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What is Internet
Internet is an Inter-connection
among several computers of different
types belonging to various networks
all over the globe.
It is often described as “network of
networks” because all the smaller
networks of organisations are linked
together into one giant network.
Internet is a world wide organisation
of computer network. When you are
at Internet, you become a part of
that group of millions of people who
use the computer for exchanging
their idea and information.
Internet is also referred as web.
Internet is Information Super
Internet is called the Highway of
information. When you travel on a
highway, you come across different
people, incidents and groups,
likewise Internet is also a treasure or
source of information.
History of Internet
1969 is the birth year of Internet
ARPAnet (Advanced Research
Projects Agency Network) was the
first network started by Department
of Defence (DOD) of United States of
It began in with one computer at
California and three at Utah.
Later to share the software and
hardware resources, the military
allowed Universities to join the
network and gradually by the year
1979, it started being known as
The OSI Model
->Open system Interconnection (OSI)
was developed by ISO (International
->OSI that follows a set of protocols
that allows any two different systems
to communicate with each other
regardless of their underlying
The OSI model is a layered framework
for the designing of network systems
that allows communication between all
types of computer systems.
It consists of seven separate but related
layers, each of which defines a part of
the process of moving information
across a network.
What are the seven layers ?
Layer 7 Application
Layer 6 Presentation
Layer 5 Session
Layer 4 Transport
Layer 3 Network
Layer 2 Data Link
Layer 1 Physical
In the sense of purpose and responsibility,
each layer is separate and independent
Each has its own function, but also provides
a service to those layers above and below
The model should be considered an aid to
understanding the nature of communication
on the network – and useful in sorting out
troubles that might occur on a network
By providing, it allows both software
engineers and hardware manufacturers
ensure their products work together.
The layers at work
NODE A NODE B
Sending Device Receiving Devic e
Layer 7 Supports the communication between Layer 7
Application Layer applications over the network Application Layer
Layer 6 Presents data to the receiver Layer 6
Presentation Layer in a form it recognises Presentation Layer
Layer 5 Establishes a connection and Layer 5
Session Layer terminates it when no longer required Session Layer
Layer 4 Acknowledges the flow of data Layer 4
Transport Layer including re-transmission where required Transport Layer
Layer 3 Adds the appropriate network Layer 3
Network Layer addresses to packets Network Layer
Layer 2 Adds the MAC addresses to packets Layer 2
Data Link Layer Data Link Layer
Layer 1 Transmits the data on the medium Layer 1
Physical Layer Physical Layer
How does data flow 1 ?
When data is sent from the application on
the source computer the following
Data in the form of a packet moves down
through the layers
When it reaches the Physical Layer it is
ready to be sent along the cable
At the Physical Layer the bits may be
analogue or digital, in the form of
electrical, light or radio waves
How does data flow ? (2)
The data is transmitted to the
It travels up through the layers of the
OSI model, reaching the user.
As data moves down through the layers
it is encapsulated – ie additional
information is added.
The data in the packet does not change
How does internet
Customer Web server
Customer Web server
Internet uses a protocol called TCP\IP
Each system is assigned with an IP
Each server has a name called Domain
We refer to the server with Domain
A DNS (Domain Naming Service)
Server resolves the IP address with
What do we need to connect
Account with ISP
A Computer is the basic requirement
to access Internet.
Modem is the modulator and
demodulator which converts analog
to digital signal and vice-versa.
It can be internal or external.
Connecting Media can be
Ordinary Telephone line
ISP (Internet Service Provider)
ISPs are those who connect the
individual users to the Internet. They
setup a server which are connected
to the Internet through dedicated
lines round the clock.
Some common ISPs
It is a software and necessary tool for
exploring the web. It helps to move
from one web site to another web
Some popular web browsers are
How to access Internet
The user has to register himself to
any one of the ISPs by paying the
Different ISPs have different tariffs
and different ways of registrations.
Why do we use Internet
To get in touch with near and dears
Electronic mail (E-mail)
To access to lots of databases,
libraries and news groups around the
world for gaining information on any
topics of your interest.
To access and share information on
all topics ranging from agriculture to
To stay up-to-date with news, sports,
weather & world wide current affairs.
To listen sounds, music and watch
To enjoy a number of interactive
multimedia games and gain knowledge
through several educational tools.
To visit an electronic zoo or a
To get latest information about
movies & your favorite stars.
You can also publish information
about yourself, your family, your
organisation, hobbies and
To learn foreign language & to
make friends globally.
And there is no limit to it.
(The Internet as a post man)
Electronic mail or e-mail is the
process of sending and receiving of
messages by one user to one or
more other computer users over a
computer network in a digital form.
It is very similar to our traditional
mail system with post boxes, post
offices, envelopes and addresses.
The difference is that instead of
sending it manually, it is sent
By using email, you will be able to electronically
Send messages or memos
Receive and read messages
Reply to messages
Send the same message to a list of
people with one stroke
Attach a text file such as a report to
your email message
Save mail to a file and print the
How does it work
The process of e-mail is also very similar
to traditional mail.
An e-mail is made up of two parts, the
address and the message. Depending on
the address, the message is sent to the
receiver of the letter. But the message is
not delivered. Instead, it is stored in the
mail server. When the receiver logs in and
checks In-box, he gets his message.
To become an e-mail user, you need to
setup your own email-account.
There are number of sites with whom
you can register your e-mail account.
They also provide additional services
such as receiving regular news from
various sites of your choice.
Some of them are free whereas for
others, you have to pay
Some of the sites to provide free e-
mail services are
Some of the sites to provide paid e-
mail service are
Setting of e-mail account
Click at New User? Sign up
In order to receive or send email,
you need to have an email address
and you need to know the address of
the person to whom you wish to
send a message.
Addresses are made up in a
standard way using the following
User identification e.g. egtoget,
your name or a name you wish to
choose. It is usual to have part of
your own name to make it easily
The @ or at symbol to separate
user name and domain name
The domain name of the computer
receiving your mail e.g. yahoo for
The type of organisation e.g. co
for commercial organisation or gov
And finally in to locate the address
The final address will look like this:
How to send e-mail
Email messages are generally sent
from and received by mail servers-
computers that are dedicated for
processing & directing e-mail. Once a
server has received a message, it
directs it to the specific computer to
which the e-mail is addressed
Advantages of E-mail
Speed: It is a fast means of
Multimedia: Along with text, sound,
images, video and computer
software can be sent.
Cost: It is lot cheaper than postal
Disadvantages of E-mail
You can’t send anything without an
You can’t send anything physical like
money, book or floppy.
Chatting is one of the most popular
activities on the Internet and
involves people of all ages coming
together in areas where they can join
in on in a variety of topics that they
are interested in with people all
around the world.
One of the most popular forms of
online chatting is Web-based
chats. Web-based chats are,
essentially, specially designed Web
sites that allow visitors to
exchange messages with one
another in real-time.
When you visit a Web-based chat site for
the first time, you will be asked to
choose a name (or 'alias') and a
password. You can choose any name
you like and that is the name by which
you will be known to all other
participants on that particular site.
The password is used to confirm your
identity each time you visit the site
(only you should know the password
that you selected when you signed
The best feature of Web-based chats is that
you access them with your Web browser–
no special software is required.
When you’ll click on any chat
category, the next screen will display
the chat rooms i.e. the chat areas.
Chat rooms can have specific or
broad themes. One chat room might
be dedicated to teenagers. Another
might be dedicated to sports buffs or
cartoon fanatics. The chat rooms
themselves will be clearly labeled,
and you will be provided with
instructions on how to access
particular chat rooms on the site
Chat rooms generally include a text box
for typing your messages, a large window
area used to display the messages typed
by chat participants and a smaller window
with a list of all the participants in the chat
To help you keep track of who is saying
what, each message is preceded by the
name of the person that sent it. Also, on
some chat systems, messages are
displayed in different colours.
As a general rule, your messages are
broadcast to the screens of all the other
chat participants as soon as you elect to
send it (usually by clicking the 'send'
icon or hitting the Return/Enter key).
Some of the more advanced
Web-based chats allow you to
hold private conversations, so
that your messages only appear
on the screens of those
participants that you wish to talk
The Web isn't the only place where you
can meet people online.
Instant messaging is becoming an
increasingly popular means of
communicating one-to-one with friends.
Web-based chats are generally 'public'
forums, so everyone can read your
Instant messaging largely overcomes
these problems, but to take advantage of
instant messaging features, users must
first download and install special
Each time you connect to the Internet and
run your instant messaging software, a list
of all your friends currently online is
displayed. You can then compose and
send messages to your friends. The
messages will be displayed immediately on
their computer screens. Alternatively, their
instant messaging software will 'beep' to
alert them of an incoming message.
Instant messaging software
Some of the instant messaging
What is video conferencing
If you would like to be a receiver – that is
only ‘see and hear the conversation’, you
will be able to do this any standard Mac
and if you have a Sound card and Video
card on any standard PC.
If you would also like to be a sender that
is-’transmit your voice and video’, you
will also need a digital camera and PC
users will need a microphone.
How to download files
Downloading refers to the actual
transferring of the document from the
internet to your own computer.
Setting up a separate download
directory to store your downloaded files
into it so that they don’t get mixed up
with any other programs/files on your
system, and so you always know where
you can find them should you have to
reinstall or find the files at a later date.
What is search Engine
Search engines exist to help you find
the relevant information you require.
With a search engine, you can sort
through vast amounts of online
information and pinpoint the material
Search engines work by matching
words you enter with the same
words found in various information
sites on the internet
Some of the famous search engines
Internet helps students to get
information from a to z in maths
through many free sites. Some of
Some sites providing free information
about sports are:
Some sites that provide free
information related to science are:
Some of the sites where you can gain
Various sites to get online news
We can view the clippings of any
movie on net through these sites: