Creating and Administering Wireless Networks
`
`Maithew S. Gast
`
`O’REILLY”
`
`IPR2024-01050
`Apple EX1021 Page 1
`
`

`

`802.11 Wireless Networks
`The Definitive Guide
`
`IPR2024-01050
`Apple EX1021 Page 2
`
`

`

`802.11 Wireless Networks
`The Definitive Guide
`
`Matthew S. Gast
`
`O’REILLY*
`
`IPR2024-01050
`Apple EX1021 Page 3
`
`

`

`802.11 Wireless Networks: The Definitive Guide
`by MatthewS. Gast
`Copyright © 2002 O'Reilly & Associates, Inc.All rights reserved.
`Printed in the United States of America.
`
`Published by O'Reilly & Associates, Inc., 1005 Gravenstein Highway North,
`Sebastopol, CA 95472.
`O'Reilly & Associates books may be purchased for educational, business,or sales promotional
`use. Online editionsare also available for mosttitles (safari.oreilly.com). For more information
`contact our corporate/institutional sales department: (800) 998-9938 or corporate@oreilly.com.
`
`Editor:
`
`Mike Loukides
`
`Production Editor:©Matt Hutchinson
`
`Cover Designer:
`
`Ellie Volckhausen
`
`Printing History:
`April 2002:
`
`First Edition.
`
`Nutshell Handbook, the Nutshell Handbooklogo, and the O'Reilly logo are registered
`trademarks of O’Reilly & Associates, Inc. Manyofthe designations used by manufacturers and
`sellers to distinguish their productsare claimed as trademarks. Where those designations appear
`in this book, and O'Reilly & Associates, Inc. was aware ofa trademarkclaim,the designations
`have beenprinted in capsorinitial caps. The association between the imageof a horseshoe bat
`and 802.11 wireless networks is a trademark of O'Reilly & Associates, Inc.
`
`802.11® andall 802.11-based trademarks andlogos are trademarksorregistered trademarks of
`IEEE,Inc.in the United States and other countries. O'Reilly & Associates,Inc.is independentof
`IEEE.
`
`While every precaution has been taken in the preparation ofthis book,the author and publisher
`assumenoresponsibility for errors or omissions,or for damages resulting from theuse of the
`information contained herein.
`
`ISBN: 0-596-00183-5
`
`(M]
`
`IPR2024-01050
`Apple EX1021 Page 4
`
`

`

`
`
`Table of Contents
`
`FrePAGE acs (a wa Wate dark see Gad sawn EON MURA E NS aS ERRNO LED HUN ix
`1.
`Introduction to Wireless Networks ...........-..2s2e2eeeeee eee ee recess 1
`Why Wireless?
`A Network by Any Other Name...
`
`5
`
`2. Overview of 802.11 Networks ........ 0.00. c cece eee ere e ee ere eee eee 7
`IEEE 802 Network Technology Family Tree
`8
`802.11 Nomenclature and Design
`9
`802.11 Network Operations
`16
`Mobility Support
`20
`3. TheSO2.11 MAC ...... ccc cree cece eee renee renee ent e ence eee ene nes 23
`Challenges for the MAC
`25
`MAC Access Modes and Timing
`27
`Contention-Based Access Using the DCF
`31
`Fragmentation and Reassembly
`34
`Frame Format
`35
`Encapsulation of Higher-Layer Protocols Within 802.11
`43
`Contention-Based Data Service
`44
`
`4. 802.11 Framing in Detail
`Data Frames
`Control Frames
`Management Frames
`Frame Transmission and Association and Authentication States
`
`............0.seeceee seer teens nnn es 51
`51
`60
`66
`83
`
`IPR2024-01050
`Apple EX1021 Page 5
`
`

`

`5. Wired Equivalent Privacy (WEP) ...........-2-csee cece eceeueeeeeeeeee 86
`Cryptographic Background to WEP
`86
`WEPCryptographic Operations
`89
`Problems with WEP
`93
`Conclusions and Recommendations
`96
`
`6. Security, Take 2:802.1K.......0.ccccccenesceveseeeesceveenercscneees 99
`The Extensible Authentication Protocol
`100
`802.1x: Network Port Authentication
`105
`802.1x on Wireless LANs
`110
`
`7. Management Operations ...............cccccceseeeneeeeeseneeneees 114
`Management Architecture
`114
`Scanning
`115
`Authentication
`120
`Association
`124
`Power Conservation
`128
`Timer Synchronization
`137
`
`8. Contention-Free Service with the PCF ....... 0... 6. ccc eee renee es 140
`Contention-Free Access Using the PCF
`140
`Detailed PCF Framing
`144
`Power Managementand the PCF
`149
`
`9. Physical Layer Overview ............csccccreceser rer seaeeseeeneans 151
`Physical-Layer Architecture
`151
`The Radio Link
`152
`RF and 802.11
`158
`
`10. The ISM PHYs: FH, DS, and HR/DS .......... 00-0 cece eee e eee ee eee 164
`802.11 FH PHY
`164
`802.11 DS PHY
`176
`802.11b: HR/DSSS PHY
`189
`
`11; O21 1ar5-GHZOFDM PHY iy sense calas .aiie cts Goi anian a amaees van 198
`Orthogonal Frequency Division Multiplexing (OFDM)
`199
`OFDMasApplied by 802.11a
`205
`OFDM PLCP
`208
`OFDM PMD
`211
`Characteristics of the OFDM PHY
`212
`
`
`
`vi
`
`|
`
`Table of Contents
`
`IPR2024-01050
`Apple EX1021 Page 6
`
`

`

`Using 802.11 on Windows ...........-.-.00000
`Nokia C110/C111
`Lucent ORINOCO
`
`OT re 214
`215
`
`229
`
`Using 802.11 on Linux ........... 2.60 eee seen ee
`A Few Wordson 802.11 Hardware
`PCMCIA Support on Linux
`linux-wlan-ngforIntersil-Based Cards
`Agere (Lucent) Orinoco
`
`saw canes ceneeenane te 236
`237
`238
`244
`254
`
`Using 802.11 Access Points .............0.00s0e:
`General Functions of an Access Point
`ORiNOCO(Lucent) AP-1000 Access Point
`Nokia A032 Access Point
`
`bac a mENCe aN me 262
`262
`269
`
`279
`
`802.11 Network Deployment.............-..55:
`The Topology Archetype
`Project Planning
`The Site Survey
`Installation and the Final Rollout
`
`nse DAPeG URGE HeEUN 293
`294
`307
`314
`325
`
`802.11 Network Analysis ...........005e scenes
`Why Use a Network Analyzer?
`802.11 Network Analyzers
`Commercial Network Analyzers
`Ethereal
`802.11 Network Analysis Examples
`AirSnort
`
`SATE Grsacns ER aeEeE 329
`329
`331
`332
`332
`348
`363
`
`802.11 Performance Tuning .......-......000ee:
`Tuning Radio Management
`Tuning Power Management
`Timing Operations
`Physical Operations
`Summary of Tunable Parameters
`
`enna renee ened 368
`368
`371
`373
`373
`374
`
`The Future, at Least for 802.11 ............-.055
`Current Standards Work
`The Longer Term
`The End
`
`aon oom AUS WEEN HON 376
`376
`378
`382
`
`IPR2024-01050
`Apple EX1021 Page 7
`
`

`

`By COZ TMB:
`
`» wesee sess nen ccenaded Rat aewe hres les aperetare ame 383
`
`B. 802.11 onthe Macintosh ..............cc cece cece cece eects ee eens 396
`
`GLOSSARY. ss 55k 55 58 Sass Se RE BES POS AS Be ORE RR 411
`
`DON 655s PRS ERE ER ES BRS AS ROS FANS OE Fee eS ces a OS 419
`
`viii
`
`|
`
`Table of Contents
`
`LE
`
`IPR2024-01050
`Apple EX1021 Page 8
`
`

`

`Introduction to Wireless Networks
`
`CHAPTER1
`
`Overthe pastfive years, the world has becomeincreasingly mobile. Asa result, tradi-
`tional ways of networking the world have proven inadequate to meet the challenges
`posed by our new collective lifestyle. If users must be connected to a network by
`physical cables, their movementis dramatically reduced. Wireless connectivity, how-
`ever, poses no such restriction and allows a great deal more free movement on the
`part of the network user. As a result, wireless technologies are encroaching on the
`traditional realm of “fixed” or “wired” networks. This changeis obvious to anybody
`who drives on a regular basis. One ofthe “life and death” challenges to those of us
`who drive on a regularbasis is the daily gauntlet oferratically driven cars containing
`mobile phoneusers in the driver’s seat.
`Weare on the cusp of an equally profound change in computer networking. Wire-
`less telephony has been successful becauseit enables people to connect with each
`other regardless of location, New technologies targeted at computer networks prom-
`ise to do the samefor Internet connectivity. The most successful wireless network-
`ing technology this far has been 802.11.
`
`Why Wireless?
`To dive into a specific technology at this point is getting a bit ahead of the story,
`though. Wireless networks share several important advantages, no matter how the
`protocols are designed, or even whattype of data they carry.
`_ The most obvious advantage of wireless networking is mobility. Wireless network
`_ Users can connectto existing networks and are then allowedto roam freely. A mobile
`telephone user can drive miles in the course of a single conversation because the
`phone connects the user through cell towers. Initially, mobile telephony was expen-
`_sive. Costs restricted its use to highly mobile professionals such as sales managers
`and important executive decision makers who might need to be reached at a
`moment's notice regardless of their location. Mobile telephony has proven to be a
`
`IPR2024-01050
`Apple EX1021 Page 9
`
`

`

`accommodate as manyusers as needed. Although wireless LANs have somewhatlim-
`ited bandwidth, the limiting factor in networking a small hot spotis likely to be the
`cost of WAN bandwidth to the supporting infrastructure.
`Flexibility may be particularly important in older buildings because it reduces the
`need for constructions. Oncea buildingis declared historical, remodeling can be par-
`ticularly difficult. In addition to meeting owner requirements, historical preservation
`agencies mustbesatisfied that new construction is not desecrating the past. Wire-
`less networks can be deployed extremely rapidly in such environments because there
`is only a small wired network to install.
`Flexibility has also led to the development of grassroots community networks. With
`the rapid price erosion of 802.11 equipment, bands of volunteers are setting up
`shared wireless networks open to visitors. Community networksare also extending
`the range of Internet access past the limitations for DSL into communities where
`high-speed Internet access has been only a dream. Community networks have been
`particularly successful in out-of-the way places that are too rugged for traditional
`wireline approaches.
`Like all networks, wireless networks transmit data over a network medium. The
`medium is a form ofelectromagnetic radiation.” To be well-suited for use on mobile
`networks, the medium must be able to cover a wide area so clients can move
`throughout a coverage area, The two media that have seen the widest use in local-
`area applications are infrared light and radio waves. Most portable PCs sold now
`_ have infrared ports that can make quick connections to printers and other peripher-
`als. However, infrared light haslimitations;it is easily blocked by walls, partitions,
`and otheroffice construction. Radio waves can penetrate mostoffice obstructions
`andoffer a wider coverage range.It is no surprise that most,if not all, 802.11 prod-
`ucts on the market use the radio wave physicallayer.
`
`Radio Spectrum:The Key Resource
`Wireless devices are constrained to operate in a certain frequency band. Each band
`has an associated bandwidth, which is simply the amount of frequency space in the
`band. Bandwidth has acquired a connotation of being a measure of the data capacity
`fa link, A great deal of mathematics, informationtheory, and signal processing can
`pe used to show that higher-bandwidth slices can be used to transmit more informa-
`n. As an example, an analog mobile telephony channel requires a 20-kHz band-
`Width. TV signals are vastly more complex and have a correspondingly larger
`bandwidth of 6 MHz.
`
`
`
`eetis also used by somewireless networking applications, but the extreme focus of a laser beam
`1 apiedonlyforapplicationsinwhichtheendsarestationary. “Fixedwireless” applications,inwhich
`eplace other access technology suchasleased telephone circuits, are a common application.
`
`IPR2024-01050
`Apple EX1021 Page 10
`
`

`

`that have proven to be quite valuable to DSL and cable modem customers. In spite of
`the hype andpress from 3G equipmentvendors,the rollout of commercial 3G ser-
`vices has been continually pushed back.
`In contrast to Bluetooth and 3G, equipmentbased on the IEEE 802.11 standard has
`been an astounding success. While Bluetooth and 3G may be successful in the
`future, 802.11 is a success now. Apple initiated the pricing moves that caused the
`market for 802.11 equipmentto explode in 1999. Price erosion made the equipment
`affordable andstarted the growth that continuestoday.
`This is a book about 802.11 networks. 802.11 goes by a variety of names, depending
`on whois talking about it. Some people call 802.11 wireless Ethernet, to emphasize
`its shared lineage with the traditional wired Ethernet (802.3). More recently, the
`Wireless Ethernet Compatibility Alliance (WECA) has been pushingits Wi-Fi (“wire-
`less fidelity”) certification program.’ Any 802.11 vendor can haveits products tested
`for interoperability. Equipmentthat passes the test suite can use the Wi-Fi mark. For
`newerproducts based on the 802.11a standard, WECAwill allow use of the Wi-FiS
`mark, The “5” reflects the fact that 802.11a products use a different frequency band
`of around 5 GHz.
`Table 1-2 is a basic comparison ofthe different 802.11 standards. Products based on
`802.11 wereinitially released in 1997. 802.11 includedan infrared (IR) layer that was
`never widely deployed, as well as two spread-spectrum radio layers: frequency hop-
`ping (FH) anddirect sequence (DS). (The differences between these tworadio layers
`is described in Chapter10.) Initial 802.11 products were limited to 2 Mbps, which is
`quite slow by modern network standards. The IEEE 802.11 working group quickly
`began working onfaster radio layers and standardized both 802.11a and 802.11b in
`1999. Products based on 802.11b were released in 1999 and can operate at speedsof
`up to 11 Mbps. 802.11a uses a third radio technique called orthogonal frequency
`division multiplexing (OFDM). 802.11a operates in a different frequency band
`entirely and currently has regulatory approvalonly in the United States. As you can
`see from the table, 802.11 already provides speeds faster than 10BASE-T Ethernet
`and is reasonably competitive with Fast Ethernet.
`
`Table 1-2. Comparison of802.11 standards
`
`IEEEstandard©Speed Frequencyband—Notes
`
`802.11
`1 Mbps
`2.4 GHz
`First standard (1997). Featured both frequency-hopping and
`2Mbps
`direct-sequence modulation techniques.
`upto54Mbps
`Secondstandard (1999), but products notreleased until late 2000.
`5.5 Mbps
`Third standard, butsecond wave ofproducts. The most common
`11. Mbps
`802.11 equipmentasthisbook was written.
`upto54Mbps
`Not yet standardized.
`
`5GHz
`2.4GHz
`
`2.4GHz
`
`
`
`802.11a
`802.11b
`
`802.119
`
`* More details on WECA and the Wi-Ficertification can be foundat http://www.wi-fi.org/.
`
`6
`
`| Chapter1: Introduction to Wireless Networks
`
`IPR2024-01050
`Apple EX1021 Page 11
`
`

`

`Network Administration
`
`O’REILLY°
`
`802.11 Wireless Networks: The Definitive Guide
`
`
`
`Using a wireless networkis a liberating experience. But underneath the experiencelies
`a complex protocol, and even more complex issues arise when yourdata isn’t limited
`to traveling on physical wires. How do youstructure your network so mobile users can
`move aroundeffectively? How do you extend wireless coverageso it's available every-
`where you needit? What kinds of security issues do wireless networks raise? How do you tune your
`network for optimal performance? How do you provide enough capacity to support the users you
`expect initially, and how do you deal with the problemsthat arise as more users join the network?
`
`802.11 Wireless Networks: The Definitive Guide discusses all these issues, and more. This book is
`for the serious system or network administrator who is responsible for deploying or maintaining a
`wireless network. It discusses how the 802.11 protocols work, with a view towards understanding
`which options are available and troubleshooting problems that arise. It contains an extensive dis-
`cussion of wireless security issues, including the problems with the WEP standard and a look at the
`802.1x security standard. Since network monitoring is essential to any serious network administra-
`tor, and commercial packet sniffers for wireless applications are scarce and expensive, this book
`shows howto create a wireless packet sniffer from a Linux system and open source software.
`
`In addition to the current 802.11b standard, 802.11 Wireless Networks: The Definitive Guide also
`looks forward to the newest developments in wireless networking, including the two new 54-Mbps
`standards: 802.11a and 802.11g,It also surveys other efforts moving through the standards track,
`including workto facilitate mobility between access points, quality of service, spectrum manage-
`ment, and powercontrol.
`
`Finally, 802.11 Wireless Networks: The Definitive Guide shows you how to configure wireless cards
`and Linux, Windows, and OS X systems, and how to work with access points. Few booksin any
`field combine the theory you need to know with the practical experience and advice you need to
`get things working. 802.11 Wireless Networks: The Definitive Guide is one of those books. If you
`are responsible for a wireless network, you need this book.
`
`ISBN 0-596-00183-5
`
`$44.95
`
`Visit O'Reilly on the Web at www.oreilly.com
`
`CAN Sia88 TIOjy
`
`IPR2024-01050
`Apple EX1021 Page 12
`
`