Question: When a TDF receives a single instance of the Granted-Service-Unit AVP with a Monitoring-Time AVP from the PCRF, what action does the TDF take at the monitoring time regarding the usage threshold?
Option 1: The TDF retains the current usage threshold without any changes.
Option 2: The TDF resets the usage threshold to zero (0) for all service units.
Option 3: The TDF resets the usage threshold to the remaining value of the Granted-Service-Unit AVP, excluding accumulated volume and/or time usage.
Option 4: The TDF ignores the Monitoring-Time AVP and continues without adjusting the threshold.
Explanation: According to the specified behavior, at the monitoring time, the TDF must reset the usage threshold to the remaining (unutilized) portion of the previously granted service unit, accurately reflecting unused resources after accounting for accumulated usage up to that point, ensuring precise tracking and management of service units over time.