On the Impact of Greedy Strategies in BitTorrent Networks: The Case of BitTyrant

The success of BitTorrent has fostered the development of variants to its basic components. Some of the variants adopt greedy approaches aiming at exploiting the intrinsic altruism of the original version of BitTorrent in order to maximize the benefit of participating to a torrent. In this work we study BitTyrant, a recently proposed strategic client. BitTyrant tries to determine the exact amount of contribution necessary to maximize its download rate by dynamically adapting and shaping the upload rate allocated to its neighbors. We evaluate in detail the various mechanisms used by BitTyrant to identify their contribution to the performance of the client. Our findings indicate that the performance gain is due to the increased number of connections established by a BitTyrant client, rather than for its subtle uplink allocation algorithm; surprisingly, BitTyrant reveals to be altruistic and particularly efficient in disseminating the content, especially during the initial phase of the distribution process. The apparent gain of a single BitTyrant client, however, disappears in the case of a widespread adoption: our results indicate a severe loss of efficiency that we analyzed in detail. In contrast, a widespread adoption of the latest version of the mainline BitTorrent client would provide increased benefit for all peers.