Inter-Asterisk EXchange (IAX)
Inter-Asterisk EXchange (IAX) is a protocol to provide control and transmission of streaming media over IP-based networks. IAX can be used for any type of streaming media including video, but is targeted primarily at the control of IP voice calls (VoIP).
IAX is an open source initiative that can be used as an alternative for SIP. The primary design goal for the IAX protocol is to provide minimum bandwidth usage for both control and media with specific emphasis on individual voice calls.
The current version of IAX is version 2, commonly referred to as IAX2.