A distributed multimedia conferencing system

We present the design of a desktop multimedia conferencing system, called Nebula, built with a distributed conference control infrastructure with fault tolerance capability. The system provides for considerable flexibility in conferencing facilities: it supports three different modes of floor control passing and switching between these modes during a conference. Conferees can join a conference in various ways, with selection of chairperson according to seniority defined in the agenda file. To handle the concurrency problem, only the floor holder can modify shared data in the public windows. Each conferee holds a copy of shared data and only update operations are sent so as to improve response time and minimize network traffic. A simple and well defined application user interface (API) is provided and a number of multimedia applications has been developed using the API.<>