What is BitTorrent?

When I started messing with BitTorrent in 2002 I thought it had the potential to become the next big thing in file sharing. Now it definitely has reached that level. The main idea behind BitTorrent is to help increase the supply of files that are in high demand better than a conventional server.

For example, when Microsoft released Service Pack 2 for Windows XP, even with all its servers, they could not release it to everyone at once. So they did it in phases - first to developers and manufacturers, then to a few more special people, then to the general public after a week or two. Why the delay to the masses? Because if millions of people connect at the same time to their servers download speeds will be terrible or not connect at all because the demand would be too high for their finite amount of bandwidth.

So the idea behind BitTorrent is to allow quicker distribution of files by making everyone a server. It increases the availability of a file to meet the higher demand. Lets go through a hypothetical example. Say one person starts with a file that is 100MB, and 10 people want it. All these 10 people could connect to this one guy, and he could upload it 10 times - that would be 1GB of bandwidth he would have to upload.

Or those same 10 people could use BitTorrent. The file will be divided it into tiny pieces - for now lets say there are 1000 of them, at 100KB each. When those same ten people connect to the initial user on BitTorrent, they all download different pieces from him. User number one may get pieces 2, 57 and 384, user two 78, 216, and 784, etc. Notice the pieces they get are random. Once a user has a few pieces he searches for some of the other 9 people that are downloading. He finds out what pieces they have, and begins to download the pieces they have from them. At the same time he also uploads the pieces he has to some of the other 9 people. Its like a huge trading game.

With conventional servers the initial person with the file would have only given the file to 3 other people if he uploaded 300MB. On BitTorrent by the time he has uploaded that much there may be dozens of people with the complete file.

This could be great for small businesses. Encourage customers to download your product with BitTorrent, and it would save your bandwidth. Some groups like Lindows even gives its users discounts for using BT to download their software. As I showed with the service pack example above, it could work well for big companies and high demand files as well.

On the other hand, there has always been a ton of people who want files right after they come out. These are the people that download music, movies, tv shows, games, etc. Say you want the episode of your favorite reality show you forgot to tape when you went out last night. With conventional servers finding the file can be relatively easy. But there are usually huge waiting times to get access them - sometimes on the order of days. With BitTorrent you can begin downloading immediately. And the more users there are, the more bandwidth there is to go around.