Question: In the context of IP flow mobility, what triggers the PCEF to modify or remove an already installed routing rule related to an IP-CAN Session?
Option 1: Receipt of updated flow binding information from the User Equipment (UE)
Option 2: Periodic review of routing rules by the Policy and Charging Enforcement Function (PCEF) for optimization
Option 3: Direct instruction from the Policy and Charging Rules Function (PCRF) via the Gx reference point
Option 4: Expiration of a predefined timer set for all installed routing rules
Explanation: The correct answer is Option 1 because, in IP flow mobility management, the PCEF modifies or removes an installed routing rule based on updated flow binding information received from the User Equipment (UE), ensuring seamless service delivery as the UE's connectivity changes.