2. Overview of Computer Network
A computer network is a collection of interconnected computers and
other devices to share data and other resources.
3. Advantages of Computer network
Resource Sharing
The primary use of a network is to
share among users applications,
programs, data. For example, sharing
database, audio and video files,
printers and scanners etc.
We can share data and applications to
devices connected to network
irrespective of their physical location.
4. Reliability of data
Reliability means backing up of
data, i.e., data can be copied and
stored on multiple computers.
In a network system, all
computers are connected to
each other, so the chances of
data getting lost are very less.
5. Central Storage of data
Files can be stored on a
central node that can be
shared and made available to
each and every user in an
organization.
With centralized processing,
data is stored and retrieved
from a single central location.
6. Types of Networks
A computer network may be small or big depending upon the numbers of
devices linked together.
Networks vary in size, they can be on a table, in a room, building, city,
country, across continents or around the world.
▪ PAN
▪ LAN
▪ MAN
▪ WAN
7. Personal Area Netw0rk (PAN)
The network that belongs to a
single person or user is known as
PAN.
It is a small network and may
include wireless keyboard and
mouse, Bluetooth-enabled
headphones, wireless printers
and TV remotes.
8. Local Area Network (LAN)
It is privately owned computer
network covering a small
geographical area, like a home,
office or a building such as
school.
Its range is of few kilometres
and its key purpose is to share
resources.
9. Metropolitan Area Network (MAN)
MAN’s network is larger and can
cover a city and its surrounding
areas.
A MAN is typically owned and
operated by a single entity such as
government body or a large
corporation.
A good example is the
interconnected offices of a
Multinational corporation.
10. Wide Area Network (WAN)
AWAN interconnects all the
computers across the world.
It is a telecommunication
network which spreads over a
large geographical area across
countries and continents.
The internet is the largest
WAN spanning the entire
planet.
11. Transmission Media
All the computers or communicating devices in the network must be
connected to each other to communicate and share data and other
resources.
To connect to each other, there must be some medium over which the data
can travel from one computer to another.
This is termed as Transmission media or Channel.
Wired Network
Wireless Network
12. Wired Network/Media
Twisted Pair Cable
It is the most common type of media
which consists of four insulated pairs
of wires twisted around each other.
It is available in ShieldedTwisted
Pair (STP) or UnshieldedTwisted
Pair (UTP).
13. Coaxial Cable
It consists of two solid insulated
conductors that share a common
axis.The inner conductor is a
straight wire surrounded by wired
mesh, each separated by some
kind of foil or insulator.
It is mostly used in CableTV
transmission.
14. Optical Fibre Cable
It consists of long, thin strands of
glass or glass-like material and
carries light. It transmits light
(photons) instead of electricity over
glass or plastic “fibres”.
Fibre optics are very good for high-
speed, high capacity data
transmission due to lack of
attenuation.
15. Wireless Media
RadioWaves
Radio Communication uses radio
frequencies in range of 3 KHz to 3 GHz.
These are used for communication over
distances ranging from a few metres to an
entire city.
Cordless phones, garage door openers,
etc., are examples of radio wave
transmission.
16. Microwaves
Microwave signal are used to transmit
data without the use of a cable. It is a
line of sight transmission as signal
travels in a straight line.
In big cities where land is very costly,
microwave antennas can be put on
top of highrise buildings and
communication can be started in a
short time.
17. InfraredWaves
Infrared wave network allows
devices to communicate within a
short range of approx. 5 metres
using wireless signals.
These signals do not cross through
solid objects, that's why you
cannot controlTV in another room
with the remote in your hand.
18. Bluetooth
Bluetooth is a wireless technology
used for creating personal networks
operational within a range of 10
metres. It uses 2.4 GHz unlicensed
band.
It can connect upto eight devices
simultaneously, but data transfer
rate is slow (upto 1 Mbps).
19. Network Devices
Network devices are also termed as communication devices and they
constitute a data communication network. Other than the transmission
media, many other devices are requires to form computer networks.
20. Network Interface Card (NIC)
It is a device that enables a computer to connect to a network and
communicate.
A computer communicates with other devices on a network with the help
of an NIC only. NIC works with MAC address.
21. Hub
A Hub is an electronic device that connects several nodes to form a
network and redirects the received information to all the connected
nodes in broadcast mode.
It connects multiple computers together to form a Local Area Network.
22. Switch
A Switch is an intelligent device that connects several nodes to form a
network and redirects the received information only to intended node(s).
A switch is an intelligent hub. It sends the information selectively only to
those computers for which it is intended.
23. Repeater
A Repeater is a device that is used to regenerate a signal which is on its
way through a communication channel. A repeater regenerates the
received signal and re-transmits it to its destination.
24. Router
Routers are networking devices that forward data packets from the
source machine to the destination machine using the shortest path.
Routers work on IP addresses for connecting two or more LANs orWANs
using routing table.
25. Cloud Computing
Cloud Computing is a
type of internet-based
computing that
provides shared
computer processing
resources and data to
computers and other
devices on demand.
It allows storing,
accessing data and
programs using the
internet.
26. Network Security
The digital world is changing
at a tremendous pace. New
communication technologies
open up new possibilities,
but by using them you also
expose yourself, and others
to various risks.
So, here are few methods to
protect yourself from these
threats.
27. Strong Password
By assigning strong
passwords to the users
of a system, it can be
ensured that only
authorized people
access a computer.This
helps in increasing the
computer as well as
network security.
A weak password can
be cracked in a few
attempts.
28. Firewall
A firewall is a
hardware device or a
software that is
installed to monitor
the data entering the
computer or leaving
it.
A firewall permits
only that data to
enter or leave a
computer for which
permissions have
been granted by the
computer.
