Sample 4 Out-of-band Ringback without Progress Message

When there is no progress indicator included in the Alerting message, then there is out-of-band ringback. The system maps the Alerting message to a SIP 180, but it it does not include SDP in the SIP 180. This call flow shows that there is no Progress message and that media cannot be set up until after H.323 Connect and SIP messages are sent.