Public and private BitTorrent communities: a measurement study

BitTorrent communities, both public and private, are immensely popular in the Internet, with tens of millions of users simultaneously active at any given moment. Public and private BitTorrent communities are managed in different ways – for instance, some private communities enforce sharing ratios, have strict rules for content management, have a certain level of community oversight, and maintain a strong sense of exclusiveness. In this paper, we present the results of extensive measurements of more than half a million peers in five communities, ranging from highly popular and well-known public communities to elite private communities that can only be joined by invitation. We observe that the performance experienced by downloaders in the private communities is by far superior to the performance in the public communities, and we observe significant differences in connectability, seeder/leecher ratio, and seeding duration. Based on our results, we conjecture that when effective ratio enforcement mechanisms are in place, BitTorrent’s tit-for-tat mechanism is hardly influential anymore. Our multi-community, multi-swarm measurements are significantly broader and more extensive than any earlier measurement study on BitTorrent.