Question: What is the primary purpose of the Gy reference point in the Policy and Charging Control architecture, as defined between the Online Charging System (OCS) and the Policy and Charging Enforcement Function (PCEF)?
Option 1: To enable offline billing for voice services
Option 2: To facilitate online credit control for service data flow based charging
Option 3: To manage policy rules for Quality of Service (QoS)
Option 4: To provide subscriber profile updates to the PCEF
Explanation: The Gy reference point is specifically designed for online credit control, allowing real-time charging decisions based on service data flow. This is crucial for operators to manage and monetize data services effectively, distinguishing it from offline billing, QoS policy management, and subscriber profile updates, which are not the primary purposes of the Gy reference point.