Question: When is an additional E-RAB considered successfully established for the purpose of incrementing the 'Number of additional E-RABs successfully established' measurement in an E-UTRAN?
Option 1: Upon receipt by the UE (User Equipment) of an E-RAB SETUP REQUEST message from the eNodeB/RN.
Option 2: Immediately after the eNodeB/RN sends an E-RAB SETUP RESPONSE message, regardless of UE acknowledgment.
Option 3: When the UE acknowledges the E-RAB SETUP RESPONSE message with a successful setup confirmation.
Option 4: On transmission by the eNodeB/RN of an E-RAB SETUP RESPONSE message, indicating successful establishment.
Explanation: According to the provided context, the measurement is incremented 'On transmission by the eNodeB/RN of an E-RAB SETUP RESPONSE message,' which signifies that the eNodeB/RN has successfully established the additional E-RAB. This point in time is crucial for counting successful establishments, as it reflects the network's capability to set up requested resources without relying on further acknowledgments from the UE.