This paper reports a joint work between the Hong Kong University of Science and Technology and the Brandenburg Technical University of Cottbus, Germany, in developing a global video conferencing framework called OCTOPUS that interconnects local conferencing systems over long distances. The system makes use of both high level information provided by the participants (to decide which videos are more important to them) as well as low level adaptive mechanisms to perform media scaling as the network and the processor intensities change. It is possible to provide customized service to each conference participant according to hisher needs and the resources available at each site. OCTO-PUS itself makes no assumption on the architecture of the local video conference systems. The paper presents the architecture and the design philosophy of the OCTOPUS framework.Index termsmultiparty video conferencing systems, media scaling, scalability, floor control, adaptive resource management, quality of service, group communication.

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Video conferences have become a popular application in modem high performance networks. Advanced technologies allow their installation on desktop computers. Currently videoconferences are mainly deployed for large open group conferences in the Internet to transmit lectures, conferences, talks, and discussions. Multiparty video conference tools for c10sed group meetings are less broadly used. On the other hand, most meetings in every-day life are meetings of closed groups with a more or less confidential character. UnJike open group conferences cJosed group meetings require asender related transmission paradigm, i.e. the sender must know the receivers ofthe data streams. This is usuaHy solved by using a centralized group server for the group and the QoS management. The shortages of this approach are server failures and performance problems. The decentralized approach is more flexible, but it requires more sophisticated mechanisms to preserve the consistency ofthe management data at each participant. In the paper we present the signalization protocol GCP to support decentralized c10sed group video conferences. It provides an atomic, ordered, and reliable data delivery service and supports a dynamic join and leave ofparticipants. We present two versions of the protocol: one for A TM networks using overlaid multi cast connections and one for IP-based networks.