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BitTorrent

From iA wiki

See also: Distributed file storage | Mirror | iA Torrent links | /Background Script

Home Page: http://bitconjurer.org/BitTorrent/

File extension: .TORRENT

License: MIT

FAQs: infoAnarchy's FAQ, Official, wiki.theory.org, Idolcrash's Tutorial

IRC: #bittorrent channel on irc.freenode.net

This page is by far the most popular page on infoAnarchy.

BitTorrent is a file-sharing system. Its core (official) software is cross-platform (Windows, OS X, *nix, and more) and is very simple to install and use. However, BitTorrent itself is merely a transfer protocol (like Web downloading, Instant Messengers and FTP) and requires separate software to make it work. BitTorrent's protocol traffic has been estimated to BitTorrent is estimated by some sources to make up between 50 and 85 percent of all Internet traffic.

BitTorrent works by enabling individuals who download information to re-upload it to other users both during and after its download. A real world analogy might be that of chain mail, though not as annoying: someone copies information and gives it to 10 neighbors, who then copy it and gives it to 10 other sources. In a short time, a single individual has dispersed over 1,000,000 copies. However, there is no degradation associated with real-world facsimiles (copy of a copy) as BitTorrent is digital and all files exchanged are identical.

BitTorrent's official (that is, developed by the protocol's author Bram Cohen) software is open source, and contains no adware or spyware. While some unofficial implementations have added spyware, most open source derivative clients, including the very popular Azureus, do not.

Contents

Torrents

The system is based on small, easily exchanged "Torrent" files. These have a file name followed by .torrent and are usually only a few kilobytes in size yet allow many gigabytes of information to be downloaded. In this way, an individual can move terabytes of data. The system is also being used by Web sites that do not have the capacity to handle massive downloads (see Slashdot Effect).

Magnets

Torrents can also appear as Magnet data, which are long strings of letters and numbers. Magnets have a variety of uses but in BitTorrent, they allow for distributed torrents.

There are a variety of reasons for Web sites to use Magnet files:

  1. Torrent files, although small, can take up an enormous amount of internet traffic for Web sites that host thousands of torrents for hundreds of thousands of people. A simple string of letters and numbers is far more efficient.
  2. Some firewalls block the download of files ending in ".torrent".
  3. Magnet files are easier to exchange, especially over Instant Messaging clients, which sometimes have difficulty exchanging data files.

An example of what a magnet string:

magnet:?xt=urn:btih:ASWSKOQ8OQPFVNVEK2IOEHYF4RHSAESE

Note: Not all BitTorrent software use magnet strings. Azureus (at this writing) uses them from the menu: "File - Open - Torrent File" and clicking "Add URL". Paste the magnet string into the box provided and click OK. See the Azureus Web site for more info.

Torrent Links

An iA-maintained list of BitTorrent links (moved to a separate page due to size).

How it Works

BitTorrent connects to multiple other users who are downloading the same file, speeding up the process for everyone. This type of interaction is called a Hive or multi-source system growing popular in p2p where files begin sharing before fully downloaded. Any file downloaded by BitTorrent is then checked against a hash file contained in the torrent to confirm its integrity. This eliminates many of the problems with false file exchanges, so long as one trusts a file's source.

Quote from the homepage:

"The key to cheap file distribution is to tap the underutilized upload capacity of your customers. It's free. Their contribution grows at the same rate as their demand, creating limitless scalability for a fixed cost."
"Problem: more customers require more bandwidth - The BitTorrent Solution: customers help distribute content"

Arguably the most successful P2P-based file distribution system, BitTorrent's use goes way beyond simple warez and ex-Napster music downloaders, enabling access to much-requested high-volume data such as with Web-based independent movies and the free software community (such as Linux Distributions). Most Free Software, to save money, is distributed (sometimes exclusively) via BitTorrent.

Using BitTorrent

Once you have downloaded and installed the client, visit one of many Links/BitTorrent Sites for a variety of software, music, and data distributed via BitTorrent. When you have found a ".torrent" file, your browser should automatically start BitTorrent and begin downloading. If it does not, save it somewhere on your computer and click twice on the file. A download box should appear.

When your download has completed, wait to click "finish" for as long as possible. This allows the file to continue uploading even after you have the entire file and assist others in downloading as well.

Continue uploading later

You can always come back to the torrent later and continue sending to other users.

First, make sure you have original .TORRENT file (right-click and "Save Target As"). Click twice on the .TORRENT file and save where the previous file was located. This will not overwrite your current file. After confirming the contents, which may take a few minutes depending on size, the file will begin searching for sources to upload to.

For more information or to ask a question, visit the iA BitTorrent Frequently-Asked Questions.

BitTorrent's power

BitTorrent is a solution for Web sites that cannot handle massive traffic but must distribute an enormous amount of information.

If a fan wishes to distribute his up-and-coming band's music, BitTorrent can allow him to exchange it with an almost unlimited number of people without requiring a whole new Web server or to pay extra for the increased bandwidth. Should his band become suddenly popular, the bandwidth costs could otherwise be prohibitively high.

As is common, downloaders have varying connection speeds of T1, DSL, and dial-up but the server in this example can only upload 20 kilobytes per second to any one outside computer. With hundreds of requests, either some will be denied or get 1 kilobyte per second. This will take weeks to distribute to hundreds of people.

Until file sharing systems, the only other option was shipping the music using postal mail or moving to an expensive, high-end server, not possible for most users. Even with most modern file sharing systems, users had to know what file they were looking for and worried the resulting downloading might be corrupted. With BitTorrent, one person on a slow network can distribute the contents of a regular Compact Disk (~700 megabytes) to hundreds or even thousands in a matter of hours - not weeks - because other users share whatever they receive. A tiny amount of data can be downloaded and then exchanged among all users because higher-bandwidth users assist lower-bandwidth users and everyone hands back to everyone else; users upload files while simultaneously downloading them.

BitTorrent or direct-download?

Some sites give the option of downloading from the Web site or from an available BitTorrent link (such as the machinima production RedvsBlue.com). Because Internet traffic usually costs Web site operators money, its usually best to use BitTorrent but for overall speed, you should choose depending on time of day (considering the time zones of all the other users too):

  • During peak Internet usage times (usually 6-9 P.M. weekdays): BitTorrent - the program scales inversely to the demand, making download speeds quite high.
  • Low usage times (3 a.m. on a Sunday): Direct Download - getting the data from the Web site directly may be faster as the Web site's traffic is more available.

Note for slow/mobile connections (Dial-up or laptops): because BitTorrent can resume downloading more effectively than many other download options, it may be a better tool for those that may need to disconnect and continue later.

Other uses for BitTorrent

  1. Files gained over other file sharing systems (like Gnutella's range of clients) can be checked using BitTorrent for integrity (a Hash file).
  2. BitTorrent checksums can be included on a CD to later test archives for an accurate burn (also see MD5).

Versus other types of file sharing

Positive

  • BitTorrent software and ".TORRENT" files are very small and easy to download and host.
  • Files have an included hash system to make sure they're fully downloaded and all portions of the file are accurate.
  • Simplicity - other file sharing systems have so many other features.
  • It forces you to share and go faster at the same time, so the community benefits from it.

Negative

  • An intense focus on simplicity that also means lack of features, for instance no built-in search capability (but there are some BitTorrent search engines on the web).
  • When users use BitTorrent like other file sharing software such as KaZaA Lite or Gnutella, they often experience BitTorrent distribution sites have downloads that occasionally stop in the middle and must request that someone "re-seed" the file. Although this is a small percentage of the time, often files are distributed for a week or less and then abruptly thrown away by the community. As such, some file sharing systems have instead integrated BitTorrent to balance and improve on the system's benefits. After a file downloads, the network continues to share it as part of those users' "shared" folders.
  • Resource-intensive - slower machines (400mhz or less) may experience a performance hit while running BitTorrent.
  • If you are behind a firewall, BitTorrent uses multiple ports, which can be a security issue.
  • Not anonymous. Users are visible and trackable.

The Peer Distributed Transfer Protocol (PDTP) tries to solve some of the above problems which exist in the BitTorrent protocol.

Other services using BitTorrent

Other clients (Unofficial)

  • Azureus - Sourceforge Project - a Java-language BitTorrent client with multiple downloads, excellent rate limiting for users on asymmetric connections, a pretty UI and for a wide variety of languages. One of the most developed programs on SourceForge. Azureus Japan
  • DemocracyTV - TV true Torrents. Give it a try ;)
  • TorrentFlux - Feature-rich graphical Linux client (tested on Debian and RedHat). Free Software that uses PHP and accessible anywhere.
  • QTorrent - A QT graphical client for BitTorrent coded in Python and QT. It is based on a version of TheSHAD0W's Experimental BitTorrent client which it bundles.
  • TheSHAD0W's Experimental BitTorrent client - Based on and much like the official BitTorrent client with a few, useful features like statistics and fine-grain options.
  • CTorrent - Portable BitTorrent client in C for the CLI. Full speed ahead, captain!
  • BitComet - Windows An extremely good closed source BitTorrent client for windows, has proprietary extensions
  • Opera - This web browser now includes BitTorrent capabilities
  • BitSpirit - a more graphical version of BitTorrent for Windows "easy-to-use BitTorrent client, which provides not only full BitTorrent protocol implementation but also many personalization functions."
  • BitThief - Non-uploading unofficial BitTorrent client
  • BitTyrant - Non-uploading BitTorrent client based on the Azureus codebase

Complimentary Software

Links

Related


See also: list of BitTorrent links