P2p-vod System Model And Its Key Technologies

With the development of Internet, video on demand streaming media service in the Internet has become an immensely popular service. Traditional VoD streaming media service systems are mainly based on C/S (Client/Server) architecture. The performance and the out bandwidth of server are the top two factors influence the quality of VoD streaming media service. But given the enormous costs associated with C/S architecture - due both to the increasing video quality and to the enormous demand, server gradually becomes a system bottleneck.VoD streaming media service systems that based on C/S architecture can't provide highly scalable and reliable service. In recent years, researchers began to research how to providing VoD media streaming service based on P2P networks. In a P2P network, peers are both suppliers and comsumers of resources, in contrast to the traditional C/S architecture where only servers supply and clients consume. P2P technology can make full of use of idle network bandwidth resource and participants'resources (such as processing power, disk storage or network bandwidth). Through data exange among peers, it can greatly reduce the burden on server. At present, P2P file downloading system and live streaming system have been widely used. Building a P2P-VoD system with large-scale, high scalability, reliability and performance in a dynamic P2P network environment is a new challenge.After studying the existing P2P technology and streaming technology, this thesis proposes a VoD system named VoDBB based on BitTorrent.Firstly, this thesis introduces the VoDBB system from an overall perspective. It is composed of Tracker servers, Web servers, back-up streaming servers and VoDBB clients. Then this thesis simply describes those entities'functions and relationship.Moreover, this thesis describes the design and implementation of VoDBB client. There are many considerations for deciding the size of the segment such as overhead, flexibility. Due to these conflicting requirements, there are two levels of segmentation of a movie in VoDBB system, piece and slice. VoDBB client uses Bitmap mechanism to manage pieces. VoDBB proposes a mechanism to manage peers. Using this mechanism, peers can quickly find eachother and build high-quality connections. VoDBB uses a mixed strategy to decide which piece should be downloaded first, and it uses back-up streaming servers to guarantee high service quality. Through using cache management strategies, VoDBB can improve memory utilization and increase the amount of videos. In addition, VoDBB applys anchor point mechanism to support man-machine function.Finally, simulation results show that VoDBB can provide a good viewing experience and reduce the burden of the streaming server.