scope:

This ETS specifies the functional requirements applicable to a Multipoint Control Unit (MCU), or a set of interconnected MCUs, which allows several audiovisual terminals to communicate simultaneously using single or multiple digital channels up to 1 920 kbit/s when interconnected through the pan-European Integrated Services Digital Network (ISDN).

This ETS specifies the basic in-band signalling procedures to be supported to control the operation of MCU and audiovisual terminals involved in a simple multipoint communication or a basic video/ audiographic conference as specified in other standards.

This ETS includes an overall description of the basic and optional functionalities of a MCU, and lists the related requirements.

Annex A (informative) describes the various requirements which apply to audiovisual terminals in order to ensure their capability to take part in multipoint communications.

A MCU with any interface connected to the ISDN via a Channel Aggregation Unit (CAU) and/or special interface adapters may be used for multipoint communication when the composite equipment complies with all requirements specified in this ETS. However, the various related pieces of equipment are outside the scope of this ETS.

A MCU may establish conferences which include not only audiovisual terminals connected through an ISDN, but also some audiovisual terminals directly linked through digital leased lines.

A MCU may set up a conference where the connected terminals include not only videoconference and videotelephony terminals but also Audiographic conference, 7 kHz telephony or 3,1 kHz telephony terminals. The description of protocols and requirements is limited to the basic multipoint communication established between various terminals supporting 3,1 kHz telephony, 7 kHz telephony, or the Videotelephony teleservice. The protocols and requirements necessary to support more sophisticated services, such as Videoconference, Audiographic conference, or applications based on data transmission are not considered here.

NOTE 1: The T.120 series of ITU-T Recommendations presently developed by ITU-T SG 8 should be used to support such enhanced functionalities.

Use of the protocol specified in ITU-T Recommendation H.243 to support these functionalities should be precluded since it would result in incompatibilities between MCUs and/or terminals.

NOTE 2: In the case of interworking with Public Switched Telephone Network (PSTN) or mobile telephony terminals, echoes and/or transmission delays can degrade the audio communication quality to an unacceptable level.

A MCU may be owned either by a public service provider or by a private customer. In the latter case the equipment is part of a Private Telephone Network.

The D-channel signalling protocol used to set up, modify and clear a multipoint communication is outside the scope of this ETS.

On line procedure and/or protocol to be used by an end user to require, modify or cancel a conference reservation is outside the scope of this ETS.

Implementation of the T.120 series of ITU-T Recommendations for the support of the enhanced functions associated to various options of the videoconference service (e.g. Conference control, multipoint data communication service) is outside the scope of this ETS.

Conformance to this ETS will be demonstrated by checking that all mandatory functional requirements are supported during execution of a test suite which is specified in other ETSs.