BPEX: Localizing BitTorrent Traffic via Biased Peer Exchange

In recent years, BitTorrent traffic accounts for a substantial percentage of Internet traffic in the world. However, the current BitTorrent protocols disregards traffic cost at the underlying network and generate a large amount of inter-AS traffic. As a result, BitTorrent peers may suffer from slow download of files due to long delays. Moreover, ISPs may limit BitTorrent traffic to reduce inter-AS traffic. In this paper, we propose a new approach localizing BitTorrent traffic within neighboring ASes, gBPEXh, in which a controller and peers directly exchange lists of peer in the vicinity through BitTorrent's PEX protocol. Conducting experiments on Planet Lab, we show that BPEX significantly reduces inter-AS traffic and peers' download completion time.