Question: In IMS networks employing PCC for a session with STUN relay servers, what is the primary reason for setting up predefined PCC rules to allow UE communication with the STUN relay server prior to session establishment?
Option 1: To guarantee high bandwidth for all subsequent media sessions.
Option 2: To facilitate NAT traversal without impacting gating control in IP-CANs lacking default/best effort flows.
Option 3: To ensure dynamic PCC rules can differentiate between voice and video traffic based on ports assigned by residential NAT.
Option 4: To bypass Policy and Charging Enforcement Point for STUN relay communications.
Explanation: The correct answer, Option 2, highlights the importance of predefined PCC rules in enabling communication with STUN relay servers before session establishment, particularly in IP-CANs that don't support default or best effort flows. This approach ensures NAT traversal mechanisms are supported without disrupting gating control, aligning with the nuances of telecom network management and policy enforcement as outlined in the context of IMS and PCC procedures.