1. Internet
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2. Internet
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Internet is the
network of networks
i.e. global network
which make WWW
(world wide web)

3. The Internet
The internet
A network of networks
The internet transmits data from one computer
(called a host) to another
Internet networks
Linked networks that work much the same way --
they pass data around in packets, each of which carries
the addresses of its sender and receiver
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4. A network of networks, joining many government,
university and private computers together and providing
an infrastructure for the use of E-mail, bulletin boards,
file archives, hypertext documents, databases and other
computational resources
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6. History
1968 - DARPA (Defense Advanced Research Projects Agency)
contracts with BBN (Bolt, Beranek & Newman) to create
ARPAnet
1970 - First five nodes:
UCLA
Stanford
UC Santa Barbara
U of Utah, and
BBN
1974 - TCP specification by Vint Cerf
1984 – On January 1, the Internet with its 1000 hosts
converts en masse to using TCP/IP for its messaging
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7. Development of the Internet
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1956 USSR launches Sputnik, 1st satellite; USA Department of
Defense (DOD) forms Advanced Research Projects Agency
(ARPA)
1962 Packet-switched network concept
1969 DOD starts ARPANET for networking research
1974 Protocol for packet internetworking Transmission Control
Program (TCP)
1981 BITNET (Because Its Time Network) provided widespread
email access.
Minitel is deployed across France by French Telecom

8.  1982 Internet Protocol (IP) established TCP/IP
 1984 Domain Name Server (DNS) introduced and
number of host is 1,000
 1986 NSFNET created a high speed backbone
(56Kbps) to interconnect supercomputer centers
 1987 Number of hosts breaks 10,000
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1989 Number of hosts breaks 100,000 and NSFNET is upgraded to
T1 line (1.544 Mbps)
Commercial email carrier (Compuserve) connects to the
Internet
1990 ARPANET ceases to exist;
MCI mail connects to the Internet
1991 WAIS released by Thinking Machines Corporation to aid
information search
Gopher released by U of Minnesota

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1992 WWW released by CERN (a physics research institute in
Switzerland)
Number of hosts breaks 1,000,000
NSFNET upgraded to T3 line (44.736 Mbps)
1993 WWW annual growth rate 341,634%
Whitehouse goes online president@whitehouse.gov
United Nations & World Bank go on-line.
US National Infrastructure Act championed by Al Gore.
Mosaic developed by National Supercomputer Center

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1994 Netscape
Communities become wired to the Internet For example,
Blacksburg, VA - bus & movie schedules on-line, town
meetings, etc.
US Senate and House go on-line
Mass marketing frenzy on the Internet
USA sales at cybermalls grows to $200 million versus $50
billion in catalog sales & $1.5 trillion in total USA retail sales.
1995 *.com sites exceed *.edu sites
1996 Electronic commerce gets going seriously
1998 The government uses the Internet for public dissemination of
information (or political assassination ) by publishing Starr’s
report on the Internet.

12. History
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The Internet grew out of an experiment in the 1960s by
the U.S. Department of Defense. The DoD wanted to
create a computer network that would continue to
function in the event of a disaster, such as a nuclear war.
If part of the network was damaged or destroyed, the
rest of the system still had to work. That network was
ARPANET, (Advanced Research Projects Agency
Network) which linked U.S. scientific and academic
researchers. It was the forerunner of today's Internet.

13. The Creation of the Internet
The creation of the Internet solved the following challenges:
Basically inventing digital networking as we know it
Survivability of an infrastructure to send / receive high-speed
electronic messages
Reliability of computer messaging
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14. Internet Growth Trends
1977: 111 hosts on Internet
1981: 213 hosts
1983: 562 hosts
1984: 1,000 hosts
1986: 5,000 hosts
1987: 10,000 hosts
1989: 100,000 hosts
1992: 1,000,000 hosts
2001: 150 – 175 million hosts
2002: over 200 million hosts
By 2010, about 80% of the planet will be on the Internet
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15. How the Internet Works
Transport control protocol (TCP)
A protocol that operates at the transport layer and is
used in combination with IP by most Internet
applications
Backbone
An Internet high-speed, long distance
communications links (like a bus; wire that connects
nodes)
Uniform resource locator (URL)
An assigned address on the Internet for each computer
E.g., http://www.yorku.ca/
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16. Three Ways to Access the Internet
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17. Access to the Internet
LAN servers
Local servers can provide access to the Internet through normal
connections (e.g., Ethernet)
Serial line internet protocol (SLIP) and
Point-to-point protocol (PPP)
Communications protocol software that transmits packets over telephone
lines, allowing dial-up access to the Internet
Connection via an on-line service
Examples are America Online and Microsoft Network. These services
usually require sign-up procedures
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Net structure
The Web physically
consists of your
personal computer,
web browser software,
a connection to an
Internet service
provider, computers
called servers that host
digital data, and routers
and switches to direct
the flow of
information.

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Web Browser
A web browser is the software
program you use to access the World
Wide Web, the graphical portion of
the Internet. The first browser, called
NCSA Mosaic, was developed at the
National Center for Supercomputing
Applications in the early 1990s. The
easy-to-use point-and-click interface
helped popularize the Web. Microsoft
Internet Explorer and Netscape
Navigator are the two most popular
ones.

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Navigating the Web
The Web is known as a client-
server system. Your computer is
the client; the remote computers
that store electronic files are the
servers. To visit the website, enter
the address or URL of the website
in your web browser. Browser
requests the web page from the
web server that hosts the
requested site. The server sends
the data over the Internet to your
computer. Your web browser
interprets the data, displaying it on
your computer screen.

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Navigating the Web
The "glue" that holds the Web together is called hypertext
and hyperlinks. This feature allows electronic files on the
Web to be linked so you can jump easily between them.
Web pages are written in a computer language called
Hypertext Markup Language or HTML.

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Web Addresses
World Wide Web is a network of electronic files stored on
millions of computers all around the world. Hypertext links
these resources together. Uniform Resource Locators or
URLs are the addresses used to locate the files. Every URL is
unique and identifies one specific file.
example:
http://www.du.ac.in
The home page of Delhi University.

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Domain Names
Every computer that hosts data on the Internet has a unique
numerical address. For example, the numerical address for
the White House is 198.137.240.100. But since few people
want to remember long strings of numbers, the Domain
Name System (DNS) was invented. DNS, a critical part of
the Internet's technical infrastructure, correlates a numerical
address to a word. To access the White House website, you
could type its number into the address box of your web
browser. But most people prefer to use
"www.whitehouse.gov." In this case, the domain name is
whitehouse.gov.

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The Structure of a Domain Name
A domain name has two or more parts separated by dots and
consists of some form of an organization's name and a three
letter or more suffix. For example, the domain name for
IBM is "ibm.com"; the United Nations is "un.org." The
domain name suffix is known as a generic top-level
domain (gTLD). It describes the type of organization.

26. Domain Affiliations
Domain Affiliations
arts cultural and entertainment activities
com business organizations
edu educational sites
firm businesses and firms
gov government sites
info information service providers
mil military sites
nom individuals
net networking organizations
org organizations
rec recreational activities
store businesses offering goods for purchase
web entities related to World Wide Web activities
net networking organizations
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Bookmarks and Favorites
Bookmarks and Favorites save Web addresses so you can return to
them quickly. To save a web page, go to the Bookmarks or
Favorites menu or click on its icon and select Add. When you click
on the icon again, the title of the page you recorded will appear at
the bottom of the list. To access the page, just double-click on the
title.

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TCP/IP
TCP/IP ensures that messages are properly routed from
sender to receiver and that these messages arrive intact.
UDP – User datagram protocol
With UDP, computer applications can send messages, in this
case referred to as datagrams, to other hosts on an Internet
Protocol (IP) network without requiring prior communications
to set up special transmission channels or data paths. UDP is
sometimes called the Universal Datagram Protocol.

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The Internet architecture is based on the standard TCP/IP
protocol, designed to connect any two networks which may be
very different in internal hardware, software, and technical
design.
Once two networks are interconnected, communication with
TCP/IP is enabled end-to-end so that any node on the Internet
has the ability to communicate with any other no matter where
they are.
An IP address is a 32 bit long identifier that encodes a
network number (or network prefix) and a host
number
192.168.11.2
Network Address
Host Address

30. Dotted Decimal notation
IP addresses are written in a so-called dotted decimal
notation
Each byte is identified by a decimal number in the range
[0..255]:
Example
10000000 100100001000100110001111
1st
byte 2nd
byte 3rd
byte 4th
byte
128.143.137.14430

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Packet Switching
TCP = TRANSMISSION
CONTROL
PROTOCOL
(Breaks messages into packets
and reassembles them)
IP = INTERNET
PROTOCOL
(Moves packets around
the Internet)
SOURCE: J. DECEMBER

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Protocol
protocols define format, order of msgs sent and received
among network entities, and actions taken on msg
transmission, receipt
It is a set of rules and regulation.

33. HUB
A common connection point for devices in a network. Hubs
are commonly used to connect segments of a LAN. A hub
contains multiple ports. When a packet arrives at one port, it
is copied to the other ports so that all segments of the LAN
can see all packets.
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34. Packets
A piece of a message transmitted over a packet-switching
network. One of the key features of a packet is that it
contains the destination address in addition to the data. In IP
networks, packets are often called datagrams.
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35. Router
A router is a networking device whose software and
hardware are usually tailored to the tasks of routing and
forwarding information. For example, on the Internet,
information is directed to various paths by routers.
Cisco 1800 Router
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36. Nortel ERS 8600
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37. Search engine
Index..
Web Crawling
Before a search engine can tell you where a file or document is,
it must be found. To find information on the hundreds of
millions of Web pages that exist, a search engine employs
special software robots, called spiders, to build lists of the
words found on Web sites. When a spider is building its lists,
the process is called Web crawling. (There are some
disadvantages to calling part of the Internet the World Wide
Web -- a large set of arachnid-centric names for tools is one of
them.) In order to build and maintain a useful list of words, a
search engine's spiders have to look at a lot of pages.
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