Research And Implementation Of VoD System Based On P2P Technology

With the spread of broadband communications and the rapid development of network technology, contents on Internet have gradually changed from simple texts to multimedia data including text,audio and video. VoD(Video-on-Demand) has become one of the greatest potential value-added services on Internet.Traditionally streaming media VoD applications with poor scalability are based on C/S model. It may easily make server the bottleneck and can not effectively support the large-scalable streaming data distribution. When P2P (peer-to-peer) thinking is introduced to streaming media technology, VoD system use the common nodes' bandwidth,storage and other resources to serve other nodes, so that it reduce loads of server and network greatly and has scalability and decentralized services.This paper presents and evaluates PPVoD, a scalable Video-on-Demand streaming system that combines the popular Bit-Torrent peer-to-peer file-transfer technology with a simple dedicated streaming server to decrease server load and increase client transfer speed. The system includes a modified version of BitTorrent that supports streaming data delivery and that communicates with a VoD server when the desired data cannot be delivered in real-time by other peers.However, BitTorrent Protocol is not originally designed for time-sensitive content distribution and indeed is not suitable for time-sensitive data distribution. In this dissertation, we make modifications to BitTorrent Protocol in the following aspects. First, in order to guarantee high QoS to users, media server is added in the system. Second, instead of the original rarest-first piece pick policy, We propose a hybrid schedule algorithm of order-first and beta random with probable selection. At last, Owing to high bandwidth of streaming media, the PPVoD system extends the buffer management and puts forward the buffer algorithm.In addition, we make an experiment on PPVoD system and design the simulation on NS2 according to the main performance indicators of media distribution。The PPVoD system plays a good performance in media distribution according to the experimental results. The system not only presents little dependent on the media server, but also shows low latency and high media playback fluency. In one word, the dissertation makes a foundation to the optimization for P2P streaming system performance and provides valuable reference to the experimental results and the solutions.