Transcript ch1 - FAU College of Engineering

Topic 1 - Introduction to the Internet,
Web, and Web browsers
Outline
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History of the Internet
The Internet today
Host Machines and Host Names
The Client/Server Software Model
Personal Computing
The World Wide Web
Web Browsers
Searching the Internet
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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History of the Internet
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ARPAnet
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Implemented in late 1960’s by ARPA (Advanced
Research Projects Agency of DoD)
Networked computer systems of a dozen universities
and institutions with 56Kbps communications lines
Grandparent of today’s Internet
Intended to allow computers to be shared
Became clear that key benefit was allowing fast
communication between researchers – electronicmail (email)
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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History of the Internet
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ARPA’s goals
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Allow multiple users to send and receive info at
same time
Network operated packet switching technique
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Digital data sent in small packages called packets
Packets contained data, address info, error-control info
and sequencing info
Greatly reduced transmission costs of dedicated
communications lines
Network designed to be operated without
centralized control
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If portion of network fails, remaining portions still able to
route packets
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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History of the Internet
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Transmission Control Protocol (TCP)
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Name of protocols for communicating over ARPAnet
Ensured that messages were properly routed and that
they arrived intact
Organizations implemented own networks
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Used both for intra-organization and communication
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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History of the Internet
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Huge variety of networking hardware and
software appeared
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ARPA achieved inter-communication between all
platforms with development of the IP
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Internetworking Protocol
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Current architecture of Internet
Combined set of protocols called TCP/IP
The Internet
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Limited to universities and research institutions
Military became big user
Next, government decided to access Internet for
commercial purposes
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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History of the Internet
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Internet traffic grew
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Businesses spent heavily to improve Internet
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Better service their clients
Fierce competition among communications carriers and
hardware and software suppliers
Result
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Bandwidth (info carrying capacity) of Internet increased
tremendously
Costs plummeted
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The Internet today
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The Internet is a network of networks that are spread
all over the world
Networks that are geographically close are called Local
Area Networks (LANs)
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Often in the same building
The university’s network is a prime example
The Internet is a largely heterarchical network
containing many individual LANs
A heterarchical network contains many nodes that are
interconnected.
A hierarchical network contains a tree-like structure
where some nodes are superior to others.
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The Internet today
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The Internet today
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A characteristic of a heterarchical network is
that it is a robust network.
If some nodes are removed, data can still be
sent between nodes
Hierarchical networks do not lend themselves to
robustness
The Internet also has dynamic routing, where
the route of the data is determined at the time
of transmission based on current network
conditions.
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The Internet today
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How big is the Internet?
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Number of networks
Number of servers
Number of domain hosts
Number of (indexed) web pages / web sites
Usage statistics
Number of countries
Amount of stored information
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What about the Deep Web?
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Host Machines and Host Names
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Each computer on the Internet is a host
machine.
Each computer has a unique Internet Protocol
(IP) address, such as 124.110.24.1
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Some computers have a permanent IP address
Some computers borrow an IP address while they
are connected to the Internet
An IP address is not human-friendly
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Host Machines and Host Names
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The IP address for most host machines are
mapped to a Domain Name Service (DNS)
address in order to be more people-friendly
The DNS address consists of a host name
followed by a domain name
Example DNS Address: mail.yahoo.com
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Host Name is: mail
Domain Name is: yahoo.com
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Host Machines and Host Names
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Each domain name consists of:
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Institutional site name
Top Level Domain name (TLD)
Example: cse.fau.edu
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cse.fau is the Dept. of Computer Science and
Engineering at Florida Atlantic University
edu refers to an educational site
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Host Machines and Host Names
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Examples of TLDs include:
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.com
a commercial organization
.edu
a US educational site
.net
a network site
.au
Australia
.fr
France
.hk
Hong Kong
.es
Spain
... (many others)
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Host Machines and Host Names
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New TLDs have been added as the original set
became overloaded
While each machine has a unique IP address, it
can have multiple DNS addresses (called
aliases)
Anyone can register a DNS address
When you type in a DNS address, a domain
name server translates it into an IP address.
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The Client/Server Software Model
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Clients and servers are host machines
A client is the host machine that requests
information from the server
The server is a resource that provides a service
for (many) clients
The client/server interaction is the foundation
for all Internet communication
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The Client/Server Software Model
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The Client/Server Software Model
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Some companies use servers that do not need
to be installed on the client to supply
commercial software to clients
Application Service Providers (ASPs) provide
software through subscriptions
The software is “rented” with this arrangement
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Personal Computing
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IBM
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1981, introduced IBM Personal Computer
Made personal computing legitimate in business,
industry and government organizations
Computers were “stand-alone” units
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Machines could be linked
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Info only shared between computers through exchange of
discs
Over telephone lines
Over Local Area Networks (LANs)
Led to distributed computing
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Personal Computing
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Computers today
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As powerful as million dollar machines from 20 years ago
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Workstations
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Most powerful desktops today
Provide users with enormous capabilities
Information easily shared over networks
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Networks controlled by servers
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Popular operating systems
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Common programs and data used by client computers
UNIX, MacOS, Windows XP, Linux
Portable devices (PDAs, tablet PCs, cell phones) with great
computing power
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The World Wide Web
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The World Wide Web (WWW or Web) has become a
popular means of accessing information and services.
The Web allows computer users to easily locate and
view multimedia-based documents.
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Introduced in 1990 by Tim Berners-Lee
The Web and the Internet (Net) are not the same.
A Web browser is the software necessary to view
information.
Some browsers are integrated into other software, such
as an email client.
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The World Wide Web
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Navigating the Web only takes a few
commands.
The information in the Web is organized as
hypertext, graphics, video, and sound
The text in a Web page may contain hyperlinks
that, if clicked, allows you to view related
information on other Web pages.
You control where you go and what information
you see via these hyperlinks
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The World Wide Web
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A Web page is a document on the Web that you
view through your Web browser
The act of reading Web pages and clicking on
hyperlinks is called browsing
Browsing can be seen as a way of exploring
Each Web page has a unique address called a
Uniform Resource Locator (URL) that you can
use to jump directly to it
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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The World Wide Web
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World Wide Web Consortium (W3C)
(www.w3.org)
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Founded in 1994 by Tim Berners-Lee
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Devoted to developing non-proprietary and interoperable
technologies for the World Wide Web and making the Web
universally accessible
Standardization
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W3C Recommendations: technologies standardized by W3C
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include Extensible HyperText Markup Language (XHTML),
Cascading Style Sheets (CSS) and the Extensible Markup
Language (XML)
Document must pass through Working Draft, Candidate
Recommendation and Proposed Recommendation phases
before considered for W3C Recommendation
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Web browsers
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Popular browsers (and market share as of Jan 2005)
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(Source: http://www.w3schools.com/browsers/browsers_stats.asp)
Microsoft’s Internet Explorer: 69.9%
Firefox: 18.7%
Mozilla: 4.1 %
Opera: 2.1%
Netscape: 1.4 %
Others (Safari, Camino, Epiphany, iRider, and several others...): 3.8 %
Browser portability
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Great challenge
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Great diversity of client browsers in use
Many different platforms also in use
Difficult to
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Know capabilities and features of all browsers and platforms in use
Find correct mix between absolute portability, complexity and usability
of features
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Web browsers
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Different browsers can be distinguished from each other by the
features they support. Modern browsers and web pages tend to
use many features and techniques that did not exist in the early
days of the web.
Some of contemporary browsers’ elements and features:
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ActiveX
Ad filtering
Autocompletion of URLs and form data
Bookmarks for keeping track of frequently accessed locations
Cascading Style Sheets
Cookies which enable a website to track a returning user
Caching of web content
Digital certificates
Download management
DHTML
Embedded images using established graphics file formats such as
GIF, PNG, JPEG, SVG
Flash
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Web browsers
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Browser elements and features (cont’d)
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Favicons
Fonts, size, color
Forms for submitting information
Frames and IFrames
History of recently visited pages
HTTPS
Integration with other desktop applications
Offline browsing of cached content
Java applet
JavaScript for dynamic content
Plug-ins
Session management
Tabbed browsing
Tables
XHTML and XML
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Searching the Internet
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Search engines
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Web sites that sort through by keywords and
categories
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Google (www.google.com)
The rest
Store information in databases
Returns list of sites as hyperlinks
Meta-search engines
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Do not maintain databases
Aggregate results from multiple search engines
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Meta Crawler (http://www.metacrawler.com/)
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Fun Assignment (FA) # 1
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Select a browser of your preference and:
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Explore all its menus and options
Customize it to your needs and preferences
Compare against other browsers
Use it to explore Google
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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Links of the day
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Blackboard @ FAU:
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Wikipedia, the free encyclopedia:
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http://en.wikipedia.org/wiki/Web_browser
Google:
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http://blackboard.fau.edu/
http://www.google.com/
Contribute your own favorite links via Bb’s
Discussion Board (“Useful links” forum)
Fall 2005 - Introduction to Internet Computing
Copyright © 2005 Dr. Oge Marques
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