CBSE CLASS XII COMPUTER SCIENCE,

1. COMMUNICATION AND NETWORK
CONCEPTS
MOHNISH SAHU
PGT (C.S.)

2. INTRODUCTION
• NETWORK:-Collection of large number of
separate but interconnected computers.
• GOAL:- a)Resouce Sharing.
b)Reliability.
c)Cost Factor.
d)Communication Medium.

3. EVOLUTION OF NETWORKING
• ARPANET:-Advance Research Project Agency
NETwork is planted in 1969 to connect
computers at U.S. defense & different
universities.
• NSFnet:-National Science Foundation in 1980
was started to make a high capacity network for
academic & engineering research.
• INTERNET:-In 1990 the internetworking of
ARPANET,NSFnet & other private networks
resulted into Internet.

4. • INTERNET:-It is inter connection of large and small
networks around the globe.
• Protocol:-It is common set of rules communication
over internet.
• TCP:-Transmission Control Protocol is responsible
for dividing & reassembling the file into packets on
the source & destination computer.
• IP:-It is responsible for handling the address of
destination computer so that each packet is routed
to its proper destination.
• Interspace:-It is client/server software that allows
users to communicate online real time.e.g
FACEBOOK,TWITTER,WHATSAPP etc.

5. • NODES or WORKSTATIONS:-It refers to the
computers that are attached to a network.
• SERVER:-A computer that facilitates the sharing of
data, software, and hardware resources on
network is termed as a server.
a)Dedicated Server b) Non-Dedicated Server
NIU (NETWORK INTERFACE UNIT):-It is a device that
is attached to each of the workstations

6. SWITCHING TECHNIQUES
• CIRCUIT:-In this techniques physical connection
between two computers is established then data
are transmitted.
• MESSAGE:-In this source computer sends data to
the switching office first, which stores the data in its
buffer. It then look for free link to another office
and then send. It is also known as store ad forward.
• PACKET:-It transfer a fixed size of packet which can
be transmitted across the network is specified. All
the packet are stored in main memory.

7. TRANSMISSION MEDIA
Twisted pair:-The wires come in pairs, are twisted
around each other. Twisting reduce cross talk.
Advantages:-It is physically flexible. It can be easily
connected, easy to install and maintain.
Disadvantages:-Because of high attenuation, it is
incapable carrying a signal over long distances
without the use of repeaters.
Its low bandwidth capabilities make it unsuitable for
broadband applications. Min speed of 1Mbps max of
10 Mbps.

8. Coaxial Cable
• This type of cable consists of a solid wire core
surrounded by one or more wire shields, each
separated by some kind of plastic insulator. Inner
core carries the signal, and the shield provides the
ground.
• Advantage:-It can be used for broadband
transmission. Offer higher bandwidth upto 400
Mbps.
• Disadvantage:-Not compatible with twisted pair

9. Optical Fibers
• It consist of thin strands of glass material which re
constructed that they carry light from a source at
one end to other. The bandwidth of the medium is
potentially very high.
• It consist of three pieces:-1)Core 2)Cladding
3)Protective coating.
• Advantages:-It is immune to electrical and magnetic
interference. It can be used for broadband
transmission where several channels are handled in
parallel.

10. MICRO WAVE
• Microwave signals are used to transmit data
without the use of cables. It consists of a
transmitter, receiver and atmosphere. In this
parabolic antennas are mounted on towers to send
a bead to other antennas tens of kilometers away.
The higher the tower, greater the range. It transmit
in line of sight transmission.
• It have ability to communicate over oceans.
• Signals may split up and propagate by slightly
different paths to the receiving antenna. It is
susceptible to weather effects like rains, thunder
storms etc.

11. RADIO WAVE
• It use continuous sine waves, each different radio
signal uses a different sine waves frequency and
that is how they are all separated. The receiver
receives the radio waves and decodes the message
from the sine wave it receives. Both the transmitter
and receiver use antennas to radiate and capture
the radio signal.
• Advantages:-It offers mobility.
• Disadvantages:-Radio wave communication is an
insecure, susceptible to weather and storms etc.

12. Satellite
• Satellite communication is special case of
microwave relay systems. The earth station consists
of a satellite dish that functions as an antenna and
communication equipment to transmit and receive
data from satellites passing overhead.
• Advantages:-Area coverage through this
transmission is quite large.
• Disadvantages:-Technical limitations preventing the
deployment of large, high gain antennas on the
satellite platform.

13. Infrared & Laser
• It transmits data through the air and can propagate
throughout a room but will not penetrate walls.
• Laser requires direct line of sight. It is unidirectional
but has much higher speed than microwaves. The
laser transmission is point to point transmission,
typically between buildings.

14. Communication terminology
• Channel-It is a medium to carry information.
• Baud-It is unit of measure for information carrying
capacity.
• BPS-It refers to the speed at which data transfer is
measured.
• Bandwidth-It refers to the difference between the
highest and lowest frequencies of transmission
channel. High bandwidth channels are called
broadband. Lower is called narrowband.

15. TYPES OF NETWORKS
• LAN-Small networks that are confined to an office,
building or a factory. The key purpose of a LAN is to
serve its users in resource sharing.
• MAN-It is spread over a city. Cable tv networks that
are spread over a city.
• WAN-It is spread across countries. The largest WAN
in existence is the Internet.

16. TOPOLOGIES
• The pattern of interconnection of nodes in a
network is called topologies.
It is set according to:-
Cost
Flexibility
Reliability
Topologies are:-
1) STAR 2)BUS 3)RING 4)MESH 5)TREE 6)GRAPH

17. NETWORK DEVICES
• MODEM:-It is device that allows us to connect and
communicate with other computers via telephone
lines.
• RJ-45:-Registered Jack-45 is an eight-wire connector,
which is commonly used to connect computers.
• Ethernet card:-It is LAN architecture developed by
xerox corporation. It used bus topologies and can
transfer data upto rates of 10Mbps.
• Hub:-It is used to connect several computers
together

18. • SWITCH:-A switch is a device that is used to
segment networks into different subnetworks called
subnets. It is responsible for filtering.
• Repeater:-It is device that amplifies and restores
signals for long distance transmission.
• Bridge:-This device lets you link two networks
together.it is smart enough to know which
computers are on which side of the bridge, so they
only allow those messages that need to get to the
other side to cross the bridge.
• Router:-It handles different protocols, It uses logical
address.

19. • Gateway:-It is used to connects dissimilar networks.
It expands the functionality of routers by
performing data translation and protocol
conversion. It connect local and external networks
with completely different structures.

20. LAN DESIGN
• 80-20 RULES
• LAN HARDWARES
• FLOODING
• SPANNING TREE
• MEDIA

21. COMMUNICATION PROTOCOLS
• A protocol means the rules that are applicable
for a network. It defines standardized formats
for data packets, techniques for detecting and
correcting errors and so on.

22. • HTTP:-Hyper Text Transfer Protocol is set of rules for
transferring hypertext on www.
• FTP:-File Transfer Protocol is a standard for
exchange of files across internet.
• TCP/IP:-Transmission Control Protocol/Internet
Protocol is a layered set of protocols. It is base
communication protocol, IP uses numeric IP
addresses to join network segments and TCP
provides reliable delivery of messages between
networked computers.
• SLIP:-Serial Line Internet Protocol is for delivering IP
packets over dial-up lines.
• PPP:-Point to Point Protocol is for transmitting IP
packets over serial lines.

23. WIRELESS/MOBILE COMPUTING
• GSM:-Global System of Mobile
• SIM:-Subscriber Identification Module
• CDMA:-Code Division Multiple Access
• WLL:-Wireless in Local Loop
• 3G and EDGE:-Third Generation and Enhanced Data
rates for Global Evolution.
• SMS:-Short Message Service
• Email:-Electronic Mail
• Voice-Mail
• Chat
• Video Conferencing

24. INTERNETWORKING TERMS AND
CONCEPTS
• WWW
• TELNET
• WEB BROWSER
• WEB SERVER
• WEBSITES,WEB ADDRESS AND WEB PAGES
• URL AND DOMAIN NAMES
• WEB HOSTING
• WEB 2.0
• HTML
• XML
• DHTML
• WEB SCRIPTING

25. OPEN SOURCE BASED SOFTWARES
• FREE SOFTWARE
• OPEN SOURCE SOFTWARE
• GNU
• FSF
• OSI
• W3C
• PROPRIETORY SOFTWARE
• FREEWARE
• SHAREWARE

26. NETWORD SECURITY
• AUTHORIZATION
• AUTHENTICATION
• ENCRYPTED SMART CARDS
• BIOMETRIC SYSTEMS
• FIREWALL
• COOKIES
• HACKERS AND CRACKERS
• CYBER LAW
• CYBER CRIMES
• IPR(Intellectual Property)

27. VIRUSES
• Computer virus is a malicious program that requires
a host and is designed to make a system sick. They
are:-
• File infectors, Boot sectors, Macro viruses.
• Trojan Horses
• Worms
• Virus Prevention

28. THANK YOU