is the difference between RRCConnectionReconfiguration and RRCre-establishment?

RRC CONNECTION RECONFIGURATION message is the command to modify an RRC connection.

The purpose of this procedure is,

· To establish/modify/release Radio Bearers

· To perform Handover

· To setup/modify/release Measurements

· To add/modify/release SCells

· Dedicated NAS Information might also be transferred from eNodeB to UE

While the purpose of RRC CONNECTION RE-ESTABLISHMENT procedure is to re-establish the RRC connection, which involves the resumption of SRB1 operation and the re-activation of security (without changing algorithms). The UE shall only initiate this procedure when AS security has been activated.

The UE initiates the RRC CONNECTION RE-ESTABLISHMENT procedure when one of the following conditions is met:

Upon detecting radio link failure; or

Upon handover failure; or

Upon mobility from E-UTRA failure; or

Upon integrity check failure indication from lower layers; or

Upon an [ RRC CONNECTION RECONFIGURATION ] failure

rrc1

reference: