Question: When a PCRF (Policy and Charging Rules Function) disables usage monitoring for a specific monitoring key, what action is expected from the TDF (Traffic Detection Function) in response to this change?
Option 1: The TDF continues to monitor usage without reporting until re-enabled.
Option 2: The TDF sends a new CCR with CC-Request Type set to "INITIAL_REQUEST" and reports all historical usage.
Option 3: The TDF sends a new CCR command with CC-Request Type AVP set to "UPDATE_REQUEST" and Event-Trigger AVP set to "USAGE_REPORT" to report accumulated usage for the disabled key(s).
Option 4: The TDF stops all monitoring activities until a new monitoring key is enabled by the PCRF.
Explanation: This is the correct answer because, when the PCRF disables usage monitoring, the TDF must report accumulated usage since the last report. This is achieved by sending a new CCR with "UPDATE_REQUEST" and "USAGE_REPORT" settings to ensure the PCRF receives necessary updates for accurate billing and policy enforcement.