Vod System Based On P2p Technology And Realization

As the rapid development of the computer network and multimedia technology, the Video-on-Demand technology combined with technology of computer network and multimedia also gets great development. On Client-Server Architecture, servers provide the video bandwidth and video data for the users who want the services. However, due to the traditional transmission mode based on the unicast is easy to cause the server's performance bottleneck which cann't effectively support the streaming media's distribution of large-scale data, the VoD system doesn't have satisfactory play-quality.When the P2P (Peer-to-Peer) idea is introduced to streaming media technology, the VoD system can use the common nodes'bandwidth, memory space and other resources to render services to other nodes. So it can reduce the server and network's burden greatly and make the system enjoy excellent extensibility. Furthermore, it let access internet data that users want are not necessary to connect to a fixed server.Along with the BitTorrent (BT) technology wide spread application,BT in the last years has been one of the most effective mechanisms for P2P content distribution, which has the"the connection more, downloading is quicker"feature. So, BitTorrent is one of the most famous and effective technologies for the transfer of distributed files, with choking algorithms based on tit-for-tat policy and rarest piece first selection mechanism.In thesis the BT's unique features is found out, such as special pubkishing content, peer distributing, pipelining, piece selection algorithm and choking algorithms, with analyzing its usage, protocol, algorithm and the implementation. Then the difference of BT by compare the BT model with C/S model and other P2P model is pointed out. In thesis, analysised the related protocols of the BT network, and described the main classes of both client side and server side particularly, then analysised the running process of some kernel arithmetics specially.The pieces'download time sequence and rate of the BT algorithm are researched. Then the BT-S algorithm is proposed which can support the streaming media base on BT. This BT-S becomes aware of streaming order of the piece and give each piece a priority set, which is different from the BT's piece selection mechanism. The simulation results show that the BT-S algorithm can not only meet the streaming media's transmission requirements but also inherit the BT's high transmission efficiency.