Digital

Bit Torrent

Did you know that about one third of all of the data flying across the internet at any given point is being sent by an application called BitTorrent? You may not even know what it is, because previously it has mainly been used for illegal nefarious purposes, but now it's hitting the mainstream, and once you try it you'll never know how you managed to live without it.

So what is it? In short, it is the answer to the age-old (internet age-old, that is, ie about four years) problem of how to distribute a very large file to lots of people at high speed without spending an awful lot of money. People hosting websites are charged by the amount of data served - size of file x number of viewers - so although internet connections have been fast enough to send large files for a few years, an enormous file watched by an audience of millions would cost the host an inordinate amount of money in hosting fees - not an option for the majority of creatives who are not rolling in cash.

BitTorrent's genius lies in taking the onus off the original server hosting the content by sharing the burden of the file download between everybody who is downloading it. This may sound strange, so let's have an example: Imagine that I place a 1Gb video on my website, and you want to download it. Instead of you, and thousands of others, downloading the full 1Gb's worth of data directly from me, and sending my hosting bills sky-rocketing, you download a tiny file (about 5k) which is known as a 'torrent'. You open this file using a BitTorrent application, and the file tells the application the address where the video can be found, and also - and this is the important bit - the addresses of all the other people currently downloading the file. BitTorrent splits the original gigantic file into manageable slices, and as soon as you have downloaded one slice, you start uploading this file to other people (the group of up- and downloaders are collectively known as a 'swarm').

Because the BitTorrent application downloads the file not only from its original source, but from all the other people downloading it at the same time, it is incredibly efficient, because it doesn't even need the original file to be online in order for you to download it - as long as all the different slices are available in aggregate somewhere in the swarm, your download will complete. BitTorrent allows me to make my incredibly large video file available to the world, because I myself only need to have it running over my own wires, and racking up my own bills, for a short period, before enough people download it to make it selfsupporting. Because such a small proportion of the activity is happening at any one point in the swarm, the work gets distributed very efficiently using relatively little of any one individual's bandwidth.

The swarm effect also means that files are downloaded much more quickly than usual, because there is not just one server that gets clogged up and slow when a lot of people access it - on the contrary, the more people there are in the swarm, the faster the download is likely to be.

This means that people can distribute exceptionally large files, such as high-definition format TV and entire music concerts, where just a couple of years ago the cost of sharing such enormous files would have been prohibitive.

As is common with new technology which can do things quickly and cheaply, much of the material being downloaded using BitTorrent is illegal. There are a host of sites that will try to tempt you with all sorts of film and TV shows - there's currently legal action being taken by the MPAA (Motion Picture Association of America) against a range of sites that host links to various torrents, because of copyright infringements. Many MP3s and similar that are available are also in fact in breach of copyright.

However, there are plenty of totally legal things to download with a clear conscience. First off, you need to grab a BitTorrent client from here. Then take a look at what's on offer at LegalTorrents, which provides a wealth of material, from movies to music and books, and etree.org which offers live concert recordings of hundreds of bands, from such luminaries as the Grateful Dead and Pearl Jam.

A quick search on google will turn up masses of torrent sites, but be aware that unless it is specifically stated that they will only list non-copyrighted (or released under a Creative Commons license) material, you are likely to find a mixture of legal and illegal downloads on any one site.

Published on 19th January

07-07-2011