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other advantages including processing of information for error detection and correction, applying encryp-
tion and decryption techniques to sensitive information, and many more. Thus, digital information trans-
mission technology has become the dominant technology in the field of communications [9,18].
As indicated earlier, communication technology has experienced phenomenal growth over the past
several decades. The following two factors have always played a critical role in shaping the future of
communications [20]:
• Severity of user needs to exchange information
• State of the technology related to communications
Historically, inventions have always been triggered by the severity of needs. It has been very true for
the field of communications as well. In addition, there is always an urge and curiosity to make things
happen faster. When electricity was discovered and people (scattered around the globe) wanted to exchange
information over longer distances and in less time, the telegraph was invented. Morse code was developed
with shorter sequences (of dots and dashes) for more frequent alphabets. That resulted in transmission
of messages in a shorter duration of time. The presence of electricity and the capability of wires to carry
information over longer distances led to the development of devices that converted human voice into
electrical signal, and thus led to the development of telephone systems. Behind this invention was also a
need/desire to establish full-duplex (two-way simultaneous) communication in human voice. As use of
the telephone became widespread, there was a need for a telephone user to be connected to any other
user, and that led to the development of switching offices. In the early days, the switching offices were
operated manually. As the state of the technology improved, the manual switching offices were replaced
by automatic switching offices. Each telephone user was assigned a telephone number for identification
purposes and a user able to dial the number for the purpose of establishing a connection with the called
party. As the computer technology improved and the computers became easier to afford and smaller in
size, they found countless uses including their use in communications. The computers not only replaced
the automatic (electromechanical) switching offices, they were also employed in many other aspects of
communication systems. Examples include conversion of information from analog to digital and vice
versa, processing of information for error detection and/or correction, compression of information, and
encryption/decryption of information.
As computers became more powerful, there were many other applications that surfaced. The most visible
application was the amount of information users started sharing among themselves. The volume of infor-
mation being exchanged among users has been growing exponentially over the last three decades. As
users needed to exchange such a mammoth amount of information, new techniques were invented to
facilitate the process. There was not only a need for users to exchange information with others in an
asynchronous fashion, there was also a need for computers to exchange information among themselves.
The information being exchanged in this fashion has different characteristics than the information being
exchanged through the telephone systems. This need led to the interconnection of computers with each
other and that is what is called computer networks.

38.3 Computer Networks

A computer network is an interconnection of computers. The interconnection forms a facility that
provides reliable and efficient means of communication among users and other devices. User commu-
nication in computer networks is assisted by computers, and the facility also provides communication
among computers. Computer networks are also referred to as computer communication networks.
Interconnection among computers may be via wired or wireless transmission medium [5,6,10,13,18].
There are two broad categories of computer networks:

• Wide area networks
• Local/metropolitan area networks

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