Modeling And Analyzing VoD System Based On BitTorrent

As the increasing of technology of broadband, video on demand(VoD) has been getting widely used.At present, three technologies are used inVoD systems to provide service:1) Unicast, the VoD server assigns ervery user a different data stream, which increases the cost of server and bandbroad, and is easily to cause flash-crowd. So unicast is hard to satisfy large scale user request;2) Multicast, using Multiplexing to reduce the load of server and bandbroad. But the existing devices of Internet Content Provider can not support multicst well. Multicast still has limitation in reliability and congestion control, which hinders the extension of multicast technology;3) CDN (Content Delivery Network), through deploying server widely in internet, CDN disperses user request to the nearest server to reduce the load of server and bandbroad. But the widely deployed servers increase the cost and are hard to manage, charging as per byte also increases the expenditure of ICP.So the traditional client/server model is not fit for present VoD service. P2P VoD technology attracted more and more attention.Based on the observing and modeling analysis of BT system, we proposed VoD system based on BT protocol, then analyse the system through modeling. Our work is as follows:1) Observed the two biggest BT system in China (5q.com and icefish.org) for 41 days. The collected data is more than 40GB, including online user count, user count, seed, user of finishing download, user ID of uploading . torrent file, upload time and file size of every BT swarm. Based on the observed data, we analysed the daily-cycle property, ability of handling flash-crowd, free-riding and file popularity of BT system.2) Through analyzing the BT protocol and the abserved data, we proposed the BT system's ability model in flash-crowd and daily-cycle model. Through comparing with the abserved data, we proved the veracity of our model. According to the models, we proposed the project of increasing BT system's servicy ability.3) Based on the research above, we proposed the structure of VoD system based on BT protocol.4) We modeled the VoD system based on BT protocol.The main results and problems remained to be solved are presented in the conclusion.