An interconnected collection of autonomous computers is called a computer network. Networks allow computers to share resources like hardware, software, databases, and communicate with each other. The first network was ARPANET in 1969 which connected universities and defense organizations in the US. Later networks like NSFnet and the Internet improved capacity and connectivity. A network uses nodes, servers, network interface units, and types of networks can be LANs, MANs, or WANs depending on geographical reach. Networking evolved to improve sharing, reliability, and reduce costs.

2. An interconnected collection of
autonomous computers is called
Computer Network. It means two
computers are said to be interconnected
if they are capable of exchanging the
information.

3. Need for Networking
Sharing of Hardware , Software
Resources and the database.
Reliability
To enable different computers to
communicate
To reduce cost of transfer of
data

4. Disadvantages of Network
Protection from Viruses
Central dependency on
software and files
System becomes more
complex and sophisticated

5. Evolution of Networking
1. ARPANET : This was the first
network which was planted in 1969. It
means Advanced Research Projects
Agency NETwork. Its aim was to connect
different computers of different
universities and U.S. defense to
exchange messages and data. This
network was expanded very soon by the
students , scientists , engineers etc. for
their work. The users were able to share
their interests.

6. 2. NSFnet : This was the
network which was started
in 1980 by National Science
Foundation. It was a high
capacity network than
ARPANET which was more
capable than ARPANET . It
was used to do research
work on the network and
some kind of private
business.

7. 3. INTERNET : It is a worldwide
network of Computers network. It was
developed in 1990 by different
companies to allow the users to connect
one network to the other to
communicate. It is a super network. It
uses a set of protocols called TCP/IP.
4. INTERSPACE : It refers to a vision
of what the internet will become in
future. It is a client/server software
program that allows multiple users to
communicate online with real time audio ,
video and text in dynamic 3D
environment.

8. Basic Terminology
Nodes or Server
Workstations A Computer
The different which facilitates
terminals or the sharing of
computers which data , software
are attached to a and hardware
network and are resources like
able to share the Printer , Modem
resources are etc. on the
called nodes or network is called
workstations. a Server.

9. Network Interface Unit
It is an interpreter which is
attached to server and all the
workstations to maintain the
connection between them. It is
also called Terminal Access Point
(TAP).

10. TYPES OF NETWORK
 LOCAL AREA NETWORK (LAN )
 METROPOLITAN AREA NETWORK
(MAN)
 WIDE AREA NETWORK (WAN )

11. LOCAL AREA NETWORK ( LAN )
It is a small computer network that are
confined to a localized area like an office , a
building etc. Only a definite number of
computers can be connected in this network to
share the resources . Its range can be up to a
few Kilometers.Its main features are
• Total diameter not more than 5 km
• Data communication at the rate of 100 Mbps
• Owned by single organization
• Low Error Rates
• Provides user access to several resources like
printers, Modem etc.

12. Metropolitan Area Network ( MAN )
This network is larger in size than
LAN and it spreads over a city. It
means a very large number of
computers can be connected in this
in a city or from one city to the
other.
Example : The Cable TV networks
which are spread over a city.

13. WIDE AREA NETWORK ( WAN )
This network spreads across the countries and
it is a group of computers that are separated
by very large distances. The computers of even
one continent can be connected to the other
continent.
Its main features are :
• Spans large geographical area, often a country
or continent
• Helps in E-Mailing
• Data can be received from or sent to remote
areas with the help of satellite with less cost

14. LAN WAN .
• Diameter of not more • Span entire countries
than a few kms.
• Total data rate of at • Data rate less than 1
least several Mbps Mbps
• Complete ownership be • Owned by multiple
a single organization organizations
• Very low error rates • Comparatively higher
error rates.

15. MODEM
( MOdulation/DEModulation )
The device which is used to connect and
communicate with computers with the help of
telephonic lines . It converts digital data into
analog form and vice versa.
Working :A modem is a computer peripheral that
allows to connect and communicate with the other
computers through telephone lines. In MoDem ,
Mo stands Modulation and Dem stands for
Demodulation . Modulation means to convert
digital signals to analog signals and Demodulation
is reverse of that. The data is transferred form
source to the destination through telephone
wires and they can only understand analog signals
so there is need to convert digital signals to
analog . And computer can only understand digital
signals . This conversion is done by MoDem.

16. WORKING OF MODEM
Analog signals Analog signals
MODEM MODEM
Digital Signals
Digital Signals
Source Computer
Destination (Remote Computer)

17. Types of MoDem
( 1 ) Internal MoDem : The
MoDem which is connected inside
the computer is called Internal
MoDem.
( 2 ) External MoDem : The
MoDem which is connected
externally to a computer is called
External MoDem.

18. Network Topologies
The way of interconnection of the nodes in a network is called the
Topology.
The different factors on which selection of a topology depends are :
( a ) Cost : A Network of computers can reduce the cost to a large
extent.
( b ) Reliability : It is more reliable to work in a Computer Network .
Hence if a node fails to work the data can be achieved from some
other nodes.
( c ) Flexibility : The topology should allow for easy reconfiguration
of the network.
The different topologies are :

19. Star Topology
It is consisted of a central node to which all other nodes are
connected by a single path. Its different advantages and
disadvantages are :
Advantages :
( 1 ) One Device per connection : In this topology failure of a
single connection typically involves disconnecting one node
from an otherwise fully functional network.
( 2 ) Simple Access protocols : In this access protocols are very
simple.
Disadvantages :
( 1 ) Long Cable Length : This topology uses a very long cable as
each node id directly connected to the centre.
( 2 ) Central Dependency : If the central node fails , the entire
network stops working.

20. WS1 WS3
Server
WS2 WS4

21. Bus or Linear Topology
It is consisted of a single length of the transmission medium
onto which the various nodes are attached . Its different
advantages and disadvantages are :
Advantages :
( 1 ) Short Cable Length : There is a single common data path
connecting all nodes , so this topology uses a very short cable .
( 2 ) Easy to Expand : In this topology additional nodes can be
connected at any point along its length.
Disadvantages :
( 1 ) Fault detection : In this topology it is very difficult to detect
a faulty node .
( 2 ) Nodes must be intelligent : All the nodes working in this
topology must be intelligent.

22. Server WS1 WS2
WS3 Printer WS4

23. Ring or Circular Topology
In this each node is connected to two and only two
neighbouring nodes. Data is transmitted from one to another
node and is transmitted onwards to another. In this topology
the data travels only in one direction.
Its different advantages and disadvantages are :
Advantages :
( 1 ) Short Cable Length : There is very short cable which is
used to develop a Computer Network
( 2 ) Suitable for optical fibers : In this topology for very fast
speed transmission optical fibers can be used.
Disadvantages :
( 1 ) Node Failure causes network failure : In this topology if one
node fails to pass the data through itself , the entire network
fails.
( 2 ) Network reconfiguration is difficult : It is not possible to
shut down a small section of the ring .

24. C1 C2 C3
C6 C5 C4

25. Tree Topology
A variation of bus topology is the tree topology. The shape of
the network is just like an inverted tree with the central root
branching and sub-branching to the extremities of the
network.
Advantages :
( 1 ) Easy to Expand : It is very easy expand this topology . It
means nodes can be connected easily.
( 2 ) Fault isolation is easy : It is easy to find the faulty node in
this topology.
Disadvantages :
( 1 ) Dependency on root computer : The total dependence is on the root
computer . If it fails to work , the entire network will stop working.
( 2 ) Complex Access Protocols : The protocols designed for this topology are
generally very complex.

26. Server
WS1 WS3
WS2 WS4 WS5 WS6

27. Backbone Network
• A backbone is a central interconnecting
structure which is used to connect two or
more networks e.g. LANs together to form
a WAN
e.g. FDDI – Fiber Distributed Data Interface

28. REPEATER
A repeater is a device that amplifies
a signal being transmitted on a
network for long distances.
It is used in long network lines, which
exceed the maximum rated distance
for a single run.

29. Bridge
A bridge is used to connect
two LANs which are physically
separated but logically same i.
e. following the same topology.

30. Router
It is a device that links two
networks which can handle
different protocols. The routers
use physical addresses. It
improves the performance of the
network.

31. Gateway
A gateway is a device that connects
dissimilar networks. It gives an intelligent
connection between a local network and
an external network with different
structures .
It is a special device which allows
different networks to talk to internet that
uses TCP/IP.

32. The 80-20 Rule
80 percent of the traffic on a given network segment is
local and 20 percent of the network traffic should need
to move across a backbone networks (sub-network.)
How to Improve Performance of a LAN ?
1.Moving resources ( files etc. ) from one server to
another server to contain traffic locally within a
workgroup.
2.Moving users logically within a workgroup.
3.Adding servers to access them locally without
crossing the backbone networks.

33. Network Security
The different Prevention methods are used while working in Network
environment for security.
( 1 ) Authorization : It determines whether the ISP has granted the
access to the web service or not. It is done by asking the user legal
login-Id.
( 2 ) Authentication : It is a way to check the password protection of
an authorised user.
( 3 ) Firewall : It is a system designed to prevent the unauthorised
users to access to or from a private network. In this we can also
encrypt the data.
( 4 ) Encrypted Smart cards : It is smart hand-held card that can
generate a token that a computer can recognise. Every time a new
token is generated.
( 5 ) Biometric System : It includes some unique aspect of a person’s
body such as finger prints etc. To establish his identity.

34. THANK YOU