How does SIP compare to H.323?
The H.323 protocol came on the scene in the mid-’90s as a transmission and session setup protocol for videoconferencing over ISDN networks. It comes out of the International Telecommunication Union (ITU), a 54-year-old standards body for technologies and protocols for the international phone network. H.323 is not a single protocol in one vertical integrated stack, but it is a suite of protocols that cover codecs, call control, conferencing, and many other functions. The advantage to this approach is that by strictly controlling so many aspects of the implementation it is easier to ensure that H.323 based systems function well together. On the down side, H.323 has become heavy and cumbersome. Flexibility is sacrificed as one is tied to a single family of technologies. For a field as young and fast changing as IP telephony, where many problems and solutions are still under debate, flexibility is an important aspect. SIP is part of this flexible approach, as it uses a wide variety of prot
