P2p Video Conferencing System, Key Technology Research

Video conferencing is a Kind of communication network, in which participants of a meeting can transfer words, voice, video or other kinds of data through Internet or Intranet. With the improvement of communication technology, Video conferencing has been applied in many fields, such as economy, politics, education, etc.Most of existing video conferencing systems comply with H.323 protocol, and have a video server to receive and transfer the voice and video. Because of the limitation of CPU, memory and bandwidth resource of the server, the quality of video and voice in conferencing gets worse quickly when the number of clients increases. So the video sever becomes the bottleneck of existing video conferencing scale. Recently P2P technology can distribute the server's load to peers in its system. If P2P can be applied to Video conferencing, video conferencing will make a great breakthrough.After analyzing the characters of P2P and video conferencing, the article puts forward a P2P video conferencing structure with a core server. The server only manages clients and meeting rooms, but do nothing for data transmission between clients. Every client is a peer. Peers transfer data by ALM (applicant layer multicast). The media stream is transferred by IP layer multicast in LAN, while by IP layer unicast between LANs. Based on above ideas, the article puts forward an algorithm to create and retain ALM trees in our system. We set up a prototype system in JAVA based above our ideas.