Question: What is the primary trigger for counting an event in the 'Attempted RRC re-establishments' measurement in a UMTS network?
Option 1: Handover failure between two UTRAN cells
Option 2: Receipt by the RNC of a CELL UPDATE message due to 'Radio link failure'
Option 3: Successful RRC connection setup after three failed attempts
Option 4: UE's initial access to the UTRAN network
Explanation: The correct answer is linked to the specific condition that triggers the count for attempted RRC re-establishments. A 'Radio link failure' indicated by a CELL UPDATE message received by the Radio Network Controller (RNC) is a key event necessitating an RRC connection re-establishment attempt, making it the primary trigger in UMTS networks, highlighting radio link maintenance's importance for continuous connectivity and service quality.