This object reports the caller ID (originating phone number) of the user who dialed into the device that started this VPDN tunnel session, when that information is available. Administrators use it to identify which physical caller a session belongs to, for example when tracing abuse or billing disputes, though it can be empty if the dial device does not supply caller ID. For example, an empty caller ID field on a session dialed in through an older dial device would be expected rather than a fault.