Inter-Asterisk eXchange (IAX) is a communications protocol native to the Asterisk private branch exchange (PBX) software, and is supported by a few other softswitches, PBX systems, and softphones. It is used for transporting voice over IP telephony sessions between servers and to terminal devices.

IAX没有使用 实时传输协议 （RTP），而是利用运行在单一Internet端口（4569端口）上的 用户数据报协议 （UDP）发送和接收信令和媒体。 IAX可轻松穿越 防火墙，消耗的开销大大低于RTP。 当使用G.729压缩 编解码器 时，IAX可以将1M 带宽 传送的呼叫数量增加两倍。 例如，当同时使用G.729和IAX协议时，1M 带宽 上至少可以传送103个呼叫。 IAX不解析文本命令，而使用纯二进制数据，因为这是机器相互通信的自然方式。 IAX协议把响应传回到它们的源地址，而不必协商 …

会话发起协议或SIP，以及Inter-Asterisk eXchange，也被称为IAX，是两个可用于VoIP的额外协议。 SIP和IAX之间的主要区别是，IAX比SIP更有效地使用带宽。 IAX的开发主要是出于这个原因。

IAX 是 Inter-Asterisk eXchange 的缩写，也就是 Asterisk 内部交换协议。 IAX最初用在Asterisk上。 IAX优点： 只用一个UDP端口：4569，来传输通信数据，包括控制信令和媒体数据等。 媒体数据并不需要额外的RTP流，所以可以轻易穿越NAT。 媒体数据会用一个迷你帧来发送，迷你帧帧头只有4字节，不携带控制或信令数据，有效载荷比较大。 迷你帧是不可靠传输，但由于语音通话通常是实时发送的，因此丢失的帧太旧而无法重新集成到音频流中，以至于无法重新传输，所以 …

Abstract: This chapter contains sections titled: What Does IAX Stand For? Is IAX Specific to the Asterisk Platform? What is the Difference between IAX2 and IAX? Why another New VoIP Protocol? How Does IAX Solve VoIP Pains? How is Calls Multiplexing Achieved? And What About Demultiplexing? What Port Number Does IAX Use? What Transport Protocol ...

IAX is the Inter-Asterisk eXchange protocol, which facilitates VoIP connections between servers, and between servers and clients that also use the IAX protocol. IAX was created through an open source methodology rather than through a traditional, standards-based methodology.

2005年3月22日 · IAX2 uses ONLY one udp port for both control and data traffic. As outlined in point 4 of the IAX versus SIP topic with IAX you will always have audio if the control connection can be established. IAX2 supports PKI-style authentication and trunking. The Asterisk IAX2 driver has a jitter buffer.

2016年9月2日 · IAX es un protocolo pensado para VoIP y transmisión de video y presenta funcionalidades interesantes como la posibilidad de enviar o recibir planes de marcado (dialplans) que resultan muy interesante al usarlo conjuntamente con servidores Asterisk.

The Inter-Asterisk eXchange protocol, version 2 (most commonly known as IAX ) is Asterisk’s own VoIP protocol. It is different from SIP in that the signaling and media are carried in the same connection.

IAX is a transport protocol (much like SIP) that uses a single UDP port (4569) for both the channel signaling and media streams. As discussed later in this chapter, this makes it easier to manage when behind NATed firewalls.