Sunday, January 4, 2009

Heard of torrent downloads? What is that?

Torrents are specialized files utilized in peer-to-peer (P2P) network environments. P2P is a network of personal computers that communicate with one another by running proprietary P2P software. The first P2P software designed to utilize torrents was BitTorrent by Bram Cohen. Other torrent clients have followed.

Torrents are distinguished by a unique transfer process. To compare how torrents download to standard files, let’s first consider how normal files download off the Internet.

At any given website a user might click on a file to transfer it to his or her computer. Upon clicking on the file, the website’s server starts sending the file to the visitor in discreet data packets. These packets travel various routes to reach the user’s computer and are reconstructed upon receipt to complete the file transfer.

While this works fine for smaller files, it is cumbersome to transfer larger files this way. If the server is busy, download time can be very slow. Communication between your server and the computer can even crash, causing corruption in the transfer, or at best, delays.

Unlike downloads off the Web, torrents do not point to a single source on a P2P network when requesting files. Instead, torrents contain specific information that multiple computers in the network can read to send various parts of the requested file simultaneously and en masse. Torrents keep active track of which parts of the file are needed to complete the request. By downloading bits of the file from dozens, hundreds, or even thousands of sources, large files can download very quickly.

Working with torrents is also unique for another reason. At the same time the user is downloading file parts, the computer is also uploading parts already received to others. This decreases download time because users do not have to wait for file sources to have completed torrents before receiving needed parts of a requested file.

Once requested torrents have downloaded in full, you become a seed for those files. A seed refers to someone that has the entire file available. It is considered rude to download torrents and disconnect, referred to as leeching. Instead, users are encouraged to participate by seeding the file for others so that a minimal 1:1 share ratio is maintained. A swarm refers to the entire group of people transferring a file at any given time.

To encourage sharing, software used for downloading torrents keeps track of the share ratio. The torrent client will automatically allocate more bandwidth for downloading at faster speeds when a user shares more than he or she downloads. This usually means leaving the computer running while doing other things, as upstream bandwidth is much slower for most of us than downstream bandwidth. While it might take 40 minutes to download a 250MB freeware suite, it can take several times longer to upload that same amount of data.

Torrents are archived in libraries that are searchable with a Web browser. One cannot download torrents without installing a torrent client first. There are many free torrent clients available, some of which are open source. Once a desired torrent is found, clicking on it will open the torrent client to begin the download process. The user may have to configure his or her firewall to allow the use of certain communication ports.

Many types of files are shared as torrents, including software, music and videos. While P2P sharing is not illegal, sharing copyrighted material without permission from the copyright holder is illegal. The Recording Industry Artists of American (RIAA), and Motion Picture Association of America (MPAA) have targeted some websites that cater to archiving illegal torrents.


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