Figure 2-5. 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)
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.
After Barney has connected to ISP2, he can communicate with
computers in Company A, Company B, and with his buddy, Fred. Like Company A,
Barney pays his ISP (ISP2) a fee for allowing him to access the Internet.
The Internet revolution has affected the world as profoundly as
almost any invention in history. The ability to communicate across cultures,
across national boundaries, relatively quickly, and with (relatively) unfettered
freedom of speech has forever changed the way in which people live. News stories
routinely emerge more quickly via the Internet than via the world's most
powerful news services can find the story.
The ability to communicate between computers in different
companies' enterprise networks, as well as with individual users, allowed
several popular applications to emerge. This section covers a few of the more
popular applications, including web browsing, electronic mail (e-mail), file
downloading, and file transferring.