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The UCL Transcoding Gateway (UTG)

Version 1.2

Overview

UTG addresses two issues in order to provide conferencing connectivity to users over N-ISDN or other low speed point-to-point connection.

The first is concerned with the mismatch of link speeds. In existing applications, each sender transmits at the same rate to all receivers. With heterogeneous receivers, the source would have to run at a rate that matches the most constrained receiver. When N-ISDN is used, the available bandwidth is limited to 64 Kbps (1 B-channel) or 128 Kbps (2 B-channel). Currently most MBone transmissions use a target rate of 128 Kbps for video and 64 Kbps for radio, precluding simple bridging of MBone sessions across 128 Kbps ISDN line. Thus some kind of rate control - reducing rate by transcoding or reducing frame-rate (for video) - becomes necessary.

The second issue concerns network configuration. Multicast routing is not yet ubiquitous, and so there are sites that wish to participate in MBone sessions but cannot do so. This applies in particular to workstations situated at the end of ISDN lines running IP (usually PPP) over ISDN. Such workstations often do not wish to run full Multicast routing, or cannot do so if they are running any Microsoft operating system without a local Multicast router, and so an alternative solution is required.

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If you have comments or require further information please contact UTG support.

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Click here for more information on UCL-CS.
Last updated 19 November 1998 by Roy Bennett