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A network is a connected system of objects
or people. The most common example of a network is the telephone
system, which is widely known as the Public Switched Telephone Network (PSTN). The PSTN allows people in virtually every corner of the world
to communicate with anyone who has access to a telephone.
In a similar fashion, a computer network allows users to
communicate with other users on the same network by transmitting
data on the cables used to connect them. A computer network is
defined as having two or more devices (such as workstations,
printers, or servers) that are linked together for the purpose of
sharing information, resources, or both.
It is important to understand that networks are multilayered.
A network consists of many overlapping systems, such as cabling,
addressing schemes, or applications. The layers work together to
transmit and receive data. The Open Systems Interconnection
(OSI) model
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The link can be made through a variety of copper or fiber-optic
cables or it can be a wireless connection that uses radio signals,
infrared technology (laser), or even satellite transmission. The
information and resources shared on a network can include data
files, application programs, printers, modems, or other hardware
devices. Computer networks are used in businesses, schools,
government agencies, and even some homes.
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which was created to define these multiple layers,
is discussed later in the chapter. The different ways in which
computers can be networked in order to share resources are also
discussed.