Transcript CEA 217

Chapter 1: Using the Internet
i-Net+ Guide to the Internet
Third Edition
Objectives
• Learn about the many systems that use the Internet
for communication.
• Examine the organization of the Internet
infrastructure.
• Investigate Internet service providers, and learn how
to select one.
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The Internet and Systems That Use It
• The Internet is many networks connected together,
all of which use the same method of communication.
• The beginnings of the Internet occurred in 1969 when
the Advanced Research Projects Agency (ARPA),
charged with developing an internet work that could
withstand nuclear attacks on the United States,
connected two university networks to create a
network called the Advanced Research Projects
Agency Network (ARPANET).
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The Internet and Systems That Use It
(Continued)
• A protocol is a language or a set of rules for
communication, and the Internet uses many different
protocols in many different situations.
• The Internet is a public network made up of hundreds
of thousands of private networks that can also
communicate using these same protocols.
• These private networks that use the same protocols,
standards, and equipment as the Internet are called
intranets.
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The World Wide Web
• The World Wide Web (WWW or W3) is a collection
of interconnected information that is stored on
computers all around the world.
• A Web browser is software designed to display files
available on the Web to the user.
• Most of the information on the World Wide Web is
stored in files that are formatted using Hypertext
Markup Language (HTML).
• Essentially, HTML is a set of codes that are included
in the text describing how the text should be
displayed or printed.
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The World Wide Web (Continued)
• Files that include HTML code are called hypertext,
hypertext files, hypertext documents, Web pages,
or simply pages.
• Web communication and standards of HTML are
controlled and monitored by the World Wide Web
Consortium (W3C), an organization made up of
private, educational, and governmental organizations
from around the world.
• The software that receives the request from the
browser is called a Web server, and the computer
that is running the Web server is called a server.
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The World Wide Web (Continued)
• A Web site is a group of Web pages and related text,
databases, graphics, audio, and video files that are
served up by a Web server to present information.
• The first publicly available Web browser that could
display graphics was Mosaic, released in 1993 by
the National Center for Supercomputing Applications
(NCSA) at the University of Illinois.
• Today, the most popular Web browser is Microsoft
Internet Explorer, distributed by Microsoft.
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Using Web Browsers
• A URL (Uniform Resource Locator) is an address for a
Web page file or other resource on the Internet.
• The first part of the URL shown in Figure 1-3 is http,
which stands for Hypertext Transfer Protocol.
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Using Web Browsers (Continued)
• Domain names are easy for humans to remember
and use, but the devices on the Internet rely on
numeric addresses to identify every host on every
network that is connected directly to the Internet.
• Such a numeric address is called an IP address
(Internet Protocol address).
• A group of controlling protocols is called TCP/IP
(Transmission Control Protocol/Internet
Protocol), and sometimes is called a protocol
stack.
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Microsoft Internet Explorer
• Microsoft Internet Explorer was first introduced in
October 1995, and is included in Windows XP and
other Windows operating systems.
• Some people still use earlier versions of the software
because of the overhead associated with the later
versions.
• Overhead is the amount of system resources
required by the software to function, such as space
on the hard drive and computing power.
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Microsoft Internet Explorer (Continued)
• The basic tools for navigation using Internet Explorer
are shown in Figure 1-5.
• Use the Back and Forward buttons to move back and
forth among the pages you have downloaded.
• Internet Explorer is holding these pages in a
temporary Internet folder on your hard drive called a
cache, and can display them without having to go
back to the Web server to download again.
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AutoComplete Feature
• Internet Explorer keeps track of the URLs you enter
in the Address bar.
• Internet Explorer also keeps track of data you enter in
data-entry forms on Web pages, to make it easy for
you to reenter the same data at a later time.
• To customize AutoComplete, follow the directions for
Windows XP as illustrated on pages 10 and 11 of the
text.
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Remembering URLs for Later Use
• You can save a URL so it’s easier to access later.
• In Internet Explorer terminology, this is called adding
the page to a list of your “Favorites.”
• To add a URL to your list of Favorites in Internet
Explorer use the directions shown on page 12 of the
text.
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Making Web Pages Available for Off-Line
Viewing
• Looking again at Figure 1-8, note the Make available
offline check box in the Add Favorite dialog box.
• When you check this option and a favorite, your Web
browser saves the Web page in a cache so you can
view the page when you are not connected to the
Internet.
• Follow the directions to make a Web page available
off-line in Internet Explorer as shown on page 13 of
the text.
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Saving Files on the Web to a Floppy Disk
or Hard Disk
• Sometimes, it’s helpful to save a Web page to a
floppy disk or a folder on your hard drive other than
the browser cache folder.
• To save a Web file on a floppy disk, use the
directions on pages 14 and 15 of the text.
• Also follow the directions on page 15 when you want
to view a page that you previously saved to a floppy
disk.
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Limiting the Content Available to a
Browser
• Internet Explorer 5 and higher versions support the
World Wide Web Consortium’s specifications for
content selection, called the Platform for Internet
Content Selection (PICS).
• These specifications allow parents and other
responsible individuals (such as employers and
educators) to limit the content available to a browser.
• PICS is a voluntary rating system in which Web
developers assign their site a rating based on
language, nudity, sex, and violence.
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Introducing HTML
• HTML is a subset of the Standard Generalized
Markup Language (SGML), a standard developed in
1986 to retain formatting and linking information in a
document as it is moved from one computer or
software application to another.
• An HTML file is sometimes called hypertext, a
hypertext file, a hypertext document, a Web page, or
a page.
• A tag is special HTML or SGML code in a text file that
controls how certain parts of the text are to be
formatted.
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Introducing HTML (Continued)
• Some possible formatting options include boldface,
underlining, and indentations.
• A tag is read by, or interpreted by, the browser as it
displays an HTML page.
• Tags also can be used as links to point to other Web
pages.
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Web Pages Built with Frames
• Frames allow a Web site designer to display
different information in two or more separate
areas of the screen.
• More than one Web page can be displayed on
the same screen, each in its own frame.
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Hyperlinks
• A Web page often contains a text or graphic that you
can click to jump to some other place in the same
document or to a different Web page.
• This text or graphic is called a hyperlink, a hot link,
or simply a link.
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Search Engine Web Sites
• Search engine Web sites are devoted to the purpose
of helping users find information anywhere on the
Web.
• A subject directory gets its information from
someone manually entering the data into a database.
• A spider search engine searches Web sites all over
the Web to get information for its database.
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Search Engine Web Sites (Continued)
• A meta search engine gets its information from
databases on other search engine sites.
• A spider search engine gets data by using automated
search engine software called a spider, robot, or a
Web crawler.
• This software independently searches the entire Web
for keywords in Web sites.
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Search Engine Web Sites (Continued)
• Meta tags are tags that contain information about the
Web page content.
• Meta tags can include information about the author of
the Web page, the software used to build it, the date
and time it was built, information used by PICS, and
so forth.
• A meta tag included on the page specifically for a
spider or Web robot to find and use is called a meta
robot tag.
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Searching an Individual Web Site
• The Web site show in Figure 1-18 includes a Search
box.
• This Search box might link to another Web site, but
many times a search utility searches only the current
site.
• Several ways to search a site are summarized in the
following list.
– Find
– Static index
– Site map
– Keyword index
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– Full text index
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Search Engines
• A search engine is used as a software application to
search for words in documents or in a database.
• A search engine like Google at www.google.com is
used by hundreds of thousands of people everyday
to find useful information on the Web.
• Google has quickly become the most popular search
engine on the Web.
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Using Search Boxes Effectively
• When using search utilities on the Web, knowing how
to use Search boxes effectively can make your work
easier.
• The expressions AND, OR, NOT, and NEAR can be
used to narrow a search and the keywords lost, link,
title, and image can make your searches more
powerful.
• Table 1-2 lists explanations and examples of each.
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Evaluating Good Design
• The following list describes some guidelines to use
when evaluating the overall design of a Web site.
– The very best Web sites are shortcuts.
– The Web site should create the feeling of community.
– Web sites should have a user-friendly home page that
loads quickly, gets the user’s attention, and clearly
presents what is found on the site.
– The remainder of this list appears on page 30 of the
text.
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Web Sites That Help You Evaluate and
Design Web Sites
• Some Web sites that can help you evaluate other
sites and design your own site are:
– builder.com.com by CNET
– www.developer.com by Earth Web
– www.wpdfd.com by Joe Gillespie
– www.colin.mackenzie.org by Colin Mackenzie
– The list is continued on page 30 of the text.
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Sending and Receiving E-Mail
• E-mail is a method for sending a text message or a
file to an individual or group of individuals via the
Internet.
• Internet e-mail addresses have three parts: the user
name, the @ symbol, and the name of the mail
server that receives and then delivers the message.
• E-mail consists of four components: the sending
client, sending server, receiving server, and receiving
client, as shown in Figure 1-24.
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Sending and Receiving E-Mail
(Continued)
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Chat Rooms
• A chat room is a data communications link that
several people share for text transmissions in real
time.
• Real-time communication occurs when people type
messages to each other and instantly receive a
response.
• Chat rooms use an application called Internet Relay
Chat (IRC), originally written by Jarkko Oikarinen,
that, like e-mail and the World Wide Web, uses the
client/server method.
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Chat Rooms (Continued)
• Another real-time communication technology called
instant messaging is based upon the chat room
concept.
• Instant messaging does not use IRC, but instead
uses proprietary software that users must install onto
their computers.
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Newsgroups
• A newsgroup is a service on the Internet or on a
private network that allows a group of people to post
articles and respond to those articles, so information
can be shared among the members of the group.
• A newsgroup can be private or public.
• It might have a subscription fee, such as the
newsgroups of ClariNet, a commercial newsgroup
organization whose main contributor is United Press
International.
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Newsgroups (Continued)
• An ISP can subscribe to ClariNet for a fee, and then
can control access to this newsgroup.
• Another example of a newsgroup service is Usenet,
which consists of thousands of free newsgroups that
circulate over the Internet.
• Usenet is the most popular newsgroup service.
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A Brief History of the Internet
• The Internet came into existence in 1969 when
Advanced Research Projects Agency (ARPA)
connected the computers of four major universities in
the United States (UCLA, Stanford, UC Santa
Barbara, and the University of Utah).
• Until the late 1980s, it was a loosely organized group
of interconnected networks that were used
predominantly by major academic institutions in the
United States for research and development.
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A Brief History of the Internet (Continued)
• In 1986, the National Science Foundation (NSF)
formed its network called NSFnet to connect five of
these major academic institutions, which were spread
from the East Coast to the West Coast: New York,
New Jersey, Pennsylvania, Illinois, and California.
• Because NSFnet connected smaller networks to
each other, it was called a backbone network.
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Network Access Points (NAPs)
• A NAP is a major Internet connection point that is used to
connect and route traffic between smaller commercial
backbones.
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Internet Service Providers (ISPs)
• An Internet service provider (ISP) is a business that
provides connectivity to the Internet.
• ISPs can be a small business that provides
connectivity in only one city, or a large company with
access points in many cities and countries.
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Services Offered by an ISP
• The primary purpose of an ISP is to provide access
to the Internet.
• To connect to the Internet, a computer needs a
physical connection to the ISP, software to
communicate over the Internet, and an address so
others on the Internet can identify the computer.
• To connect to an ISP, a computer must be using an
operating system that supports the communication
protocol of the Internet, which is TCP/IP.
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Services Offered by an ISP (Continued)
• Windows XP, Windows 2000, Windows 98, Windows
95, Windows Me, Windows NT, Linux, and the
Macintosh operating system all support TCP/IP.
• The final thing needed to connect to the Internet is an
Internet address so the computer can be identified on
the Internet.
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Ways to Connect to an ISP
• Regular telephone lines are the most common way
for an individual to connect to an ISP.
• In addition, two competing high-speed methods are
available.
• Both were introduced to the marketplace at about the
same time, cost about the same, and attain about the
same speeds.
• These two methods are DSL lines and cable
modems.
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How an Internet Service Provider Works
• After you connect to an ISP by cable modem, DSL, or
telephone line, the ISP connects you to the Internet.
• The ISP’s equipment can be very simple or complex,
depending on the ISP’s size.
• Figure 1-36 shows an example of how a small ISP
might connect to the Internet.
• A local area network (LAN) is a group of computers
and other devices networked together that is confined
to a small area, such as one building.
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How an Internet Service Provider Works
(Continued)
• A router is a device that connects two or more
networks and can intelligently make decisions about
the best way to route data over these networks.
• The two networks in Figure 1-36 are the ISP’s LAN
and the regional ISP’s network.
• This regional network is an example of a wide area
network (WAN), a network that covers a large
geographical area and might use a number of
communications technologies.
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How an Internet Service Provider Works
(Continued)
• Before data gets onto a T1 line, it must be cleaned
and formatted by a device called a CSU/DSU, which
is really two devices in one.
• The Channel Service Unit (CSU) acts as a safe
electrical buffer between the LAN and a public
network accessed by the T1 line.
• A Digital Service Unit or Data Service Unit (DSU)
ensures that the data is formatted correctly before it’s
allowed on the T1 line.
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How an Internet Service Provider Works
(Continued)
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What You Can Expect from an ISP
• An ISP is expected to offer access to the World Wide
Web, e-mail services, and possibly FTP services.
• Some offer chat room and newsgroup services, as
well as some space for a personal Web site.
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Point of Presence
• A small ISP might have only local telephone number
that you can dial for access, but some larger ISPs
have local telephone numbers in many major cities
and other countries.
• A POP (point of presence) is a connection point to
the Internet, either a telephone number you can call
to access your ISP or an IP address provided by your
ISP.
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Performance, Price, and Service
• It goes without saying that performance, price, and
service are three important factors to consider when
selecting an ISP
• An ISP should have a technical support desk
available in the evenings, on weekends, and on
holidays.
• Another important service is the ability to access your
e-mail from a Web site in the event you need to
check your mail from someone else’s computer.
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Summary
• The Internet is a group of networks that encircle the
entire globe.
• The client/server concept works like this: Client
software on one computer requests information from
server software that is on another computer.
• Web pages are written as hypertext documents using
HTML, and are transmitted on the Internet using
HTTP.
• A search engine is software used to search a Web
site, a group of sites, or the entire World Wide Web.
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Summary (Continued)
• A Web search site such as Google gets its
information by spiders or robots that search Web
sites.
• Most individuals and small companies use an Internet
service provider (ISP) to connect to the Internet by
way of regular telephone lines, DSL lines, or cable
modems.
• An ISP most often provides e-mail, World Wide Web,
chat room, newsgroups, and FTP services.
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