Preston Gralla
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| Publisher | Stacy Hiquet |
| Associate Publisher | Juliet Langley |
| Acquisitions Editor | Lysa Lewallen |
| Development Editor | Paula Hardin |
| Copy Editor | Margo Hill |
| Technical Reviewer | Mark Butler |
| Production Editor | Barbara Dahl |
| Proofreader | Jeff Barash |
| Cover Illustration | Mina Reimer |
| Cover Design | Regan Honda and Megan Gandt |
| Book Design | Carrie English and Bruce Lundquist |
| Lead Illustrator | Mina Reimer |
| Contributing Illustrators | Sarah Ishida, Karl Miyajima, Joan Carol, and Chad Kubo |
| Page Layout | M.D. Barrera |
| Indexer | Valerie Robbins |
Copyright © 1996 by Macmillan Computer Publishing USA. All rights reserved.
PART OF A CONTINUING SERIES
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.
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.
THE INFORMATION AND MATERIAL CONTAINED IN THIS BOOK ARE PROVIDED “AS IS,” 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.
ISBN 1-56276-441-1
This book wouldn’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.
And, as always, I’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.
The Internet has been hailed by many as the most revolutionary technology that computing has seen. It’s a technology that affects not just the computing world, but the noncomputing world as well: You can’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.
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—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.
When Internet technology is applied and used inside a corporation, and open only to its employees, it is referred to as an intranet. 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 firewall.
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.
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—such as workgroup applications—are often required to be far more complex than those generally found on the Internet.
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—it can all seem a jumble.
This book will help make it all much clearer. It will show you, in carefully detailed illustrations, how the Internet actually works. Whether you’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.
The book is divided into four major sections. In Part 1, “An Intranet’s Building Blocks,” we’ll take a look at the underlying technologies that make an intranet possible. We’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’ll also see how some of an intranet’s most important hardware works. We’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.
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.
And in Part 1, we’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’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.
In Part 2, “Security and Intranets,” we’ll turn our attention to what for many is the most complex part of any intranet—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.
In this part, we’ll look at how firewalls use a variety of techniques to keep out intruders. We’ll see how filtering routers examine all packets coming into the intranet, and based on what they find, allow some packets—and people—in, while keeping others out. We’ll take a close look at bastion servers—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.
Other security issues we’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.
Part 3, “Intranets and Groupware,” shows how some of the newest intranet technology works—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.
We’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.
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.
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.
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’re marking up. In this way, people separated geographically can work together on the same document-a proposed budget for example.
The final section of the book, Part 4, “Applying the Intranet,” 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.
Usually an intranet is built well after a corporation has databases and networks in place, and so in this section we’ll also see how these so-called legacy systems can be accessed from, or even integrated into, a corporate intranet.
This section of the book also looks at intranet search tools—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.
We’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’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.