Question: In UMTS networks, when is a successfully established Radio Access Bearer (RAB) for the CS domain counted towards the 'Successful RAB establishments without queuing' measurement?
Option 1: Upon receipt of a RANAP RAB ASSIGNMENT REQUEST message by the RNC, regardless of traffic class.
Option 2: When a UE initiates a CS domain call setup, before the RNC processes the request.
Option 3: After a queuing process is completed for the CS domain RAB establishment.
Option 4: Upon transmission by the RNC of a RANAP RAB ASSIGNMENT RESPONSE message for CS domain, if no queuing was involved.
Explanation: This option correctly aligns with the specified condition for counting successful RAB establishments without queuing. The measurement is incremented when the RNC sends a response for the CS domain, provided that the RAB was not queued and this is its first successful setup or modification, ensuring accurate tracking of non-queued RAB setups in UMTS networks.