ICID IM CN subsystem Charging Identifier
The ICID is used within the IMS (IP Multimedia Subsystem) to correlate session level charging information in both the visited and home networks. It is generated at the edge of the IMS, either by the P-CSCF (Proxy - Call Session Control Function) in the case of MO (Mobile Originated) sessions and the I-CSCF (Interrogating - Call Session Control Function) for MT (Mobile Terminated) sessions. All subsequent billable events for the session are associated with this identifier.
