BitTorrent

Abstract

The above quote if from Bram Cohen, BitTorrent's author, in an interview with Wired in 2005[184]. The first version of the BitTorrent protocol was presented in the first CodeCon conference[185]¹ in San Francisco in February 2002 and subsequently became one of the most popular Internet file sharing protocols [184]. In essence, BitTorrent introduced two key concepts that were novel to its file-sharing competitors at the time. First, rather than providing a search protocol itself, it was designed to integrate seamlessly with the Web and made files (torrents) available via Web pages, which could be searched for using standard Web search tools. Second, it enabled so-called file swarming; that is, once a peer starts downloading that file, it also makes whatever portion of the file that is downloaded immediately available for sharing. The file-swarming process is enabled through the use of a tracker, which is an HTTP-based server used to dynamically synchronise and update the peers as they are downloading as to the locations and availability of pieces of the file in question on the network. The tracker also can monitor users” usage on the network and can implement a tit-for-tat scheme, which divides bandwidth according to how much a peer contributes to the other peers in the network. The result of the file swarming techniques made BitTorrent an extremely attractive tool for sharing files because it allowed users to download files to the maximum of their download capability of their broadband connection by enabling simultaneous downloads of pieces of the same file from multiple users. This is significant because typically a broadband connection has a far lower upload bandwidth than a download one (the upload bandwidth can be typically ten times slower than the download). This means that being able to connect to, say, ten peers, will balance this mismatch and enable the full potential of your Internet link, which results in files being downloaded several times faster than other file sharing systems on the Internet at that time. The BitTorrent protocol therefore has had a massive impact on file sharing applications and similar schemes have been adopted by competitors since. Further, its use has far outgrown the illicit file-sharing arena and nowadays the BitTorrent protocol or similar techniques are used in a multitude of different applications in science and business and it has even being integrated into hardware devices. In this sense, the protocol has grown up and is now taken very seriously throughout the Internet community.