Conceptual View of the Internet

Figure 2-5 shows Company A with a line connecting it to ISP1. The line represents a cable that can allow the enterprise network and ISP1 to communicate. ISP1 has created a network, with the details hidden by a network cloud. ISP1's network allows individual computers, such as Fred's, to connect to it. It also allows corporate networks, such as Company A, to connect. So, Fred could communicate with computers inside Company A, assuming that the security policies at Company A allowed it. But that's another story for Chapters 17, "Accepting the Right People and Rejecting the Wrong People," and 18, "Keeping a Watchful Eye over Who Drives into (Your Network) Neighborhood."

Company A created its enterprise network using hardware, software, and cabling paid for by Company A. ISP1 creates its network as well, using its own funds. ISP1 agrees to allow Company A's traffic to pass through ISP1 and on to other ISPs so that Company A can communicate with the rest of the world. In return for allowing Company A to communicate to the rest of the Internet using ISP1, Company A pays ISP1 an ongoing fee.

Similarly, Figure 2-5 shows Barney connected to ISP2. Barney probably used his phone line, his computer, and a modem to connect to ISP2. A modem is a device that allows a computer to communicate with another computer using a plain old telephone line. The vast majority of individual Internet users use a modem and a phone line to connect to the Internet.