Question: Which IMS node supports online charging using the ISC interface, specifically when interacting with the Session Charging Function of the OCS?
Option 1: S-CSCF (Serving-Call Session Control Function)
Option 2: P-CSCF (Proxy-Call Session Control Function)
Option 3: I-CSCF (Interrogating-Call Session Control Function)
Option 4: BGCF (Breakout Gateway Control Function)
Explanation: The S-CSCF is uniquely identified as supporting online charging through the ISC interface, particularly when communicating with the OCS's Session Charging Function. This distinction highlights the S-CSCF's role in managing session-related charging in real-time, contrasting with other IMS nodes that rely on offline charging.