A computer network is a
telecommunication network that
allows computers to exchange
data. The physical connection
between networked computing
devices is established using either
cable media or wireless media.
Network devices that originate, route
and terminate the data are called
network nodes. Nodes can include hosts
such as servers and personal
computers, as well as networking
hardware. Two devices are said to be
networked when a process in one device
is able to exchange information with a
process in another device.
A Personal Area Network or PAN is a
computer network used for communication
among various electronic devices such as
personal computers, mobile phones in a
close proximity. The area of a PAN is
typically a few meters. PANs can be used
for communication among the devices or
for connecting to the Internet. A PAN
may use wireless connection as well.
A Local Area Network (LAN) is a
computer network that interconnects
computers in a limited area such as a
home, school, computer laboratory, or
office building using network media.
It is the most common type of
network. Usually, local area network
has not more than 100 computers.
A Metropolitan Area Network (MAN)
is a network that interconnects users
with computer resources in a
geographic area or region larger than
that covered by even a large local area
network but smaller than the area
covered by a wide area network. The
term is applied to the interconnection
of networks in a city into a single
A Wide Area Network (WAN) is a
network that covers a broad area
using private or public network
transports. It connects local and
metropolitan area networks together.
The networks that make up a wide
area network, may be located
throughout a country or even around
Campus Area Networks are usually a
connection of many small LAN networks
which are often used on university
campuses and office buildings. Campus
Area Networks allow for easy file sharing
between different departments as all the
files are usually shared on the server
machines of each LAN network. This type
of network offers a lot of simplicity in the
transfer and downloading of files.
The network stores most of the
information on a central computer.
Storing information on one or two central
computers makes it easy for people to
work with and manage their files.
A network also allows people to access
their information from other computers
on the network.
The network has dedicated
computers that allow people to
connect to the company’s network
using a modem.
Once users are connected to the
network, they can work with any data
available on the network. Network
makes it easy for people to access
office information from home.
Computers connected to a network can
share equipments and devices including
printers and hard drives. These
equipments and devices are called
resources. The ability to share
resources reduces the cost of buying
computer hardware. For example,
instead of buying a printer for each
person on network, everyone on the
network can share one central printer.
You can use a network to
exchange information with
other people. Information can
be in any form of data, such as
documents created in a word
processing program, information
provided by a school database.
Using computers connected to a
network people exchange information
with one another. When employees
can easily access and exchange
information, they can work more
efficiently. For example, network
allows people in different offices to
work on a project together.
Most of the people who are connected
to a network, use a central computer to
work with different programs such as
word processors and spreadsheets.
Network makes installing programs
simple because only one copy of a
program needs to be installed on a
Network hardware includes the physical
components that are used to create a
network. All computer networks require at
least the following network hardware :-
A connector is a device that joins two
computers on network together.
Cables are the wires that
connect computers and
resources on a network.
Different kinds of cables
can be used, depending on
the type and size of the
A Network Interface Card (NIC) is a
device that joins a cable to a computer.
Most NICs are installed inside a
computer. The edge of the card can be
seen at the back of the computer. A
NIC has a port where the network
cable plugs in.
The most important job of a network
is to link computers together. When
computers are linked, the people
using the computer can work more
Data security concerns
A poorly secured network puts critical data at
risk. For example: When files are shared among
user then there is always a threat that
unauthorized users can alter of use the sensitive
To setup a network requires investment in
hardware and software. For small network of
few PCs this cost is smaller but for large
network this cost can run in thousands or more
Threat from viruses
The effect of viruses on a network is more as
compared with stand- alone systems because
viruses can easily spread one computer to
another over networks
A protocol is a set of rules that
governs the communications
between computers on a network.
These rules include guidelines that
regulate the following
characteristics of a network:
access method, allowed physical
topologies, types of cabling, and
speed of data transfer.
Internet Protocol (IP) is the protocol by which data
is sent from one computer to another on the Internet.
Each computer on the Internet has at least one IP
address that uniquely identifies it from all other
computers on the Internet. When you send or receive
data, the message gets divided in the form of
packets. These packets contain both the sender’s
Internet address and the receiver’s address. The
Internet Protocol just delivers them.
Topologies define the arrangement of
computers taking part in the network. These
should be properly planned and implemented
because a good selection of topology can result
in proper and adequate use of resources while
a mismanaged arrangement of computers can
lead to inefficient use of resources, loss of
data and time.
In a bus topology, all of the nodes are
connected to a central cable called bus. In
bus topology, a bus is a single continuous
Transmission from any node travels the
length of the bus in both directions and
can be received by all other nodes. The bus
has terminators at either ends which
absorbs the signal, removing it from the
It is quite easy to set up.
Failure of one node does not affect the rest of
It offers limited flexibility for change.
A signal on the bus must be strong enough to
reach the receiver.
In a ring topology, the nodes are
connected in a closed loop so that
each device is connected to two
others, one on either side.
The computers in a ring topology are
connected in the shape of a closed
Data travels only in one direction in a
ring. Each computer passes the data
to the next one on the line
The ring works well where there is no
central-site computer system.
It is more reliable than a star network.
The ring network requires more complicated
Failure of the one node results in the failure
of the entire network.
Star topology id the most common
type of network topology that is used
in homes and offices. In Star
Topology, there is a central connection
point called the hub. Each computer on
a star network communicates with a
central hub that resends the message
either to all the computers in a
broadcast star network or only to the
destination computer in a switched
Star topology has minimal line cost.
If any of the local computer fails, the
remaining portion of the network is unaffected.
The system crucially depends on the central
switch. If it fails, the entire network goes
The cabling cot is more as each node is
connected individually to the hub.