cwna Certified Wireless Network Administrator Official Study Guide phần 1 pptx

CWNP™ Certification Program The Certified Wireless Network Professional Training & Certification Program is intended for individuals who administer, install, design, and support IEEE 802

Vendor-neutral wireless network

training and certification

CWNP™ Certification Program

The Certified Wireless Network Professional Training & Certification Program is intended for individuals who administer, install, design, and support IEEE 802.11 compliant wireless networks Because the CWNP program is vendor neutral, candidates who achieve the different levels of CWNP Certification will be trained and qualified to administer and support many different brands of wireless LAN hardware Although there are many manufacturers of wireless LAN hardware, the technologies behind the hardware – Radio Frequency and Local Area Networking – are the same for each piece of gear Each manufacturer approaches these technologies in different ways

The CWNP program consists of 4 levels of certification:

Copyright © 2002 Planet3 Wireless, Inc., P.O Box 412, Bremen Georgia 30110 World rights reserved No part of this publication may be stored in any retrieval system, transmitted, or reproduced in any way, including but not limited to photocopying, photographing, magnetic, electronic, or other record, without the prior written agreement and written permission of Planet3 Wireless, Inc

of the contents herein and accept no liability of any kind including but not limited to performance, merchantability, fitness for any particular purpose, or any losses or damages of any kind caused or alleged to be caused directly or indirectly from this book

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We at Planet3 Wireless would like to dedicate this book to our Lord Jesus Christ It is through Him that

we have had the talent, time, encouragement, and strength to work many long months in preparing this text Our goal through the creation of this book and through all things that He allows us to do going forward is to glorify Him We acknowledge His hand in every part of our company, our work, and our friendships We would also like to thank our families who have been amazingly supportive, our friends

who have encouraged us and everyone that contributed to this book in any way

“I can do all things through Christ, who strengthens me.” – Philippians 4:13

Acknowledgements

Devin Akin Kevin Sandlin Scott Turner Robert Nicholas Josh McCord Jeff Jones Stan Brooks Bill Waldo Barry Oxford

Planet3 Wireless, Inc would like to acknowledge and thank the following people for their tireless contributions to this work:

Devin Akin, whose knowledge of wireless LANs, networking, and radio frequency surprised even us His talents to convey, teach, write, and edit were essential in making this the most accurate and comprehensive writing on wireless LANs in today's market

Scott Turner, who constantly keeps us in line and focused on what is important Scott's work in formatting, framing, content organization, and graphics creation was

indispensable Scott's eye for detail and his motivation for perfection in everything he does keep us in awe

Kevin Sandlin , for his intellect to make difficult concepts sound simple, his skill to write

and edit the most difficult material, and his ability to motivate every member of the team

to do their best and to keep their eyes on the sometimes moving target His leadership skills are second to none

Robert Nicholas, for his ability to conceptualize and create difficult graphics and radio frequency concepts, his savvy in presentation of difficult material, and his ability to find the answer to even the most vague concepts through diligent research and study His effort in support of this book is greatly appreciated

Jeff Jones and Josh McCord , who have been with Planet3 since the beginning of this

project Their willingness to volunteer as much time and effort as was needed to make all

of it possible has been amazing They have been an inspiration to the entire team Their relentless pursuit of perfection in support of Planet3's mission is recognized and greatly appreciated

Stan Brooks, Bill Waldo, and Barry Oxford, each of whom brought a unique set of skills to the review and quality assurance process for this publication Their time, effort and eye for necessary changes were immeasurable, and helped to publish this book in a timely manner

vi Contents

Contents at a Glance

Chapter 2 Radio Frequency (RF) Fundamentals 17

Chapter 4 Wireless LAN Infrastructure Devices 71

Chapter 6 Wireless LAN Organizations and Standards 145

Chapter 9 Troubleshooting Wireless LAN Installations 223

Radio Frequency (RF) Fundamentals 17

Gain 19Loss 19Reflection 20Refraction 21Diffraction 22Scattering 23

Equivalent Isotropically Radiated Power (EIRP) 28

Milliwatt 30Decibels 30dBm 32dBi 34

viii Contents

Chapter 4

Security 61

Wireless LAN Infrastructure Devices 71

Access Point Mode 81

Chapter 5

Placement 115Mounting 116

Orientation 116Alignment 117Safety 117Maintenance 118

x Contents

Chapter 6

Standards 145

Advantages and Disadvantages of License-Free Bands 147

European Telecommunications Standards Institute 154

Chapter 7

HomeRF 156Bluetooth 156

Roaming 183Standards 184Connectivity 185Reassociation 185

Fragmentation 204

Point Coordination Function Interframe Space (PIFS) 208Distributed Coordination Function Interframe Space (DIFS) 208

Modulation 214

Solutions for Co-location Throughput Problems 239

Use 802.11a Equipment 240

802.1x and Extensible Authentication Protocol 278

Wireless LAN Equipment Inventory & Security Audits 281

Paper 311

Documentation 321

Wired Data Connectivity & AC Power Requirements 325

RF Coverage Areas 328

Appendix A

Throughput 328Interference 328

Drawings 329Hardware placement & configuration information 329

xvi Introduction

Introduction

This Official CWNA Study Guide is intended first to help prepare you to install, manage, and support wireless networks, and second to prepare you to take and pass the CWNA certification exam As part of the CWNP Training and Certification program, the CWNA certification picks up where other popular networking certification programs leave off:

wireless LANs

Your study of wireless networking will help you bring together two fascinating worlds of technology, because wireless networks are the culmination of Radio Frequency (RF) and networking technologies No study of wireless LANs would be complete without first making sure the student understands the foundations of both RF and local area

The wireless LAN industry is growing faster than any other market segment in networking Many new careers will be presenting themselves in support of the added responsibilities network administrators must deal with when they add wireless LANs to their networks Getting a head start on wireless technology now will enable you to compete effectively in tomorrow's marketplace

Who This Book Is For

This book focuses on the technologies and tasks vital to installing, managing, and supporting wireless networks, based on the exam objectives of the CWNA certification exam You will learn the wireless technology standards, governing bodies, hardware, RF math, RF behavior, security, troubleshooting, and site survey methodology After you achieve your CWNA certification, you will find this book to be a concise compilation of the basic knowledge necessary to work on wireless LANs

The best method of preparation for the CWNA certification exam is attending an official CWNA training course If you prefer to study and prepare at your own pace, then this book and a practice exam should adequately prepare you to pass the exam

New To Wireless

If you’ve been working on networks – LANs, MANs, WANs, etc – but not yet taken on wireless, then this book and the subsequent certification exam are great introductions into wireless LAN technology Be careful not to assume that wireless is just like any other form of networking While they certainly serve as an extension to wired LANs, wireless

LANs are a field of study all their own An individual can spend many more than the standard 40 hours in a week learning and using wireless LAN technology With wireless LAN security now clearly in focus, the industry is piling on knowledge requirements that wireless LAN administrators must master quickly in order to keep pace Wireless LANs are reaching into new areas with each passing month that nobody thought they would ever reach If you administer LANs, there's simply no avoiding wireless Wireless is here to stay

Wireless Experts

If you are experienced in wireless networking already, there is substantial material covered in this book that will benefit you Most people who attend a CWNA class

marvel from the first day about how much they don’t know If you have been working

with wireless LANs for years, be careful you don’t assume that you know all there is to know about them Even experts who spent 12 hours each day studying wireless material

in order to stay up-to-date cannot keep up with the technology Many new solutions, both for seamless connectivity and for security, are released each week There are new solutions that are designed each month and before you can blink, there are 3 or 4 companies producing products supporting these new technologies This book will be kept up-to-date as the wireless industry progresses so that the reader always knows that they are receiving the latest information

While our program was still in its infancy, we were privileged to have some industry experts take part in our testing We found out very quickly that their status of "expert" was in question There is such a broad base of knowledge required to be a wireless expert that it will likely feel overwhelming at times As you will soon see, this book is geared toward the beginner and intermediate reader alike We hope that it will take you further than you had expected to go when you first picked it up, and we hope that it will open your eyes to a wonderful new field of study

RF Experienced

Some of you may have worked with RF for years, perhaps in the military, and have moved into the networking industry Your knowledge and experience is right on track with the evolution of wireless LAN technology, but you have probably never measured your knowledge of these two technologies by taking a certification exam This

measurement is the purpose of the CWNA certification exam Fields of study like Electrical Engineering, RF Metrology, Satellite Communications, and others typically provide a solid background in radio frequency fundamentals In this book, we will address specific topics that you may or may not be familiar with, or you may just have to dust off that portion of your memory Many people have crossed over from careers in radio frequency to careers in Information Technology (IT), but never dreamed where the two fields of study might meet Wireless LAN technology is the meeting place

New to Networking

Finally, if you are stepping into the networking world for the very first time, please make sure you have a basic understanding of networking concepts, and then jump right in! The wireless LAN industry is growing at a phenomenal rate Wireless networking is

replacing and adding to the mobility of conventional network access methods very

xviii Introduction

quickly We won’t pretend to know which technology will ultimately hold the greatest market share Instead, we cover all currently available wireless LAN technologies Some technologies, like 802.11b, hold a tremendous market share presently, and those will be covered at length in this book Again, as the industry and market place change, so will this book in order to stay current

How Is This Book Organized?

This Official CWNA Study Guide is organized in the same manner as the official CWNA course is taught, starting with the basic concepts or building blocks and developing your knowledge of the convergence of RF and networking technologies

Each chapter contains subsections that correspond to the different topics covered on the CWNA exam Each topic is explained in detail, followed by a list of key terms that you should know after comprehending each chapter Then, we close each chapter with comprehensive review questions that cause you to apply the knowledge you’ve just gained to real world scenarios

Finally, we have a complete glossary of wireless LAN terms for continual reference to you as you use your new wireless LAN knowledge on the job

Why Become CWNA Certified?

Planet3 Wireless, Inc has created a certification program, not unlike those of Cisco, Novell, and Microsoft, that gives networking professionals a standardized set of measurable wireless LAN skills and employers a standard level of wireless LAN expertise to require of their employees

Passing the CWNA exam proves you have achieved a certain level of knowledge about wireless networking Where Cisco and Microsoft certifications will prove a given level

of knowledge about their products, the CWNA exam is proof of achievement about wireless technology that can be applied to any vendor’s products The wireless LAN industry is still in its infancy, much like the world of networking LANs and WANs was

in the early 1990s Learning wireless networking sets you apart from your peers and your competition

For some positions, certification is a requirement for employment, advancement, or increases in salary The CWNP program is positioned to be that certification for wireless networking Imagine if you had CCIE, MCSE, or CNE in 1993! Advancement in wireless technologies will follow the same steps as other certifications – an increase in responsibilities within your organization, perhaps followed by increases in salary