SipInviteAckNotReceived

This event informs application software that the far end of an incoming phone call did not respond with a final SIP INVITE ACK after the media engine agreed to enter into a phone call session by sending a "200 OK" response to the original INVITE.

There are three primary reasons this event will be sent to application software:



ACK not sent by the far end of the call:

In this case, the far end of the call (the initiating side of the call) did not send the final ACK in response to the media engine sending out its "200 OK" response to the original INVITE. If your application gets this event due to this situation, you may want to ignore final ACK loss by calling the ConnectIncomingCallWithoutInviteAck API procedure. If your application calls the ConnectIncomingCallWithoutInviteAck API procedure, the loss of the final ACK will be ignored by the media engine and the incoming call will be established.



ACK sent by the far end of the call but was lost in the network:

This case has the same ramifications as the previous case. In this scenario, the far end of the call did send the final ACK but for some reason it was not delivered by the network. You may want to call the ConnectIncomingCallWithoutInviteAck API procedure in order to solve this issue.



ACK sent by the far end of the call but arrived too late:

In this case, the far end of the call sent the final ACK but it arrived at the media engine too late. The Media Engine will only wait a fixed amount of time for the final ACK to arrive. To change the default time the media engine will wait for the reception of final ACKs, call the SetInboundInviteAckTimeout API procedure.