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Torrents 101: How Torrent Downloading Works

Part 1) An Overview of Bittorrent P2P File Sharing

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Young woman lying on bed wearing headphones and using laptop
Guy Crittenden/Photographer's Choice/Getty Images
April, 2014

Question: What exactly is "bittorrent" sharing?

Answer: Bittorrent networking is the most popular form of modern P2P (peer-to-peer) file sharing. Since 2006, bittorrent sharing has been the primary means for users to trade software, music, movies, and digital books online. Torrents are very unpopular with the MPAA, the RIAA, and other copyright authorities, but are much beloved by millions of college and university students around the planet.

Bittorrents (also known as "torrents") work by downloading small bits of files from many different web sources at the same time. Torrent downloading is extremely easy to use, and outside of a few torrent search providers, torrents themselves are free of user fees.

Torrent networking debuted in 2001. A Python-language programmer, Bram Cohen, created the technology with the intent to share it with everyone. And indeed, its popularity has taken off since 2005. The torrent community has now grown to millions of users worldwide in 2009. Because torrents strive to screen out dummy and corrupt files, are mostly free of adware/spyware, and achieve amazing download speeds, torrent popularity is still growing fast. By straight gigabytes of bandwidth used, bittorrent networking is the most popular activity on the Internet today.

How are torrents special? How is the torrent community different from Kazaa and other networks?

Answer: Like the other file-sharing networks (Kazaa, Limewire (now defunct), Gnutella, eDonkey, and Shareaza) Bittorrent's primary purpose is to distribute large media files to private users. Unlike most P2P networks, however, torrents stand out for 5 major reasons:
 
  1. Torrent networking is NOT a publish-subscribe model like Kazaa; instead, torrents are true Peer-to-Peer networking where the users themselves do the actual file serving.
  2. Torrents enforce 99% quality control by filtering out corrupted and dummy files, ensuring that downloads contain only what they claim to contain. There is still some abuse of the system, but if you use a community torrent searcher like www.isohunt.com, users will warn you when a torrent is a fake or dummy file.
  3. Torrents actively encourage users to share ("seed") their complete files, while simultaneously penalizing users who "leech".
  4. Torrents can achieve download speeds over 1.5 megabits per second.
  5. Torrent code is open-source, advertising-free, and adware/spyware-free. This means that no single person profits from torrent success.
     
Related: How to speed up your torrent download speeds with port forwarding...

Next: A non-technical explanation of bittorrents

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