Question: What triggers the increment of the 'Successful radio link deletions on Iub' performance measurement in a UMTS network?
Option 1: Receipt of a RADIO LINK DELETION RESPONSE message (NBAP) from NodeB to the RNC, confirming a successful deletion.
Option 2: Sending a RADIO LINK SETUP REQUEST message from the RNC to NodeB for a new radio link establishment.
Option 3: Detection of a radio link failure in the UtranCell, prompting automatic deletion.
Option 4: Periodic radio resource reconfiguration initiated by the RNC.
Explanation: The correct answer is Option 1 because the counter is incremented upon receipt of a RADIO LINK DELETION RESPONSE message from NodeB to the controlling RNC, confirming a successful deletion. This process is crucial for monitoring and managing radio resource utilization efficiently in UMTS networks.