Question: What triggers the generation of a Partial Call Detail Record (CDR) for a Push-to-talk over Cellular (PoC) session, aside from the Accounting-Interim-Interval parameter expiration?
Option 1: Reception of a Diameter Charging Data Request [start] message by the Charging Data Function (CDF)
Option 2: Change in the PoC Server's IP address
Option 3: Session modification procedure (e.g., change in media), change to user location, or reaching a usage threshold (e.g., volume, duration)
Option 4: Termination of the SIP session indicated by a Charging Data Request [stop] message
Explanation: According to telecom charging management principles for PoC services, partial CDRs are generated in response to specific events that require updates to the billing information. Among the provided options, only session modification (like a change in media), a change in the user's location, or reaching predefined usage thresholds (such as volume, duration, etc.) are recognized triggers for sending a Diameter Charging Data Request [Interim] message, which in turn leads to the generation of partial CDRs. This ensures accurate and up-to-date billing information for dynamic PoC sessions.