Inter Asterisk eXchange, lovingly called IAX (pronounced: eeks), is the
protocol used by the Asterisk PBX system for inter-asterisk-communication.
Other applications may use libiax to communicate with each other and other
asterisk servers. IAX is a high performance, feature rich protocol unrelated
to SIP or H.323. Its single-socket design allows it to interoperate with NAT
and PAT masquerade firewalls. It supports internationalization, remote
dialplans, and voice, HTML, image, DTMF, and video content.