Transcript Internet and the World Wide Web

Internet and the World Wide
Web
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The Internet is made up of more than
100,000 interconnected networks in over 100
countries, comprised of commercial,
academic and government networks.
From the user’s point of view, the Internet is
a way of connecting to essentially any other
machine on the network.
Main Uses of the Internet
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electronic mail (email)
World Wide Web
newsgroups and bulletin boards
chat rooms and instant messaging
telnet
ftp
Email
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Uses mail composing and reading
programs (e.g., MS Outlook)
Email can be sent directly from many
Microsoft applications like Word and
Excel, with the corresponding
documents or spreadsheets included as
attachments.
World Wide Web
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Provides a standardized way for information
residing on one computer (the web server) to
be downloaded and read by another
computer (the client).
The file(s) to be downloaded from the server
use HTML (hypertext markup language), and
the downloading takes place using HTTP
(hypertext transfer protocol).
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On the client computer, a web browser is
used to display the information contained in
the downloaded files.
The most commonly used web browsers are
Netscape and Internet Explorer.
Web pages can provide access to a wide
variety of information, all of which can
potentially be downloaded to any computer.
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Usenet (User Network) newsgroups,
which allow anyone to post messages
and read everyone else’s postings, have
been around since long before the Web
was created.
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These newsgroups are organized
around specific subjects of interest to
particular subscribers.
Newsgroups can be selected and read
directly from your Web browser.
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Chat rooms provide another popular
Internet service.
Internet Relay Chat (IRC) offers
multiuser text conferencing on diverse
topics.
Dozens of IRC servers provide hundreds
of channels that anyone can log onto
and participate in via the keyboard.
Internet Access
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Today, all the major online services
provide full Internet access.
In addition, thousands of Internet
service providers (ISPs) have risen out
of the woodwork to offer individuals
and organizations access.
TCP/IP
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All data is transmitted along the Internet
using what is called TCP/IP.
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TCP stands for Transmission Control
Protocol and IP stands for Internet
Protocol.
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These protocols were developed by
DARPA (Defense Advanced Research
Projects Agency) to enable
communication between different types
of computers and computer networks,
back when when what is now the
Internet was just a small collection of
widely distributed experimental
networks known as the ARPAnet.
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The Internet Protocol is a
connectionless protocol which provides
packet routing.
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A packet is a unit of data formatted for
transmission on a network.
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Data is broken up into packets for
sending over a packet switching
network.
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All the data packets making up a single
message may not take the same route
to get to their destination; they are
reassembled once they have arrived.
Internet Services
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Although most new users interact with
the Internet via their Web browsers, for
years, command-line UNIX utilities have
been used.
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For example, an FTP (File Transfer
Protocol) program allows files to be
transferred between machines.
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Telnet is a terminal emulation program
that lets you log onto a computer in the
Internet and run a program, assuming
you have an account that lets you
access that computer.
Note: In the CCS labs, use F-Secure
SSH, which is a more secure version of
telnet.
World Wide Web
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The World Wide Web is an Internet facility
that links documents locally and remotely.
The Web document is called a Web page, and
links in the page let users jump from page to
page (hypertext) whether the pages are
stored on the same server or on servers
around the world.
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The fundamental Web format is a text
document embedded with HTML
(Hypertext Markup Language) tags that
provide the formatting of the page as
well as the hypertext links (URLs-Uniform Resource Locators) to other
pages.
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HTML codes are common alphanumeric
characters that can be typed with any
text editor or word processor.
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Numerous Web publishing programs,
such as Frontpage, provide a graphical
interface for Web page creation and
automatically generate the codes.
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Many word processors, such as Word,
and publishing programs also export
their existing documents to the HTML
format, allowing Web pages to be
created by users without learning any
coding system.
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Web pages are maintained at Web sites,
which are computers that support the
Web's HTTP (Hypertext Transfer
Protocol) protocol.
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When you access a Web site, you
generally first link to its home page,
which is an HTML document that serves
as an index to the site's contents.
Large organizations create and manage
their own Web sites. Smaller ones have
their sites hosted on servers run by
their Internet service providers (ISPs).
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Many individuals have developed
personal Web home pages since many
ISPs include this service with their
monthly access charge.
Individuals can post their resumes,
hobbies and whatever else they want as
a way of introducing themselves to the
world at large.
How to transfer a file over the
Internet
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There are two ways to transfer files
over the Internet.
One is to send a file along with an email message, and
the other is to use an FTP program.
Via E-mail
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E-mail programs have the ability to
"attach a file" to a message, which
means that any type of file (program,
graphics, spreadsheet, etc.) can be
transmitted along with the text
message.
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This is the simplest way to send a file
via the Internet.
However, although widely used, it can
be problematic.
Old e-mail programs, light versions of email programs and some mail gateways
can cause problems.
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The standard Internet mail protocol
supports only text.
And if the computer receiving the
message does not have the Word
program, for example, an attached
Word document will be unreadable by
the recipient.
Sending files via FTP and the
Web
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The protocol on the Internet that was
designed to handle file transfers is FTP
(file transfer protocol).
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With a Web browser, you can download
from an FTP site.
You would use the ftp:// prefix and
address (URL), which includes the
domain name and directories.
Internet addresses
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There are two kinds of addresses that
are widely used on the Internet.
One is a person's e-mail address, and
the other is the address of a Web site,
which is known as its URL.
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The format for addressing an email
message to an Internet user is USER
NAME @ DOMAIN NAME.
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For example, your address might be
[email protected].
There are no spaces between any of
the words.
ldecaprio is the user name and
lynx.neu.edu is the domain name.
The .edu stands for the academic top
level domain category.
How to Find Someone Else's
Address
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There are Web sites that maintain
directories, or white pages, of e-mail
addresses.
New sites are coming online all the
time. You may have to try several sites
to find someone, and there's no
guarantee. In the meantime, check out:
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www.bigfoot.com
www.four11.com
www.whowhere.com
www.switchboard.com
www.infospace.com
IP address
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An Internet Protocol address is the
physical address of a computer
attached to a TCP/IP network.
Every client and server station must
have a unique IP address.
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Client workstations have either a
permanent address or one that is
dynamically assigned to them each dialup session. IP addresses are written as
four sets of numbers separated by
periods; for example, 204.171.64.2.
URL
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Uniform Resource Locator is the address that
defines the route to a file on the Web or any
other Internet facility.
URLs are typed into the browser to access
Web pages, and URLs are embedded within
the pages themselves to provide the
hypertext links to other pages.
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For example, http://www.ccs.neu.edu
retrieves the home page of the College
of Computer Science Web site. The
http:// is the Web protocol, and
www.ccs.neu.edu is the domain name.
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If the page is stored in another
directory, or if a page other than the
home page is required, slashes are used
to separate the names.
For example,
http://www.ccs.neu.edu/index.html
points to the index page.
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If a required page is stored in a subdirectory,
its name is separated by a slash.
Like path names in DOS and Windows,
subdirectories can be several levels deep.
For example, the components of the following
hypothetical URL are described below:
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http://www.abc.com/clothes/shirts/formal.ht
ml means the following:
http://
protocol
www.abc.com/ domain name
clothes/
subdirectory name
shirts/
subdirectory name
formal.html
document or file name
Internet domain names
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An Internet domain name is an
organization's unique name combined
with a top level domain name (TLD).
For example, ccs.neu.edu is the domain
name of the College of Computer
Science.
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The following are the top level domains (the
.edu, .mil and .gov domains are traditionally
U.S. domains).
.com commercial
.net gateway or host
.org non-profit organization
.edu educational and research
.gov government
.mil military agency
.int international intergovernmental
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The .int domain name is not widely
used.
Outside of the U.S., the top level
domains are typically the country code;
for example, uk for United Kingdom.
Country code
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A country code is a two-character component
of an e-mail or Web address that identifies a
country.
Web servers read addresses from right to left.
So, on encountering [email protected],
the message would first be sent to Sweden,
since se is the country code for Sweden.
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Swedish routers would then send the
message to univ.oslo.net where it will
be waiting for Sven the next time he
logs on.
Search Engines and Sites
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There are various Web sites that
maintain databases about the contents
of other Web sites.
Most sites are free and are paid for by
advertising banners, while others
charge for the service.
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Some of the best known search sites
are:
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Yahoo!
Lycos
Infoseek
Altavista
There are many others. Here is a more
complete list of such sites:
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www.altavista.digital.com
www.excite.com
www.hotbot.com
www.infoseek.com
www.lycos.com
www.metacrawler.com
www.opentext.com
www.search.com
www.webcrawler.com
www.yahoo.com
Special-Purpose Search Sites
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Following are popular sites for
searching specific topics.
For example, Four11 searches a
database of the nation's white pages for
phone numbers and addresses.
Deja News searches a database of
postings to Usenet newsgroups:
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Authors & Books,
www.amazon.com
Automobile Buyers Guides,
www.edmunds.com
Book Reviews,
www.nytimes.com/books
Business News, www.wsj.com
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Computer Supersite, www.cmp.com
Computer Supersite, www.cnet.com
Computer Supersite, www.zdnet.com
Consumer Info,
www.consumerworld.org
Education & Career Info,
www.petersons.com
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Government (U.S.),
http://thomas.loc.gov
Health & Medicine,
www.healthatoz.com
Jobs & Careers, www.occ.com
Legal Resources, www.findlaw.com
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Literature (Great Works),
www.promo.net/pg
Mailing Lists (Internet), www.liszt.com
Maps & Driving Directions,
www.mapquest.com
Microsoft Support,
www.microsoft.com/support
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Music & Videos, www.cdnow.com
Newsgroups (Usenet),
www.dejanews.com
Package Tracking & Drop Offs,
www.fedex.com
Package Tracking & Drop Offs,
www.ups.com
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Parenting Library,
www.parentsoup.com
Recipes & Cooking,
www.epicurious.com
Research, www.clearinghouse.net
Research, www.elibrary.com
Restaurant Menus,
www.menusonline.com
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Shareware, www.shareware.com
Shareware, www.softseek.com
Subculture, www.disinfo.com
Tax Forms, www.1040.com
White Pages (people),
www.four11.com
Yellow Pages (business),
www.zip2.com
Zipcodes, www.usps.gov
Microsoft Internet Explorer
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Internet Explorer (IE) is a Web browser
from Microsoft that runs under
Windows 95/98/NT, Mac and UNIX.
In Windows 98, Internet Explorer is
fully integrated into the desktop.
How to download a picture
from the Web
Point to the picture and right click.
 Select Save Picture As from the menu.
 Specify the name (and location) of the
file where you want the picture to be
saved.
This picture file is then available to be
inserted into a Word document or a
PowerPoint presentation, for example.
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Cache
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While you explore the Web, your browser is
working behind the scenes, keeping track of
the sites you've visited, and even saving
images from these pages on your hard disk
so they'll load faster when you return.
The saved files are collectively referred to as
your "temporary Internet files" (or more
broadly termed, your disk cache).
Browsing speed
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Having Web pages and files (such as
graphics) stored on your desktop computer
allows you to open pages you frequently visit,
and have already seen, a lot faster, since you
can open them from your hard disk instead of
from the Internet.
This capability also makes it easy for you to
save money because you can view Web files
without being connected to the Internet.
IE disk cache operations
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To empty your IE cache, or change the
amount of disk space allocated for it:
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On the View menu of your IE toolbar, click
Options.
In the resulting dialog box, click the
Advanced tab.
In the Temporary Internet Files area, click
Settings.
The remaining step should then be obvious.
Cookies
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A cookie is a set of data that a website
server gives to a browser the first time
the user visits the site, that is updated
with each return visit.
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The remote server saves the
information the cookie contains about
the user and the user's browser does
the same, as a text file stored in the
Netscape or Explorer system folder.
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Not all browsers support cookies.
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Cookies store information such as user
name and password and what parts of
the site were visited; this information
can be updated with each visit
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The browser only shares each cookie
with the server that originated it; other
servers can only read their own cookies.
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I.E. 4.0 can be set up to alert the user
when a cookie is being sent so the user
can accept it or not, by means of the
Network Preferences window.
There are also downloadable
applications that eat cookies such as
Cookie Killers, Cookie Monster (Mac),
and Kill Cookie Batch File (PC).
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A good illustration of how cookies are used
can be found in various movie links.
They provide information about movie times
at theaters in cities across the country.
The first time you visit their site, the link asks
you to type in your zip code to let them know
where you are.
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The next time you visit, the site
automatically knows to show you
information about theaters and show
times in your area.
That saves you from having to log in
multiple times and from having to enter
your interests multiple times. That
saves you time.
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Basically, the site uses a cookie to
customize the experience for you.
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Because of this ability to customize
according to your areas of interest,
some people fear that cookies somehow
invade their privacy.
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In many ways, a cookie provides an
added level of privacy
By storing information on your own
computer rather than Internet servers,
you can examine the data files and see
exactly which information is being
recorded by the Internet service using
cookies.
Viruses on the Net
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Once you log on to the Internet, you're
entering a vast online society. And, as in
human society, not everyone there is nice.
Threats to security exist in the online world,
just as they do in the rest of the world.
By learning to protect yourself – your
computer and your data – you'll ensure that
your time online is productive and fun.
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You've probably heard dire warnings about
the possibility of downloading a computer
virus from the Internet. Don't ignore them.
The truth is that there are viruses, and they
can be destructive.
Fortunately, by following a few easy
guidelines and using some common sense,
you can keep your computer virus-free.
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You can pick up a computer virus only when
you interact with another computer.
So when you're downloading free software
from the Internet, sharing files with friends,
or even transferring files from work to home,
take the precautions outlined below, and your
computer and your data should stay
reasonably safe.
Know your source!
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On the Internet, knowing a source
means downloading files only from Web
sites you know to be safe.
Generally, this warning applies to
program files or applications because
viruses are most often hidden within
programs and become activated only
when the programs are run.
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However, executable files can also be
attached to special-action Web files,
video files, active software agents, and
email messages.
Generally you will see a warning
message on your screen whenever such
an application is about to be
downloaded.
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When downloading a file, you will be
presented with the choice to open it or
save it to disk.
If you aren't sure an application is safe,
or you don't know whether you can
trust the site it is coming from, you
might want to cancel the download at
this opportunity.
Immunize your computer
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Many anti-virus programs are available that
function, in effect, like virtual inoculations
against known viruses.
Make sure you have an up-to-date anti-virus
program on your computer and use it.
But also be aware that new viruses are
constantly being developed, so you need to
update your anti-virus programs frequently.