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Lesson 1: What Is a Network?
This lesson introduces some basic principles of computer-based networking,
discusses advantages of networking, and presents the idea of connecting
computers together to form a local area network (such as a corporate intranet)
and a wide area network (such as the Internet).
The Concept of Networking
The idea of networking has been around for a long time and has taken on
many meanings. If you were to look up "network" in your dictionary, you
might find any of the following definitions:
Obviously, the last definition is the one we are concerned with in this
course. The key word in the definition is "share." Sharing is the purpose
of computer networking. The ability to share information efficiently is
what gives computer networking its power and its appeal. And when it comes
to sharing information, human beings are in many ways similar to computers.
Just as computers are little more than collections of the information they
have been given, so we are, in large part, collections of our experiences
and the information given to us. When we want to expand our knowledge,
we broaden our experience and gather more information. For example, to
learn more about computers, we might talk informally with friends in the
computer industry, go back to school and take a class, or work through
a self-paced training course like this one. Whichever options we choose,
when we seek to share the knowledge and experiences of others, we are networking.
An openwork fabric; netting
A system of interlacing lines, tracks, or channels
Any interconnected system; for example, a television-broadcasting network
A system in which a number of independent computers are linked together
to share data and peripherals, such as hard disks and printers
Another way to think of networking is to envision a network as a team.
This might be a sports team, such as a football team, or a project team,
such as the one that created this training course. Through the efforts
of all involved—the sharing of time, talent, and resources—a goal is accomplished
or a project is completed. Similarly, managing a computer network is not
unlike managing a team of people. Sharing and communicating can be simple
and easy (a quarterback calling a play in the huddle) or complex (a virtual
project team located in different time zones around the world that communicates
through teleconferencing, e-mail, and multimedia presentations over the
Internet to complete a project).
Introducing Computer Networking
At its most elementary level, a computer network consists of two computers
connected to each other by a cable that allows them to share data. All
computer networking, no matter how sophisticated, stems from that simple
system. While the idea of connecting two computers by a cable may not seem
extraordinary, in retrospect it has proven to be a major achievement in
Computer networking arose as an answer to the need to share data in
a timely fashion. Personal computers are powerful tools that can process
and manipulate large amounts of data quickly, but they do not allow users
to share that data efficiently. Before networks, users needed either to
print out documents or copy document files to a disk for others to edit
or use them. If others made changes to the document, there was no easy
way to merge the changes. This was, and still is, known as "working in
a stand-alone environment." (See Figure 1.1.)
Figure 1.1 Stand-alone environment
Copying files onto floppy disks and giving them to others to copy onto
their computers was sometimes referred to as the "sneakernet." This early
form of computer networking is one that many of us have used and perhaps
still use today. See Figure 1.2; it might bring back some fond memories.
Figure 1.2 The sneakernet
This system works well in certain situations and has its advantages—it
allows us to stop for a cup of coffee or socialize with a friend while
we exchange and merge data—but it is far too slow and inefficient to meet
the needs and expectations of today's computer users. The amount of data
available to be shared and the distances we want the data to travel far
exceed the capabilities of the sneakernet.
But what if the computer shown in Figure 1.1 were to be connected to
other computers? Then, it could share data with the other computers and
send documents to the other printers. This connecting together of computers
and other devices is called a network, and the concept of connected
computers sharing resources is called networking. (See Figure 1.3.)
Figure 1.3 A simple computer network
Why Use a Computer Network?
With the availability and power of today's personal computers, you might
ask why networks are needed. From the earliest networks to today's high-powered
personal computers, the answer has remained the same: networks increase
efficiency and reduce costs. Computer networks achieve these goals in three
More specifically, computers that are part of a network can share:
Sharing information (or data)
Sharing hardware and software
Centralizing administration and support
And more sharing options exist. The capabilities of networks are constantly
expanding as new ways are found to share and communicate by means of computers.
Documents (memos, spreadsheets, invoices, and so on).
Illustrations, photographs, videos, and audio files.
Live audio and video broadcasts.
CD-ROM drives and other removable drives, such as Zip and Jaz drives.
Sharing Information (or Data)
The ability to share information quickly and inexpensively has proven to
be one of the most popular uses of networking technology. It has been reported
that e-mail is by far the number-one activity of people who use the Internet.
Many businesses have invested in networks specifically to take advantage
of network-based e-mail and scheduling programs.
By making information available for sharing, networks can reduce the
need for paper communication, increase efficiency, and make nearly any
type of data available simultaneously to every user who needs it. Managers
can use these utilities to communicate quickly and effectively with large
numbers of people and to organize and schedule meetings with people drawn
from an entire company or business enterprise far more easily than was
previously possible. (See Figure 1.4.)
Figure 1.4 Scheduling a meeting with Microsoft
Sharing Hardware and Software
Before the advent of networks, computer users needed their own printers,
plotters, and other peripherals; the only way users could share a printer
was to take turns sitting at the computer connected to the printer. Figure
1.5 shows a typical stand-alone workstation with a printer.
Figure 1.5 A printer in a stand-alone environment
Networks make it possible for several people to share data and peripherals
simultaneously. If many people need to use a printer, they can all use
the printer available on the network. Figure 1.6 shows a typical network
environment in which five workstations share a single printer.
Figure 1.6 Sharing a printer in a networking
Networks can be used to share and standardize applications, such as
word processors, spreadsheets, inventory databases, and so on, to ensure
that everyone on the network is using the same applications and the same
versions of those applications. This allows documents to be shared easily
and creates training efficiencies: it is easier for people to master one
word processing application thoroughly than to try to learn four or five
different word processing applications.
Centralizing Administration and Support
Networking computers can simplify support tasks as well. It is far more
efficient for technical personnel to support one version of one operating
system or application and to set up all computers in the same manner than
to support many individual and unique systems and setups.
The Two Major Types of Networks: LANs and WANs
Computer networks are classified into one of two groups, depending on their
size and function. A local area network (LAN) is the basic
building block of any computer network. A LAN can range from simple (two
computers connected by a cable) to complex (hundreds of connected computers
and peripherals throughout a major corporation). (See Figure 1.7.) The
distinguishing feature of a LAN is that it is confined to a limited geographic
Figure 1.7 A local area network (LAN)
A wide area network (WAN), on the other hand, has no geographical
limit (see Figure 1.8). It can connect computers and other devices on opposite
sides of the world. A WAN is made up of a number of interconnected LANs.
Perhaps the ultimate WAN is the Internet.
Figure 1.8 A wide area network (WAN)
What is a computer network?
What are three advantages of using a computer network?
Give two examples of a LAN configuration.
Give two examples of a WAN configuration.
The following points summarize the main elements of this lesson:
The primary reasons for networking computers are to share information,
to share hardware and software, and to centralize administration and support.
A local area network (LAN) is the smallest form of a network and is the
building block for larger networks.
A wide area network (WAN) is a collection of LANs and has no geographical