Analyzing and Improving BitTorrent Performance
Ashwin R. Bharambe, Cormac Herley, Venkata N. Padmanabhan · 2005
ABSTRACT In recent years, BitTorrent has emerged as a very popularand scalable peer-to-peer file distribution mechanism. It hasbeen successful at distributing large files quickly and ef-ficiently without overwhelming the capacity of the originserver.EarlymeasurementstudiesverifiedthatBitTorrentachievesexcellentuploadutilization,butraisedseveralquestionscon-cerningutilizationinsettingsotherthanthosemeasured,fair-ness, and the choice of BitTorrent’s mechanisms. In this pa-per, we present a simulation-based study of BitTorrent. Ourgoal is to deconstruct the system and evaluate the impact ofits core mechanisms, both individually and in combination,onoverallsystemperformanceunderavarietyofworkloads.Our evaluation focuses on several important metrics, includ-ing peer link utilization, file download time, and fairnessamongst peers in terms of volume of content served.OurresultsconfirmthatBitTorrentperformsnear-optimallyin terms of uplink bandwidth utilization, and download timeexcept under certain extreme conditions. On fairness, how-ever, our work shows that low bandwidth peers systemati-cally download more than they upload to the network whenhigh bandwidth peers are present. We find that the