A performance study of peer-assisted file distribution with heterogeneous swarms

Abstract

Peer-to-peer file-sharing protocols, such as BitTorrent, have been widely used to improve the performance and scalability of file distribution systems. In this paper, we study the performance of peer-assisted file distribution systems with heterogeneous peers. Based on a measurement study of BitTorrent on PlanetLab, we made two key observations: (i) there is a fixed pattern in the utilization of the available bandwidth over the course of a download, and (ii) peers enjoy an amount of service that is commensurate with their contribution. Building on these insights, we developed an analytical model to estimate the download time for each class of peers in a well-provisioned peer-assisted file distribution system based on BitTorrent. Our model accurately predicts the download time and achieves an average error rate of 16.5% for heterogeneous swarms up to 150 nodes in size. We demonstrate how it can be used to estimate the server capacity for achieving a specific quality of service in a large heterogeneous swarm. © 2011 IEEE.