Question: When a P-CSCF requests information about the type of IP-CAN from the PCRF during an IMS session setup, what additional action must the P-CSCF take within the same command operation?
Option 1: Unsubscribe from all existing notifications
Option 2: Request additional UE location information
Option 3: Initiate a new SIP session for verification
Option 4: Subscribe to notifications for changes of the IP-CAN type used by the UE with Specific-Action AVP set to IP-CAN_CHANGE
Explanation: This is because, when the P-CSCF requests information about the type of IP-CAN, it must also subscribe to notifications for changes in the IP-CAN type used by the UE within the same command operation, ensuring the P-CSCF remains updated on any changes crucial for managing sessions effectively.