I'm going to start this chapter with a little Networking 101. It will be fun really. For those of you who already know everything about TCP/IP and how IP networks operate, you can skip ahead a few paragraphs.
Communication over the Internet takes place using something called the TCP/IP protocol suite. TCP/IP actually stands for Transmission Control Protocol/Internet Protocol, and it is the basic underlying means by which all this magic communication takes place. Everything you do on the Net, whether it is surfing your favorite sites, sending and receiving emails, chatting via some instant messaging client, or listening to an audio broadcast all these things ride on TCP/IP's virtual back.
TCP/IP is often referred to as a protocol suite, a collection of protocols that speak the same language. Essentially, this comes down to the transmission and reception of IP packets. Those packets have to get from place to place, and that means they need to know how to get there. IP packets do this in exactly the same way that you get from your house to someone else's house. They have a home address from which they go to a remote address.
Each and every computer connected to the Internet has a unique address called an IP address, four numbers separated by dots (i.e., 192.168.22.55). Some systems that are always online (banks, Web sites, companies, etc.) will have a static address. Dial-up connections for home users tend to be shared when you aren't connected, someone else may be using the same address which is referred to as a dynamic IP address.
You may be wondering how a symbolic Web site address such as www.marcelgagne.com translates to the dotted foursome I mentioned above, and that would be an excellent question.
Think of the real world again. We don't think of our friends as "136 Mulberry Tree Lane" or "1575 Natika Court," but rather by their names. To find out where our friends live, we check the phone book (or ask them). The same holds true in the digital world, but that phone book is called a domain name server (DNS). When I type a symbolic (i.e., human-readable) address into my Web browser, it contacts a DNS (assigned by my Internet Service Provider [ISP]) and asks for the IP address. With that IP address, my packets almost know how to get to their destinations.
To reach an address in the real world, you get out of your driveway and enter some road to which all other roads are connected. If you drive long enough, presumably you get to Rome (having often been told that all roads lead to Rome). Before you can get to Rome, you enter your default route, namely, the street in front of your house. The same principle exists in the virtual world. For your IP packages (an email to your mother, for instance) to get to its destination, it must take a particular route, called a default route. This will be the IP address of a device that knows all the other routes. Your ISP will provide that route.
That concludes Networking 101. Not particularly complicated, is it?