1. Sagarika Dissanayake

2. Chapter 01
The Internet and globally accessible
information
 Objectives
1. How the Internet is organized and governed?
2. How its structure global access to
communication?
3. Key concepts related to computer data and
networking.

3. What is the Internet?
•The Internet is a computer network made up
of thousands of computer networks connecting
millions of computer to each other across vast
spaces and international borders.

4. The structure of the Internet.
How big is the internet?
•An internet is in a constant state of change.
Computers connect to network and then
disconnect.
•Information is constantly updated, upgraded
and modified .Users find new uses for
computers every day and the Internet
accommodates them all.

5. What is network of networks?
•An internet is network of network.
•Networks can run in variety of organizations.
Such as research and educational institutes,
government and military entities and
telecommunication utilities.
•These networks constitute the basic wiring
“backbone” that connects one computer to
another.

6. Administrative control
•No one entity could possible control the Internet
because the way that it’s structured.
•All computers on the internet are essentially
equal to each other.
•Internet is like a series of interconnected spider
webs. There are a huge number if different paths
between any two points on the network.

7. Digital Information
•All information in the network passed from one
computer to another in digital format. Using “1”
and “0” s.
•All information is electrical impulses and break
up them in to small standard size packets.

8. Client server relationship
•Computers on the internet communicate with
one another using standardized language known
as Transmission Control Protocol /Internet
Protocol.(TCP/IP)
•It allows information to exchange in a reliable
and meaningful way.
•To facilitates this exchange use a client / Server
architecture.

9. The University of Information.
The Equality of computers
•The structure of the internet is characterized by a
basic equality of access.
•This is not to say that all computers on the
Internet are equally powerful or fast or large .

10. The Potential for cross-Cultural Communication
Point to Mass Communication
•This technology was used to transmit a single
message to a huge number of receivers.
•Examples
Radio broadcasting
Magazine publisher

11. Point to point Communication
•It allows masses of people to communicate with
masses of others in a way that very much feels like
a personal conversation.
•Examples
Telephone system

12. Modulation / Demodulation
•Computer is ready to transmit data to another
computer over a phone line, the modem converts
the digital data into these waves- it “ modulates”
them.
•These analog waves arrives at the receiving
computer its modem convert them back in to
digital data by “ demodulating” them.

13. Cyberspace
•Cyberspace is "the notional environment in
which communication over computer networks
occurs.
•Peoples and institutions in the developing world
take advantage of the Internet.

14. Chapter 02
History and structure of the Internet
 Objectives
1. How the internet began?
2. How is the structure of the Global network?

15. A history of Computer Networking?
Early Networks.
•In 1960 there was certainly no internet.
•Programs were stored on magnetic tapes or on
punched paper cards.
•Communication occurred between two
computer to another by physically carried that
tape.
•After few years computers were begin wired
together so that files passed from one to
another using digital signals.

16. The U.S Military and ARPAnet
•In the late 1960s, the Advanced Research
Projects Agency (ARPA) of the Department of
Defence began experimenting with linking
computers to each other.
•ARPA used “packet Switching” technology.
•There is four goals for ARPA’s network.
(Refer book- page no 10)

17. Human Communication via Computer Networks.
•This System allowed computers to share data and
researchers to communicate with each other by
exchanging electronic message known as “email”.
•TCP /IP standards introduced and it allows links
all sorts of computers across national boundaries.
•By the close of the 1970s links or “gateways”
developed between ARPAnet, NSFnet,BITnet and
USEnet in the U.S.

18. The Birth and growth of the “ Internet”.
•In the 1980s, this network of network which
became known collectively as the Internet.
•Size of the internet increasing day by day.
The Internet in Sri Lanka.

19. The Structure of the Global Network.
Network Backbone.
•The original backbone in the U.S was built in
1970s by the National Science Foundation to
facilitate NSFnet traffic between the large
research universities.
•This backbone consisted of a series of super
computers located in dozen geographically
dispersed sites.

20. Persistent vs. Intermittent Connections.
Persistent Connection Intermittent Connection
All computers on the so called
backbone and virtually connected to
network all the time.
Computer consider as server, receives
an IP address to use while connected
and then releases that back to server
when it disconnects.
Have permanent IP address. Have temporary IP address.
More expensive to maintain. Less Expensive.
E.g: Educational and commercial
information distributers.
Eg: Email-servers.

21. Names and Addresses
•Every computer on the internet has an address
that has two forms.
1.Domain name –Text form
openuniversity.lk
2.IP Address-Numeric form
192.168.168.1

22. Security, Password, and Firewalls
•Each computer on the Internet is responsible for
its own security.
•Intermittent connection- Given password that
secure the file space allotted you.
•Persistent Connection- You run a server on a
computer you responsible to safeguard your
computer from unwanted observations.
•Good password always
1.Keep it secret
2.Change it frequently
3.Make it hard to guess

23. •Examples of good password
2B0ro2B
S1mplE*3443
•Many host computers use a combination of
software and hardware that protect their files
from unauthorized use known as a firewall.
•A firewall is a gateway through which all Internet
traffic moves.

24. Chapter 03
Using the internet: E-Mail, Discussion
Groups and Newsgroups.
 Objectives
1. Electronic mails
2. How works Discussion groups?
3. Use of Usenet Newsgroups.

25. E-Mail at its simplest.
Electronic Postal System
•E-mail stands in Electronic mails.
•Using emails you can send mails to any
receiver very fast and sending the same
message to a hundred peoples within seconds.

26. Asynchronous Communication
•It means messages need not be time specific.
•Just like regular mail, you send an e-mail
message whenever he or she is connected to
the Internet at the time or not.
•Even their server is temporally off the
network, your mail message will likely get
through since your server will the message
several times before returning “ return to
sender” message to you.

27. E-Mail Drawbacks.
•The recipient needs access to the Internet to
receive email.
•Viruses are easily spread via email attachments .
•Phishing - sending an email to a user falsely
claiming to be a legitimate company to scam the
user into providing information, such as personal
information and bank account numbers on a bogus
website.
•No guarantee the mail will be read until the user
logs on and checks their email.
•Spam - unsolicited email, ie junk mail.

28. E-Mail Addressing
abc@gmail.com
User Name Domain Name
•Domain name-tells the name of the
organization.
•American addresses end in an organizational
suffix.
Eg: .com-bussiness

29. .org-non profit organizations
.gov-government agencies
.mil- military agencies
.edu-college or university
•Some countries use two letter code to represent
their country.
.in-India
.pk-Pakistan
.lk-Sri Lanka

30. Internet Host Systems: Dial up, SLIP, PPP
•A dial-up connection is a connection from an end
user to an Internet service provider (ISP) that can
be created over a conventional telephone line
without any special arrangement with the
telecommunications carrier.
•The Serial Line Internet Protocol (SLIP) is an
encapsulation of the Internet Protocol designed to
work over serial ports and modem connections.
•PPP (Point-to-Point Protocol) is a protocol for
communication between two computers using a
serial interface, typically a personal computer
connected by phone line to a server.

31. Distributed Mail
•We can send the same message to group of
addresses in same time.
•There are two major options for organizing
groups.
1.Open or closed- Anyone can join an
open group by just clicking “ subscribe to list”.
Closed group require the approval of a human
being to join the list.
Discussion Groups

32. 2.Moderated or unmoderated:
In moderated group a human being reads
every message send to the list server and
decides which ones are passed to the list. In
unmoderated groups , the computer program
simply passes all messages it receives.

34. Etiquette and netiquette
•Netiquette, or net etiquette, refers to
etiquette on the Internet. Good netiquette
involves respecting others' privacy and not
doing anything online that will annoy or
frustrate other people.
•Three areas where good netiquette is highly
stressed are e-mail, online chat, and
newsgroups.

35. •For example, people that spam other users with
unwanted e-mails or flood them with messages
have very bad netiquette. You don't want to be
one of those people.
•If you're new to a newsgroup or online chat
room, it may help to observe how people
communicate with each other before jumping in.

36. Posting to a Newsgroups
•After emails most popular messaging system is
Usenet newsgroups.
•Message about any subject can be posted and
others can read.
•Rather than the discussion groups this allows to
avoid conversation you are uninterested.
Usenet Newsgroups

37. News Reader
•To access Usenet newsgroup you must have a
news reader –client server software that run on
host computer and perhaps also on your computer
that knows how to read the huge database of
messages in a newsgroup and present them to you
in a manageable fashion.

38. Flames and Flame Wars
•Most newsgroups are serious and allow anyone to
post whatever they want without problem.
•Sometimes , however, individuals post messages
that other members find annoying, distasteful or
even threatening. Often such people are subjected
to “Flames” by other members of the newsgroup.
•Flame wars-Break out where the group
deteriorates into an electronic shouting match and
entire newsgroup is disbanded.

39. Chapter 04
Using the internet: Telnet, FTP and Gopher
 Objectives
1. Reviewing the network connection and
software options.
2. What is Telnet?
3. Why we using FTP?
4. What is Gopher?

40. Connectivity and Software Options
Direct and On-demand Direct Connectivity
Internet Connection
Persistent Connection Intermittent Connection
•Always available to other
computers on the Internet.
•Have an IP address that
does not change.
•All servers have such a
connection.
•Temporary connection.
•Use when accessing network
through commercial provider
or through university.

41. Intermittent Connection
Dial Up SLIP/PPP
•Turns your desktop computer
into a “dumb” terminal of the
host computer.
•Issue commands to the host
computer’s software.
•On Direct Demand
connectivity.
•Get an IP address that use
temporally.
•When you disconnected the
address goes back to the host’s
pool and you off the Internet.

42. Telnet
Remote logon
•Telnet is one of the oldest and most
straightforward method of access shared files.
•Using telnet commands can access files faster
than emails.
•If you are in another city or country, you can use
telnet to logon to your local host back home and
issue command you would normally issue to say
read your e-mail or send a post to a Usenet
Newsgroup.
•Telnet can be used to access documents whether
they are stored as FTP or WWW or one of the
other protocols.

43. A Telnet Session
•Refer page number 30 on your text book.

44. FTP
A File Transfer Protocol Session
•That enables files to be transferred between
computers.
•You can use it to download files from a remote
server and to upload files from your computer to a
server.
•The basic steps in an FTP session are similar to
Telnet Session.

45. Directory Structure
•FTP sites are organized in to hundred of
directories and sub directories with in them.
•You can view the list of names of file names
issuing the commands “dir” for directory listing.
•There are some programs that run on many
systems still that do keyword searches of all FTP
computers, the most common is called Archie.
•Archie and other provide you with documents
complete Internet addresses.
Eg : ftp://rs.internic.net/internic/faq File name
Sub directory nameDomain name

46. FAQ or Frequently Asked Questions
•FAQ file is one that is often quite beneficial.
•This file is usually a collection of good questions
asked about a procedure , system, achieve or
whatever and good answers to those questions.

47. Gopher
The Golden Gopher
•The gopher program is a menu-driven application
that allows you to hop around the global looking for
information.
•Gopher’s interconnected menus allow you to
“burrow” deeper and deeper until you find the
information that you looking for.
•It was developed by the University of Minnesota.