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Raghavendra S.
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P2P protocol has made decentralised file sharing efficient

The Pirate Bay, which is a ‘torrent indexing’ site, migrated most of the torrent information as magnet links earlier this year.
The Pirate Bay, which is a ‘torrent indexing’ site, migrated most of the torrent information as magnet links earlier this year.

Among the most significant contributions of the World Wide Web is that it has enabled simple sharing of files, and has made replication and dissemination of information fast, efficient and widely accessible.

The conventional, centralised file-sharing mechanism involved a file server that holds a copy of files for the clients to download. As the number and size of files, and the numbers of clients increase, resource requirements in terms of storage, processing and bandwidth at the server end naturally shoots up.

Add to this, the backup quandary while increasing back up will eat into resources, not having back up means taking the risk of losing data in case of hardware failure.

The Napster model

This conventional mode of file sharing was thrown to the wind when the controversial Napster music-sharing model became wildly popular in the late 90s. Based on this model, which was shut down at the behest of music companies, various ‘distributed’ mechanisms are available for users to download and share files.

P2P file sharing

Peer-to-peer (P2P) file sharing protocol has made decentralised file sharing such as the popular BitTorrent fast and efficient.

In the P2P file-sharing protocol, entire files are not hosted on few dedicated file servers, but are distributed horizontally among many users (peers) divided into smaller pieces or sections. These small pieces are put together by using referencing data called the hashes, to recreate the whole file after a host has downloaded all the pieces from more than one peer on the network.

When part of a P2P network, users can download files from other users and upload their own files for other users to download from. Users who have complete files and upload are called ‘seeders’. Users downloading files from seeders are termed ‘leechers’ in the BitTorrent jargon.

Exhaustive repository

In a P2P model, all files with users are in a sense available for other peers on the network, leading to an exhaustive repository of media, electronic literature, software and other forms of digital information, points out Bhargav Raghunathan, a network design consultant and a P2P file sharing enthusiast.

“Sharing files on a P2P is like eating at a potluck, with access to a wide spectrum of files from various users,” he

BitTorrent is the most famous P2P implementation, used by millions of users daily.

Sites such as The Pirate Bay, Mininova and Isohunt are ‘torrent indexing’ sites. These sites do not host any files for direct download except for the information about where the files are available for download. These tiny files (just a few kilobytes in size) containing information about lengths of pieces, hash code lists and trackers of other peers are called torrent files.


Using a BitTorrent client such as Bitcomet and Transmission, users can fetch the smaller files from hundreds of users and reassemble the original file at the host computer using the hash lists. These torrent files do take up a small amount of storage on servers.

With the increasing threat of confiscation of servers for copyright infringement, most of the major indexing sites are migrating to a more robust means of linking up peers using magnet links.

What are magnet links?

So, what are magnet links? Magnet links can be thought of as Uniform Resource Locators (URLs) with various parameter fields that can hold values.

The URL points to the location of files in the network and is a path to the files, not the files themselves. If torrent files have tracker details, hash lists and size of data in them, magnet links could hold this information in their parameter fields. This avoids the need for indexing sites to create and store torrent files on their servers.

The Pirate Bay, which calls itself ‘The galaxy’s most resilient BitTorrent site’, migrated most of the torrent information as magnet links earlier this year. To the end user, there will be very little difference, for all the latest BitTorrent clients also support magnet links.




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