So what exactly is Peer-to-Peer (P2P)?

In "Always Use Protection" I talk about P2P networks like Kazaa, but don't really go into what peer-to-peer actually means.

First, think about what happens when you connect to a web site. You're actually connecting to a computer that hosts the web site. That computer is called the server (because it's serving web data) and your computer is called the client. One web server can serve a web site to thousands or millions of clients.

Now think about what happens when you open a direct connection on instant messenger or try to send a file. The file is on your friend's computer, and to access that file you try to open a connection directly to that computer. Now, that computer isn't really a server - it's another computer just like yours. In other words - it's a peer computer. Peer-to-peer refers to any situation where computer connect to each other for information instead of going to a central server.

Chapter 5 in "Always Use Protection: A Teen's Guide to Safe Computing" explains how you can configure your firewall to allow these types of peer to peer connections. By default most firewalls only allow client-server connections to web servers.

So what's all the fuss about peer to peer?

Imagine, for a moment, if music downloading were completely legal. Someone could put their music collection on a server and invite people to download the music. But if hundreds or thousands of people tried to download it at once, the server wouldn't be able to handle it - especially if its connection to the Internet was slow.

So someone came up with a great idea - instead of having everyone download songs from a server or group of servers, why not let them download songs from each other? Each person would share their music collection, and when you wanted a song you would go to a server and ask for a list of people who already had the song. Then you would start downloading from them, maybe even download parts of the song from several computers and then stitch them together to form the complete song. Because each of these "peer" computers would only be sending data to a few other computers, you wouldn't have the problem of one overworked server.

This is what Napster did a few years back, forming the largest P2P network of the time. They were ultimately shut down because the courts determined that having a central database of song information was illegal, even if the servers did not host the actual songs.

Other networks such as Kazaa work without a central database of songs. Instead your computer seeks out other computers called supernodes that help spread out the search to numerous computers. 

True P2P networks are very annoying to record companies because not only is it less clear that they are violating the law, they are much harder to shut down even if it is determined that they are - there is no central point you can turn off.

So instead, the record industry got together through the RIAA, and started targeting those individuals who are actually breaking the law by distributing copyrighted material. You see, in order for you to connect to someone else's machine, you (or rather, the software you are using) has to know their IP address. So if a computer is advertising that it has music available by allowing people to connect to it, people can find out the IP address of the computer. Because your Internet service provider knows who has which IP addresses, it is ultimately possible to find out who you are. This is how the RIAA tracks down the people it sues for sharing music.

So you see, the "issues" that people have with P2P aren't with the technology itself - it's with the fact that some people are using it in an illegal manner. Many people use P2P to exchange files with friends using instant message services, and as long as they aren't violating a license or copyright, it's perfectly legal.

As time goes on, you'll probably see more and more advanced P2P technology. One example is BitTorrent (http://bitconjurer.org/BitTorrent) which actually works faster as more people try to download a file. Some of it will be increasingly annoying to record companies and movie producers. Much of it will make it easier for you to work in collaboration with others - for example: working together on a homework report or editing video over the Internet. Either way, P2P in some form is probably in your future.