In the process of the development of Asterisk a new protocol has gathered the
attention among the VoIP users - the Inter-Asterisk eXchange, or IAX (TM),
Protocol, used as a the native communication protocol between Asterisk PBX
Servers. What is particularly good in it is that it requires only one UDP port
per endpoint to create a successful communication channel for VoIP calls. This
makes it much friendlier for users behind NAT, which is not the case with SIP
and H.323 - they required specific router configurations for their channel
establishment, thus hindering faster spread of VoIP on the home and corporate
desktop.