A Proxy System Based On Peer-to-Peer VOD Platform

Source server is the only stable media streaming provider in the existing P2P VOD System and all data requests which can not be found in P2P network are directed to the source server. Too frequently of data requests will cause over-load of the source server and the response of which to peers will be too long as the scale of system increases. As a result, how to improve the total data service capacity is a key problem of whether it can provide high quality VOD service.The proxy system in P2P VOD System GridCast resolve the problem efficiently. Proxy system consists several proxy servers which locate between source server and peers, proxy servers have a certain capacity of storage and data service but smaller than souce server. Each proxy server caches the most valuable chunks of current time and provide media service directly. If the requested is not found locally proxy server will get the chunk from source server and service peer, and cache the chunk in the same time. The proxy system uses chunk-based caching strategy, using Berkeley DB to manage these mass chunks efficiently and using buffer-map to increase the index efficiency. On the basis of analyzing the shortage of the existing replacement policy, the paper proposed a popularity-based replacement policy and implement the policy using the thought of statistic list.C++ language is used to implement all modules of proxy server which can cross -platform and analyze the performance of the system and the replacement policy through simulate. The result shows that proxy-based architecture reduce the load of source server and the bandwidth consumption by 20%. Also, it shows that the popularity based replacement policy improves the hit rate of data request by 10% and the hit rate raises as the increasing of caching scale. Thus the overall performance of the system is greatly improved.