We describe the architecture and implementation of our comprehensive multi-platform collaboration framework known as Columbia InterNet Extensible Multimedia Architecture (CINEMA). It provides a distributed architecture for collaboration using synchronous communications like multimedia conferencing, instant messaging, shared web-browsing, and asynchronous communications like discussion forums, shared files, voice and video mails. It allows seamless integration with various communication means like telephones, IP phones, web and electronic mail. In addition, it provides value-added services such as call handling based on location information and presence status. The paper discusses the media services needed for collaborative environment, the components provided by CINEMA and the interaction among those components.

In this paper we survey the conferencing architectures in H.323 and SIP. We give a compact review of the H.323 framework and capture the current status of the emerging SIP conferencing architecture. Subsequently we present a qualitative comparison of the schemes under study. The evaluation criteria are scalability to large conference sizes and to large geographical dispersion of participants ,as well as adaptiveness to heterogeneity in media streams format and protocol implementation. Our findings suggest that both architectures have certain advantages and limitations. Wherever possible we propose measures to overcome the latter. Concluding, we propose future work to mitigate the identified gaps in the SIP conferencing framework.

Abstract: As various multimedia communication services are increasingly required by Internet users, several signaling protocols have been proposed for the efficient control of multimedia communication services. However, the model and architecture of multimedia conferencing are several. This paper first introduces some SIP multimedia conferencing architectures, and their advantages, disadvantages and performance. According to a centralized multimedia conferencing model, feasible system architecture is constructed, which can support middle scale multimedia conference. Then it analyzes the key technologies in centralized SIP multimedia conference, such as media server design and audio mixing. Then, a multimedia conference system is designed based on SIP. The SIP-based control mechanism for achieving the scalability has been designed in details. Finally, the system’s performance is evaluated and discussed. Key words: SIP; multimedia conference; conference server 1.

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