Modeling and Analysis of Sharing Ratio Enforcement in Private BitTorrent Communities
Providing incentives for user contribution has been one of the primary design goals of Peer-to-Peer systems. The newly-emerged BitTorrent private communities adopt Sharing Ratio Enforcement (SRE) on top of BitTorrent's incentive mechanism, Tit-For-Tat, in order to strictly enforce a minimum contribution a member has to provide, and in relation to the amount of service it has received. In this paper, the authors provide a theoretical model to analyze how SRE provides seeding incentives, and how SRE influences the download performance in the system. Specifically, they study the influence of the SRE threshold (i.e., the minimum sharing ratio requirement) and the bandwidth heterogeneity of the peers in the system.