• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8B
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• pp.1197-1203
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• 2010

A strength of BitTorrent, which is widely used for file sharing today, is due to its peer selection mechanism which is designed to encourage peers to contribute data. In the peer selection phase in BitTorrent, peers to upload the file in a swarm are selected by determining which peers upload the most to themselves. However, the number of peers to upload (i.e., number of unchoked peers) is fixed to four in its peer selection mechanism of BitTorrent, which yields inefficiency because the situation of the swarm may vary frequently (e.g., number of peers in the swarm, download rates, and upload rates). In this paper, we analyze the swarming system performance when the number of unchoked in BitTorrents is not static, but dynamic. For empirical investigation, we established a testbed in Seoul National University by modifying an open-source BitTorrent client, which is popular. Through our experiments, we show that an adaptive mechanism to adjust the number of unchoked peers considering the situation of the swarm is needed to improve the performance of BitTorrent.