The BitTorrent P2P filesharing protocol has been steadily picking up users since its release in 2003, but over the last six months it has really taken off — its creator Bram Cohen claims that BitTorrent accounts for a third of all Internet traffic. Most recently it hit the headlines when Cohen met with the head of the MPAA (the US cinema industry association) to discuss how BitTorrent could be used for legitimate commercial services, and agreed to remove any links to copyrighted content from his website.
Comment: Firstly, let's clear up the issue of what BitTorrent is and isn't. The press reports on Cohen's meeting with the MPAA have somewhat misleadingly implied that BitTorrent is a P2P network, such as FastTrack or Gnutella, or a software application such as Kazaa or Grokster. It isn't really either of these things — when people say "BitTorrent", they generally mean the open source protocol that can be used to share files over the Internet. There is no BitTorrent network, and neither is there any single piece of client software, although Cohen created the original client, which is also called BitTorrent. However, this is far less popular than other BitTorrent clients from different developers, such as Azureus, BitTornado and BitComet, which have more functionality.
Files are shared by means of a very small "torrent" file placed on a Web site; when a user opens this link with their BitTorrent client, they are connected to a network made up of all the users uploading/downloading that particular file. The BitTorrent protocol works by breaking each file into a large number of small pieces, which are simultaneously uploaded and downloaded by those who are connected to that particular file. In this way, BitTorrent maximises network efficiency by enabling users to simultaneously upload and download the same file.
BitTorrent is almost entirely de-centralised, but there is usually a central "tracker" machine that manages connections between users' machines, although more recently "trackerless" torrents have started to appear. Note that at no point does the file being downloaded have to be uploaded to a Web server — the user who creates the torrent (the "seeder") acts as the initial uploader, until other users have completed their downloads and can also act as seeders.
Trouble with the law
The BitTorrent protocol was designed as a means of solving the difficulty of transferring large files over the Web to multiple users without wasting bandwidth or crippling networks. However, it was quickly taken up by those wishing to share copyrighted content, as its fast download speeds and ability to deal with large file sizes make it ideal for the sharing of content such as movies, DVDs and software.
A proliferation of sites quickly sprung up offering torrent files for a wide variety of copyrighted content, and as the sites themselves are not hosting any of this content, they have proved very difficult for the authorities to shut down. It is largely due to BitTorrent that filesharing activity has swung away from music towards movies, which often appear only hours or days after (or sometimes before) their cinema release — hence the involvement of the MPAA. Indeed, more than 50 percent of filesharing activity on the Web is now attributed to BitTorrent — and this figure is growing.
However, BitTorrent has a great many legitimate applications. Indeed, its creator sees it as a means of democratising who can distribute large files over the Web. For example, I could rapidly distribute a piece of software I have written or a film I have made, without the need for powerful and expensive servers on which to host my content. BitTorrent also has many applications in open source software distribution, allowing for the easy daily distribution of new software builds.
If you can't beat 'em...
So, BitTorrent is great for distributing things for free — therein lies its greatest strength and its greatest weakness. The music labels, movie studios and software houses are increasingly realising that BitTorrent is not only hugely popular, but that its decentralised nature means it is virtually unstoppable — as soon as one torrent link site is shut down, another five pop up to take its place, and the lack of a central network makes it hard to find targets for concrete legal action.
Rather than fruitlessly chasing those using BitTorrent to spread copyrighted material, the content owners should look towards using it to offer an easier to use and more reliable alternative.
Jonathan Arber is a research analyst working within Ovum's Consumer Telecoms practice.
