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How Torrents Work

Part 2) A Non-Technical Explanation

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Question: How exactly does bittorrent sharing work?

Answer: Torrent sharing is about "swarming and tracking", where users download many small bits from many different sources at once. Because this format compensates for bottleneck points, it is actually faster than downloading a large file from a single source.
 
  • "Swarming" is about splitting large files into hundreds of smaller "bits", and then sharing those bits across a "swarm" of dozens of linked users.
  • "Tracking" is when specific servers help swarm users find each other.
  • Swarm members use special Torrent client software to upload, download, and reconstruct the many file bits into complete usable files.
  • Special .torrent text files act as pointers during this whole process, helping users find other users to swarm with, and enforcing quality control on all shared files.


Comment: Torrent vs. Kazaa. Torrents are different from the competing Kazaa network in one significant way: torrents are true P2P sharing. Instead of "publisher servers" dishing out files, torrent users do the file serving. Torrent users voluntarily upload their file bits to their swarm without payment or advertising revenue. You could say torrent users are motivated, not by money, but by a "Pay-It-Forward" cooperative spirit. If you recall the Napster.com model of the 1990's, bittorrent swarming is the same, but with sharing incentive added.

Torrent sharing goes like this: if you share files via bittorrents, you will be rewarded with increased download speed. Conversely, if you choose to "leech" and not share your files upwards, you will be punished with slow Torrent download speeds.

Download speed is controlled by torrent tracking servers, who monitor all swarm users. If you share, tracker servers will reward you by increasing your alotted swarm bandwidth (sometimes up to 1500 kilobits per second). Similarly, if you leech and limit your upload sharing, tracking servers will choke your download speeds, sometimes to as slow as 1 kilobit per second. Indeed, the "Pay It Forward" philosophy is digitally enforced! Leeches are not welcome in a bittorrent swarm.

Next, Part 3: "OK. I want to try torrent downloading. How do I start?"

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