Internal Program Version: libiax2  0.2.3

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.

https://sf.net/projects/iaxclient