Core Algorithm Analysis And Improvement Based On BitTorrent

P2P network is the combination of distributed system and computer network which breaks the traditional Client/Server(C/S) mode and provides all the Peers in P2P networks "freedom, equality and interconnectivity". In P2P mode, there is no distinction between client and server and each pair of Peers could share files and communicate between each other.The well-known BitTorrent network appeared in 2002, it was called "BT" for it has been the synonym of "free download, file sharing". As the most popular P2P protocol, BitTorrent is known for its two core algorithms:fragment selection algorithm and node selection algorithm.In the clip selection algorithm of BitTorrent protocol, it uses the strategy of minimum number of slice copies. A tremendous of existing research proved that this strategy could not make the number of fragments close to the optimal uniformity. We use the improved SmartSeed algorithm to improve this strategy and according to our experiments, the uniformity of the number of sub-clips, download speed and the average download time all have beed largely improved.The node selection algorithm used in BitTorrent protocol can be divided into Tracker node selection algorithm and upload node selection algorithm. Tracker node selection algorithm is very important for it is the main part of the download process. Tracker node selection algorithm is similar to a random selection strategy which is random and uncertain. It takes a long time to search for the right service provider. To address this issue, we use the improved node selection algorithm to help find the right node in the shortest time. Experiments results show the improved algorithm has significantly improved download speed, and the speed did not decrease significantly in the final stage.People started to look for a suitable network transmission carrier since the streaming media technology existed. P2P technology precisely adapted to the requirements of streaming media. This thesis improved the core algorithm of BitTorrent and made it also as the carrier of video on demand (VOD). We introduced the sliding window algorithm to improve the strategy and made the video resource played quickly and orderly. Finally, we used the experiment to validate the VOD based on BitTorrent could play video resource smoothly and meet the requirements of people.