BitTorrent Traffic Measurements and Models

Sammanfattning: The Internet has experienced two major revolutions. The first was the emergence of the World Wide Web, which catapulted the Internet from being a scientific and academic network to becoming part of the societal infrastructure. The second revolution was the appearance of the Peer-to-Peer (P2P) applications, spear-headed by Napster. The popularity of P2P networking has lead to a dramatic increase of the volume and complexity of the traffic generated by P2P applications. P2P traffic has recently been shown to amount to almost 80% of the total traffic in a high speed IP backbone link. One of the major contributors to this massive volume of traffic is BitTorrent, a P2P replication system. Studies have shown that BitTorrent traffic more than doubled during the first quarter of 2004, and still amounts to 60% of all P2P traffic in 2005. This thesis reports on measurement, modelling and analysis of BitTorrent traffic collected at Blekinge Institute of Technology (BTH) as well as at a local ISP. An application layer measurement infrastructure for P2P measurements developed at BTH is presented. Furthermore, a dedicated fitness assessment method to avoid issues with large sample spaces is described. New results regarding BitTorrent session and message characteristics are reported and models for several important characteristics are provided. Results show that several BitTorrent metrics such as session durations and sizes exhibit heavy-tail behaviour. Additionally, previously reported results on peer reactivity to new content are corroborated.