LeechLock: Preventing Selfish Clients in the BitTorrent Protocol
Although the BitTorrent protocol incentivizes sharing by increasing a peer's download rate, tools have demonstrated that the tit-for-tat mechanism alone is insufficient to prevent peers from downloading content without reciprocation. The authors propose an enhancement to the BitTorrent protocol, called Leechlock, which uses globally shared tables to track peers' ratings over time within the swarm. The selfish peers who contribute sufficiently little to the swarm will be marked as non-contributors, and denied further requests for pieces. They show that with LeechLock enabled in a BitTorrent swarm, selfish peers are able to download only a small amount of data before they are locked out of the swarm with 100% accuracy. Finally, they run simulation tests to explore the effects of additional swarm parameters in a controlled fashion.