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Telcos use a separate control protocol to set up the `virtual circuits' between two telephone sets, each time you place a regular telephone call. They talk about call `set up' and `tear down', etc. but what they mean is that your dial tones travel a very different path and are treated very differently from the `data' which is your voice packets. In the case of VoIP, the control and the data are all traveling over the same underlying network, the IP. Hence a need for an `embedded' control protocol, a way to set up and tear down a connection over the same IP that carries the voice packets themselves. H323 is one such protocol that has become popular. OpenH323 is an Open Source stack, or a family of related protocols. OpenH323's most prominent piece of application software is Voxilla, see below. Their home is at

Ed Sternin