A Series of Tubes

Ted Stevens, former U.S. Senator from Alaska, used to be the head of a committee that regulates the Internet in the United States. He became famous for many things, but one of them was when he tried to describe the Internet. He tries to use a metaphor (tubes) to explain bandwidth issues, but he ends up sounding like a crazy man.

"And again, the Internet is not something that you just dump something on, it's not a big truck. It's... it's a series of tubes!!"


The Internet is, simply put, millions of computers worldwide connected together under the TCP/IP protocol. If your computer is connected to the Internet, that means that it is now a part of that network.


Now, how does that work? What does that look like?

Take the computers in the lab you are working in. Our lab has 24 computers (including my laptop), plus two printers connected to the network. All the devices are connected by hubs, and all are connected to the network serverA "server" is a general term for a computer with software that handles information requests over a network. There are many kinds of servers; the one I mention here is a "network server," but there are also web servers, database servers, file servers, and many more. (which also acts as a file server). The network server, in turn, is connected to the Internet. See the map below, where red squares are computers, green triangles are printers, yellow circles are hubs, the purple lines are LAN cables, and the blue pentagon is our server. The light blue avenue is a fiber-optic connection to the Internet:

Our server, the blue pentagon above, is in turn connected to other servers at our ISP, which is connected to more servers across the country. There is a large web of connections between computers and servers all across the world, which makes it possible for your computer to contact almost any other computer in the world. This is the Internet.

There are many ways you could map the Internet; one way of doing it, representing many (but not even close to all) of the web servers on the main transmission lines of the Internet, is shown below. Now, keep in mind that our little lab here is not even on this map--it's too small. No, our server is one of many servers connected to a larger server which is at the very end of just one of the tiny lines somewhere on this map:

In this map, the end of every small thread is a server, which can host up to 256 other servers; each server can host hundreds more computers each. Each junction of lines is also a server. You get the idea of how big things are: there are a lot of computers linked together.

This is not a perfect representation, but it perhaps begins to give you an idea of what the mass of connections looks like. For a slightly different view, see this map of United States servers only.

The important thing to remember, however, is that it is just a network--it is a lot of computers connected together. It may be impressive because of its size, but what makes the Internet work is protocols.


Protocols: Tubes Within Tubes

There are many services on the Internet, each defined by a protocol. To give a few examples:

  • Most people use the Internet for browsing on web sites. Your browser uses the HTTP protocol for doing this.
  • Another common use is email. Your email program uses the POP3 protocol, or possibly the IMAP protocol, to collect email, and the SMTP protocol to send email.
  • You might open Skype and start a text chat, voice conversation, or video call; you are using a special protocol used just by Skype to communicate.
  • If you share files (legally, one hopes!), you might be using the Gnutella or BitTorrent protocols.
  • If you create a web site, you may use a special program to upload files to your web host. That program would use the FTP protocol.

There are dozens of protocols, in many different layers. The layers shown above are from the 7th, or the "Application" layer. (Don't worry, protocol layers will not be on the test.)

A protocol is important because it is how all computers agree to communicate (remember, a protocol is a set of rules and language that everyone agrees to use). When a new service becomes available on the Internet, it might use a new protocol.

Each computer has the basic protocols built-in, and you can add more protocols by downloading software and installing it. For example, if you download Skype and install it, you have added another protocol to your computer.

While the physical network of computers forms the main "Tube" of the Internet, the protocols are like smaller tubes (or wires) inside that main tube. The protocols are the real "Internet," in that they make all of your activities possible.

Think of the Internet as a pipe or 'tube' (as Senator Stevens said). It might look like this:

If the Internet is a tube, then your computer is one slice of this "tube." Your computer has all the protocols of the Internet--web, email, chat, etc.--and when you add all the computers together, they make up the whole Internet "tube."

I think of this as the "Internet Salami" metaphor.

Like all metaphors, however, it falls short. The computers are not all adjacent; instead, they are connected by a variety of transmission lines, such as old-style-telephone lines or high-speed fiber-optic cables. The point I am making, however, is that within your computer are several protocols which connect to other computers with the same protocols, making smaller groups within the larger network. Your computer is on the Internet, but it is also part of the sub-networks known as "email," "chat," "the World Wide Web," and so on.


Note that the World Wide Web is part of the Internet. The Web is smaller than the Internet (or, the Web is a subset of the Internet).

Many people mistake these names, and think that the "Internet" and the "Web" are the same thing. They're not. The "World Wide Web" is web pages using the HTTP protocol, and is inside the Internet.