Seth Nielson, Developing Better Incentives for Improved Robustness in BitTorrent

BitTorrent is a widely-deployed, peer-to-peer file transfer protocol engineered with a ``tit for tat'' mechanism that encourages cooperation. Unfortunately, there is little incentive for nodes to altruistically provide service to their peers after they finish downloading a file, and what altruism there is can be exploited by aggressive clients like BitTyrant. This altruism, called seeding, is always beneficial and sometimes essential to BitTorrent's real-world performance. We propose a new long-term incentives mechanism in BitTorrent to encourage peers to seed and we evaluate its effectiveness via simulation. To support our experiments, we built a high-performance, flow-level simulator that, with a standard workstation, can simulate 1000 peers two times faster than real-time, and 100 peers 30 times faster. Our simulations demonstrate a clear advantage for rewarded seeders even for peers using aggressive clients such as BitTyrant.