A sleep-and-wake technique for reducing energy consumption in BitTorrent networks

File sharing is one of the leading Internet applications of P2P technology. Given the high number of computer nodes involved in peer-to-peer networks, reducing their aggregate energy consumption is an important challenge to be faced. In this paper, we show how the sleep-and-wake energy saving approach can be exploited to reduce energy consumption in BitTorrent, one of the most popular file sharing peer-to-peer networks. We describe BitTorrentSW, a sleep-and-wake approach for BitTorrent networks that allows seeders (ie, peers that hold complete files) to cyclically switch between wake and sleep modes to save energy while ensuring good file sharing performance. The decision to switch to sleep mode is taken independently by each seeder based on local information about the composition of the peer-to-peer network. BitTorrentSW has been evaluated through PeerSim using real BitTorrent traces. The simulation results show that, in all the configurations under analysis, the percentage of energy saved by BitTorrentSW is much higher than the percentage of increase in download time. For instance, in a network with 50% of seeders, about 20% of energy is saved using BitTorrentSW, with an increase of only 7% of the average time needed to complete a file download compared to a standard BitTorrent network in which all seeders are always powered on.