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Differences between H.323 and SIP

Learn about the differences between SIP and H.323 protocols in this expert response.

What is the difference between H.323 and SIP?

H.323 and SIP both support VoIP and multimedia communications. H.323 is an older standard developed by the ITU. A good chunk of it is based on ISDN which comes from the traditional telephony world. H.323 is a binary protocol and is fairly complex in nature. SIP was developed by the Internet Engineering Task Force (IETF) and is text based (similar to HTTP). Much of the infrastructure already in place to support HTTP has been adapted to support SIP. IT managers within businesses are generally more comfortable with SIP because they are used to handling HTTP traffic. SIP is an open standard and solutions based on SIP are highly interoperable. A lot of effort has gone into ensuring interoperability and many manufacturers work together to regularly test to ensure this. Very few manufacturers are working on new H.323 implementations. SIP has become the standard of choice and is being worked on by large companies such as Microsoft and Cisco.

This was last published in March 2005

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