What is the Bit Torrent Network

This article answers the following questions:
What is the Bit Torrent Network?
How did the Torrent Network begin?
What are Torrents files?

Definitions of Bit Torrent

Bit Torrent Inc gives the following description:

BitTorrent is a peer-assisted, digital content delivery platform that provides the fastest, most efficient means of distributing, discovering, and consuming large, high-quality files on the Web. Our mission is simple: to deliver the content that entertains and informs the digital world.


Wikipedia defines the Bit Torrent as the following:

BitTorrent is a peer-to-peer (P2P) file distribution protocol, and a free software implementation of that protocol. The protocol was originally designed and created by programmer Bram Cohen, and is now maintained by BitTorrent, Inc. BitTorrent is designed to distribute large amounts of data widely without incurring the corresponding consumption in costly server and bandwidth resources.

Users browse the web to find a torrent file of interest, download it and open it with a BitTorrent client program. The client connects to the tracker specified in the torrent file, which sends it a list of other peers currently downloading pieces of the file to be downloaded. The client connects to those peers to obtain the various pieces. Such a group of peers connected to each other to share a torrent is called a swarm. If the swarm contains only the initial seeder, the client connects directly to it and begins to request pieces. As peers enter the swarm, they begin to trade pieces with one another, instead of downloading directly from the seeder.

Clients incorporate mechanisms to optimize their download and upload rates; for example they download pieces in a random order, to increase the opportunity to exchange data, which is only possible if two peers have a different pieces of the file. The effectiveness of this data exchange depends largely on the policies that clients use to determine to whom to send data. Clients may prefer to send data to peers that send data back to them (a tit for tat scheme), which encourages fair trading. But strict policies often result in suboptimal situations, where newly joined peers are unable to receive any data (because they don't have any pieces yet to trade themselves) and two peers with a good connection between them do not exchange data simply because neither of them wants to take the initiative. To counter these effects, the official BitTorrent client program uses a mechanism called “optimistic unchoking,� where the client reserves a portion of its available bandwidth for sending pieces to random peers (not necessarily known-good partners, so called preferred peers), in hopes of discovering even better partners and to ensure that newcomers get a chance to join the swarm.