IAX (Inter-Asterisk Exchange Protocol, pronounced "eeks") is a communications protocol for setting up interactive user sessions. IAX is similar to SIP (Session Initiation Protocol ). Mark Spencer developed IAX as a robust, user-friendly alternative to SIP, MGCP (Media Gateway Control Protocol) and RTP (Real-Time Transport Protocol).
IAX is well suited for control and transmission of streaming media and VoIP (Voice over Internet Protocol). Because IAX works well with all codecs, it is adaptable to almost any type of data transmission. Communications bandwidth and latency are minimized by means of multiplexing and trunking. IAX works well in conjunction with firewalls and allows the transmission of several data channels over one link. IAX uses the same path for both signaling and media.
In IAX, handshaking is not required when a call is initiated, which renders the communication vulnerable to denial-of-service (DoS) attacks. However, the risk can be reduced by the use of firewalls, passwords and other standard security countermeasures.