Barter, or tit-for-tat, file sharing systems such as BitTorrent have proven to be remarkably effective in dealing with highly popular content. However, in situations where a file is not as popular, or the rate of demand is not high, it is frequently difficult to obtain the file in a timely manner. In this paper we describe our explorations with two techniques that attempt to address this issue by making certain peers (those with complete copies) more "selfish." Counterintuitively, this approach can be shown to improve total network performance in various metrics.

PDF (1.2 MB), SIGecom Exchanges 5(4):31-40, July 2005.