It is estimated that between 25% to 35% of all Internet traffic today is BitTorrent. That is a staggering amount. From this observation, one can draw an obvious conclusion: BitTorrent is providing some form of benefit for millions of people. So what is that benefit?
Bandwidth Limitation of File Serving Technology
When you download a file on the Internet it is usually a one-way street. Someone on the other end has the file you want. You ask for it and it moves bit-by-bit from them to you. When a lot of people want the same file at the same time, it will take each of them longer to get it. If you have hundreds of people trying to download something and one person making it available, then that one person has to have the bandwidth for hundreds of people.
This distribution model works if the file sizes are small or the number of people wanting to download the file are few in number. Also, the server may have additional costs for the extra bandwidth they use.
The problem with P2P file-sharing networks like Kazaa is that uploading and downloading do not happen at equal speeds. Broadband providers allow their users to download at superfast rates, but
let them upload only very slowly, creating a bottleneck: If two peers try to swap a compressed copy of Meet the Fokkers - say, 700 megs - the recipient will receive at a speedy 1.5 megs a second, but the sender will be uploading at maybe one-tenth of that rate. Thus, one-to-one swapping online is inherently inefficient. It's fine for MP3s but doesn't work for huge files.
Swarming is an Alternative Approach
The basic calculation of BitTorrent is that there are lots of bandwidth available, its just that it is not being used. Each computer has unused, excess uploading bandwidth even when they are busy downloading. So, Cohen put both sides of the street to work in BitTorrent and this is what has changed everything.
BitTorrent works by breaking big files into many smaller files. First, one Internet user somewhere has something to offer -- say a copy of a movie. Then, others want to get that same file. You all start to download, but everyone get a different part of the file. As soon as it arrives, your computer automatically starts uploading your bit for other people to download. Eventually everyone gets all of the parts. Its called 'swarming' for obvious reasons. And all you need to put the puzzle together is a small program called a 'torrent' file.
The goal of a BitTorrent swarm is to get thousands of people to share the same Torrent at the same time. Paradoxically, when more people download using BitTorrent, the download get faster.
Amongst the interesting side effects of swarming are these:
The provider of the torrent file (a.k.a., 'a Tracker') has a very small bandwidth requirement. Therefore, BitTorrent swarms are a very economical solution for individuals and businesses that want to distribute files across the Internet.
BitTorrent is just a tool, software, it is not a file sharing service like KaZaa. BitTorrent does not provide content to share. It works best for large files.
