A scalable distributed VoIP conferencing using SIP

Session initiation protocol seems to be proffered standard for voice-over-IP. In this paper, we consider the limitations of existing SIP conferencing methods and propose a distributed architecture using controllers (SIP proxy servers) and conference servers which facilitate the control and media handling of a VoIP conference. The conference servers are designed on the basis of H.323's multipoint processors and handle the audio part of the conference. We provide conferencing messages on SIP that bring these controllers and conference servers together along with the clients for scalable conference on the Internet. The schematic of the proxy server and conference server is presented to aid in implementation. We also explain the mechanism we use to improve the quality of mixed output speech by selecting the streams at the clients.