Introduction

The current development on telecommunications industry is changing the use of telecommunications networks remarkably. People use telephone lines more and more for data transfer instead of ordinary voice calls. So its desirable to integrate data and voice data in a single network.

Convergent networks

Obviously these changes has strong affection to the networks and operators. Public networks are moving from circuit switched networks to packet switched networks. This will cause telecommunications networks and data-communications networks, which are mainly IP based. This will eventually cause that voice calls are transmitted over IP based networks, as well. IP telephony, or voice over IP, means that voice and fax calls are transmitted over an IP network such as the Internet, rather than over the familiar public switched telephone network (PSTN).

Technical background

H.323 is a umbrella standard that specifies components, protocols and procedures that provide multimedia communication over packet switched networks. H.323 is part of a family of ITU-T recommendations called H.32x that provides multimedia communication services over a variety of networks.

These standards apply to H.323:

Call signaling and control

Audio codecs Video codecs Related standards

Versions of H.323

The first version of H.323 protocol was published in 1996 and was "designed for local area networks". Later companies tried to use H.323 in large private networks and it worked very well. Today we are using H.323 on the Internet. Due to this shift in 1998 Version 2 (H.323v2) was passed. Enhancements included security, better performance, scalability and better supplementary services. In 1999 version 3 arrived providing better PSTN integration and fast start capabilities. Version 4 was approved in November 2000 and focus on scalabilities, services and provides a flexible extendible Framework. And still development is under way.