What Is a Torrent?

A torrent file stores data about files for use with BitTorrent, a peer-to-peer file-sharing protocol that enables users to send and receive files in small pieces to and from computers across the Internet. Hundreds of millions of people use BitTorrent globally, as of January 2012, according to the protocol's creator. Because of the distributed nature of BitTorrent sharing, and the fact that small pieces of the files are downloaded and then reassembled by the software, BitTorrent uses less resources than direct downloading of files, resulting in faster speeds for the downloader and lower bandwidth costs for the file provider. For this reason, companies such as Blizzard, makers of World of Warcraft, and Canonical, makers of Ubuntu Linux, use BitTorrent to distribute their software, as of February 2012.

How Torrenting Works

All torrenting takes place using a torrent program. Examples of torrenting programs include uTorrent, Azureus and the original BitTorrent. These programs enable your computer to send and receive pieces of files on a specific port and interpret the data from torrent files. The torrent files contain all of the information about a specific torrent: who started it, what the torrent contains, and how to download and upload information corresponding to that torrent. When the torrent file is opened by a torrent program, the torrent program connects to other users who have portions of the file and downloads those pieces from them. Once it receives portions of the file, your computer becomes able to "seed," or upload, the file to other users. Once the torrent program has received all portions of the file, it assembles them into a usable file using the instructions found in the original torrent file.

Trackers

Torrenting begins and ends at large network servers known as trackers. Your torrent program, known as a client, connects to these servers using a list found in the original torrent file. Trackers have a list of all users connected to them and which files they're able to seed. Your client picks from these users and downloads data from them accordingly. Upon connecting to a tracker, it registers your computer and the files that you are able to seed. Trackers also keep logs of your share ratio -- how much your computer uploads, measured against how much your computer downloads -- and determine the amount of bandwidth you receive, based on that ratio.

Ratio and the Fair Share Policy

All torrent trackers incorporate a "fair share" policy, which restricts or grants access to bonus bandwidth accordingly. Fair share policies basically say that if you're not seeding as much as you are downloading, called leeching, you receive less bandwidth. Conversely, if your seeding to leeching ratio is high, you can download files quicker than someone with a low ratio. Priority on the tracker is also given to those with higher ratios. This means they connect to other users on the server faster.

Torrent Culture

A large culture has sprung up around torrenting, including free-culture and open-source software advocates and independent media creators. This culture generally promotes fair share policies and file-sharing honesty, and discourages copyright infringement or file theft. Generally, these communities are invite-only. Open membership is only granted at specific times, such as once a month. Anyone wishing to join who doesn't want to wait until membership becomes open must secure an invite from someone else who's already part of the community. Other torrent sites are completely private and may require tests or interviews before extending an invitation.

Controversy

Since its creation in 2001, torrenting has been highly controversial. Because trackers cannot and do not keep track of what information can be found in their torrents, the potential for copyright infringement and file theft is high. Media industry organizations such as the RIAA pursue legal activity against torrent trackers and users under claims of copyright infringement. However torrenting remains a common way to transfer large amounts of data from and to users at high speed.

References

• BitTorrent: BitTorrent and µTorrent Software Surpass 150 Million User Milestone
• BitTorrent: What Is BitTorrent?
• BitTorrent: The BitTorrent Protocol Specification
• Ubuntu: Alternative Downloads
• Network Uptime: The Blizzard Downloader
• BoingBoing: 20,000 US BitTorrent Users Sued; 30,000 More Lawsuits Pending

Resources

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