SipSendSessionProgress

This event informs application software that the telephony engine is sending a session progress indication to the far end of the incoming call. Most application software can ignore this event.

Note:
Session progress indications to the far end are no longer used by the telephony engine. This event is maintained for compatibility with earlier versions of the telephony engine. New applications can completely ignore this event notification. If you use network sniffer software to monitor SIP protocol activity, you will no longer see SIP session progress packets being transmitted by the telephony engine.