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Installing, Troubleshooting, and Repairing Wireless Networks Jim Aspinwall McGraw-Hill New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Sing

Troubleshooting, and Repairing Wireless Networks

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Installing,

Troubleshooting, and Repairing Wireless Networks

Jim Aspinwall

McGraw-Hill

New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto

Copyright © 2003 by The McGraw-Hill Companies, Inc All rights reserved Manufactured in the United States of America Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher

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DOI: 10.1036/0071429255

Most authors select one or a few people that have inspired them throughtheir work—and for those few special people who have inspired me thereare many, many more who have fueled their inspirations and ability toinspire I cannot limit myself to the select few without calling to mindthe many—by name or your inspirational efforts

Events of the past 2–3 years have provided the truly exceptional

opportunity and pleasure of working with so many wonderful people

applying themselves in many different fields and ways towards worthycauses Just as I feel strongly about acknowledging the work of the peo-ple behind projects such as this, I feel moved to elation and tears by peo-ple applying themselves towards the basics of life that make it possible

to write, produce and ultimately read the work we produce

There is so much that touches us one way or the other—and it canaffect us and those around us deeply and most importantly—and I feel itdeserves some thought and taking advantage of an opportunity for a call

to action To that, my modest words to recognize and apply positive

ener-gy to all efforts of awareness, enlightenment, encouragement, educationand action Technology is nothing without the people we share it with.First and perhaps specifically—to the literally thousands and thou-sands of people who have given incredible amounts of time and physicaleffort participating or in support of charitable efforts to raise funds forthose baffling diseases we have yet to solve Almost anyone can fix myri-

ad computer problems—it takes thousands, perhaps millions of ustogether working towards treatment and cures for the many cancers anddisorders that alter our lives or the lives of those we know and love insome way, and too all to many who unfortunately pay the ultimate sac-rifice The monsters must be conquered

And so to the walkers, crews and volunteers of the Avon breast cancerfundraising efforts—we know the love, the work, the tears—eventually

we will know the cure We do not want any more of our families orfriends to know this monster “Just a little bit farther” my friends!

To the efforts of the participants and teams contributing to leukemiaand lymphoma One of my “fan club” of people frequently asking for helpwith her computer was recently diagnosed with leukemia—I cannot cure

her disease but I hope someone can so that she and others are able to

continue to experience and accomplish computer challenges, and moreimportantly the essential qualities a long healthy life has to offer!

To those who work towards detecting and solving diabetes—some of

my very best mentors have been affected and I want them and others to

be well and mentoring others

To mentors and teachers—the ability and dedication to share mation to enrich our lives through raising interest and improving abili-ties is so special indeed Hopefully you are inspired directly or indirectly

infor-by the lives you help move forward

To our audience—those new to my work and those who make up themarket and inspiration to produce such works I would have no reason

to do this if it were not for you

To my wonderful wife Kathy—an all too frequent “author’s widow”through the creation of this work and my hobbies, and a two-time Avonwalker and crew member who exposed me to the most awesome opportu-nities for awareness and inspiration I may ever know I love you

“Good job Keep going!”

Dedication

vi

Chapter 2 Wireless Network Criteria

and Expectations 19

Who Will Design, Install, and Maintain

Chapter 3 Wireless Network Basics 33

How Did Wireless Suddenly Come to Involve Wires? 41

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Chapter 4 Antennas and Cables 43

Antenna Radiation Polarity and Diversity 56

Chapter 5 Common Wireless Network Components 69

Power Limitations for 802.11b Systems 78

Wireless Internet Service Providers 100

Contents

viii

Chapter 7 Hardware Installation and Setup 105

What the Instruction Manual Will Tell You 108

Connecting and Configuring Your Access Point 111Connecting and Configuring Your Client Adapters 112

Antennas versus Adding a Bridge and Access Point 140

Avoiding Channel Overlap and Other Networks 146

Chapter 10 Software for Wireless Networks 163

Chapter 11 Wireless Access and Security Solutions 177

Funk Software: Odyssey Installation 178

Configure Dynamic DNS Updates and Always-On KeepAlives 247Local Firewall Security and Virus Protection 249

Contents

x

Chapter 14 Neighborhood and Community

Wireless Networks 253

Chapter 15 Upcoming Standards and Trends 267

Using Radios and Resources for Networking 268Going Beyond Current Wireless Networking Standards 274

Boy Scouts and Mariners Need Not Apply 288

Mast and Antenna Installation Materials 291Good Neighbor Policy and Local Regulations 294

Appendix C On the CD-ROM 323

Wi-Fi or 802.11b is being heralded as the “next big thing.” It is beingused to create “hotspots” or points of wireless access to the Internet andbeyond in airports, hotels, coffee shops and other places where themobile workforce congregates

Wi-Fi is also being installed in more homes and offices than everbefore The Wi-Fi association states that in 2002 more than thirty mil-lion Wi-Fi devices were sold at retail and in 2003 this number couldmore than double Notebook computer companies are building Wi-Ficapability into most of their products and the cost of the infrastructure(access points) as well as PC card devices has plummeted

Wi-Fi proponents believe that Wi-Fi connections will become nearlyubiquitous over the next few years with both “for fee” and free access tothe Internet becoming so prevalent that the need for wide-area wirelessdata systems will be compromised and all of us will be able to wirelesslyconnect via this technology almost anywhere New players are emergingalmost daily The latest, Cometa, is a joint venture between AT&T,Intel, and several investment companies Cometa’s goal it is to installand operate 20,000 hotspots in the top fifty cities in the United States.Today there are about 5,000 hotspots in operation—adding 20,000 more

is a big undertaking

But is Wi-Fi really easy to use? Is it secure? Will notebook and PDAusers flock to hotspots? At the moment, there are more questions thananswers in the Wi-Fi world A newer, faster version of Wi-Fi is beingembraced by the consumer electronics industry to be used for distribu-tion of video and audio content in our homes Computer makers havedecided to hedge their bets by building both versions of Wi-Fi into theirproducts starting in 2003

Jim Aspinwall is a “hands on” person We have worked togetherinstalling radio systems on mountaintop radio sites and we have spentmany hours discussing the issues surrounding the convergence of com-

xiii

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puting and communications Jim is particularly well qualified to duce you to the world of Wi-Fi and draws on his experience in both thecomputer and communications fields as he explains this complex topic insimple, easy-to-understand terms I believe that you will find the follow-ing pages to be a well written, valuable source of information.

intro-Andrew M SeyboldEditor-in-Chief

Forbes/Andrew Seybold’s Wireless Outlook

Foreword

xiv

thou-There are many to acknowledge as such an effort is conceived,

creat-ed, implementcreat-ed, and distributed Writing a book may be the easiestpart Producing one that delivers useful information, looks good, andmakes sense is the task of many people behind the scenes In this casethere is no question where to start in acknowledging and appreciatingthose involved

Judy—my beloved acquisitions editor She got stuck with me and

“IRQ, DMA, & I/O” back in 1995 and encouraged me through a lot ofinteresting work since that eventually led to the conception of this proj-ect I am forever grateful!

Patty—our typesetter on this project She makes my words look like areal book

The production staff at McGraw-Hill I do not know you all by name

or the work you do, but thank you very much for doing it!

Tim Pozar—RF engineering genius Years of experience and a anced nature towards real world applications of RF and technology arerare assets Making human readable sense of the FCC rules is but one ofhis contributions to this field Thank you Tim!

bal-Andy Seybold—can insight get any better? If it’s radio, bal-Andy’s done it

If it’s computing, Andy’s done it To put them together and figure outthe reasonable from the fantasy in economic or practical value is unique.Thank you Andy for your inspiration and good words!

BAWUG—the Bay Area Wireless User Group I’ve snooped anddropped a few little “bombs” on their mailing list and attended a couple

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of meetings, and must acknowledge that technology is truly driven bysome very sharp, wary, and forward thinking people.

Some first-class contributing hardware and software vendors Sharon

at HyperLink Technologies The folks in marketing and PR at LinkSys,Orinoco Wireless, Amphenol-Connex, Funk Software, WiMetrics, Wild-Packets, AirMagnet, and several others

Acknowledgments

xvi

Wireless Essentials

CHAPTER

1

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This book focuses on what is commonly known as 802.11 and WiFiwireless networking technologies—their implementation and prob-lem-solving To set perspective, it briefly covers the wireless context,history, benefits, costs, and governmental issues related to the cur-rent state of wireless networking.

The term wireless is generic, and while it is typically synonymous

with radio, it is not limited to radio Wireless can also be defined asultrasonic (sound) or infrared (light) wave communication betweentwo devices

When wireless is used in the context of radio wave (the portion ofknown spectrum between sound and light waves) communications,dozens of issues come into play—most of them regulatory and technical

In terms of networking, wireless replaces the patch cables, patchpanels, hubs, and network adapters or hard-wiring between a com-puter, printer, or similar device and another; or replaces larger scalecommon network equipment with a different style of networkadapter—essentially a “data radio”—perhaps an additional externalantenna and the airwaves Of course the connection between the dataradio or wireless networking adapter and an antenna involves awire—but far less wire than dragging a cumbersome cable across thefloor around your living room or a meeting room at the office, andmuch less than trying to get wired to a network connection a fewmiles away

When you think of wireless networking, visions of connecting to theInternet, or a home or office network with your personal computer(PC) or personal digital assistant (PDA) as readily as using a cellularphone come to mind While desirable, this ideal situation is not aseasily achievable or reliable as the creation and maintenance of sub-scriber-based cellular phone services—backed by major corporationswith billions of dollars and a recurring revenue stream Some of thesecomplexities will become obvious as we delve into this chapter.Wireless networking also brings up security issues—your data are

no longer safely tucked within the confines of a set of wires overwhich you have control—because radio signals have few tangible orcontrollable boundaries It is this lack of tangible, controllable bound-aries that makes wireless both attractive and complex in many ways

Chapter 1

2

Wireless Defined

Wireless has been, and will be, a part of everyday life and ing in a couple of different forms The first is infrared or light-wavecommunications between specific devices and a virtual port on a

comput-PC Other implementations use radio communications—fromNational Semiconductor’s Airport modules, which essentially create

an over-radio null-modem extension between two PCs’ serial portsfor use with programs such as pcAnywhere or LapLink, throughcellular-phone-aware modems, to a variety of 400 MHz, 900 MHz,and 2400 MHz (2.4 GHz) radio connections All of these have incommon the benefit of not having to use a variety of different con-nectors, adapters, and wires, to transfer data between one deviceand another

Wireless Equals Infrared

Infrared (IR) or light-wave communications is most prevalent inremote control devices for televisions, VCRs, and stereos, and hasfound its way into computer keyboards, pointing devices, printers,and PDAs IR devices are good miniature models for studying someaspects of radio frequency wave communications—particularly forhigher frequency applications such as cellular phones, Bluetooth,and 802.11 wireless networking devices

Light waves are a strictly line-of-sight means of getting tion from one device to another This means that both devices musthave a clear, unobstructed visual path between them Obstructionsmay be as obvious as the back of your favorite chair blocking the(invisible) light beam from reaching the TV, or as subtle and baffling

informa-as the smoked-glinforma-ass door on your stereo cabinet A less obvious form

of interference with IR remote control devices is bright artificial ornatural sunlight overwhelming the detector in the appliance you arecontrolling, making it difficult or impossible to determine what com-mand you are sending

There are some work-arounds to the challenges presented to of-sight communications You can, of course, play tricks with mirrors

line-to “bend” light around corners, which is a valuable example of thecharacteristics of radio wave behavior You may also place detectors

and retransmitters or repeaters in between the devices to extend orbend the signals around corners too—which is exactly the servicenetwork repeaters and back-to-back radio links do for radio-basedsystems If you could see IR light waves and play with them like youcan laser beams and simple flashlights, you could study these con-straints quite easily Your next best substitute would be to use a the-atrical fogger or some dry ice and flashlights or a laser pointer toplay with light dispersion, distortion, reflection, and refraction to get

an idea of how radio waves work

IR devices are easy implement Light waves are not regulated byany institution or government interests, and the applications forthem are a lot simpler than radio systems and high-speed network-ing We cannot neglect that visible light communications—perhapsthat of smoke signals and certainly that of naval intership communi-cations by light beacons—share the line-of-sight, low-cost, ease ofimplementation and limited benefits of IR communications

Wireless Equals Radio Frequencies

Moving up in capabilities, benefits, and complexity, but also down inwavelength, we come to the radio spectrum of wireless communica-tions Using radio in general—and for high-speed data specifically—

is more complex for several reasons:

■ The radio frequency (RF) spectrum is regulated (in the UnitedStates) by the Federal Communications Commission (FCC) Typi-cally in other countries the postal or telecommunications agency

is charged with regulating radio use, and most countries also ticipate in global radio consortiums What can and cannot beplaced on and make use of specific portions of RF spectrum, andresolving interference and jamming disputes, is the domain ofthese agencies

par-■ Exposure to RF waves is regulated (in the United States) by theFCC and Occupational Safety and Health Administration (OSHA)guidelines (and is the subject of much environmental debate andcellular telephone safety issues) Although wireless networkingproducts emit very low levels of RF power, they are often placed

in the company of other much higher powered RF devices thathave known detrimental effects on human tissue Simply climb-

Chapter 1

4