Transcript The World Wide Web

CIS 1203
Web Technologies
Introduction to the Internet and the
WWW
Lesson Objectives
 Students should:
– Understand the Internet and its history
– Understand the WWW, its history and how it
relates to the Internet
– Discuss the evolution of the WWW
– Identify and describe the fundamental
technologies of the Web
– Explain how the Web works
Information Technology
 IT  all aspects of managing & processing
information using technology
– Mainly computers and computer networks:
• Hardware
• Software
• Connectivity (Networks)
Hardware
Software
Navigation software  Steer clear of danger
Image compression software  More image returns
Hardware
Software
Operating system  Control HW and other SW
Web browser Surf the net
Photo gallery  Organize photos
Text editor  Compose and manage text messages
Connectivity
 Computer networks and telecommunications
infrastructure allow multiple hardware
devices to connect and share data and
information
Transmits
data back
to earth
Transmits voice
and data to other
devices
Computer Networks
 A network is a group of two or more
computers connected
– Why connected?
• To communicate, share resources and exchange
information
Types Of Networks
 LAN
– Local Area Network
» Computers are connected in a confined geographical area
 WAN
– Wide Area Network
» Computers span a large geographical area
The Internet
 A network of networks
– A worldwide collection of computer networks, cooperating
with each other to exchange data using a common
software standard
 Multiple data systems
–
–
–
–
–
Email
FTP (File Transfer Protocol)
TELNET
The World Wide Web (WWW)
And more
History of The Internet
 The Advanced Research Projects Agency (ARPA

A Department of Defense project to establish US lead in science and technology
applicable to the military
 Operation ARPANET
– A need for a bombproof communications system
– Link computers together throughout the US
– Gradual shift from a military pipeline to communications tool for scientists
 In late 1980s, DOD decommissioned the ARPANET to NSF (National
Science Foundation) Network called NSFnet
– Large telecommunication companies created high speed data lines and
connected to NSFnet
 The rest is history…
But What is The WWW?
 Created in 1989 in CERN
 The “information superhighway”
– A method of posting and accessing interactive
multimedia information
 Hyper what?
– The WWW is based on a concept called
hypertext
• The organization of information units into
connected associations that a user can choose
to make (links)
Web 1.0
 Web pages connected together via hyperlinks
 Mostly static and very little interaction
between the user and the webpage
 Focus is companies that own create and own
their content
Web 2.0
 Dynamic web pages that are data-driven and
user-centric
 High level of interactivity with user-generated
content (blogs, forums, social networks, video
sharing, etc.)
 Rich interfaces made possible through AJAX
– AJAX  Asynchronous JavaScript And XML
Mobile Web
 Web resources are being accessed via mobile
devices
 Companies are developing mobile versions for
their websites
 Mobile commerce is an emerging trend
The Client-Server Model
Client-Server Model: describes the relationship between two computer
programs in which one program, the client, makes a service request from
another program, the server, which fulfills the request
Server Side
Client Side
HTTP request
Internet
Web Server
HTTP response
Web Browser
What is HTTP?
 HTTP (Hypertext Transfer Protocol) is the
foundation of data communication for the
WWW
 A protocol defines a set of rules that enable
effective communications between computers
 HTTP is part of a protocol framework called
the Internet Protocol Suite which includes
TCP/IP
TCP/IP
 Transmission Control Protocol (TCP):
– Establishes connections among sending and receiving Web computers
– Handles assembly of packets at point of transmission, and reassembly
at receiving end
 Internet Protocol (IP):
– Provides the Internet’s addressing scheme
Internet Protocol (IP) Addresses
 IPv4:
sbaserver1.sba.muohio.edu
134.53.40.2
– 32-bit number
– Expressed as series of four sets of separate numbers
marked off by periods
• 201.61.186.227
• Class C address: Network identified by first three sets, computer
identified by last set
 New version: IPv6 has 128-bit addresses, able
to handle up to 1 quadrillion addresses (IPv4
can only handle 4 billion)
Routing Internet Messages: TCP/IP
Web Browser Overview
 A tool for “traveling” the internet
 A “client” software for “surfing” the WWW
 Browser war
– Different vendors
– Non standard extensions
– Different viewing experience of the same web page
 Then came the standards
– World Wide Web Consortium (w3c)
• http://w3c.org
•
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•
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Internet Explorer
Safari
FireFox
Mozilla
Opera
Lynx
Web Browsers and Devices
The way a webpage is displayed depends on the
monitor size and screen resolution
Some browser might not support flash or other
multimedia objects
Some browsers are so small, the whole webpage
layout must be different
How Browsers Work
 Enter URL or click a link
 The browser breaks the address into 3 parts
1. Protocol
2. Server and domain name 1
3. The resource name (webpage)
2
3
How Browsers Work
 The browser then communicates with a
domain name system (DNS) server that
translates the domain name into IP address
I found it. The IP
address is:
DNS Server 2
Du Web Server
Sorry I don’t know
this address. Let me
check another server
DNS Server 1
How Browsers Work
 Your browser sends an HTTP request to the
server using its IP address
 Some level of authentication takes place
 The server sends the requested page coded in
HTML
 Your browser reads the markup of HTML and
interprets it into the web page that you view
Domain Names, DNS, and URLs
 Domain name
– IP address expressed in natural language
 Domain name system (DNS)
– Allows numeric IP addresses to be expressed in natural
language
 Uniform resource locator (URL)
– Address used by Web browser to identify location of
content on the Web
– E.g. http://hct-portal.hct.ac.ae/students
Top-Level Domain (TLD) Names
Domain
aero
biz
com
coop
edu
info
gov
mil
museum
name
net
org
pro
Signifies
Air-transport industry
Business organization
US commercial
Coooeratives
US educational
Unrestricted
US government
US military
Museums
Individuals
US network
US non-profit
Professionals
Domain
au
br
ca
cn
de
fi
fr
gb
in
it
jp
ru
za
Signifies
Australia
Brazil
Canada
China
Germany
Finland
France
Great Britian
India
Italy
Japan
Russia
South Africa
URL
 Uniform Resource Locator
A separator
http://samer.ecommerce.hct.ac.ae/fw/index.php
Double slash means a
system address will
follow
File Name
Path
Domain Name
Access method
or Protocol