BitTorrent

Its intention, different from other P2P networks, was to create a more efficient way to distribute the same file to a large group of people by having everybody that downloads a file also upload it to others. First, a small file with a .torrent extention is distributed via conventional means. This file is static, so it is often distributed via ordinary HTTP websites. Then, that file is used by BitTorrent to verify the original source of the download and find other computers on the Internet with the file on it. Next, the file is downloaded from a number of sources in normal P2P methods. After that, the completely downloaded file is checked for accuracy with the .torrent file.

When a user begins downloading a file, BitTorrent does not necessarily start at the beginning of the file. Random pieces of the file are initially downloaded by all users. Then, users connect with one another to download other pieces of the file. If enough users are connected to one another, all will eventually obtain the entire file. Of course, initially someone must possess the entire complete file to begin the process. This method has the unique behavior of causing download speeds to increase when more users connect to download a file. Under traditional file distribution systems, download speeds decrease as more users connect.

While initially created to distribute legal files, such as Linux distributions or large movie trailers[?], it is also increasingly being used by some to download copyrighted music, movies, and software, similar to many other peer-to-peer networks. It is still contested whether or not this is legal; see peer-to-peer for more information. BitTorrent was blamed for the initial distribution of a high-quality copy of The Matrix Reloaded just days after the movie was released in theaters.

BitTorrent uses "tit-for-tat" downloading, meaning that for every unit of data uploaded, a unit may be downloaded.

BitTorrent is written in pure Python.

External Link

• BitTorrent website (http://bitconjurer.org/BitTorrent/)