Transcript Chapter 9 - SISF WEB SITE Starting Page

Computer
Confluence 7/e
© 2006 Prentice-Hall, Inc.
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Computer Confluence 7/e
Chapter 9
Inside the Internet and the World Wide
Web
© 2006 Prentice-Hall, Inc.
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Chapter 9
Objectives
 Explain how and why the Internet was created
 Describe the technology that is at the heart of the Internet
 Describe the technology that makes the Web work as a
multimedia mass medium
 Discuss the tools people use to build Web sites
© 2006 Prentice-Hall, Inc.
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Objectives (cont.)
 Discuss the trends that are changing the Internet and the way
people use it
 Discuss some of the most important social and political issues
raised by the growth of the Internet
 Describe various ways that governments restrict access to the
Internet
© 2006 Prentice-Hall, Inc.
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ARPANET Pioneers Build an Unreliable
Network ... on Purpose
 The Advanced Research Projects Agency NETwork (ARPANET)
is the predecessor to the Internet:
 Developed at the request of the Department of Defense by a team of
visionary computer scientists
 Launched in 1969
 Its peer-to-peer networking philosophy and protocols were copied in other
networks in the 1980s
 Disbanded in 1990, having fulfilled its research mission, but its technology
spawned the Internet
© 2006 Prentice-Hall, Inc.
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Inside the Internet
Counting Connections
The Internet: an interconnected network
of thousands of networks
 Links academic, research, government, and
commercial institutions
Connects computers to about every
country in the world.
 Growing too fast to measure its growth
 Too decentralized to quantify
 A network with no hard boundaries
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Inside the Internet
Internet Protocols
 Transmission Control
Protocol/Internet Protocol,
TCP/IP…
 At the heart of the Internet
 Allows cross-network communication
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Inside the Internet
 TCP breaks messages into packets
 Each packet has all the information needed to travel from network to
network
 Host systems called routers determine how to route transmissions
 IP is the address for the packets
 Each Internet host computer has a unique IP address
 Each address is comprised of four sets of numbers separated by periods,
such as 123.23.168.22
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Internet Addresses
 The host is named using DNS (domain name system), which
translates IP addresses into a string of names
 Top-level domains include:
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.edu - educational sites
.com - commercial sites
.gov - government sites
.mil - military sites
.net - network administration sites
.org - nonprofit organizations
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Inside the Internet
 The Internet Ad Hoc Committee recently created seven additional
top-level domain names:
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.aero
.biz
.coop
.info
.museum
.name
.pro
Air transport organizations
Businesses
Cooperative businesses such as credit unions
Information services
Museums
Personal registration by name
Licensed professionals, including lawyers, doctors, and
accountants
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Inside the Internet
An email address includes:
[email protected]
 username is the person’s
“mailbox”
 hostname is the name of the host
computer and is followed by one
or more domains separated by
periods:
 host.domain
 host.subdomain.domain
 host.subdomain.subdomain.domain
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Inside the Internet
© 2006 Prentice-Hall, Inc.
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Inside the Internet
Internet Access Options
 Direct (Dedicated) Connection
Computer has its own IP address and is
attached to a LAN
No need to dial up
Files are stored on your computer
Quick response time
 Dialup Connection
Limited connection using a modem
Full access dialup uses SLIP or PPP via
modem
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Inside the Internet
 Broadband Connections
 DSL Service
 Newer, faster, and cheaper than ISDN
 Can share phone line with voice traffic
 Cable Modem Connection
 Allows Internet connections using shared TV cables
 Can exceed DSL speeds
 Carries increased privacy and security risks
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 Satellite Connection
 Provides connection using DirecTV
satellite dishes
 Wireless Broadband Connection
 Allows multiple computers to connect to a
base station using short-range radio waves.
 Internet Service Providers (ISPs)
 Local ISPs provide connections through local telephone lines
 National ISPs offer connections on a nationwide scale
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Inside the Internet
 Internet Servers
 E-mail server acts like a local post office for a particular Internet host—a
business, an organization, or an ISP
 File servers are common within LANs
 Also used to share programs, media files, and other data across the Internet
 File transfer protocol (FTP) allows users to transfer files
 Download files from remote servers to their computers
 Upload files to remote computers
 File compression saves storage space on disk and saves transmission time when
files are transferred through networks
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 Application server stores applications—PC office applications, databases,
or other applications
 Makes them available to client programs that request them
 Might be housed at an application service provider (ASP), a company that
manages and delivers application services on a contract basis
 Web server stores Web pages and sends pages to client Web browsers
© 2006 Prentice-Hall, Inc.
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Inside the Web
Web Protocols: HTTP and HTML
WWW is a distributed browsing and searching system developed
at CERN and designed to give Internet documents unique
addresses
HTML was created for encoding and displaying documents
 An HTML document includes code that determines the format, layout, and
structure of a Web document
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Inside the Web
HTML Is Not WYSIWYG (What You See Is What You Get)
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Inside the Web
 Browser software was built for viewing documents from
remote locations
 The Web is built around a naming scheme that allows every
information resource on the Internet to be referred to using a
uniform resource locator, or as it’s more commonly known,
a URL. A typlical URL looks like this:
http://weatherunderground.com/satellite/vis/1k/US.html/
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Inside the Web
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Inside the Web
Publishing on the Web
 Programs that convert document format features into HTML
codes:
 Microsoft Word, PowerPoint, FileMaker
 Web authoring programs:
 Macromedia Dreamweaver, Adobe GoLive, Microsoft FrontPage
By expanding the number of people who
have the power to transmit knowledge,
the Web might trigger a power shift that
changes everything.
—Howard Rheingold,
Virtual Communities
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Inside the Web
From Hypertext to Multimedia
 Typical Web pages can contain:
Tables
 Streaming audio and
video
Frames
 Real-time live
Forms
audio or video
Downloadable
audio and video  3-D environments
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 Plug-ins are software extensions that add new features:
 Windows Media Player
 QuickTime
 Shockwave/Flash
 RealPlayer
 Adobe Reader and Acrobat (Adobe)
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 Dynamic HTML
 Adds more programming power to HTML by allowing code to
automatically modify itself under certain circumstances
 JavaScript
 Scripting language for enhancing HTML Web pages
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Inside the Web
Rules of Thumb: Weaving Winning Web Sites
Start with a plan
Write for the Web
Keep it simple
Keep it consistent
Make it obvious
Keep it small
Keep it honest
© 2006 Prentice-Hall, Inc.
 Offer contact information
 Think like a publisher and a
multimedia designer
 Test before you publish
 Think before you publish
 Keep it current
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Inside the Web
Dynamic Web Sites: Beyond HTML
 Java
 Full-featured, cross-platform, object-oriented programming language
 Java Applets
 Small Java programs
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Automatically downloaded onto your client computer
Can run on any platform
 ActiveX
 Collection of programming technologies and tools for creating
controls or components—
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Similar in many ways to Java applets
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WML (Wireless Markup Language)
 Helps create Web documents containing stock quotes, phone numbers, and other
small nuggets of information
XML (Extensible Markup Language)
 Will replace HTML plus provide additional features and extensions
XHTML
 A sort of cross between HTML and XML
VRML (Virtual Reality Modeling Language)
 Creates 3-D virtual worlds
SMIL (Synchronized Multimedia Integration Language)
 Makes it possible to link time-based streaming media
 Sounds, video, and animation can be tightly integrated
© 2006 Prentice-Hall, Inc.
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Inside Web Applications
Search Engines
 Designed to make it easier to find
information on the Web
Web Crawlers or Spiders
 Software robots that systematically search
the Web
 Some search engines use keywords
and Boolean logic to conduct searches
 Other search engines conduct searches using a hierarchical
directory or subject tree
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Inside Web Applications
 Meta-Search Engines (such as MetaCrawler, OneSeek, and
Apple’s Sherlock)
 Conduct parallel searches using several different search engines and
directories
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Inside Web Applications
Portals
 Web entry stations that offer quick
and easy access to a variety of
services
 Consumer portals include search engines,
e-mail services, chat rooms, references, news
and sports headlines, shopping malls, and
other services
 Corporate portals on intranets serve the
employees of particular corporations
 Vertical portals are targeted at members of a
particular industry or economic sector
© 2006 Prentice-Hall, Inc.
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Inside Web Applications
Rules of Thumb: Working the Web
 Handle URLs with care
 Get to know your search engines
 If you’re in a hurry, dispense with
frills
 Organize your favorite bookmarks
 Be selective
© 2006 Prentice-Hall, Inc.
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Protect your privacy
Be conscious of cookies
Shop with bots
Shop smart
Remember why you’re there
Think before you publish
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Inside Web Applications
Push Technology: Notifications and Alerts
 The Web was built with pull technology
 Browsers on client computers “pull”
information from server machines
 Browser asks for information
 With push technology, information is
delivered automatically to the client
computer
 New product descriptions
 Automatic software upgrades
 Updated news
© 2006 Prentice-Hall, Inc.
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Inside Web Applications
Peer-to-Peer and Grid Computing
 Peer-to-Peer (P2P) Computing
 Users share music, movies,
and other files without going
through a central directory
 Grid Computing
 Anyone can plug in from
anywhere and rent processing
power and software from anywhere
on the Net
© 2006 Prentice-Hall, Inc.
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Inside Web Applications
Intranets, Extranets, and Electronic Commerce
 Intranets: self-contained intra-organizational networks that offer email, newsgroups, file transfer, Web publishing, and other Internetlike services
 Firewalls prevent unauthorized communication and secure
sensitive internal data
Our customers are moving at
Internet speed. They need us
to respond at Internet speed.
—Laurie Tucker, Federal
Express vice president
© 2006 Prentice-Hall, Inc.
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Inside Web Applications
 Extranets: private TCP/IP networks designed for outside use
by customers, clients, and business partners of the organization
which owns the extranet
 Electronic data interchange (EDI): a decade-old set of specifications for
ordering, billing, and paying for parts and services over private networks
 Electronic commerce involves business transactions through
electronic networks
 Business-to-business (B2B) e-commerce: transactions that involve businesses
providing goods or services to other businesses
 Business-to-consumer (B2C) e-commerce: transactions that take place on the
Internet because consumers don’t have access to an extranet
© 2006 Prentice-Hall, Inc.
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Inside Web Applications
Web Services
 Web services involve new kinds of
Web-based applications that can be
assembled quickly using existing
software components
 Examples:
 Plug a shopping cart component into an
existing Web site
 Design applications that can be accessed through a
variety of Web-enabled devices
© 2006 Prentice-Hall, Inc.
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The Evolving Internet
Internet2 and the Next Generation Internet
Internet2 was launched by the government and various
corporations in 1998 to provide faster network
communications for universities and research institutions
Next Generation Internet (NGI) will consist of a
nationwide web of optical fiber integrated with intelligent
management software to maintain high-speed connections
© 2006 Prentice-Hall, Inc.
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The Evolving Internet
Internet Issues: Ethical and Political Dilemmas
 Filtering software to combat inappropriate content
 Digital cash to make online transactions
easier and safer
 Encryption software to prevent credit
card theft
 Digital signatures to prevent e-mail forgery
 Access and Censorship
 The Digital Divide
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The Evolving Internet
Cyberspace: The Electronic Frontier
 Science fiction writers suggest that tomorrow’s networks will
take us beyond the Internet into an artificial reality that has come
to be known as cyberspace
 Today’s computer networks are still light years from these
futuristic visions
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The Evolving Internet
Inventing the Future: The Invisible
Information Infrastructure
 Vint Cerf, one of the Internet’s founders, thinks the Internet is headed
for space–the InterPlaNet project
 Tim Berners-Lee, the inventor of the Web, is planning a Semantic
Web, a Web full of data that is meaningful to computers as well as
humans
 A variety of Internet appliances, network computers, set-top boxes,
PDAs, mobile phones, and other devices connected to the Internet in
offices and homes
© 2006 Prentice-Hall, Inc.
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Lesson Summary
 The Internet is a network of networks that connects all kinds of
computers around the globe and uses standard protocols to allow
Internet communication to occur
 No single organization owns or controls the Internet
 You can connect to the Internet in several ways that provide
different degrees of access to Internet services
 Most Internet applications are based on the client/server model
 The Web uses a set of protocols to make a variety of Internet
services and multimedia documents available to users through a
simple point-and-click interface
© 2006 Prentice-Hall, Inc.
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Lesson Summary (continued)
 In addition to Web sites, a variety of applications are built on the
protocols of the Internet and the Web. For example, people who
use the Web depend on search engines to find the information
they need
 Peer-to-peer computing was popularized by music sharing
services, but its applications go beyond music sharing
 Many businesses are exploring ways to apply P2P technology
 Grid computing goes beyond P2P computing by enabling people
to share processor power
 E-commerce is built on Internet technology
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Lesson Summary (continued)
 Businesses use the Internet and the Web for business-tobusiness and business-to-customer communication
 Many businesses have private networks, called intranets, based
on Internet technology
 Extranets are also private networks, based on the same
technology that enables businesses to connect with their
partners
 As the Internet grows and changes, issues of privacy, security,
censorship, criminal activity, universal access, and appropriate
Net behavior are surfacing
© 2006 Prentice-Hall, Inc.
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