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CHAPTER - 4
COMPUTER NETWORK
Dr. BALAMURUGAN MUTHURAMAN
2015-2016
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INTRODUCTION OF NETWORK
A Computer Network may be defined as an
interconnection
computers.
of
Two
two
or
computers
more
are
autonomous
said
to
be
interconnected if they can share or exchange
information.
In a computer network each computer
operates independently on separate tasks. Each
computer is a complete unit itself with its own CPU,
memory and other peripheral devices.
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LAN, MAN & WAN
Network in small geographical Area (Room,
Building or a Campus) is called LAN (Local
Area Network)
Network in a City is call MAN (Metropolitan
Area Network)
Network spread geographically (Country or
across Globe) is called WAN (Wide Area
Network)
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TYPICALLY NETWORKS COMPONENTS
In a client/server network arrangement, network
services are located in a dedicated computer
whose only function is to respond to the requests
of clients.
The server contains the file, print, application,
security, and other services in a central computer
that is continuously available to respond to client
requests.
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ADVANTAGES OF CLIENT-SERVER NETWORK
 Very secure
 Better performance
 Centralized backup
 Very reliable
DISADVANTAGES OF CLIENT-SERVER NETWORK
Requires professional administration
More hardware-intensive
More software intensive
Expensive dedicated software
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ADVANTAGES OF NETWORKS
Data Sharing :
Data sharing is one of the biggest advantages
provided by the computer networks. All the data and
resources like documents, files, accounts information,
reports, multi media etc. can be shared with the help of
computer networks. Hardware sharing and application
sharing is also allowed in many organizations such as
banks and small firms.
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Instant and Multiple Accesses :
Computer Networks are multiply processed, many
of users can access the same information at the same time.
Immediate commands such as printing commands can be
made with the help of computer networks.
High Reliability :
High reliability is achieved by replicating
important data or files on two or three machines. This
cause that if one of machines goes down, the user can still
access the data through some other machines on the
network.
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Video Conferencing :
Before the arrival of the computer networks
there was no concept for the video conferencing.
LAN and WAN have made it possible for the
organizations and business sectors to call the live
video conferencing for important discussions and
meeting.
Internet Service :
Computer networks provide internet service
over the entire network. Every single computer
attached to the network can experience the high
speed internet, fast processing and work load
distribution.
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COMPUTER NETWORKING DEVICES
Computer networking devices are units
the mediate data in a computer networks.
These are also called networks equipment,
Intermediate System (IS) or Inter Working
Unit (IWU). Units which are the last receiver
or generate data are called hosts or data
terminal equipment. Computer networking
devices also known as communication
devices and they constitute a data
communication network.
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BASIC COMPUTER NETWORKING DEVICES
1.
2.
3.
4.
5.
Router
Network Switch
Modem
Firewall
Proxy Server
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ROUTER
A router is communication device that is used to connect
two logically and physically different networks, two LANs,
two WANs, and a LAN with WAN. The main function of the
router is to sorting and the distribution of the data packets to
their destination based on their IP addresses. Routers
provide the connectivity between the enterprise business,
ISPs and in the internet infrastructure, router is a main
device.
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NETWORK SWITCH
A network switch or switching hub is a computer
networking devices that connects network segments.
The term commonly refers to a multi-port network
bridge that processes and routes data at the data link
layer of the OSI (Open System Interconnection)
model.
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MODEM
A modem (modulator-demodulator) is a device that
modulates an analog carrier signal to encode digital
information, and also demodulates such a carrier signal
to decode the transmitted information. The goal is to
produce a signal that can be transmitted easily and
decoded to reproduce the original digital data. Modems
can be used over any means of transmitting analog
signals, From light emitting diodes to radio.
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FIREWALL
The term firewall originally referred to a wall intended
to confine a fire or potential fire within a building. A
firewall is a device or set of devices designed to permit or
deny network transmissions based upon a set of rules and is
frequently used to protect networks from unauthorized
access while permitting legitimate communications to pass.
Many personal computer operating systems include
software-based firewalls to protect against threats from the
public Internet.
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PROXY SERVER
In computer networks, a proxy server is a server (a
computer system or an application) that acts as an
intermediary
for
requests
from
clients
seeking
resources from other servers. A client connects to the
proxy server, requesting some service, such as a file,
connection, web page, or other resource, available
from a different server. The proxy server evaluates the
request according to its filtering rules.
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