Question: What are the primary functions of a SIP Application Server (SIP AS) in the context of Service Enabler Architecture Layer for Verticals (SEAL), on behalf of a Vertical (VAL) service?
Option 1: Managing UE's IP address allocation and DNS resolution
Option 2: Handling SMS/MMS routing and interworking with non-IP networks
Option 3: Influencing SIP sessions and supporting event subscription/notification
Option 4: Controlling QoS policies for guaranteed bitrate in multimedia services
Explanation: In the SEAL architecture, a SIP AS plays a crucial role in interacting with VAL services. Its primary functions include influencing and impacting ongoing SIP sessions (e.g., call setup, teardown, or modification) and supporting event subscription (where the VAL service expresses interest in certain events) and subsequent event notifications (informing the VAL service about occurrences of subscribed events). This enables VAL services to integrate seamlessly with the telecom domain's session management capabilities.