BitTorrent is being used by an increasing number of companies to deliver applications worldwide

Several broadband suppliers have recently announced 8Mbit/s upgrade options for most of their customers.

The only catch is that some insist you renew your broadband contract for a year or so to gain the extra speed. In a world of rapidly falling prices and a wide choice of broadband and telephone bundling deals, this is not a simple decision to make.

But contracts aside, I sometimes wonder what all this internet bandwidth is used for. Some experts say over half of internet traffic is generated by BitTorrent.

If you have not come across it, BitTorrent is a file transfer protocol that makes it quick and easy to download huge files, such as software installation disks and DVD movies. Designed by Bram Cohen and first shipped a few years ago, it was something of an overnight success. If Cohen had a penny for every time someone had used his protocol, he’d probably be a millionaire by now.

The trick to BitTorrent is that it can download fragments of a file from several different places at the same time, and then stitch the fragments together. The fragments tend to come from other people who are downloading the file at the same time. This means that downloads tend to run at the fastest speed your DSL service can handle, and are not limited to the bandwidth of one or two distribution servers. It also means you are likely to get fast downloads from popular files and a slower performance when downloading more obscure material.

BitTorrent also does some fairly clever error detection to ensure the downloaded file is identical to the source. This might seem like overkill when downloading an episode of Buffy the Vampire Slayer, but it is comforting when downloading software destined for your production server farm.

So successful is BitTorrent that it is used by Red Hat and Suse to distribute their Linux installation CD-Roms, and it is also used by firms like VMware to distribute files containing virtual appliances. Given that BitTorrent traffic accounts for half the data travelling on the internet, it also seems to be used by rather a lot of people to download movies and television shows. And this number is set to increase following Warner Brothers’ announcement this month that it would distribute video and other content to US buyers using BitTorrent.

So far from it being simply just another file-swapping tool, BitTorrent has an important role for some global companies, both inside and outside the IT industry.

Software developers should also take note: BitTorrent was developed using the Python scripting language, which presumably made it quicker to develop than using low-level languages like C. As an interpreted language, Python also has the advantage of being able to run the same code on different platforms, which is always a good trick if you can do it.