www.bittorrent.com
BitTorrent is a peer-to-peer (P2P) file distribution program and protocol where users connect to each other directly to send and receive portions of files. The key philosophy of BitTorrent is that users upload (transmit outbound) at the same time as they download (receiving inbound.) In this manner, network bandwidth is utilised as efficiently as possible. The more people interested in a certain file, the more efficiently the program works.
BitTorrent breaks files down into smaller segments (around 256 KB), which users can download from each other and upload those that they already have to users that request them. This means that users start uploading segments to their peers before they have downloaded the entire file. Sharing begins when the first complete segment is downloaded; this can be uploaded as soon as another peer requests it.
These transfers are coordinated by special text files called torrent files (which use the extension .torrent), which help the BitTorrent clients (programs) coordinate the peer-based transfers.
Downloading files using BitTorrent consists of three parts: the torrent file, the tracker and the client (the program). The torrent file contains all the necessary information on what the file is and what tracker it uses to connect people. Each person who wants to download the file first downloads the torrent and opens it in the BitTorrent program. The torrent file tells the program the address of the tracker, which in turn keeps a log of which users are downloading the file and where the file and its segments reside. The program then requests segments from other users. Once a file fragment has been downloaded, the program then begins looking for someone to upload the fragment to.
