How to Survive and Thrive in a Private BitTorrent Community

Many private BitTorrent communities employ Sharing Ratio Enforcement (SRE) schemes to incentivize users to contribute. It has been demonstrated that communities that adopt SRE are greatly oversupplied, i.e., they have much higher seeder-to-leecher ratios than communities in which SRE is not employed. Most previous studies focus on showing the positive effect of SRE in achieving high downloading speed. However, in this paper we show through measurements that SRE also induces severe side-effects. Under SRE, users are forced to seed for excessively long times to maintain adequate sharing ratios to be able to start new downloads, though most of the time their seedings are not very productive (in terms of low upload speed). We also observe that many users who seed for very long times still have low sharing ratios. We find that this is due to the counter-intuitive phenomenon that long seeding times do not necessarily lead to large upload amounts. Based on these observations, we discuss possible strategies for users to gain sharing ratios efficiently, which help them to survive and thrive in private communities.