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214 Chapter 6 The Cloud

A local area network (LAN) connects computers that reside in a single geographic loca-
tion on the premises of the company that operates the LAN. The number of connected com-
puters can range from two to several hundred. The distinguishing characteristic of a LAN is
a single location. A wide area network (WAN) connects computers at different geographic
locations. The computers in two separated company sites must be connected using a WAN.
To illustrate, the computers for a college of business located on a single campus can be con-
nected via a LAN. The computers for a college of business located on multiple campuses must
be connected via a WAN.
The single- versus multiple-site distinction is important. With a LAN, an organization can
place communications lines wherever it wants because all lines reside on its premises. The
same is not true for a WAN. A company with offices in Chicago and Atlanta cannot run a wire
down the freeway to connect computers in the two cities. Instead, the company contracts with a
communications vendor that is licensed by the government and that already has lines or has the
authority to run new lines between the two cities.
An internet is a network of networks. Internets connect LANs, WANs, and other internets.
The most famous internet is “the Internet” (with an uppercase letter I), the collection of net-
works that you use when you send email or access a Web site. In addition to the Internet, pri-
vate networks of networks, called internets, also exist. A private internet that is used exclusively
within an organization is sometimes called an intranet.
The networks that make up an internet use a large variety of communication methods and
conventions, and data must flow seamlessly across them. To provide seamless flow, an elabo-
rate scheme called a layered protocol is used. The details of protocols are beyond the scope of
this text. Just understand that a protocol is a set of rules and data structures for organizing
communication. Computers need to use protocols so they can exchange data. People use simi-
lar protocols to communicate. People, for example, follow a conversational protocol that says
when one person talks, the other person listens. They switch back and forth until they are done
communicating. Without a protocol for conversations, people would continually talk over each
other and nothing would be communicated.
There are many different protocols; some are used for LANs, some are used for WANs, some
are used for internets and the Internet, and some are used for all of these. We will identify sev-
eral common protocols in this chapter.

What Are the Components of a LAN?

Employers can and do monitor As stated, a LAN is a group of computers connected together on a single site. Usually the com-
employees’ online activities. puters are located within a half-mile or so of each other. The key distinction, however, is that all
What is the purpose of this of the computers are located on property controlled by the organization that operates the LAN.
monitoring, and how is it done? This means that the organization can run cables wherever needed to connect the computers.
Is there anything employees
can do about it? The Guide on Figure 6-5 shows a LAN that is typical of those in a small office or a home office (SOHO).
pages 240–241 considers these Typically, such LANs have fewer than a dozen or so computers and printers. Many businesses,
questions. of course, operate LANs that are much larger than this one. The principles are the same for a
larger LAN, but the additional complexity is beyond the scope of this text.
The computers and printers in Figure 6-5 communicate via a mixture of wired and wireless
connections. Some devices use wired connections, and others use wireless connections. The
devices and protocols used differ for wired and wireless connectivity.
The Institute for Electrical and Electronics Engineers (IEEE, pronounced “I triple E”) spon-
sors committees that create and publish protocol and other standards. The committee that ad-
dresses LAN standards is called the IEEE 802 Committee. Thus, IEEE LAN protocols always start
with the numbers 802.
The IEEE 802.3 protocol is used for wired LAN connections. This protocol standard, also
called Ethernet, specifies hardware characteristics, such as which wire carries which signals. It also
describes how messages are to be packaged and processed for wired transmission over the LAN.