In this paper, an implementation of a multimedia conference system with shared white board developed on workstations under UNIX environment is presented. During the implementation, some design issues are encountered such as how to choose transport protocols, how to resolve problems of delay jitter, how to setup and manage the connections, how to resolve the lip synchronization problems, how to assign priority to packets and how to choose encoding schemes for audio and video. These design issues will be discussed in this paper.

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Although video phone/conference applications on ISDN networks have been a popular product, a similar service on packet switched networks still faces many technical problems. In this paper, the implementation of a multimedia system on a token ring network connecting personal computers using commercially available consumer electronic devices is presented. This system allows people to interactively communicate with each other at different locations through video phone and shared white board services. Since the system transmits real-time traffic such as video and voice over the network, many design and technical issues such as the network protocol, encoding technique, delay jitter, packet size, synchronization of video and voice, and priority assignment are considered and presented in this paper.

In this paper, we describe the implementation of a desktop CSCW (Computer Supported Cooperati\r Work) system using commercially available consumer electronic devices and facilities. The s!.steni is developed on workstations under UNlX and OPEN LOOK environments connected b! . FDDI (Fiber Distributed Data Interface) networks. It pro\ides multiparty conference with shared white board. shared tcst editor, calendar. and voting capabilit?, Each confcrcncc with these features can support a groupuarc environment. The design and consideration of the framework of the system is presented. During the implementation. some performance issues. such as error control, medium synchronization and throughput improvement will also be discussed. 'This work was supported by The National Science Council of ROC under

Abstract. In this paper, a generic four-layer framework for computer supported cooperative work (CSCW) is proposed. With clear separation of functionalities in each layer of the framework, application developers could implement their specific CSCW applications easily. Based on the four-layer framework, the architecture of a general purpose CSCW platform is designed and implemented with the necessary functionalities to help the collaborations among group members. To provide the system with more features and user friendliness, multimedia processing and transmission capabilities for audio and video are incorporated into the platform. Features like application-sharing, group decision support, multimedia mail transmission, etc., are well implemented in the platform. Moreover, an efficient network transport protocol, called VXTP, is designed and implemented to avoid the transmission overhead of conventional TCP. The performance measurements using both VXTP and TCP are given in the paper for comparison. Lastly, compared with other CSCW systems, our design achieves greater flexibility and portability by adopting the generality philosophy in the framework.