Improving peer-to-peer file distribution: winner doesn't have to take all

Recent work on BitTorrent has shown that the choke/unchoke mechanism implements an auction where each peer tries to induce other peers into "unchoking" it by uploading more data than competing peers. Under such a scenario, fast peers tend to trade with one another and neglect slower peers. In this work, we revisit the peer-to-peer (p2p) file distribution problem and show that this does not have to be the case. We describe a p2p file distribution algorithm, the Tit-For-Tat Transport Protocol (TFTTP), that is able to achieve faster download performance than BitTorrent by employing a new mechanism called a promise. Our experiments show that the average throughput for TFTTP is some 30% to 70% higher than that for BitTorrent under controlled and realistic network conditions. We also show that TFTTP exhibits fairer sharing behavior and avoids the situation where "winner takes all".