Question: During an IMS Session Transfer involving a transfer from/to a CS (Circuit Switched) domain, how should charging records be handled to avoid double billing?
Option 1: Generate separate charging records in both IMS and CS domains, with each domain handling its own billing.
Option 2: Suspend charging in the IMS until the session transfer to/from CS is complete, then resume and adjust charges accordingly.
Option 3: Use a split-billing approach where the IMS charges for data portions and the CS charges for voice portions of the session.
Option 4: Correlate charging records between IMS and CS, treating the transferring-in access network as a subsequent Access Leg, and align start/stop charging times to prevent overlap.
Explanation: To prevent double billing during Session Transfer between IMS and CS domains, it's crucial to correlate charging records, ensuring continuity. Treating the new access leg as a subsequent part of the session (not altering the initial call/session direction for charging purposes) and synchronizing charging start/stop times avoids billing discrepancies, aligning with efficient and fair charging practices in telecom networks.