- Great Painters
- Accounting
- Fundamentals of Law
- Marketing
- Shorthand
- Concept Cars
- Videogames
- The World of Sports

- Blogs
- Free Software
- Google
- My Computer

- PHP Language and Applications
- Wikipedia
- Windows Vista

- Education
- Masterpieces of English Literature
- American English

- English Dictionaries
- The English Language

- Medical Emergencies
- The Theory of Memory
- The Beatles
- Dances
- Microphones
- Musical Notation
- Music Instruments
- Batteries
- Nanotechnology
- Cosmetics
- Diets
- Vegetarianism and Veganism
- Christmas Traditions
- Animals

- Fruits And Vegetables


  1. Adobe Reader
  2. Adware
  3. Altavista
  4. AOL
  5. Apple Macintosh
  6. Application software
  7. Arrow key
  8. Artificial Intelligence
  9. ASCII
  10. Assembly language
  11. Automatic translation
  12. Avatar
  13. Babylon
  14. Bandwidth
  15. Bit
  16. BitTorrent
  17. Black hat
  18. Blog
  19. Bluetooth
  20. Bulletin board system
  21. Byte
  22. Cache memory
  23. Celeron
  24. Central processing unit
  25. Chat room
  26. Client
  27. Command line interface
  28. Compiler
  29. Computer
  30. Computer bus
  31. Computer card
  32. Computer display
  33. Computer file
  34. Computer games
  35. Computer graphics
  36. Computer hardware
  37. Computer keyboard
  38. Computer networking
  39. Computer printer
  40. Computer program
  41. Computer programmer
  42. Computer science
  43. Computer security
  44. Computer software
  45. Computer storage
  46. Computer system
  47. Computer terminal
  48. Computer virus
  49. Computing
  50. Conference call
  51. Context menu
  52. Creative commons
  53. Creative Commons License
  54. Creative Technology
  55. Cursor
  56. Data
  57. Database
  58. Data storage device
  59. Debuggers
  60. Demo
  61. Desktop computer
  62. Digital divide
  63. Discussion groups
  64. DNS server
  65. Domain name
  66. DOS
  67. Download
  68. Download manager
  69. DVD-ROM
  70. DVD-RW
  71. E-mail
  72. E-mail spam
  73. File Transfer Protocol
  74. Firewall
  75. Firmware
  76. Flash memory
  77. Floppy disk drive
  78. GNU
  79. GNU General Public License
  80. GNU Project
  81. Google
  82. Google AdWords
  83. Google bomb
  84. Graphics
  85. Graphics card
  86. Hacker
  87. Hacker culture
  88. Hard disk
  89. High-level programming language
  90. Home computer
  91. HTML
  92. Hyperlink
  93. IBM
  94. Image processing
  95. Image scanner
  96. Instant messaging
  97. Instruction
  98. Intel
  99. Intel Core 2
  100. Interface
  101. Internet
  102. Internet bot
  103. Internet Explorer
  104. Internet protocols
  105. Internet service provider
  106. Interoperability
  107. IP addresses
  108. IPod
  109. Joystick
  110. JPEG
  111. Keyword
  112. Laptop computer
  113. Linux
  114. Linux kernel
  115. Liquid crystal display
  116. List of file formats
  117. List of Google products
  118. Local area network
  119. Logitech
  120. Machine language
  121. Mac OS X
  122. Macromedia Flash
  123. Mainframe computer
  124. Malware
  125. Media center
  126. Media player
  127. Megabyte
  128. Microsoft
  129. Microsoft Windows
  130. Microsoft Word
  131. Mirror site
  132. Modem
  133. Motherboard
  134. Mouse
  135. Mouse pad
  136. Mozilla Firefox
  137. Mp3
  138. MPEG
  139. MPEG-4
  140. Multimedia
  141. Musical Instrument Digital Interface
  142. Netscape
  143. Network card
  144. News ticker
  145. Office suite
  146. Online auction
  147. Online chat
  148. Open Directory Project
  149. Open source
  150. Open source software
  151. Opera
  152. Operating system
  153. Optical character recognition
  154. Optical disc
  155. output
  156. PageRank
  157. Password
  158. Pay-per-click
  159. PC speaker
  160. Peer-to-peer
  161. Pentium
  162. Peripheral
  163. Personal computer
  164. Personal digital assistant
  165. Phishing
  166. Pirated software
  167. Podcasting
  168. Pointing device
  169. POP3
  170. Programming language
  171. QuickTime
  172. Random access memory
  173. Routers
  174. Safari
  175. Scalability
  176. Scrollbar
  177. Scrolling
  178. Scroll wheel
  179. Search engine
  180. Security cracking
  181. Server
  182. Simple Mail Transfer Protocol
  183. Skype
  184. Social software
  185. Software bug
  186. Software cracker
  187. Software library
  188. Software utility
  189. Solaris Operating Environment
  190. Sound Blaster
  191. Soundcard
  192. Spam
  193. Spamdexing
  194. Spam in blogs
  195. Speech recognition
  196. Spoofing attack
  197. Spreadsheet
  198. Spyware
  199. Streaming media
  200. Supercomputer
  201. Tablet computer
  202. Telecommunications
  203. Text messaging
  204. Trackball
  205. Trojan horse
  206. TV card
  207. Unicode
  208. Uniform Resource Identifier
  209. Unix
  210. URL redirection
  211. USB flash drive
  212. USB port
  213. User interface
  214. Vlog
  215. Voice over IP
  216. Warez
  217. Wearable computer
  218. Web application
  219. Web banner
  220. Web browser
  221. Web crawler
  222. Web directories
  223. Web indexing
  224. Webmail
  225. Web page
  226. Website
  227. Wiki
  228. Wikipedia
  229. WIMP
  230. Windows CE
  231. Windows key
  232. Windows Media Player
  233. Windows Vista
  234. Word processor
  235. World Wide Web
  236. Worm
  237. XML
  238. X Window System
  239. Yahoo
  240. Zombie computer

This article is from:

All text is available under the terms of the GNU Free Documentation License: 


From Wikipedia, the free encyclopedia

This article is about the protocol. For the client, see BitTorrent client.
The BitTorrent logo
The BitTorrent logo

BitTorrent is the name of a peer-to-peer (P2P) file distribution protocol, and of 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. CableLabs, the research organization of the North American cable industry, believes that BitTorrent represents 55% of the upstream traffic on the cable company's access network.[1] CacheLogic puts that number at roughly 35% of all traffic on the Internet,[2] although there are dissenting opinions on the methodology to measure P2P traffic on the Internet.[3]

The original BitTorrent client was written in Python. Its source code, as of version 4.0, has been released under the BitTorrent Open Source License, which is a modified version of the Jabber Open Source Licence. There are numerous compatible clients, written in a variety of programming languages, and running on a variety of computing platforms.


Creating and publishing torrents

To share a file or group of files through BitTorrent, clients first create a "torrent." This is a small file which contains metadata about the files to be shared, and about the host computer that coordinates the file distribution. The exact information contained in the torrent file depends on the version of the BitTorrent protocol. However by convention, a torrent file always has the suffix .torrent. Torrent files contain an "announce" section, which specifies the URL of the tracker, and an "info" section which contains (suggested) names for the files, their lengths, the piece length used, and a SHA-1 hash code for each piece, which clients should use to verify the integrity of the data they receive.

Clients who have finished downloading the file may also choose to act as seeders, providing a complete copy of the file. After the torrent file is created, a link to it is placed on a website or elsewhere, and it is registered with a tracker. BitTorrent trackers maintain lists of the clients currently participating in the torrent.[4] The computer with the initial copy of the file is referred to as the initial seeder. There is also a trackerless system available, this trackerless, decentralized or distributed tracking essentially treats every peer in the swarm as a tracker. BitTorrent, µTorrent, BitComet and KTorrent offer decentralized tracking through the DHT method. Azureus also supports a trackerless method but it is incompatible with the DHT offered by all other supporting clients.

In November 2006, BitTorrent Inc released a service that automatically creates a torrent and tracks a download based on a website object. The service is located at and requires a BitTorrent client that supports web-seeding (currently only the official client and Azureus).

Downloading torrents and sharing files

BitTorrent greatly reduces the load on seeders, because clients generally download the file from each other. In this animation, the coloured bars beneath all of the clients represent individual pieces of the file. After the initial pieces transfer from the seed, the pieces are individually transferred from client to client. This demonstrates how the original seeder only needs to send out one copy of the file for all the clients to receive a copy.
BitTorrent greatly reduces the load on seeders, because clients generally download the file from each other. In this animation, the coloured bars beneath all of the clients represent individual pieces of the file. After the initial pieces transfer from the seed, the pieces are individually transferred from client to client. This demonstrates how the original seeder only needs to send out one copy of the file for all the clients to receive a copy.

BitTorrent clients are programs which implement the BitTorrent protocol. Each BitTorrent client is capable of preparing, requesting, and transmitting any type of computer file over a network using the BitTorrent protocol.

Users browse the web to find a torrent of interest, then download a small ".torrent" file. Opening this file with a BitTorrent client program is the first step in the download. The client then connects to the tracker, which provides it with a list of clients currently downloading the file or files. A group of peers on a BitTorrent or P2P connected with each other to share a particular torrent is generally referred to as a swarm.

Initially, there may be no other peers in the swarm, in which case the client connects directly to the initial seeder and begins to request pieces. The BitTorrent protocol breaks down files into a number of much smaller pieces, typically a quarter of a megabyte (256 kB) in size. Larger file sizes typically have larger pieces. For example, a 4.37-GB file may have a piece size of 4 MB (4096 kB). Pieces are checked as they are received using a hash algorithm to ensure that they are error-free.[4]

As peers enter the swarm, they begin trading pieces with one another, instead of downloading directly from the seeder. Clients incorporate mechanisms to optimize their download and upload rates, for example using a tit for tat scheme. Peers download pieces in a random order, to increase the opportunity to exchange data, which is only possible if two peers have a different subset of the file.

The effectiveness of the peer-to-peer data exchange depends largely on the policies used by clients to determine to whom to send data. Clients will prefer to send data to peers that send data back to them, 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 uses a mechanism called “optimistic unchoking,” where the client will reserve 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 newcomers get a chance to join the swarm.[5]

Comparison with other file sharing systems

BitTorrent 4.0.4 running under Windows XP
BitTorrent 4.0.4 running under Windows XP

Though both ultimately transfer files over a network, a BitTorrent download differs from a classic full-file HTTP request in several fundamental ways. First, BitTorrent makes many small P2P requests over different TCP sockets, while web-browsers typically make a single HTTP GET request over a single TCP socket. Second, the BitTorrent protocol limits a client's download speed to roughly its upload speed, while HTTP gives no preferential treatment to cooperative nodes. And third, BitTorrent downloads in a random or "rarest-first" approach that ensures high availability, while HTTP downloads in a contiguous manner. Taken together, BitTorrent achieves much lower cost, much higher redundancy, and much greater resistance to abuse or "flash crowds" than a regular HTTP server. However, this protection comes at a cost: downloads take time to ramp up to full speed because these many peer connections take time to establish, and it takes time for a node to get sufficient data to become an effective uploader. As such, a typical BitTorrent download will gradually ramp up to very high speeds, and then slowly ramp back down toward the end of the download. This contrasts with an HTTP server that, while more vulnerable to overload and abuse, ramps up to full speed very quickly and maintains this speed throughout. Furthermore, BitTorrent's non-contiguous download methods prevent it from supporting "progressive downloads" or "streaming playback," as is possible with HTTP.

The method used by BitTorrent to distribute files parallels the one used by the eDonkey2000 network, but nodes in eDonkey's file sharing network usually share and download a much larger number of files, making the bandwidth available to each transfer much smaller. While the original eDonkey2000 client provided little "leech resistance," most new clients have some sort of system to encourage uploaders. eMule, for example, has a credits system whereby a client rewards other clients that upload to it by increasing their priority in its queue. However, the nature of the eDonkey2000 concept means download speeds tend to be much more variable, although the number of available files is far greater.

A similar method to BitTorrent was the Participation Level introduced in Kazaa in 2002. A user's Participation Level would increase when they uploaded and decrease when they downloaded. Then when a user uploaded a file, the person with the highest Participation Level would get it first, then the next highest, and so on. This can be visualised as a pyramid, with the clients who have the most upload bandwidth available at the top and those with less bandwidth on progressively lower levels. This is the most efficient way to distribute a file to a large number of users: it is probable that even the people at the bottom of the pyramid will get the file faster than if the file was served by a non-P2P method. Unfortunately the Kazaa implementation is flawed as it relies on the client accurately reporting their Participation Level, making it easy to cheat using one of the many unofficial clients.

Legal use of BitTorrent

A growing number of individuals and organizations are using BitTorrent to distribute their own material. Many adopters report that only by using BitTorrent technology, with its dramatically reduced demands on networking hardware and bandwidth, could they afford to distribute their files.


Many sites imitating big BitTorrent trackers have turned to distribution of only legal material in general. With several different categories they often provide a working distribution method for parties who want to have big material packets available for large audience without investing loads of cash. and are among the first trackers that have got a notable community behind them providing vivid selection of legal material to public.


Many major open source and free software projects encourage BitTorrent as well as conventional downloads of their products to increase availability and reduce load on their own servers. Examples include[6], NetBSD[7] and most major Linux distributions, including Fedora[8], Mandriva [9], SUSE[10], and Ubuntu.[11] BitTorrent is also used to distribute updates to the BitTorrent client itself, as well as to other clients such as Azureus and BitComet.


Various sites on the Internet like offer authorized game files via BitTorrent; the first person shooter America's Army is offered via BitTorrent, as are the World of Warcraft in-game patches. Another such example is PlaneShift, which uses BitTorrent for its primary method of distribution. For the first time, the demo of Football Manager 2007 is offered for download through BitTorrent.

Film and video

The film studio Warner Brothers Entertainment plans to distribute its films and TV shows using Bittorrent (at[12] The fan-film Star Wars: Revelations is distributing two DVD images as well as the film by itself via BitTorrent, while Star Wreck: In the Pirkinning and Cactuses, both feature-length films, were provided for download via BitTorrent. The fan-films Star Trek: New Voyages are distributed via BitTorrent among other methods.

mariposaHD is the first HDTV series made to be distributed over the internet. The free Creative-Commons licensed videos are available in both (1080p and 720p) HD formats. By utilizing Microsoft's WMV HD video codec to compress the videos and BitTorrent to transfer the files, mariposaHD are able to distribute data intensive high definition video over the internet at relatively modest cost. (

Peter Jackson's production diaries for King Kong have been posted for download using BitTorrent. Universal Studios also released footage of its film, "Fast and Furious: Tokyo Drift" with BitTorrent ( Several anime companies have also used BitTorrent technology to release teaser episodes and trailers online for promotional purposes, as a sign of embracing technology that is often seen as a direct competitor. Furthermore, the NASA space agency recently included BitTorrent as a means to download some of their larger space image files.

BitTorrent customers will be able to select from a variety of popular film titles from 20th Century Fox, Kadokawa Pictures, Lions Gate Entertainment, Palm, Paramount and Starz Media such as "X-Men The Last Stand," "Ringu," "Saw III," "13 Tzameti," "Mission: Impossible III," and "Ghost in the Shell." TV programming will include hits like "Attack of the Show" from G4; "24" and "Prison Break" from 20th Century Fox; "City of Men" from Palm; "Laguna Beach" and "Celebrity Deathmatch" from MTV: Music Television; Emmy and Peabody-Award winning "South Park" and "Chappelle's Show" from Comedy Central; "Hogan Knows Best" from VH1; "SpongeBob SquarePants" and "Avatar: The Last Airbender" from Nickelodeon; and "Skyland" from Nicktoons Network.


Sub Pop Records, the record label credited with popularizing grunge rock and current publisher of The Shins, The Postal Service and other popular bands, is releasing numerous tracks and videos on BitTorrent.[13]

The SXSW (South by South West) music festival in Austin, Texas has released two packages of mp3 music files—nearly a thousand tracks—from their 2006 festival by BitTorrent download, along with trailers to two DVD films that can be purchased.[14] Babyshambles, Pete Doherty's band, distributes two collections of music, Shaking and Withdrawn Megamix and Untitled by Bittorrent from their official website.[15] In 2005, the rock group Harvey Danger began distributing their third full-length album, Little by Little..., using BitTorrent. Discipline Global Mobile (the record label/website begun by Robert Fripp) uses BitTorrent technology to distribute. Folk punk band Defiance Ohio distributes their music from their website using mp3's, ogg's and torrents. The free music portal Jamendo also uses BitTorrent to distribute its 1000+ albums. The band Ween uses the website[16] to distribute free audio and video recordings of live shows.

Legal issues

BitTorrent, like any other file transfer protocol, can be used to distribute files without the permission of the copyright holder. Just as photocopiers can be used to duplicate books, BitTorrent allows the same for digital content. At the same time, it makes the process much faster and cheaper. As a significant portion of files distributed through BitTorrent are distributed without proper permission, BitTorrent has received some criticism. However, many think it unfair to blame a protocol for the actions of its users.

Copyright enforcement

BitTorrent trackers have been frequent targets of raids and shutdowns due to claims of copyright infringement. BitTorrent metafiles do not actually store copyrighted data, and thus it is often claimed[citation needed] that BitTorrent trackers, which only store and track the metafiles and usually do not share any potentially copyrighted data, must therefore be legal. Despite this claim, there has been tremendous legal pressure, usually on behalf of the MPAA and RIAA, to shut down numerous BitTorrent trackers.

In December 2004, the Finnish police raided a major BitTorrent site, Finreactor.[17][18]

The case is before the courts, and 32 people, in September 2006, mostly administrators and moderators, are facing charges. Software and media companies are seeking damages worth 3.5 million euros in total. Two defendants were acquitted by reason of being underage at the time, but they are being held liable for legal fees and compensation for illegal distribution ranging up to 60,000 euros. The court set their fine at 10% of the retail price of products distributed.[19], one of the most popular early BitTorrent sites, closed in December 2004, supposedly due to the pressure felt by Sloncek, the founder and administrator of the site. In December 2004, Sloncek revealed that the Suprnova computer servers had in fact been confiscated by Slovenian authorities.[citation needed] LokiTorrent, arguably the biggest torrent source after the demise of Suprnova, closed down soon after Suprnova. Allegedly, after threats from the MPAA, Edward Webber (known as 'lowkee'), webmaster of the site, was ordered by the court to pay a fine and supply the MPAA with logs (the IP addresses of visitors).[20]

Webber, in the weeks following his receipt of the subpoena, had begun a fundraising campaign to pay lawyers fees in a legal battle against the MPAA. Webber raised approximately US$45,000 through a PayPal-based donation system. It is unclear how much of that money went to the MPAA, but taking into account the amount of damages he most likely had to pay, probably much of it.[citation needed] Following the agreement, the MPAA changed the LokiTorrent website to display a message intended to intimidate filesharers.[21] Webber did not comment on this change.

On May 25, 2005, the popular BitTorrent website was shut down by the United States Federal Bureau of Investigation and Immigration and Customs Enforcement. At first it was thought that a malicious hacker had gained control of the website, but it was soon discovered that the website had been taken over by the US government. Ten search warrants relating to members of the website were executed. - Newspaper, Butler Eagle, PA

On October 24, 2005, a 38-year-old Hong Kong BitTorrent user Chan Nai-ming (陳乃明, using the handle 古惑天皇 Lit. The master of cunning, while the magistrate referred to him as Big Crook) allegedly distributed the three movies Daredevil, Red Planet and Miss Congeniality in violation of copyright, subsequently uploading the torrent file to a newsgroup. He was convicted of breaching the copyright ordinance, Chapter 528 of Hong Kong law.[citation needed] The magistrate remarked that Chan's act caused significant damage to the interest of copyright holders. He was released on bail for HK$5,000, awaiting a sentencing hearing, though the magistrate himself admitted the difficulty of determining how he should be sentenced due to the lack of precedent for such a case. On November 7, 2005, he was sentenced to jail for three months but was immediately granted parole pending an appeal to the High Court. The appeal was dismissed by the Court of First Instance on 12 December 2006 and Chan was jailed immediately. Chan's lawyer indicated that Chan may appeal the case to the Final Court of Appeal.

On November 23, 2005, the movie industry and Bram Cohen, the creator of BitTorrent, signed a deal they hoped would reduce the number of unlicensed copies shared on the downloading network. The deal covered films found via the website run by BitTorrent, Inc. It meant had to remove any links to unlicensed copies of films made by seven Hollywood movie studios. As it covered only the website, it is unclear what overall effect this has had on copyright infringement on the network.[22]

In June 2006, the popular website, an exact replicant of Suprnova, was also subject to closure.

The Pirate Bay is another popular BitTorrent website which was formed out of a Swedish anti-copyright group. The site also contains torrents which point to copies of copyright-protected material. The Pirate Bay is notorious for its "legal" section[23] in which letters and replies on the subject of alleged copyright infringements are publicly displayed. The replies are written in a humorous manner and a hard copy of one was even sold on eBay for USD $255. On May 31, 2006, however, The Pirate Bay's servers, which are based in Sweden, were raided by Swedish police; the site owners might be facing charges for copyright infringement or facilitating it according to the accusations on the search warrant. No charges have been made so far. [citation needed] However, after securing new servers in The Netherlands and using a recent backup, The Pirate Bay was back online in less than 72 hours. Recently, The Pirate Bay has returned to Sweden. The return has been facilitated by the public and media backlash against the Swedish Government's actions. The Pirate Bay is now, supposedly, going to counter-sue the Swedish government for millions of Swedish kronor (SEK) lost from having their website shut down. [citation needed] A film relating to these incidents can be found here:

HBO, in an effort to combat the distribution of its programming on BitTorrent networks, has been sending out cease and desist letters to the Internet Service Providers of BitTorrent users. Many users have reported receiving letters from their ISP's that threatened to cut off their internet service if the alleged infringement continues. HBO, unlike the RIAA, has so far declined to sue anyone for sharing the files. [citation needed][24]

Legal defenses

There are two major differences between BitTorrent and many other peer-to-peer file-trading systems, which advocates suggest make it less useful to those sharing copyrighted material without authorization. First, BitTorrent itself does not offer a search facility to find files by name. A user must find the initial torrent file by other means, such as a web search. Second, BitTorrent makes no attempt to conceal the host ultimately responsible for facilitating the sharing: a person who wishes to make a file available must run a tracker on a specific host or hosts and distribute the tracker address(es) in the .torrent file. While it is possible to simply operate a tracker on a server that is located where the copyright holder cannot take legal action, this feature of the protocol does imply some degree of vulnerability that other protocols lack. It is far easier to request that the server's ISP shut the site down than it is to find and identify every user sharing a file on a traditional peer-to-peer network. However, with the use of a distributed hash table (DHT), a tracker is no longer required, although they are often still used so that clients that do not support DHT can still connect to the swarm.

Limitations and security vulnerabilities

BitTorrent does not offer its users anonymity. It is possible to obtain the IP addresses of all current, and possibly previous, participants in a swarm from the tracker. This may expose users with insecure systems to attacks.[5]

Another drawback is that BitTorrent file sharers, compared to users of client/server technology, often have little incentive to become seeders after they finish downloading. The result of this is that torrent swarms gradually die out, meaning a lower possibility of obtaining older torrents. Some BitTorrent websites have attempted to address this by recording each user's download and upload ratio for all or just the user to see, as well as the provision of access to older torrent files to people with better ratios. Also, users who have low upload ratios may see slower download speeds until they upload more. This prevents users from leeching, since after a while they become unable to download much faster than 1-10 kB/s on a high-speed connection. Some trackers exempt dial-up users from this policy, because they cannot upload faster than 1-5 kB/s.

BitTorrent is best suited to continuously connected broadband environments, since dial-up users find it less efficient due to frequent disconnects and slow download rates.

New developments

The BitTorrent protocol is still under development and therefore may still acquire new features and other enhancements such as improved efficiency.

In May 2005, Bram Cohen released a new beta version of BitTorrent that eliminated the need for web site hosting of centralized servers known as "trackers." It is now possible to have a torrent up in minutes, with a file, a website, and no understanding of how it works. In addition, Cohen launched a new search service on BitTorrent's website, similar to those found on other popular sites such as The Pirate Bay.

Cohen explained that the tracker removal feature is part of his ongoing effort to make publishing files online "painless and disruptively cheap". The move is only one of several designed to remove BitTorrent's dependence on centralized trackers.

This change is said to cause some trouble in the legal efforts to shut down illegal file sharing. However, Tarun Sawney, BSA Asia antipiracy director, said BitTorrent files could still be identified, since with or without the tracker sites, actual users still host the infringing files.[25][26]

Alternative approaches

The BitTorrent protocol provides no way to index torrent files. As a result, a comparatively small number of websites have hosted the large majority of torrents linking to copyright material, rendering those sites especially vulnerable to lawsuits. In response, some developers have sought ways to make publishing of files more anonymous while still retaining BitTorrent's speed advantage. The Shareaza client, for example, provides three alternatives to BitTorrent: eDonkey2000, Gnutella, and Shareaza's native network, Gnutella2. If the tracker is down, it can finish the file over the other protocols, and/or find new (Shareaza) peers over G2. The use of distributed trackers is also one of the goals for Azureus and BitTorrent 4.1.2. Another interesting idea that has surfaced recently in Azureus is virtual torrent. This idea is based on the distributed tracker approach and is used to describe some web resource. Right now, it is used for instant messaging. It is implemented using a special messaging protocol and requires an appropriate plugin. Anatomic P2P is another approach, which uses a decentralized network of nodes that route traffic to dynamic trackers.

BitTorrent search / Trackerless torrents

In June 2005, BitTorrent Inc. released a BitTorrent search engine [1], which searches the web for .torrent files, including those on popular BitTorrent trackers. BitTorrent has also licensed content which it co-mingles with search results on its website at[27] From software version 4.2.0, BitTorrent also supports "trackerless" torrents, featuring a DHT implementation that allows the client to download torrents that have been created without using a BitTorrent tracker.

  • BitTorrent Mainline DHT: BitTorrent client (4.1.0+), µTorrent (1.2+), BitComet (0.59+), and BitSpirit (3.0+): They all share a DHT based on an implementation of the Bamboo DHT [2], for trackerless torrents.

Web seeding

One recently implemented feature of BitTorrent is web seeding. The advantage of this feature is that a site may distribute a torrent for a particular file or batch of files and make those files available for download from that same web server application; this can simplify seeding and load balancing greatly once support for this feature is implemented in the various BitTorrent clients. In theory, this would make using BitTorrent almost as easy for a web publisher as simply creating a direct download while allowing some of the upload bandwidth demands to be placed upon the downloaders (who normally use only a very small portion of their upload bandwidth capacity). This feature was created by TheSHAD0W, who created BitTornado.[28]. From version 5.0 onward the Mainline BitTorrent client also supports web seeds and the BitTorrent web site has a simple publishing tool that creates web seeded torrents. The latest version of the popular download manager, GetRight supports downloading a file from both HTTP/FTP protocols and using BitTorrent.


Another proposed feature combines RSS and BitTorrent to create a content delivery system dubbed broadcatching. Since a Steve Gillmor column for Ziff-Davis in December 2003, the discussion has spread quickly among many bloggers (Techdirt, Ernest Miller, and former TechTV host Chris Pirillo, for example). As Scott Raymond explained:

"I want RSS feeds of BitTorrent files. A script would periodically check the feed for new items, and use them to start the download. Then, I could find a trusted publisher of an Alias RSS feed, and 'subscribe' to all new episodes of the show, which would then start downloading automatically — like the 'season pass' feature of the TiVo."[29]

While potential illegal uses abound as is the case with any new distribution method, this idea lends itself to a great number of ideas that could turn traditional distribution models on their heads, giving smaller operations a new opportunity for content distribution. The system leans on the cost-saving benefit of BitTorrent, where expenses are virtually non-existent; each downloader of a file participates in a portion of the distribution. One early adoption of this concept is IPTV show mariposaHD, which uses BitTorrent to distribute large (2-4 GB) WMVHD files of high-definition video.

RSS feeds layered on top keep track of the content, and because BitTorrent does cryptographic hashing of all data, subscribers to the feed can be sure they're getting what they think they're getting, whether that winds up being the latest Sopranos episode, or the latest Sveasoft firmware upgrade. (Naturally, however, ensuring that the same data reaches all nodes neglects the possibility that the original, source file may be corrupted or incorrectly labeled.)

One of the first open source attempts to create a client specifically for this was Democracy Player. The idea is already gaining momentum however, other Free Software clients such as PenguinTV and KatchTV are also now supporting broadcatching.


The BitTorrent web-service MoveDigital has the ability to make torrents available to any web application capable of parsing XML through its standard Representational State Transfer (REST) based interface.[30] Additionally, Torrenthut is developing a similar torrent API which will provide the same features, as well as further intuition to help bring the torrent community to Web 2.0 standards. Alongside this release is a first PHP application built using the API called PEP which will parse any Really Simple Syndication (RSS 2.0) feed and automatically create and seed a torrent for each enclosure found in that feed.[31]


Main article: BitTorrent protocol encryption

Protocol header encrypt (PHE), Message stream encryption (MSE), or Protocol encryption (PE) are features of some BitTorrent clients that attempt to make BitTorrent hard to throttle. MSE and PE are two names for the same protocol. At the moment Azureus, Bitcomet and µTorrent, the three biggest BitTorrent clients, support MSE/PE encryption.

Some ISPs throttle BitTorrent traffic because it makes up a large proportion of total traffic and the ISPs don't want to spend money purchasing extra capacity.[32] Encryption makes BitTorrent traffic harder to detect and therefore harder to throttle. Recently, ISPs have announced possible future hardware upgrades in order to minimize BitTorrent traffic. Several universities have already taken these steps, including the University of Maryland, College Park, Emory University, Brigham Young University, ASU, UTC, University of Washington, and WPI.[citation needed] ISPs sometimes use products such as Allot Inc.'s NetEnforcer to try to throttle encrypted BitTorrent traffic.

Peer exchange

Main article: Peer exchange

Peer exchange (PEX) is another method to gather peers for BitTorrent in addition to trackers and DHT. Peer exchange checks with known peers to see if they know of any other peers.


Another unofficial feature is an extension to the BitTorrent metadata format proposed by John Hoffman.[33] It allows the use of multiple trackers per file, so if one tracker fails, others can continue supporting file transfer. It is implemented in several clients, such as BitTornado, KTorrent and µTorrent. Trackers are placed in groups, or tiers, with a tracker randomly chosen from the top tier and tried, moving to the next tier if all the trackers in the top tier fail.

BitTorrent-related applications

Because of the open nature of the protocol, many clients have been developed that support numerous platforms and written using various programming languages.


Main article: Comparison of BitTorrent software
The main article for this category is BitTorrent client.


  • Anime fansub communities often use BitTorrent for their releases, and the most popular announce sites like Animesuki have RSS feeds.
  • Blog Torrent offers a simplified BitTorrent tracker to enable bloggers and non-technical users to run a tracker off their site. Blog Torrent also allows visitors to download a "stub" file which acts as a BitTorrent client to download the desired file, allowing users without BitTorrent software to benefit from it.[34] This is similar to the concept of a self-extracting archive.
  • The game GunZ The Duel has a built-in BitTorrent client.
  • Blizzard Entertainment uses a version of BitTorrent in World of Warcraft to distribute patches.
  • Most Linux distributions offer BitTorrent as one of the download methods for installation CDs.
  • Podcasting software is starting to integrate BitTorrent to help podcasters deal with the download demands of their MP3 "radio" programs. Specifically, Juice supports automatically processing .torrent files from RSS feeds.
  • Similarly, some BitTorrent clients, such as µTorrent, are able to process web feeds and automatically download content found within them.

See also

Find more information on BitTorrent by searching Wikipedia's sister projects:

 Dictionary definitions from Wiktionary
 Textbooks from Wikibooks
 Quotations from Wikiquote
 Source texts from Wikisource
 Images and media from Commons
 News stories from Wikinews
 Learning resources from Wikiversity

  • Comparison of BitTorrent software
  • Comparison of file sharing applications
  • Comparison of BitTorrent sites
  • Super-seeding
  • BitTorrent tracker
  • Magnet link


  1. ^ Ellis, Leslie (May 8, 2006). BitTorrent’s Swarms Have a Deadly Bite On Broadband Nets. Multichannel News. Retrieved on 2006-05-08.
  2. ^ Pasick, Adam (November 4, 2004). LIVEWIRE - File-sharing network thrives beneath the radar. Yahoo! News. Retrieved on 2006-05-09.
  3. ^ Sevcik, Peter (November 01, 2005). Peer-to-Peer Traffic: Another Internet Myth Is Born. Business Communication Review. Retrieved on 2006-05-09.
  4. ^ a b BitTorrent Protocol 1.0. Retrieved on 2006-05-06.
  5. ^ a b Tamilmani, Karthik. Studying and enhancing the BitTorrent protocol. Retrieved on 2006-05-06.
  6. ^ P2P Downloads. Retrieved on 2006-05-09.
  7. ^ NetBSD BitTorrents. Retrieved on 2006-11-03.
  8. ^ Fedora Core. Retrieved on 2006-11-21.
  9. ^ Mandriva 2007 free. Retrieved on 2006-11-24.
  10. ^ OpenSUSE Released Version. Retrieved on 2006-05-09.
  11. ^ Ubuntu download page. Retrieved on 2006-05-21.
  12. ^ Warner Bros. to sell films via BitTorrent. (May 9, 2006). Retrieved on 2006-05-09.
  13. ^ Sub Pop page on Retrieved on 2006-13-12.]
  14. ^ SXSW 2006 Clickguide for iPod. Retrieved on 2006-05-09.
  15. ^ Baby shambles official website. Retrieved on 2006-05-09.
  16. ^, the website used by Ween. Retrieved on 2006-13-12.
  17. ^ Cullen, Drew (14 December 2004). Finnish police raid BitTorrent site. The Register. Retrieved on 2006-05-09.
  18. ^ Police swoop closes down Finland’s largest file download site. HELSINGIN SANOMAT (16.12.2004). Retrieved on 2006-05-09.
  19. ^ First hearings in Finland's largest P2P case. Afterdawn (11.08.2006). Retrieved on 2006-08-14.
  20. ^ Court: Hollywood gets P2P giant's server logs.
  21. ^ LokiTorrent Shut Down.
  22. ^ Deal signed on downloading piracy. Retrieved on 2006-11-04.
  23. ^ Legal threats. The Pirate Bay. Retrieved on 2006-05-09.
  24. ^ Letter
  25. ^ LeMay, Renai (May 20, 2005). BitTorrent enemies face new hurdle. CNET Retrieved on 2006-05-09.
  26. ^ Norton, Quinn (June 2, 2005). May the source be with you. Guardian Unlimited. Retrieved on 2006-05-09.
  27. ^ Worthington, David; Nate Mook (May 25, 2005). BitTorrent Creator Opens Online Search. BetaNews. Retrieved on 2006-05-09.
  28. ^ HTTP-Based Seeding Specification (TXT). Retrieved on 2006-05-09.
  29. ^ Raymond, Scott: Broadcatching with BitTorrent. scottraymondnet: (Dec 16, 2003).
  30. ^ Main Page. Torrentocracy wiki. Retrieved on 2006-05-09.
  31. ^ pep.txt (TXT). Retrieved on 2006-05-09.
  32. ^ Encrypting Bittorrent to take out traffic shapers. (02.05.06). Retrieved on 2006-05-09.
  34. ^ Blog Torrent and Participatory Culture. Retrieved on 2006-05-09.


  • Schiesel, Seth (February 12, 2004). "File Sharing's New Face." New York Times, link
  • Thompson, Clive (January, 2005). "The BitTorrent Effect." Wired Magazine, link.
  • BBC News (May 13, 2005). "TV download sites hit by lawsuits" BBC News, link.
  • BBC News (October 25, 2005). "BitTorrent user guilty of piracy." BBC News, link.
  • BBC News (April 13, 2006). "BitTorrent battles over bandwidth." BBC News, link.
  • Rietjens, Bob (2005) "Give and Ye Shall Receive! The Copyright Implications of BitTorrent", 2:3 SCRIPT-ed 364. link
  • Roth, Daniel (November 14, 2005). "Torrential Reign." Fortune, p. 91–96.
  • Pouwelse, Johan (December 18, 2004). "A detailed study of the BitTorrent network." The Register, link.

External links

  • Official BitTorrent Inc Website
  • BitTorrent Specification
  • BitTorrent at the Open Directory Project
  • Interview with chief executive Ashwin Navin
  • BitTorrent Guide and FAQ
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