Question: What is the primary purpose of the SIP-1 reference point between the signalling user agent and the SIP core in the context of VAL (Vertical Application Layer) services?
Option 1: To exclusively manage media transfer for VAL services, ensuring QoS (Quality of Service) guarantees.
Option 2: To facilitate a range of functionalities including session management, authentication, event subscription, and media negotiation in support of VAL services.
Option 3: Solely for overload control and multicast operation communication within the network for VAL.
Option 4: Primarily for billing and charging interfaces related to VAL service usage.
Explanation: The correct answer reflects the multifaceted role of the SIP-1 reference point. It is not limited to a single function (making Options 1 and 3 incorrect) but encompasses a broad set of functionalities crucial for the operation and support of VAL services within the telecom network. Option 4 is also incorrect as billing and charging are not mentioned among the roles of SIP-1 in this context.