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this explains the working of intranets.

<H2><I><FONT SIZE=5 COLOR=#FF0000>Chapter </FONT></I><FONT SIZE=5 COLOR=#FF0000>36
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<LI><A HREF="ch36.htm#UsingMultimediaApplicationstoTrainEmployees">
Using Multimedia Applications to Train Employees</A>
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<H2><A HREF="#credit"><B><I>Credits</I></B></A></H2>
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<TABLE>
<TR><TD><B>Publisher</B></TD><TD><I>Stacy Hiquet</I>
</TD></TR>
<TR><TD><B>Associate Publisher</B></TD><TD><I>Juliet Langley</I>
</TD></TR>
<TR><TD><B>Acquisitions Editor</B></TD><TD><I>Lysa Lewallen</I>
</TD></TR>
<TR><TD><B>Development Editor</B></TD><TD><I>Paula Hardin</I>
</TD></TR>
<TR><TD><B>Copy Editor</B></TD><TD><I>Margo Hill</I>
</TD></TR>
<TR><TD><B>Technical Reviewer</B></TD><TD><I>Mark Butler</I>
</TD></TR>
<TR><TD><B>Production Editor</B></TD><TD><I>Barbara Dahl</I>
</TD></TR>
<TR><TD><B>Proofreader</B></TD><TD><I>Jeff Barash</I>
</TD></TR>
<TR><TD><B>Cover Illustration</B></TD><TD><I>Mina Reimer</I>
</TD></TR>
<TR><TD><B>Cover Design</B></TD><TD><I>Regan Honda and Megan Gandt</I>
</TD></TR>
<TR><TD><B>Book Design</B></TD><TD><I>Carrie English and Bruce Lundquist</I>
</TD></TR>
<TR><TD><B>Lead Illustrator</B></TD><TD><I>Mina Reimer</I>
</TD></TR>
<TR><TD><B>Contributing Illustrators</B></TD><TD><I>Sarah Ishida, Karl Miyajima, Joan Carol, and Chad Kubo</I>
</TD></TR>
<TR><TD><B>Page Layout</B></TD><TD><I>M.D. Barrera</I>
</TD></TR>
<TR><TD><B>Indexer</B></TD><TD><I>Valerie Robbins</I>
</TD></TR>
</TABLE></CENTER>
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<P>
<B>Copyright</B> &#169; 1996 by Macmillan Computer Publishing
USA. All rights reserved.
<P>
<B>PART OF A CONTINUING SERIES</B>
<P>
All other product names and services identified throughout this
book are trademarks or registered trademarks of their respective
companies. They are used throughout this book in editorial fashion
only and for the benefit of such companies. No such uses, or the
use of any trade name, is intended to convey endorsement or other
affiliation with the book.
<P>
No part of this publication may be reproduced in any form, or
stored in a database or retrieval system, or transmitted or distributed
in any form by any means, electronic, mechanical photocopying,
recording, or otherwise, without the prior written permission
of Macmillan Computer Publishing USA, except as permitted by the
Copyright Act of 1976, and except that program listings may be
entered, stored, and executed in a computer system.
<P>
<FONT SIZE=2>THE INFORMATION AND MATERIAL CONTAINED IN THIS BOOK ARE PROVIDED
&#147;AS IS,&#148; WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING WITHOUT LIMITATION ANY WARRANTY CONCERNING THE ACCURACY,
ADEQUACY, OR COMPLETENESS OF SUCH INFORMATION OR MATERIAL OR THE
RESULTS TO BE OBTAINED FROM USING SUCH INFORMATION OR MATERIAL.
NEITHER MACMILLAN COMPUTER PUBLISHING USA NOR THE AUTHOR SHALL
BE RESPONSIBLE FOR ANY CLAIMS ATTRIBUTABLE TO ERRORS, OMISSIONS,
OR OTHER INACCURACIES IN THE INFORMATION OR MATERIAL CONTAINED
IN THIS BOOK, AND IN NO EVENT SHALL MACMILLAN COMPUTER PUBLISHING
USA OR THE AUTHOR BE LIABLE FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL,
OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF SUCH INFORMATION
OR MATERIAL.</FONT>
<P>
<B>ISBN 1-56276-441-1</B>
<HR>
<P>
This book wouldn&#146;t have been possible without a host of people
working on it. I'd like to thank acquisitions editor Lysa
Lewallen for getting the ball rolling, and editor Valerie Haynes
Perry for her initial work on the book. Editor Paula Hardin wields
a sharp pen and tightened the writing and thinking tremendously.
Technical editor Mark Butler, as always, vetted the work for accuracy.
And thanks also to Mina Reimer, illustrator; Barbara Dahl, production
editor; Margo Hill, copy editor; and M.D. Barrera, page layout
artist. Also thanks to Carol Burbo for keeping track of everything.
 
<P>
And, as always, I&#146;d like to thank my family, Lydia, Mia,
and Gabriel, for putting up with my occasional absences into the
dark recesses of my office, as well as ignoring my odd behavior
as I mumbled too much about the domain name system or Virtual
Secure Private Networks.<P>
The

Internet has been hailed by many as the most revolutionary technology
that computing has seen. It&#146;s a technology that affects not
just the computing world, but the noncomputing world as well:
You can&#146;t turn on your television without seeing Web locations
flash across your screen, or read a newspaper without seeing a
story about the latest Internet startup that made its young entrepreneurs
instant millionaires.
<P>
The truth is, though, that Internet technology may have its greatest
impact in the next several years not on general culture, but rather
on corporations. It has already begun to revolutionize the way
that companies operate and do business&#151;and most people agree
that we've only seen the very beginnings of the its effects
on corporate culture and on the way corporations function.
<P>
When Internet technology is applied and used inside a corporation,
and open only to its employees, it is referred to as an <I>intranet</I>.
The same technologies that underlie corporate intranets form the
basis of the larger Internet. The only difference is that the
company has put up a wall around its intranet to keep intruders
out. This wall that a company builds around its intranet is known
as a <I>firewall</I>.
<P>
An intranet uses the same basic underlying architecture and network
protocols as does the Internet. Protocols such as the Transmission
Control Protocol (TCP), the Internet Protocol (IP), the Simple
Mail Transfer Protocol (SMTP), and many others are what make it
all possible. Most intranet technologies, like those on the Internet,
are client/server based. In many instances, however, the way the
technology is applied on the intranet differs from the way it
is applied on the Internet. 
<P>
Intranets are generally more complicated than the Internet itself,
for many reasons. One reason is that these Internet-specific protocols
have to coexist and cooperate with other network protocols such
as IPX. Another is that intranets are often composed of a variety
of different local area networks, and they all must be hooked
together seamlessly. And in order to serve businesses, intranet
applications&#151;such as workgroup applications&#151;are often
required to be far more complex than those generally found on
the Internet. 
<P>
Because the Internet itself changes so fast and can be confusing,
and because intranet technology is that much more complex, it
often seems impossible to ever truly understand how an intranet
actually works. Proxy servers, filtering routers, Virtual Secure
Private Networks, firewalls, password protection schemes&#151;it
can all seem a jumble.
<P>
This book will help make it all much clearer. It will show you,
in carefully detailed illustrations, how the Internet actually
works. Whether you&#146;re an intranet administrator, or just
someone who wants to know more about how a modern corporate network
works, you'll find it a great help.
<P>
The book is divided into four major sections. In Part 1, &#147;An
Intranet&#146;s Building Blocks,&#148; we&#146;ll take a look
at the underlying technologies that make an intranet possible.
We&#146;ll begin by taking a global look at an intranet, and see
how all the pieces fit together and interact with the Internet.
We'll take a close look at how the Internet's two
most important protocols-TCP and IP-work. And we'll
also see how those protocols fit in and interact with other network
protocols. In Part 1 we&#146;ll also see how some of an intranet&#146;s
most important hardware works. We&#146;ll examine how routers
and bridges transfer data packets inside an intranet, between
an intranet and the Internet, and how they make sure that the
packets don't get lost. We'll also take a look at
intranet Web servers, and gain an understanding of how they deliver
Web pages to intranet Web browsers, and how they also interact
with Internet Web servers. 
<P>
Part 1 also takes a look at the underlying technology that makes
sending and receiving data on an intranet possible, the Domain
Name System. And we'll see how e-mail works on an intranet,
and see not just how the mail is delivered to other intranet users,
but also to people out on the Internet and on other intranets.
<P>
And in Part 1, we&#146;ll also look at two extremely important
technologies that allow intranet administrators and programmers
to write customized programs that can form the basis of an intranet.
We&#146;ll see how the Common Gateway Interface works, a technology
that allows the Web to interact with other resources, such as
corporate database. And we'll look at Java, a programming
language that allows people on an intranet to build truly interactive
applications.
<P>
In Part 2, &#147;Security and Intranets,&#148; we&#146;ll turn
our attention to what for many is the most complex part of any
intranet&#151;the hardware and software that protects intranets
against outside intruders. Hackers and crackers on the intranet
often feel it a badge of honor to break into corporate computers,
and security systems are what keeps them out, while still allowing
people inside the intranet to get access to the Internet. 
<P>
In this part, we&#146;ll look at how firewalls use a variety of
techniques to keep out intruders. We&#146;ll see how filtering
routers examine all packets coming into the intranet, and based
on what they find, allow some packets&#151;and people&#151;in,
while keeping others out. We&#146;ll take a close look at bastion
servers&#151;heavily fortified intranet servers designed to be
a primary line of defense against hackers. Proxy servers, which
allow people from inside the intranet to get at Internet resources,
are examined as well. The book details how authentication systems
work. These systems allow qualified users to log in by using passwords,
while keeping others out.
<P>
Other security issues we&#146;ll look at include the touchy issue
of how to block intranet users from visiting objectionable Internet
sites, such as those containing pornography. The book will also
examine in detail Virtual Secure Private Networks, an important
emerging security technology that allows intranets to communicate
with each other securely. Finally, we'll see how server-based
virus scanning tools can keep in intranet as virus-free as possible.
<P>
Part 3, &#147;Intranets and Groupware,&#148; shows how some of
the newest intranet technology works&#151;a kind of software that
has been lumped together under the general term of groupware.
Groupware is admittedly somewhat of a fuzzy term, and is thrown
around with great abandon-and with great imprecision-these
days. Generally, however, intranet groupware refers to intranet
technology that allows people in a corporation to collaborate
with each other electronically. It covers everything from simple
messaging to complex applications that lets people see what is
on each other's computer screens.
<P>
We&#146;ll get an overview in this section of all the important
intranet groupware technologies, and see how they work together
to make people communicate more efficiently.
<P>
Intranet discussion software also gets a close examination in
this section. Discussion software allows people to communicate
with each other on what are, in essence, sophisticated computer
bulletin boards. But these discussion areas, as well see, allow
people to do more than merely talk. They also can contain links
to other corporate resources, such as Web pages and corporate
databases.
<P>
Videoconferencing systems are covered here as well. With videoconferencing,
people across the country from each other can see each other and
talk to each other on their computers. It allows for one-on-one
conferencing, as well as large group conferencing as well.
<P>
A related technology, whiteboards, lets people see what others
have on their computer screens, and allows them to mark up those
documents, and talk to them about what they&#146;re marking up.
In this way, people separated geographically can work together
on the same document-a proposed budget for example. 
<P>
The final section of the book, Part 4, &#147;Applying the Intranet,&#148;
looks at how corporations can apply the technology to their businesses.
We'll see, for example, how an intranet allows people to
get access to corporate databases by using simple forms on intranet
Web browsers.
<P>
Usually an intranet is built well after a corporation has databases
and networks in place, and so in this section we&#146;ll also
see how these so-called legacy systems can be accessed from, or
even integrated into, a corporate intranet.
<P>
This section of the book also looks at intranet search tools&#151;systems
that allow people to sift through the vast amounts of information
on an intranet and find the precise information they need. And
we'll see how intranets can be accessed not just from corporate
offices, but from people's homes and while they are traveling
as well.
<P>
We&#146;ll invent a mythical corporation in this section of the
book, the CyberMusic record company, and look at how an intranet
helps CyberMusic work better. We&#146;ll see how CyberMusic uses
an intranet to market itself, do business with its customers,
and do business with other businesses. And we'll also see
how CyberMusic uses an intranet to deliver corporate news and
information to its employees, and how it uses the intranet for
training as well.
<HR>

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