January 25, 2006

A beginners guide to Bittorrent

Bittorrent is the latest file-swapping program to hit the Internet and has in recent months hit the mainstream. According to iiNet’s CEO Michael Malone, Bittorrent traffic accounts for over half of the ISPs traffic.

Bittorrent's popularity stems from the fact that the protocol takes advantage of the distributed nature of the internet and leverages many peoples restricted uploading capacity to create very fast downloads for the end user. For individuals or businesses trying to share their information it can save a fortune in bandwidth costs by distributing the load across many users.

Bram Cohen invented the Bittorrent protocol in 2001 as a means of distributing large files without incurring heavy bandwidth expense for their publishers. Before Bittorrent, the more popular your file, the more you had to pay for bandwidth to share the file. With Bittorrent, the more people that share the file the less each person actually has to share, reducing the dependence on any one server to share the file. Bittorrent quickly became a critical tool for file sharer around the world. The Bittorrent program breaks the file up in to many small parcels of information – this parcels can be downloaded from many different computers and is then reassembled by the client program. Bittorrent files are not downloaded sequentially – you might download the last packet of information before you get the first.

Bittorrent also takes advantage of the fact that broadband Internet connections are generally asymmetrical – users can often download at a much faster rate then they can upload. A typical broadband plan is usually 512K download and only 128K upload – therefore you can download 4 times faster then you can upload. Bittorrent takes advantage of this by letting you download from multiple people simultaneously – if I download from 4 people who can upload at 128K then my effective download speed is 512K. With Bittorrent, the more people that share – or ‘seed’ a file, the faster your download is. Bittorrent users are encouraged to leave their files seeding even after the download is complete as the more people seeding the file (this group is known as the Swarm) the faster the download is for everyone.

To get started with Bittorrent head over to www.bittorrent.com and download the appropriate client for your computer (Mac, Windows and Linux are supported). Another popular download client is Azureus. Before you start downloading you may need to enable port forwarding on your router. Ensuring port 6881 is open will increase your download speed. Check out http://www.portforward.com/english/applications/port_forwarding/Torrent/Torrentindex.htm for more information on how to do this.

Once you’ve got your port open you are ready to start using bittorrent. A quick Google search on Bittorrent trackers will help you find the best places to search for files of interest. You can also use the search tool on www.bittorrent.com to find files to download. Some of my favourite sites are http://www.legaltorrents.com/ and http://www.isohunt.com