Design and Implementation of a SIP-based Centralized Multimedia Conferencing System

Multimedia conferencing is becoming a hot topic of communication in recent years. There are already a few products of multimedia conferencing based on H.323. SIP, which is a more feasible protocol, is put on the agenda of being the call signaling protocol for conferencing. Most of the researches on SIP-based multimedia conferencing, however, have still remained on theories or experiments. In this paper, we propose a feasible framework of SIP-based centralized multimedia conferencing, which meets the requirements of the standards and also develops the theories of XCON framework proposed by IETF. We also present an actual implementation of the centralized conferencing server by exploiting open source achievements, using a few accessory devices for multimedia and data collaboration applications which are also implemented in our laboratory. This paper introduces the whole architecture of the practical system, and expatiates on the flows of conference process.