Question: When re-enabling usage monitoring for a previously disabled PCC/ADC rule, what action can the PCRF take if the original monitoring key needs to be restored?
Option 1: Generate a new PCC/ADC rule with a new, randomly assigned monitoring key and remove the old rule.
Option 2: Modify the existing PCC/ADC rule by adding a new Charging-Rule-Name AVP/ADC-Rule-Name AVP without altering the monitoring key.
Option 3: Modify the monitoring key of the corresponding PCC/ADC rule to the value of the required usage monitoring group (e.g., back to its original value) using the Charging-Rule-Install AVP/ADC-Rule-Install AVP.
Option 4: Remove all existing PCC/ADC rules and re-install them with their original settings, including the monitoring key for the rule in question.
Explanation: This option correctly describes one of the methods outlined for re-enabling usage monitoring. By modifying the monitoring key back to its original value (or the value of the required usage monitoring group), the PCRF effectively restores usage monitoring for the specified PCC/ADC rule without needing to create a new rule or remove and reinstall all rules. This approach aligns with efficient network management practices, minimizing unnecessary changes to existing configurations.