High-quality multimedia conferencing through a long-haul packet network

Desktop multimedia may be just the first step toward longdistance multimedia collaboration. This paper describes both the challenges and the opportunities of transmitting high-fidelity multimedia data streams though long distance packet networks, in the context of practical experience with a worldwide videoconference system that operates over a new internet with realtime transmission capabilities. This system conveys full-motion color images and sound at nearVCR quality and is currently in use both as a research testbed and as a production videoconferencing system. It is also designed to support less common shared media such as realtime simulations or digitized maps. Its implementation incorporates a number of unusual features including the adaptation of commercial codecs to a packetized network, use of the ST-II network protocol for bandwidth reservation and multicasting, an experimental media negotiation scheme, and a new “sticky” conference control protocol designed to minimize the effects of transient network failures and to scale up gracefully to large conferences.