Overview

In many situations it is not necessary to transmit a motion video signal to achieve a satisfactory electronic conferencing capability. Instead, the conference may require only audio and graphics. This chapter describes a new ITU standard, T.120, which provides the ability to interactively exchange graphics (or any data) on a multipoint basis. The audio portion of the conference would be provided independently from the T.120 process.

Traditionally, telephony services have been confined to point-to-point operation. To support group activities, such as meetings and conferences involving physically separated participants, there is a requirement to join together more than two locations. The term multipoint communication simply describes the interconnection of multiple terminals as shown in Figure 10.1. Normally, a special network element, known as an MCU, or simply a bridge, is required to provide this function. The raw communication data stream would typically consist of one or more of the three media elements: audio, video, and data. The term multimedia is now widely used to collectively describe this grouping.

The T.120 series of recommendations applies to the data element, which would typically be used both to provide a data communications service and management of any other media services present. The T.120 ITU Recommendation introduces the T.12x series of Standards, collectively referred to as the T.120 series. The T.120 protocol is a means of telecommunicating all forms of data/telematic media between two or more multimedia terminals and of managing such communication. It can also manage real-time conversational speech and video...