Main Module Design And Realization Of The P2P Based VOD System

This thesis firstly describes the background of the IPTV system, its concepts, the architecture and the carrier network needed for running the IPTV services. By the IPTV's architecture and carrier network characteristics, the potential system bottlenecks, such as the video server's processing power and the carrier network's capability, are pointed out when deploying the IPTV's VOD service at large scale.Another technology involved here is the P2P file sharing technology. The developing process of the P2P file sharing technology is introduced. Current two major P2P file sharing implementations, BT and eMule, are depicted briefly from the file sharing and transport mechnisms.With the problems existing in the current VOD system, the necessary of introducing P2P mechanism into the VOD system is discussed. The possible VOD system adjustment of introducting P2P is discussed too. The P2P based VOD system's optimization and expansion capability are mostly analyzed, and concluding that the VOD processing power and bandwidth needed are not longer linear to the concurrent access of VOD service after introducing the P2P into the VOD system. The cost of system construction and service running will be reduced much is also concluded. These conclusions will benefit the telecom's large scale P2P based VOD system deployment.After simply comparing current two major P2P file sharing implementations, and combining with the detail requirements of the VOD system on the P2P, the thesis determines the solution which will customize BitTorrent protocol to meet the VOD system demands.The thesis then analyzes one of the open source BitTorrent implementation, libtorrent. Its classes, functions, downloading algorithm are mostly depicted. By the concrete requirements of the VOD system, the legacy BitTorrent piece/block downloading strategy is substituted, and creates one P2P based with QoS guaranteed, sequential piece/block downloading strategy capable file transferring implementation, btStream. And the expected capabilities of the btStream are verified by several test cases.At last the thesis pointed out the additional works needed be done when deploying the btStream into the production/real VOD system, such as the integration with the video player, the dynamic setting of the super seed and etc.The thesis hopes P2P mechanism will play an important role in the Telecom and Internet VOD service. The great cost reduction of P2P enabled VOD system will push forward the VOD service a big step and hence enrich the people's daily life.