SIP vs IAX?…What to Use???

The IAX protocol was developed by Mark Spencer (Creator of Asterisk) to limit some of the problems that were in SIP protocol. Later on an updated version of IAX was introduced with the name of IAX2. As both the protocols are used in VoIP technologies, we are trying to differentiate between SIP vs IAX to help you choose better for your VoIP setup.

Have a look at major differences between SIP vs IAX and decide which one is best for you..


SIP is a plain-text protocol, and hence uses comparatively more bandwidth then IAX.IAX is a binary protocol, which allows it to use less bandwidth.

IAX is a lot more efficient when utilizing bandwidth compared to SIP, while given a specific bandwidth, by using IAX you can carry a greater number of concurrent phone calls than if you used SIP.


SIP uses multiple ports for signaling and voice traffic that is why NAT problems appears in SIP.IAX uses a single port for both signaling and voice traffic and hence no NAT problems.


SIP uses multiple ports and hence less vulnerable to malicious and DoS attacks.Using a single port makes it easier for malicious people to execute resource exhaustion or DoS attacks.

Using a single port in IAX, besides advantageous to NAT, have a serious concern too.

By flooding the single port used by IAX, attackers/hackers can easily get control to the system and can prevent actual users from accessing the services. So if you are going to use IAX, you should need to arrange some extra security measures. Because SIP uses no single port in, there is no such a problem.


SIP can be extended pretty easily.Because of the lack of a generic extension mechanism in IAX, it is not as extensible as SIP.


SIP is an standardized protocol developed by the IETF long time ago and widely used by the equipment and software manufacturers.IAX on the other hand, is new and still being standardized. For that reason not many devices supports it.


SIP is a widely used and popular protocol. Many hardware and software manufacturers use SIP as their main protocol for VoIP services, which derived the term “SIP phones”. IAX is rapidly gaining popularity now a days but still it is not as popular as SIP.


Both the protocols are well designed for better experience of VoIP services, and both have their own pros and cons. It totally depends on your own requirement to choose any one from the two. However if you don’t have bandwidth issues, you can go with SIP, as it is widely used and supported. To utilize limited bandwidth you can go with IAX. And before choosing any one always consider various other aspects also.

You can also read more on SIP and IAX2 in our website.