Transcript Using the Internet - California State University, Dominguez Hills

Using the Internet
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.
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).
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.
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.
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.
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.
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 stands for
Hypertext Transfer Protocol.
http:// www.csudh.edu/cis275/first.htm
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.
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.
Microsoft Internet Explorer
(Continued)
• Internet Explorer is holding the Web 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 – Full text index
– Site map – Keyword index
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Network Access Points (NAPs)
• A NAP is a major Internet connection point that
is used to connect and route traffic between
smaller commercial backbones.
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.
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.
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.
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.
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.
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.
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.
How an Internet Service
Provider Works (Continued)
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.
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.
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.
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.
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.