TCP/IP For Dummies®

Table of Contents


About This Book

Conventions Used in This Book

Foolish Assumptions

How This Book Is Organized

Part I: TCP/IP from Names to Addresses

Part II: Getting Connected

Part III: Configuring Clients and Servers: Web, E-Mail, and Chat

Part IV: Even More TCP/IP Applications and Services

Part V: Network Troubleshooting and Security

Part VI: The Part of Tens

Icons Used in This Book

Where to Go from Here

Part I: TCP/IP from Names to Addresses

Chapter 1: Understanding TCP/IP Basics

Following Rules for the Internet: TCP/IP Protocols

Who’s in charge of the Internet and TCP/IP?

Checking out RFCs: The written rules

Examining Other Standards Organizations That Add to the Rules

Distinguishing Between the Internet, an Internet, and an Intranet

Extending Intranets to Extranets

Introducing Virtual Private Networks

Exploring Geographically Based Networks

Networks connected by wires and cables

Wireless networks

The geography of TCP/IP

Chapter 2: Layering TCP/IP Protocols

Taking a Timeout for Hardware

Starting with network connection media

Colliding with Ethernet

Stacking the TCP/IP Layers

Layer 1: The physical layer

Layer 2: The data link layer

Layer 3: The internet layer

Layer 4: The transport layer

Layer 5: The application layer

Chewing through Network Layers: A Packet’s Journey

Understanding TCP/IP: More than just protocols

Determining whether your network has a protocol, an application, or a service

Plowing through the Protocol List (In Case You Thought Only Two Existed)

Physical layer protocols

Data link layer protocols

Internet layer protocols

Transport layer protocols

Application layer protocols

Chapter 3: Serving Up Clients and Servers

Understanding the Server Side

Examining the server’s job

Identifying types of servers

Using dedicated servers

Understanding the Client Side

Defining a client

Clients, clients everywhere

Answering the Question “Are You Being Served?”

Supporting TCP/IP with Client/Server and Vice Versa

Recognizing Other Internetworking Styles: Peer-to-Peer Computing

Determining whether peer-to-peer workgroups are still handy

P2P applications — P2P across the Internet

Chapter 4: Nice Names and Appetizing Addresses

What Did You Say Your Host’s Name Is?

Playing the numbers game

Identifying a computer as uniquely yours

Translating names into numbers

Taking a Closer Look at IP Addresses

Savoring Classful Addressing

Recognizing the Parts of an IP Address

Class A is for a few enormous networks

Class B is for lots of big networks

Class C is for millions of small networks

Class D is for multicasting

Biting Down on Bits and Bytes

Obtaining an IP Address

Choosing whether to go public or stay private

Obeying the network police

Obtaining a globally unique IP address

Acquiring a static address

Getting dynamic addresses with DHCP

Finding out your IP address

Resolving Names and Addresses with DNS

Understanding the minimum amount of information about DNS

Using DNS to “Do Nifty Searches”

Describing Fully Qualified Domain Names (FQDNs)

Branching out into domains

Stalking new domains

Determining Whether the Internet Will Ever Fill Up

Choking on bandwidth

Panicking about not having enough addresses

Dishing Up More Kinds of Addresses

MAC: Media Access Control

Port numbers

Chapter 5: Need More Addresses? Try Subnetting and NAT

Working with Subnets and Subnet Masks

Defining subnet masks

Why a network has a mask when it has no subnets

Subnetting 101

Letting the DHCP Protocol Do the Work for You

One administrator’s nightmare is another’s fantasy

Understanding how the DHCP protocol works — it’s client/server again

Being evicted after your lease expires

Sharing Addresses with Network Address Translation (NAT)

Understanding how NAT works

Securing NAT

Using NAT and DHCP to work together

Swallowing NAT incompatibilities

Digesting NAT-PT (Network Address Translation-Protocol Translation)

Part II: Getting Connected

Chapter 6: Configuring a TCP/IP Network — the Software Side

Installing TCP/IP? Probably Not

Detecting whether TCP/IP is installed

Determining whether it’s IPv4, IPv6, or both

Savoring TCP/IP right out of the box

Six Steps to a Complete TCP/IP Configuration

Step 1: Determining whether your computer is a client or server or both

Step 2: Gathering client information

Step 3: Setting up your NIC(s)

Step 4: Deciding on a static IP address or a DHCP leased address

Step 5: Choosing how your host will translate names into IP addresses

Step 6: Gathering server information

Setting TCP/IP Client Properties

Configuring TCP/IP on a Mac OS X client

Configuring TCP/IP on a Linux or Unix client

Configuring a TCP/IP client on Windows Vista

Configuring a TCP/IP client on Windows XP

Setting TCP/IP Server Properties

Installing TCP/IP from Scratch

Feasting on Network Files

The local hosts file

The trusted hosts file, hosts.equiv

Freddie’s nightmare: Your personal trust file

The services file

Daemons Aren’t Devils

Relishing your daemons

Finding the daemons on your computer

Chapter 7: Networking SOHO with Wireless

Gulping the Minimum Hardware Details



Setting Up a Home Wireless Network in Four Steps

Step 1: Choose your wireless hardware

Step 2: Connect your wireless router

Step 3: Set up your wireless router

Step 4: Connect your computers

Securing Your Network

Securing the wired side

Securing the wireless side

Broadband for Everyone? We Hope

Level 1: Using wireless hotspots

Level 2: Paying for broadband wireless service

Level 3: Going anywhere you want to connect to the Internet with WiMAX

Chapter 8: Advancing into Routing Protocols

Understanding Routing Lingo

Routing Through the Layers — the Journey of a Packet

A new message heads out across the Net

The message visits the router

Into an Internet router and out again

Reaching the destination

Getting a Handle on How Routers Work

Getting Started with Routers

Swallowing Routing Protocols

Nibbling on IGP protocols

Exterior Gateway Protocols (EGP)

Understanding How BGP Routers Work

Juicing Up Routing with CIDR

C Is for Classless

CIDR pressing the routing tables

You say “subnet,” says “aggregate”

Securing Your Router

Coring the apple with Denial of Service (DoS) Attacks

Hijacking routers

Eavesdropping on BGP

It’s so sad

S-BGP (Secure BGP): Proposals to make BGP routing secure

Chapter 9: IPv6: IP on Steroids

Say Hello to IPv6

Digesting IPv4 limitations

Absorbing IPv6 advantages

If It Ain’t Broke, Don’t Fix It — Unless It Can Be Improved

Wow! Eight Sections in an IPv6 Address?

Why use hexadecimal?

There’s good news and there’s bad news

Take advantage of IPv6 address shortcuts

Special IPv6 Addresses

IPv6 — and the Using Is Easy

Checking out the network with autodiscovery

Ensuring that your address is unique

Automatically assigning addresses

Realizing that autoregistration says “Let us serve you”

IPv6 Installation

Configuring IPv6 on Windows XP and Windows Server 2003

Welcoming IPv6 to Mac OS X

Getting started with IPv6 in Unix and Linux

Other Delicious IPv6 Morsels

Security for all

Faster, better multimedia

Support for real-time applications

Improved support for mobile computing

Share the Planet — IPv6 and IPv4 Can Coexist

Stacking IPv4 and Iv6

Tunneling IPv6 through IPv4

Whew — You Made It!

Chapter 10: Serving Up DNS (The Domain Name System)

Taking a Look at the DNS Components

Going Back to DNS Basics

Revisiting Client/Server with DNS

Dishing up DNS client/server definitions

Snacking on resolvers and name servers

Who’s in charge here?

Serving a DNS client’s needs

Oops! Can’t help you

Who’s Responsible for Name and Address Information?

Understanding Servers and Authority

Primary name server: Master of your domain

Secondary name servers

Caching servers

Understanding Domains and Zones

Problem Solving with Dynamic DNS (DYNDNS)

Diving into DNSSEC (DNS Security Extensions)

Why does DNS need DNSSEC?

Glimpsing behind the scenes of DNSSEC

Part III: Configuring Clients and Servers: Web, E-Mail, and Chat

Chapter 11: Digesting Web Clients and Servers

Standardizing Web Services

Deciphering the Languages of the Web






Java and other Web dialects

Hypertext and hypermedia

Understanding How Web Browsing Works

Serving up a Web page

Storing user information as cookies

Managing cookies with your browser

Dishing up multimedia over the Internet

Feeding Web Pages with Atom and RSS

Reducing the Web’s Wide Waistline to Increase Speed

Proxy Serving for Speed and Security

Caching pages

Improving security with filtering

Setting up a proxy client

Finishing touches

Setting Up a Caching Proxy Server

Outlining the general steps for installing and configuring squid

Configuring squid for Microsoft Windows Server 2008

Browsing Securely

Ensuring that a site is secure

Using your browser’s security features

Setting Up a Web Server

Setting up the Apache HTTP Server

Speeding up Apache

Making Apache more secure

Adding Security to HTTP

Taking a look at HTTPS

Getting up to speed on SSL

Stepping through an SSL Transaction

Using Digital Certificates for Secure Web Browsing

Chapter 12: Minimum Security Facilities

What’s the Worst That Could Happen?

Jump-Starting Security with the Big Three

Installing a personal firewall

Vaccinating your system with the anti-s

Encrypting data so snoopers can’t read it

Adding a Few More Basic Protections

Chapter 13: Eating Up E-Mail

Getting the Big Picture about How E-Mail Works

Feasting on E-Mail’s Client-Server Delights

E-mail clients

E-mail clients versus Web mail clients

E-mail servers

Postfix: Configuring the fastest-growing MTA

Sharpening the Finer Points of Mail Servers

Transferring e-mail by way of store-and-forward

Transferring e-mail by way of DNS MX records

Understanding How SMTP Works with MTAs

Defining E-Mail Protocols

Adding More Protocols to the Mix





DNS and its MX records

Chapter 14: Securing E-Mail

Common Sense: The Most Important Tool in Your Security Arsenal

Being Aware of Possible Attacks


Popping up and under

Getting spied on

Meeting malware


Have you got anything without spam? Spam, spam, spam!


Finding Out Whether You’re a Victim

Playing Hide-and-Seek with Your E-Mail Address

Layering Security

Layer 1: Letting your ISP protect your network

Layer 2: Building your own walls

Layer 3: Securing e-mail on the server side

Layer 4: Securing e-mail on the client side

Layer 5: Suitely extending e-mail security

Using Secure Mail Clients and Servers

Setting up a secure IMAP or POP client

Setting up a secure mail server

Encrypting e-mail

Chapter 15: Beyond E-Mail: Social Networking and Online Communities

Thumbing to Talk About

Choosing a Communication Method

Getting together with IRC

Jabbering with XMPP

Feeding Your Craving for News

Getting Even More Social

Part IV: Even More TCP/IP Applications and Services

Chapter 16: Mobile IP — the Moveable Feast

Going Mobile

Understanding How Mobile IP Works

Sailing into the Future: Potential Mobile IPv6 Enhancements

Mobilizing Security

Understanding the risks

Using basic techniques to protect your mobile devices

Chapter 17: Saving Money with VoIP (Voice Over Internet Protocol)

Getting the Scoop on VoIP

Getting Started Using VoIP

Step 1: Get broadband

Step 2: Decide how to call

Step 3: Make the call

Step 4: Convert the bits back into voice (with VoIP software)

Step 5: Converse

Yo-Yo Dieting: Understanding How VoIP Packets Move through the Layers

Trekking the Protocols from RTP to H.323

Talking the talk with the TCP/IP stack and more

Ingesting VoIP standards from the ITU

Vomiting and Other Vicious VoIP Vices

Securing Your Calls from VoIP Violation

You, too, can be a secret agent

Authenticating VoIP-ers

Keeping voice attacks separate from data

Defending with firewalls

Testing Your VoIP Security

Chapter 18: File and Print Sharing Services

Defining Basic File Sharing Terms

Using FTP to Copy Files

Understanding how FTP works

Using anonymous FTP to get good stuff

Choosing your FTP client

Transferring the files

Securing FTP file transfers

Using rcp or scp to Copy Files

Sharing Network File Systems

Nifty file sharing with NFS (Network File System)

Solving the buried file update problem with NFSv4

Examining the mount Protocol


Configuring an NFS Server

Step 1: Edit the exports file

Step 2: Update the netgroup file

Step 3: Start the daemons

Configuring an NFS Client

Picking Up Some NFS Performance Tips

Hardware tips

Server tips

Client tips

Weighing performance against security

Getting NFS Security Tips

Sharing Files Off the Stack

Using Windows network shares

Using Samba to share file and print services

Working with Network Print Services

Valuing IPP features

Setting up Windows Server 2008 print servers over IPP

Printing with the Common Unix Print System (CUPS)

Chapter 19: Sharing Compute Power

Sharing Network Resources

Accessing Remote Computers

Using a telnet client

“R” you ready for more remote access?

Executing commands with rsh and rexec

Securing Remote Access Sessions

Taking Control of Remote Desktops

Sharing Clustered Resources

Clustering for high availability

Clustering for load balancing

Clustering for supercomputing

Sharing Compute Power with Grid and Volunteer Computing

Part V: Network Troubleshooting and Security

Chapter 20: Staying with Security Protocols

Determining Who Is Responsible for Network Security

Following the Forensic Trail: Examining the Steps for Securing Your Network

Step 1: Prescribing Preventive Medicine for Security

Step 2: Observing Symptoms of Malware Infection

Uncovering more contagions

Step 3: Diagnosing Security Ailments with netstat, ps, and Logging

Monitoring network use with ps

Nosing around with netstat

Examining logs for symptoms of disease

Syslog-ing into the next generation

Microsoft proprietary event logging

Chapter 21: Relishing More Meaty Security

Defining Encryption

Advancing Encryption with Advanced Encryption Standard (AES)

Peering into Authentication

Do you have any ID? A digital certificate will do

Getting digital certificates

Using digital certificates

Checking your certificates

Coping with certificate problems

IPSec (IP Security Protocol): More Authentication

Kerberos — Guardian or Fiend?

Understanding Kerberos concepts

Playing at Casino Kerberos

Training the dog — one step per head

Setting up a Kerberos server step by step

Setting up a Kerberos client step by step

Chapter 22: Troubleshooting Connectivity and Performance Problems

Chasing Network Problems from End to End

Getting Started with Ping

Pinging away with lots of options

And now, for “some-ping” completely different: Running ping graphically

Death by ping

Diagnosing Problems Step by Step

Pinging yourself and others

Using nslookup to query a name server

Using traceroute (tracert) to find network problems

Simplifying SNMP, the Simple Network Management Protocol

Just barely describing how SNMP works

Using SMNP programming free

Part VI: The Part of Tens

Chapter 23: Ten More Uses for TCP/IP

Find Internet Traffic Jams

Take Language Lessons on Your Phone

Visit Antarctica (Armchair Traveler)

Check on the State of the Internet

Create Animations Online

Test Your Computer’s Security for Free

Watch Diet Coke and Mentos Explode

Ride in a Big Rig Over 350 Miles of Ice

Chapter 24: Ten More Resources for Information about TCP/IP Security

Security from A to Z

CERT-ainly Don’t Forget the CERTs

Take a Virtual Museum Tour

Crime Stoppers’ Cinema

The TCP/IP Guide — Free and Online

Finding Podcasts about Internet Security

Save the Children

Microsoft TechNet Library

Security Cuisine

TCP/IP For Dummies®, 6th Edition

by Candace Leiden and Marshall Wilensky

Foreword by Scott Bradner

University Technology Security Officer, Harvard University


About the Author

Forced to learn about computers because she was afraid of slide rules, Candace Leiden has worked as a software developer, system administrator, and database designer and administrator. Formerly the president of Cardinal Consulting, Inc., Candace is now a systems and database performance consultant and instructional design consultant for international courseware in those areas. Her customers have included Cardinal Consulting, Compaq Computer, Digital Equipment Corporation, the United Nations, several major pharmaceutical corporations, Oracle Corporation, and Hewlett-Packard. Candace is an internationally recognized speaker on relational databases and the Linux and Unix operating systems. Candace is also the author of Linux Bible (Wiley Publishing). Candace met Marshall Wilensky in 1981, when they worked at the same company. She taught him everything he knows.

Marshall Wilensky has been wrangling computers and networks for more than 30 years (and still has fewer wrinkles than Candace and less gray hair). In corporate life, he has had the privilege of working for companies ranging from 25 people (who are 25 years old) to more than 300,000 worldwide. He has been a consultant, a programmer, a system administrator, and a network manager for large multivendor and multiprotocol networks, including those at the Harvard University Graduate School of Business Administration.

Marshall met Candace Leiden in 1981 when they worked at the same company. He taught her everything she knows. They are also, most importantly, married (to each other). Candace and Marshall are both members-at-large of ICANN (Internet Corporation for Assigned Names and Numbers).


Candace dedicates this book to Marshall Wilensky (no one knows the meaning of the phrase “in sickness and in health” better than Marshall) and to Emily Duncan, who is wise beyond her years. Even though she has been through some tough times, Emily rules!

Marshall dedicates this edition of the book to his late parents, Leo and Estelle Wilensky, and to Roxcy Platte and the people who help him with the toughest subject he has ever tackled.

In memory of:

Helen Louise Duncan

Christine Evans Staley

They are missed every day.

Author’s Acknowledgments

Thanks to everyone at Wiley who worked on this book. We continue to be surprised at how many people it takes to create a book. We’d like to thank the team at Wiley for putting up with us. Thanks also go to Katie Mohr, for her patience and diplomacy. So many people worked hard to turn our manuscript into a real book. Thanks also to our project editor, Kim Darosett, who never once had a discouraging word. When we finish a manuscript, Kim still has a lot of hard work to do. We’re grateful to Kim, Rebecca Whitney, Jen Riggs, and Barry Childs-Helton for their hard work. Their edits make this a better book in many ways. We appreciate the work the Composition Services department did in drawing tidy figures from our rough, hand-drawn sketches and in making our screen shots and text files look nice.

Finally, thank you to Cynthia Woods, a gifted and inspiring musician, who allowed us to use her beautiful Web page as one of our examples.

Publisher’s Acknowledgments

We’re proud of this book; please send us your comments through our online registration form located at

Some of the people who helped bring this book to market include the following:

Acquisitions, Editorial, and Media Development

Project Editor: Kim Darosett

Acquisitions Editor: Katie Mohr

Copy Editors: Barry Childs-Helton, Heidi Unger, Rebecca Whitney

Technical Editor: Allen Wyatt

Editorial Manager: Leah P. Cameron

Editorial Assistant: Amanda Foxworth

Sr. Editorial Assistant: Cherie Case

Cartoons: Rich Tennant (

Composition Services

Project Coordinator: Patrick Redmond

Layout and Graphics: Reuben W. Davis, Timothy C. Detrick, Melissa K. Smith, Christine Williams

Proofreaders: David Faust, Jessica Kramer, Lisa Young Stiers

Indexer: Estalita Slivoskey

Publishing and Editorial for Technology Dummies

Richard Swadley, Vice President and Executive Group Publisher

Andy Cummings, Vice President and Publisher

Mary Bednarek, Executive Acquisitions Director

Mary C. Corder, Editorial Director

Publishing for Consumer Dummies

Diane Graves Steele, Vice President and Publisher

Composition Services

Debbie Stailey, Director of Composition Services


For both good and ill, modern society around the world has been transformed by the Internet. But the Internet was not the first data communications network, not by a long shot. So what was it about the Internet that enabled the revolution? In a very basic way, it was the use of TCP/IP. TCP/IP enabled the Internet to be the first data network where the use could be driven by the users and not controlled by the carriers. TCP/IP is an end-to-end protocol. The network is there to carry the bits from any device at the edge of the network to any other device. This stands in stark contrast to X.25, frame relay, ATM, and other carrier-managed data networks, where the carrier determined who you could talk to, and in an even starker contrast to the phone network, where the carrier determined what you could do.

This end-to-end architecture has resulted in an amazing proliferation of applications because the network does not get in the way of individual entrepreneurs developing the next great thing and running it over the Internet. It also did not get in the way of millions of people putting up their own Web pages, or, with somewhat more controversy, swapping music and movie files. Even if you take into account the Internet boom and subsequent bust, the Internet, and TCP/IP, are here to stay. And, while here, they will continue to radically change the way we interact with employers, service providers, each other, and the world at large.

You can easily go through life without having to understand how this Internet thing works because it will continue to work even if you do not understand it. I do not have any meaningful understanding of the Theory of Relativity yet make use of its implications every day.

TCP/IP For Dummies, 6th Edition, is for those of you who aren’t just curious about how things work, but who want to actually understand what’s behind the curtain. (Hint: It’s not the Wizard of Oz.)

— Scott Bradner
University Technology Security Officer, Harvard University


TCP/IP is the glue that holds together the Internet and the World Wide Web. To be well connected (network-wise, that is), sooner or later you have to become familiar with TCP/IP applications and services. If you want to understand what TCP/IP is, what it’s for, why you need it, and what to do with it, and you just don’t know where to start — this book is for you.

If you’re on a network, whether you know it or not, odds are, you’re working with TCP/IP and its many pieces and parts. We help you understand how it all fits together. We also give you plenty of hands-on tips so that you can get all those pieces and parts set up and running.

We take the mystery out of TCP/IP by giving you down-to-earth explanations for all the buzzwords and technical jargon that TCP/IP loves.

This isn’t a formal tutorial; skip around and taste TCP/IP in little bites. If you need to impress your boss and colleagues with buzzwords, you can find out just enough to toss them around intelligently with the technocrats at meetings and parties. Or, you can go further and discover how to set up and use the most important features and tools. If you want the full TCP/IP banquet, you can explore the technical tasks that take place behind the scenes to make the Internet and the Web work. It’s right here in your hands.

About This Book

We hope you find TCP/IP For Dummies, 6th Edition, to be a fun and fast way to dive into the guts of the Internet. The book is both an introduction to the basics and a reference to help you work with Internet applications and tools on all kinds of connected computers. We added and updated the latest Internetworking protocols and servers — with examples from Microsoft Windows Server 2008, Windows 7, Windows Vista, Windows XP, Linux, Unix, and Mac OS X. Here are just a few of the subjects we describe:

Uncover the relationships among TCP/IP, the Net, and the Web.

Get up and running and keep running on the Internet, whether you have a small network or a big enterprise network and whether it’s wired or wireless.

Install and configure TCP/IP client and server applications and services.

Phone home without the phone or the bill, thanks to VoIP.

Build and enforce security everywhere on your network.

Get in on all the newest Internet security protocols and trends.

Boldly go to the next generation: IPv6.

This book is loaded with information. But don’t try to read it from cover to cover in one sitting — you may hurt yourself. If your head explodes and bits and bytes go flying, please don’t blame us.

Conventions Used in This Book

All commands that you need to enter yourself appear either in bold, like this, or on a separate line, like this:

COMMAND to type

To enter this command, you type COMMAND to type exactly as you see it here and then press Enter.

warning_bomb.epsWhen you type commands, be careful to use the same upper- and lowercase letters that we show you. (Some computer systems are fussy about this issue.)

When we want you to move through a series of menus or buttons, we say “Click” once and then point to the next place with a command arrow (⇒).

Whenever we show you something that’s displayed onscreen (such as an error message or a response to your input), it looks like this:

A TCP/IP message on your screen

Foolish Assumptions

In writing this book, we tried not to make too many assumptions about you. We figure that you’ve done a little Web browsing and e-mailing. Our only assumption is that you’re not really a dummy — you’re just trying something new. Good for you!

How This Book Is Organized

This book contains five parts, each of which contains several chapters. We don’t expect you to read the whole book from cover to cover, but please feel free to do so. Instead, you can glance at the table of contents for the topic you’re interested in and go from there. The layout of the book is easy to follow. Here’s a quick look at what you can find in each major part.

Part I: TCP/IP from Names to Addresses

Part I starts at the beginning with the buzzwords and how TCP/IP and the Internet are joined at the hip. You also find out that, contrary to its name, TCP/IP is so much more than just two protocols. We give you a quick look at the most important protocols, and you get to see all the lingo that should take you far through this century.

You’ll find that as much as people like names, computers like numbers even more. After you get some of the buzzwords under your belt, the chapters in Part I explain what an Internet protocol (IP) address is, how to build one, how to use it, and how to be frugal and save enough Internet addresses for someone else. We clue you in on different ways to make IP addresses go further. No worries — the Internet won’t get full.

Part II: Getting Connected

After you know how IP addresses are constructed, we move on to setting up your TCP/IP network, both wired and wireless, to connect to the world (the Internet). In this part of the book, we show you how hardware and software work together to make a network. We discuss just the minimum hardware you need to understand.

Then we throw in IPv6, which puts you ahead of most people in understanding the next generation of Internet addresses. If you’re not ready to go where no one (well, hardly anyone) has gone before, don’t worry — you can skip Chapter 9 entirely.

Part III: Configuring Clients and Servers: Web, E-Mail, and Chat

TCP/IP is a big set of protocols, services, and applications. Whether you’re aware of it or not, you use TCP/IP applications and services to do everything from reading news to exchanging e-mail and online conversations with your friends to copying good stuff like games, technical articles, and even TCP/IP itself. This section explains how these applications and services work behind the scenes with client/server technology. The numerous hands-on sections help you configure popular applications and services for both clients and servers.

Security is one of the stars of Part III. Hackers love to try to break into your Web, e-mail, and chat applications, and we love to show you how to thwart their every move. We throw in a quick-start security guide to get you going. If you’re interested in online shopping or banking, we walk you through a secure Internet credit card transaction.

Part IV: Even More TCP/IP Applications and Services

“How could there possibly be more?” you might ask. Well, we told you that TCP/IP consists of much more than just a couple of protocols — for example, there’s Mobile IP, for when you take your laptop to your favorite café rather than to your office. If you have a smartphone or organizer, such as a Palm or BlackBerry, you need to know this stuff. But wait! There’s more. How about saving big bucks on phone calls? With or without a phone? Voice over Internet Protocol, or just VoIP, lets you make calls, even international ones, for free. Finally, Part IV covers remote access applications, from sharing files to working on someone else’s computer when you’re 5,000 miles away.

Part V: Network Troubleshooting and Security

Part V delves into some advanced topics. If you’re a system or network administrator, you may need to know more than just the basics about network hardware. We hope that after you install and configure TCP/IP and your network applications, nothing ever goes wrong for you, but stuff happens. Part V steps you through a basic troubleshooting procedure so that you can figure out what went wrong and where. Then you can fix it.

The rest of Part V is devoted to security. You find practical security tips, and you can delve deeper, to see how to use encryption, authentication, digital certificates, and signatures. You get hands-on advice for setting up a software firewall and the Kerberos authentication server.

Part VI: The Part of Tens

You may already know that every For Dummies book has one of these parts. In it, you can find security tips, Internet traffic factoids, advice about places to go and things to do (even if you never leave your computer), and more security pointers. And all this happens in, roughly, sets of ten.

Icons Used in This Book

TechnicalStuff.epsSignals nerdy technofacts that you can easily skip without hurting your TCP/IP education. But if you’re even a part-time techie, you probably love this stuff.

Tip.epsIndicates nifty shortcuts that make your life easier.

warning_bomb.epsLets you know that a loaded gun is pointed directly at your foot. Watch out!

Remember.epsMarks information that’s important to commit to memory. To siphon off the most important information in each chapter, just skim through these icons.

security.epsMarks important TCP/IP security issues. Lots of security icons are in this book.

Where to Go from Here

Check out the table of contents or the index and decide where you want to start. If you’re an information technology manager, you’re probably interested in buzzwords and you know why everyone is on the TCP/IP bandwagon. If you’re a system or network administrator, start with Chapter 2 or 4, where we describe the major protocols and what they do. Chapters 12, 14, 20, and 21 talk about Internet security — a topic that’s for everyone concerned that their personal data is at risk.

Or, you can just turn the pages one by one. We don’t mind. Really.

Part I

TCP/IP from Names to Addresses


In this part . . .

You can’t play the game if you don’t know the rules. And TCP/IP is the set of rules, or protocols, for networks. TCP/IP is the software underpinning of the Internet and its World Wide Web. TCP/IP also includes services and applications that work with the protocols. Before we get into the hairy details of the protocols themselves, we give you some background on the people and committees who decide the direction of TCP/IP’s growth. Did you know that you can be part of these groups? We tell you how. You also become familiar with TCP/IP and Internet buzzwords.

Part I then delves into the ingredients of the TCP/IP suite: the protocols and services themselves and IP addressing. You see how the protocols fit into the layers of the TCP/IP network model, and you take a look at the most important ones. TCP/IP is a suite because it consists of more protocols than the two it’s named for, plus a set of services and applications. The TCP/IP protocols, services, and applications in the suite work together just like the rooms in a hotel suite or the pieces in a furniture suite work together. The set of protocols is also referred to as a stack.

From there, we go into Internet addressing.

People love names. Computers love numbers. You’ll hear this in each part of this book.

If your computer is named Woodstock, for example, the Internet may think of it as You get to see how to build and understand these numeric addresses. Also, if you’re worried because you think that the Internet is running low on addresses, Part I eases your worries by cluing you in to a couple of different ways to make IP addresses go further: subnetting and NAT (Network Address Translation).

Bear in mind that TCP/IP stays alive by morphing regularly — at times, daily. So, the list of protocols we describe here — the Internet’s rules — will be even longer by the time you read this book.