working principles of internet

1. WORKING PRINCIPLES OF
INTERNET
D.Seethalakshmi MCA.,M.Phil.,
Assistant Professor
Bon Secours College forWomen
Thanjavur

2. Unit I
What is the Internet?
Internet Underlying Architecture

3. What is the Internet
 TheWired World of the Internet
 How Information travels across the Internet
 HowTCP/IPWorks
 Understanding Internet Addresses and
Domains
 Anatomy of a web connection
 Internet file types.

4. Internet
•It is the largest network in the world that
connects hundreds of thousands of individual
networks all over the world.
•The popular term for the Internet is the
“information highway”.
•Rather than moving through geographical
space, it moves your ideas and information
through cyberspace – the space of electronic
movement of ideas and information.

5. The wired world of Internet
•No one owns it
•It has no formal management organization.
•As it was originally developed by the Department
of defense, this lack of centralization made it less
vulnerable to wartime or terrorist attacks.
•To access the Internet, an existing network need
to pay a small registration fee and agree to
certain standards based on theTCP/IP
(Transmission Control Protocol/Internet Protocol)
.

6. The uses of the Internet
 Send e-mail messages.
 Send (upload) or receive (down load)
files between computers.
 Participate in discussion groups,
such as mailing lists and
newsgroups.
 Surfing the web.

7. What is Web?
•The Web (World WideWeb) consists of
information organized intoWeb pages containing
text and graphic images.
•It contains hypertext links, or highlighted
keywords and images that lead to related
information.
•A collection of linkedWeb pages that has a
common theme or focus is called a Web site.
•The main page that all of the pages on a
particularWeb site are organized around and link
back to is called the site’s home page.

8. How to access the Internet?
 Many schools and businesses have direct
access to the Internet using special high-
speed communication lines and equipment.
 Students and employees can access through
the organization’s local area networks (LAN)
or through their own personal computers.
 Another way to access the Internet is through
Internet Service Provider (ISP).

9. How to access the Internet?
 To access the Internet, an existing network
need to pay a small registration fee and agree
to certain standards based on theTCP/IP
(Transmission Control Protocol/Internet
Protocol) reference model.
 Each organization pays for its own networks
and its own telephone bills, but those costs
usually exist independent of the internet.
 The regional Internet companies route and
forward all traffic, and the cost is still only that
of a local telephone call.

10. Internet Service Provider (ISP)
 A commercial organization with permanent
connection to the Internet that sells
temporary connections to subscribers.
 Examples:
 Prodigy, America Online, Microsoft network,
AT&T Networks.

11. How to access the Web?
 Once you have your Internet connection, then
you need special software called a browser to
access theWeb.
 Web browsers are used to connect you to
remote computers, open and transfer files,
display text and images.
 Web browsers are specialized programs.
 Examples ofWeb browser: Netscape Navigator
(Navigator) and Internet Explorer.

12. Hypertext Markup Language (HTML)
 The standard used on the web is Hypertext
markup language (HTML).
 HTML uses codes, or tags, to tell theWeb
browser software how to display the text
contained in the document.

13. Addresses on the Web:IP Addressing
 Each computer on the internet does have a
unique identification number, called an IP
(Internet Protocol) address.
 The IP addressing system currently in use on the
Internet uses a four-part number.
 Each part of the address is a number ranging
from 0 to 255, and each part is separated from
the previous part by period,
 For example, 106.29.242.17

14. Domain Name Addressing
•Most web browsers do not use the IP address t
locateWeb sites and individual pages.
•They use domain name addressing.
•A domain name is a unique name associated with
a specific IP address by a program that runs on an
Internet host computer.
•This program, which coordinates the IP addresses
and domain names for all computers attached to
it, is called DNS (Domain Name System )
software.
•The host computer that runs this software is called
a domain name server.

15. Domain Name Addressing
 Domain names can include any number of parts separated by
periods, however most domain names currently in use have
only three or four parts.
 For example, the domain name sob.uchicago.edu is the
computer connected to the Internet at the Graduate School of
Business (gsb), which is an academic unit of the University of
Chicago (uchicago), which is an educational institution (edu).
 No other computer on the Internet has the same domain
name.

16. Uniform Resource Locators
• The IP address and the domain name each identify a particular
computer on the Internet.
• However, they do not indicate where aWeb page’s HTML
document resides on that computer.
• To identify aWeb pages exact location,Web browsers rely on
Uniform Resource Locator (URL).
• URL is a four-part addressing scheme that tells the Web
browser:
What transfer protocol to use for transporting the file
The domain name of the computer on which the file resides
The pathname of the folder or directory on the computer on
which the file resides
The name of the file

17. Structure of a Uniform Resource
Locators
http://www.chicagosymphony.org/civicconcerts/index.htm
protocol
Domain name
pathname
filename
http => Hypertext Transfer Protocol

18. HTTP
•The transfer protocol is the set of rules that
the computers use to move files from one
computer to another on the Internet.
•The most common transfer protocol used on
the Internet is the HypertextTransfer Protocol
(HTTP).
•Two other protocols that you can use on the
Internet are the FileTransfer Protocol (FTP)
and theTelnet Protocol

19. How to find information on the
Web?
•A number of search tools have been developed
and available to you on certainWeb sites that
provide search services to help you find
information.
•Examples:
Yahoo  www.yahoo.com
Excite  www.excite.com
Lycos  www.lycos.com
AltaVista  www/alta-vista.com
MSNWebSearch  www.search.msn.com

20. File Types of Internet
•Exe
•Jpeg
•Pdf
•Doc
•Mp3
•Mp4
•etc

21. The Internet’s Underlying
Architechture
 How the Doamin name system works
 How RoutersWork
 The Internet’s client/server Architecture.

22. How the domain name server
works
• Translate – human speak to computer speak
• Alphanumeric address to numeric address
• Eg
▫ www.bdu.in to 112.45.45.113

24. How Routers Work
 The traffic cops of the Internet
 Send information to router
 Router open IP packets of data to read
destination address
 Calculate the best route
 After that send final destination

25. • 2 ports
▫ Receiving port (input)
▫ Sending port (Output)
Every port is Bidirectional
Input port receives packet, s/w routine called a routine
process.
The routing table has detailed information about ports
with various IP address.
Output port sends the data to next router

26.  The packets are sent to special holding area
called an input queue
 Number of packets received exceeds the
capacity of queue (called length of queue)
packets might be lost
 TCP will have the packets re-sent

27.  A simple kind of routing table is called static
routing table
 It cant adjust routes as network traffic, so it is
not an optimal alternative

28.  Dynamic routing have multiple routes to reach
destination.
 It has dynamic routing table to create alternate
path immediately.

29. Routing Protocols
Interior Routing Exterior Routing
Used for company’s Intranet or internal
network
Used for Routers located on the internet
Routing Information Protocol Exterior Gateway Protocol

30. The Internet’s Client server
Architecture

31.  Client – local personal computer
 Server – more powerful computer
 Connection
 A LAN
 A phone Line
 TCP/IP – basedWAN
 Many clients access common data & file stored in the
Server
 Client Browserserver

32. UNIT II
 Connecting to the Internet
 Communicating on the Internet.

33. Connecting to the Internet
 Connecting your computer
 Connecting to the Internet from online
services
 How ISDN works
 The Internet/Television connection
 How Network Computers(NCs)Work
 How the Digital Subscriber line (DSL) works
 How satellite and palmtop connections work

34. Connecting your Computer
 DumbTerminal
 A terminal that is connected to a mainframe or
other kind of computer
 Eg
 Library or universities
 Internet access than dumb terminals provide

35. Terminal Emulation
 A personal computer can connect via modem
to a large computer
 The computer works like a dumb terminal,
except it is connected via a phone line instead
of direct connection
 This kind of internet account is sometimes
called a shell account

36. Direct Connection
LANs or large computers such as mainframes
can be directly connected to the internet.
SLIP
Serial Line Internet Protocol
Full Internet connection over telephone lines
PPP(Point to Point Protocol)
Like tSLIP, via modem
it resends any damaged packets

37. ISDN line
Special digital telephone lines
speed 64 kbps to 128 kbps
cost more than normal phone lines
ASDL (Assymentic Digital Subscriber Line)
ProvideVery High speed connection
Cable Modem
CableTV system using coaxial cable
Faster than conventional medem 10 to 20 times

38. Network Computer
low cost network computer
WebTV
Using set top box through television
Online Services
No special setup is equired
Dial up connections

39. Connecting to the Internet from
other services
Compu serve or America online
Own s/w – easy to access internet
Dial directly to get resources
Firewall
It is a Security system of accepting or
blocking packets as they are transmitted across
a network.

40. How Works ISDN
Integrated Services Digital Network

42. The Internet/Television
Connection
 How Cable ModemWorks
 Coaxial Cable – Broad Band
 2 connections
 Normal set top box accessTV
 NextWire is for Broadband modem
 It carries signal simultaneously

44. How WebTV works
 Use Internet and watchTV same time
 Set top box capability to accept add-ons
 Screens use RGB colors
 Convert signal from RGB to NSTC
 Web tv box connects to web tv network
 Simple remote unit control webtv

46. How Network Computers Work
 Low cost computers with little or no local storage
 No CD – ROM Drives or Pheripherals
 EG ATM Machine
 Silicon chip, card reader,NC
 Get PIN for Authorization
 NC used for email, games or word processor

47. How the DSL works
 Digital Subscriber line
 ASDL – it doesn’t need any special wires
 Send and receive as all digital data
 It enables talk on telephone and use internet
simultaneously
 Divides phone line into 3 channels
 Receiving Data
 Sending Data
 Talking over the phone

49. How Satellite & Palmtop Work
 Satellite connection – DirecPC Satellite
 Much higher speed than normal modems
 Webserver send information to satellite ground
stataion (NOC)
 Network operations center send info to satellite
above earth at 400 kilobits per second

50. Palmtop Computers Browse on
web

51.  Palm device – proxiweb s/w
 ISP – modem
 Proxy Server
 Webserver

52. Communicating on the
Internet
 How EmailWorks
 Email spam & Blocking
 How Usenet newsgroup work
 How internet chat and Instant Messaging
work
 Making phone calls on the Internet

53. How Email Works
 Anatomy of a Mail Message
 ASCII code
 Attach pictures, sounds, videos and other files
 Automatically doing Encode and decode
 E-mail address must be In a format
 Otherwise message not sent

54. Email is Delivered the
Internet
 Send packets usingTCP/IP protocol
 Routers look address and send the mail
correct path to reach destination
 All packets are received address then
recombined to read receiver
 Subscribe to receive mails (Mail Reflector)

55. How Email Software Works
 Compose
 Send
 Inbox
 Trash
 Create group mailing
 Add Signature
 Create own folder
 Spam

56. How Email is sent between
networks

57. LDAP
 Lightweight DirectoryAcess Protocol

58. How Email Encryption works
 Avoid Snoopers & Hackers
 Public (Encrypt)& Private (Decrypt)Key
 Encryption Progam PGP
 Copy of private key have sender
 Receiver uses the private key to decrypt the
email
 Some softwares decrypted automatically
 Internet won’t understand, it see only
random characters

59. Email Spam & Blocking
 Spam – unsolicited email sent to you
 Spam is sent out bulk of emails
 To get bulk of email address from company
servers
 Spammers hide their email address
The mail have from, sender and reply
The mail come from someone not spammer
Doing this sometimes called SPAMOUFLAGE

60. How Email Spam is Blocked
 Filter out mail from certain addresses
 This feature is spam filter or spam blocker
 ISP’s and online service can block spammers
 Routing table find spammer email address
 But Spammers change therir email address
often
 So Routing table also can’t fine spammer
email address perfectly

61. How Usenet Newsgroups work
 It is a global bulletin board & discussion area
 Newsgroups can be found on many host
computers across internet.
 2 Newsgroups
 Moderated
 Unmoderated

62. Moderated Newsgroup
 A human moderator receives and reads all
the messages for the newsgroup.
 The moderator then decides which messages
are should be post.
 The messages to be posted are put on a
newsgroup server.
 Other messages are discarded.

63. Unmoderated Newsgroups
 All messages are put directly on the server.
 Newsgroups and all their messages are stored
on a Usenet server.
 Usenet server communicate with one another,
so that all messages posted on one server are
duplicated on other servers.
 Although there are many usenet servers, not
all servers carry all newsgroups.
 Each site decides which newsgroups to carry.

64.  Pictures, Multimedia files & exe programs can be
posted in newsgroups for others see & use.
 A common encoding scheme used on
newsgroups is called uuencode.
 Newsgroup reader software lets read messages
and respond to newsgroups.
 New messages will automatically be delivered to
when you check the server.
 You will also be able to cancel your subscription

66. Hierarchy of Usenet
Newsgroups
 1000’s of newsgroup .
 Divided into hierarchies of topics to make it
easier to find particular newsgroup you want
to participate.
 Not all sites carry all newsgroups.
 System administrator decide which
newsgroup carry at their site.

67.  The major topic comes first, followed by
subtopic.
 Subtopic can be further subdivided…
 Rec.arts.books
 New newsgroups are created and old one are
being eliminated.
 Newsgroup client software give a complete up-
to-date list.

69. How IRC Works
 Internet Relay Chat
 It is a way for people all over the world to
“chat” with one another by using keyboards.
 It runs on a client/server model.
 Make a internet connection & then start your
client software.
 IRC servers are located all over the world.

71.  Choose a specific channel to join & choose a
username.
 After joining channel able to see the
conservation.
 The messages sent from your server to other
servers.
 Under spanning tree server structure the
messages takes shortest route to reach
destination.
 People read & respond messages.

72. How Instant Messaging Works

73. Making Phone calls on Internet
 Using special phone s/w to send or receive
telephone calls
 Connect to special directory, the directory
contains list of people who connect internet
using that phone s/w.
 Find the IP address to connect phone call.
 High speed – High quality voice files
 The s/w breaks up the voice file into a series
of packets to be sent usingTCP/IP.

74. How Internet Telephony Works

75.  IPTelephony service
 Dial special code first, as a way of routing the
call.
 Call  PSTN Special IP voice gateway
 Gateway converts the voice signal to digital
data & compress
 Voice packet convert them back into their
original form, sends through PSTN.
 The call travels on PSTN , the person
receiving the call picks up the phone & talks.
 The same way the receiver speaks the call
travels to the sender.