Many years have passed since the introduction of H.323, and the standard was gradually developing. 7 versions have been released since 1996, when H.323 standard was approved by the International Telecommunication Union (ITU) to promote interoperability and consistency in video conference transmissions over IP networks.
The first version was rather poor, because its only goal was to establish communication between endpoints of different vendors. This version did not add to reliability, security and good quality of communications, while the endpoints which had been incompatible previously could now “communicate” only within the corporate network.
The second version which was released two years later was the real breakthrough. It was aimed at the active use of VoIP telephony in multipoint conferencing. This time the key purpose was the standard’s reliability and higher security, including such elements as authentication of the endpoints (conference participants), fixed packet data transfer and unauthorized data access protection in networks. Oddly enough, in this version users could not reject incoming calls. Additionally, this version boosted connection between endpoints and added call redirection option.
The third version added support for multiple signalling sessions over single TCP connection. It was particularly useful for network gateway equipment allowing for thousands of simultaneous calls.
The fourth version featured increasing H.323 endpoints capacity. The launch of the fifth version was aimed at general standard stabilization. TrueConf solutions are based on the fourth version of H.323 protocol.
In June 2006, the sixth version of the standard was approved including a set of changes in H.225 and H.245 transport protocols. The sixth version added support for Assigned Gatekeeper, where the endpoint from the list of alternative gatekeepers is registered. Additionally, a number of applications and documents were supported to allow use of GSM and H.264 codecs in H.323 solutions. The seventh H.323 version was released in November 2009. Among many other updates, there are two important features worth mentioning:
- Users’ details are transmitted in several different languages, allowing international organizations to support multimedia communications (including video conferencing) and interact with each other easily;
- When running group conferencing on MCU server, all H.323 endpoints receive invitation data automatically, allowing users to join the conference without entering any authorization details.
In 2021 from the latest ios UC versions(subject to change) H323 will get deprecated .This clearly shows that all future communications will be SIP Based.