Cisco ISDN GW 3241 Uživatelský manuál stáhnout pdf (Strana 11)

Chapter 2 Video conferencing today

Introduction

Video conferencing was first introduced in the 1960s but early systems were unreliable and difficult to

install, use and manage. The equipment and ISDN bandwidth were prohibitively expensive, audio and video

quality were poor.

Today IP-based video conferencing is an attractive and accessible face-to-face communications business

solution. Advances in video technology and the creation of industry standards have allowed for higher audio

and video quality, user-friendly web and desktop interfaces and seamless integration across networks.

Codian products are powerful and truly "plug and play", enabling quick and easy installation and effortless

integration into everyday business processes. Video conferencing is as easy as picking up the phone and

making a call. There is no need for prior arrangements, reservations or complex setup. There is an intuitive

on-screen audio-visual prompt, and an easy-to-use Web interface for scheduling a conference. Individual

users can use their endpoint’s remote to control their view of the conference.

H.323 protocol

One of the protocols used by Codian products for video conferencing is H.323. H.323 defines how a series

of network elements work together and the protocols to allow multimedia transmission across an unreliable

packet-based network such as the Internet. (The H.323 specification is published by the International

Telecommunications Union.)

Video conferencing elements

The H.323 specification defines a number of elements that are required for multimedia transmission.

However in everyday usage some of these element names are used more “loosely” and we try to distinguish

between the two:

 H.323 Endpoint

Strictly an endpoint is an MCU, a terminal or a gateway (see below). However, the word endpoint is

usually used interchangeably with a terminal

 H.323 Multipoint Control Unit or MCU

An MCU maintains the communications between all the participants in the conference call. An MCU

handles call control and the media exchange (for example voice and video) during a conference.

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Cisco ISDN GW 3241 Uživatelský manuál Strana 11