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Issue No. 12 - Dec. (2013 vol. 24)
ISSN: 1045-9219
pp: 2526-2537
Jiaqing Luo , The Hong Kong Polytechnic University, Hong Kong
Bin Xiao , The Hong Kong Polytechnic University, Hong Kong
Kai Bu , The Hong Kong Polytechnic University, Hong Kong
Shijie Zhou , University of Electronic Science and Technology of China, Chengdu
Piece-related algorithms, including piece revelation, selection, and queuing, play a crucial role in the BitTorrent (BT) protocol, because the BT system can be viewed as a market where peers trade their pieces with one another. During the piece exchanging, a peer selects some pieces revealed by neighbors, and queues them up for downloading. In this paper, we provide a deep understanding of these algorithms, and also propose some improvements to them. Previous study has shown that the piece revelation strategy is vulnerable to under-reporting. We provide a game-theoretic analysis for this selfish gaming, and propose a distributed credit method to prevent it. Existing piece selection strategies, though long believed to be good enough, may fail to balance piece supply and demand. We propose a unified strategy to shorten the download time of peers by applying utility theory. The design of the piece queuing algorithm has a conflict with that of piece selection strategy, because it is not possible to assume that the queued requests for a selected piece can always be available on multiple neighbors. We give a possible fix to address the conflict by allowing peers to dynamically manage their unfulfilled requests. To evaluate the performance of the proposed algorithms, we run several experiments in a live swarm. Our primary results show that they can achieve fast individual and system-wide download time.
Protocols, Heuristic algorithms, Games, Algorithm design and analysis, Peer to peer computing, Supply and demand, Degradation,peer-to-peer, BitTorrent, piece-related algorithms
Jiaqing Luo, Bin Xiao, Kai Bu, Shijie Zhou, "Understanding and Improving Piece-Related Algorithms in the BitTorrent Protocol", IEEE Transactions on Parallel & Distributed Systems, vol. 24, no. , pp. 2526-2537, Dec. 2013, doi:10.1109/TPDS.2013.8
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