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[Timer] T310 [Stop] Upon receiving N311 consecutive in-sync indications from lower layers, upon triggering the handover procedure and upon initiating the connection re-establishment procedure [At expiry] If security is not activated: go to RRC_IDLE else: initiate the connection re-establishment procedure [Start] 
Upon detecting physical layer problems i.e. upon receiving N310 consecutive out-of-sync indications from lower layers
LTE Timers ~ LTE Guide
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