Question: What does the `SUCCESSFUL_TRANSFER` (2) value of the SM-Delivery-Outcome-T4 AVP indicate in the context of device trigger delivery in a telecom network?
Option 1: The UE (User Equipment) lacks sufficient memory capacity to receive the trigger.
Option 2: The device trigger was successfully transferred to the UE (User Equipment).
Option 3: The subscriber is currently unavailable, causing delivery failure.
Option 4: The message expired in the SMS-SC (Short Message Service Center) due to validity time expiration.
Explanation: In the context of telecom networks, particularly when dealing with device trigger deliveries via Diameter-based T4 interfaces, `SUCCESSFUL_TRANSFER` explicitly indicates that the delivery process was completed without issues, and the trigger successfully reached its intended destination - the User Equipment (UE). This outcome is crucial for network operators to confirm the effective dissemination of triggers, which might be vital for various services or updates.