H.323 Fast Start

Fast Start, also known as Fast Connect is functionality where a Media DS-0 is established on two separate H.323 endpoints before the H.245 CONNECT message is sent. Fast Connect, which is a requirement for certain billing procedures, bypasses some of the call setup steps and makes it faster to establish two separate DS-0's and be operational before the CONNECT message is sent. The Fast Connect functionality operates as follows:

1. A SETUP message is transmitted from the originating endpoint. This SETUP message has the fastStart component in it. The components are a series of encoded logical channel patterns, each having their own capability media type for both the send and receive directions.

2. The Called endpoint selects one or more of the media types offered and returns its selection in a fastStart component in any H.225 message up to and including the CONNECT message. At this point, the called endpoint must be prepared to receive media along any of the channels it has selected.

The Fast Start procedure is optional in the H.323 Version 2 network, but the IMG 2020 will always attempt it. If Fast Start fails due to unmatched preferred capabilities or because the remote end does not support Fast Start, the IMG 2020 will fall back to the TermCaps procedure. For more information regarding the Fast Start procedure, refer to Version 2 of the ITU H.323 Specification. Below is a call flow diagram displaying the FastStart setup procedure for IMG 2020 in H.323 Version 2.

Open