Transcript Chapter 2

Introduction to the Web and Internet
Questions Answered in this Chapter:
– What is the internet ?
–
–
–
–
Sept 2001
What are the characteristics of the internet that make it work?
What are the content types on the web?
How are websites created?
What is behind the growth of the web and Internet?
Chapter 2: Introduction to the web
and internet
1
Exhibit 2-1
Internet Adoption Rates Versus Other Media
Internet as Mass Medium — North American Adoption Curves
120
100
TV
80
Radio
North American 60
Users / Households
(MM)
50 Million Users /
Households
Cable
Commercial
Internet
40
20
0
Radio: 38 years
TV: 13 years
Cable*: 10 years
Commercial
Internet: 5 years
Years to Reach
50 MM Users
-20
1922 1926
1930
1934 1938
1942
1946
1950 1954 1958
1962
1966 1970
1974
1978
1982 1986
1990
1994 1998E
* Launch of HBO in 1976 used to estimate the beginning of cable as an entertainment / advertising medium
1
Sept 2001
Chapter 2: Introduction to the web
and internet
2
The Original WWW
• Like the internet, radio began as a communication medium
• Early market medium known as wireless telegraphy or telephony;
radio’s point-to-point wireless messaging
• Demand for radio broadcasting surged in 1922 when it shifted from a
point-to-point communication tool to a broadcast medium
• During the 1920s, all 48 states in the US had at least one radio station
• By 1925, 27 of the original 48 stations were out of business
• Revenue sources such as programming subsides from radio-set sales,
radio taxes, generalized goodwill for corporate sponsors and
advertising emerged as new revenue generation models
• The pay for service revenue model allowed radio to compete with
telegraph and cut the price of telegraph by 30%
Sept 2001
Chapter 2: Introduction to the web
and internet
3
Exhibit 2-2
Radio Stations Opened and Closed, 1921-24
100
Stations Opened
Stations Closed
75
50
25
0
21-Sep
22-Feb
22-Jul
22-Dec
23-May
23-Oct
24-Mar
24-Aug
Source: Hanson, Ward. “The Original WWW: Web Lessons from the Early Days of Radio. 7/15/96.
2
Sept 2001
Chapter 2: Introduction to the web
and internet
4
Early networks
• Internet’s beginnings can be traced back to memos written in 1962 by
MIT’s Joseph Carl Robnett Licklider outlining the galactic networking
concept
• Great advances were made in network technology in 1960s
• To connect computers and permit transfer of information locally, many
organizations installed Local Area Networks
• LAN technology was limited by geographical distance
• To allow computer and networks separated by larger geographical
distance to communicate ARPA (Advanced Research Projects Agency)
developed a Wide Area Network (WAN) called the ARPANET
Sept 2001
Chapter 2: Introduction to the web
and internet
5
Exhibit 2-3
Wide Area and Local Area Networks
WAN
PC
PC
PC
PC
LAN
PC
LAN
PC
PC
PC
PC
PC
PC
LAN
3
Sept 2001
Chapter 2: Introduction to the web
and internet
6
Networking Software
• The two most well-known pieces of internetworking
software are the TCP and IP
• IP software set rules of data transfer over the network
• TCP software ensures the safe and reliable transfer of data
• With open system nature of TCP/IP development, software
development and computer companies could more easily
build TCP/IP compliant software and hardware
• TCP/IP standard network protocol laid the groundwork
that enabled the deep internetworking that made internet
possible
Sept 2001
Chapter 2: Introduction to the web
and internet
7
What is the Internet?
• The internet is a collection of wires, protocols and
hardware that allows the electronic transmission of data
over TCP/IP
• Any data can be transferred over the net, e.g., email,
faxes,video,voice & web pages
• Technically www (web) and the net are not the same.The
web is an application for the net
Sept 2001
Chapter 2: Introduction to the web
and internet
8
How the internet works
Characteristics that allow shared access of data in a network :
1.
Unique identification of each computer on the network
Internet is a network of millions of computers and thousands of
networks intertwined together. Thus it was important that each
computer can be uniquely identified by assigning a specific Internet
Protocol(IP) address.
e.g.,198.108.95.145
2.
Human-friendly addressing
Domain Name System(DNS) gave each computer on the network an
address comprising an easily recognizable letters and words
instead of an IP address.
e.g., www.philanthropy.com
Sept 2001
Chapter 2: Introduction to the web
and internet
9
How the internet works(cont’d)
3.
Packet Switching
To remedy delays associated with unequally sized data transfers,
instead of transferring files in their entirety, whole files are broken
up into data packets before being transferred over the network.
4.
Routing
Routers are dedicated, special-purpose computers which serve as
an intermediary between networks. They route packets efficiently
through networks. Routers are building blocks of the internet.
Sept 2001
Chapter 2: Introduction to the web
and internet
10
Sept 2001
Chapter 2: Introduction to the web
and internet
11
Sept 2001
Chapter 2: Introduction to the web
and internet
12
Exhibit 2-6
Routers
WAN
Router
Router
Router
Router
Router
Router
Large Organization
PC
PC
LAN
PC
PC
PC
Router
Router
LAN
PC
PC
PC
PC
PC
PC
LAN
6
Sept 2001
Chapter 2: Introduction to the web
and internet
13
How the internet works (cont’d)
5. Reliability and Transmission control Protocol
IP software handles packet deliveries and TCP handles safe delivery of
packages.
6. Standardization
Without the TCP/IP standardization, there would have been many
negative tradeoffs, such as inflexibility and increased functional and
switching costs.
Sept 2001
Chapter 2: Introduction to the web
and internet
14
TCP Standardization
•
•
Networking technologies are not inherently compatible.
Before the development of internetworking technology an
organization with networks had two options:
One Alternative- allow groups to have network technology best
suited to them, which was not flexible
Other alternative – have a standard
Sept 2001
Chapter 2: Introduction to the web
and internet
15
Functions of TCP/IP
•
•
•
•
•
Prevents loss of data
Checks packets
Eliminates duplicate packets
Sends confirmation when the packet is received
If confirmation is not received, then the packet is
retransmitted
• Enables reliable and error-free communication over the net
Sept 2001
Chapter 2: Introduction to the web
and internet
16
What Web pages are made of
• The entire Web is built upon three concepts: web pages
(documents seen on the browser), links (connecting one
web page to another), and servers (storing and transmitting
the information to the browsers for display)
• No special software is required to create a web page
• Majority of pages are created using Hyper Text MarkUp
Language(HTML)
Sept 2001
Chapter 2: Introduction to the web
and internet
17
Exhibit 2-7
WorldWideWeb - The First Graphical Web Browser (1993 version running on a NeXT PC)
7
Sept 2001
Chapter 2: Introduction to the web
and internet
18
Contents of the web
• Links
– Internal Anchor Links:
Internal anchors are used to connect with other locations within
the same document.
– Page Links:
Page links allow users to link to other web pages.
– Mail-to Links:
Mail links are used to let users send feedback and questions
directly to them.
• Forms
Forms are basically web pages where the user can enter information
on the fields provided on the page.Forms are useful in getting highly
structured feedback.
Sept 2001
Chapter 2: Introduction to the web
and internet
19
Contents of the web(cont’d)
• Images
The most supported image formats on the Web are Graphic Image
Format (GIF) and Joint Picture Encoding Group(JPEG).
• Multimedia
Web supports multimedia file type such as images, audio and video.
• Capturing contents and compressing data
Printed images can be captured with low cost scanners and photos can
be downloaded with digital video cameras.
• Audio
Sounds can be captured, compressed and stored for use on the web.
• Video
Video capture cards allow users to capture the analog video output of
camcorders, VCRs and DVD players.
Sept 2001
Chapter 2: Introduction to the web
and internet
20
How are Web Sites Created?
1.
2.
3.
4.
A Web page can be made by adding text-based codes called Hyper
Text Markup Language (HTML) to a text file.Text editor allows to
create WebPages and gives more flexibility and control over design
and layout.
Document conversion tools enable existing documents and new
documents to be created and posted with minimal investment in
learning markup language.
Several web authoring tools are available; e.g., Microsoft FrontPage
lets users add multimedia objects such as sound and animation to
their web pages.
High-end Web authoring tools such as Dreamweaver and Adobe
GoLive offer more powerful site creation and management features,
and allow expanded features such as database integration to be built
in a web site.
Sept 2001
Chapter 2: Introduction to the web
and internet
21
Exhibit 2-8
Browser View and Source View of a Web Page
8
Sept 2001
Chapter 2: Introduction to the web
and internet
22
Behind the Scenes
•
•
Browsers make the retrieval process transparent
Uniform Resource Locator tells the browser several things about
how to access the desired content:
1. The transmission protocol to access the content.
e.g., Hyper Text Transfer Protocol for Web Pages, File
Transfer Protocol (FTP) for transmission of files and the
extended S-HTTP for a higher degree of security.
2. The name of the computer where the content can be found
3. The directory on the computer where content is stored and
the name of the file containing the content.
Sept 2001
Chapter 2: Introduction to the web
and internet
23
Exhibit 2-9
Sharing a cable or DSL modem
Client
DSL or Cable Modem
Host
Internet
ISP Computer
Client
Ethernet HUB
9
Sept 2001
Chapter 2: Introduction to the web
and internet
24
Exhibit 2-10
Components of a URL
The
Thename
nameof
ofthe
thecomputer
computer
being
accessed
(could
being accessed (couldalso
alsouse
use
this
computer’s
IP
address
this computer’s IP address
which
whichisis 208.178.40.89)
208.178.40.89)
The
Thename
nameof
ofthe
the
file
you
want
to
file you want toview
view
http://www.monitor.com/cgi-bin/templates/index.html
Indicates
Indicatesbrowser
browsershould
shoulduse
use
HyperText
Transfer
HyperText TransferProtocol
Protocol
for
forserver
serveraccess
access
The
Thedirectory
directory
that
contains
that containsthe
thefile
file you
you want
want
to
view
to view
Adapted from Comer fig. 22.7, p. 203
1
0
Sept 2001
Chapter 2: Introduction to the web
and internet
25
Factors behind the growth of the net
•
•
•
•
•
•
•
Ease of content consumption
Browser versatility and convenience
Speed
Easy to download
Platform independence
Ease of content creation
Standards
Sept 2001
Chapter 2: Introduction to the web
and internet
26
Exhibit 2-11
Drivers of Internet Growth
Standards
Standards
Ease
Ease of
of Content
Content
Creation
Creation
Internet
Internet Growth
Growth
Ease
Ease of
of Content
Content
Consumption
Consumption
Browser
Browser
Versatility
Versatility and
and
Convenience
Convenience
1
1
Sept 2001
Chapter 2: Introduction to the web
and internet
27