802.11 Networks, The Definitive Guide

cpfeifer writes with the review below of O'Reilly's 802.11 Wireless Networks: The Definitive Guide; he warns that this is not a book for everyone setting up a casual home wireless network, but says it's excellent for its intended audience. Read on for his complete review. 802.11 Wireless Networks : The Definitive Guide author Matthew S. Gast pages 443 publisher O�Reilly & Associates rating 9/10 reviewer cpfeifer ISBN 0-596-00183-5 summary A thorough survey of the features, issues and potential solutions of deploying 802.11 based wireless networks.

The Scenario

For a lot of folks, implementing an 802.11 network involves selecting and purchasing an access point and adapter cards, and installing or compiling the proper drivers. From there, we are off and running, usually in under an hour. However for the few, the proud, the sysadmins of the world it's a whole different ballgame. Sysadmins need a deeper understanding of network technologies to be able effectively design, deploy and debug them.

What's Bad?

Most of the book is right on the mark when it comes to the sysadmin audience, however chapters 8 (the PCF, for contention free service), 10 (the ISM PHYs) and 11 (802.11a overview) are only of interest to folks who are implementing 802.11 hardware, IMHO. These chapters contain very low-level material about the 802.11 transmission protocol, and will not be generally useful since equipment manufacturers do not provide access to this layer. A dead giveaway that you can skip over chapter 8 is the phrase "The PCF has not been widely implemented." If it's not widely implemented, chances are you won't have the option of using it in a deployment.

After this bellycrawl through the weeds, chapters 12 and 14 give click-by-click instructions for installing two commercially available 802.11 access point/client adapter pairs on your Windows box. The selected products are Nokia's A032 Access Point along with their C110/C111 and Lucent's Orinoco (formerly WaveLan) Access Point and client adapter. It's worth noting that these are two of the most expensive 802.11 solutions available on the market and have enhanced features that are not present in other models. These chapters are simply rehashed vendor installation documentation for these products and provide very little added value. There's nothing that I hate more than paying $30-$50 for a book which repackages documentation that is freely available on the web. Skip these chapters; the rest of the book is excellent.

What's Good?

This book starts off with six strong chapters that cover the 802.11 protocol specification, why WEP is vulnerable, and some upcoming security specifications. The first six chapters are invaluable reading for any sysadmin that is planning (or already responsible) for an 802.11 deployment. This is your ammunition when users come and ask why the wireless network is slower than the wired network with fewer users (preventing contention adds more overhead in wireless) or why they really really should tunnel every wireless connection over SSH (because WEP is fundamentally flawed). The chapter that covers the current WEP implementation demystifies the "40 bit" vs. "64 bit" key-length sleight of hand that some vendors play. The standard WEP key length is 64 bits. However, 24 of those bits are used as WEP's initialization vector for the RC4 cipher. These bits aren't encrypted in an 802.11 packet, so by sniffing 802.11 traffic you can examine the IVs of the packets and see how many distinct keys are in use, and even retrieve the actual key once you have captured enough packets. AirSnort retrieves WEP keys by implementing the Fluhrer/Martin/Shamir attack (orig paper, Stubblefield paper). Chapter 16 covers using tools such as Airsnort and Ethereal to analyze the 802.11 traffic on your network. Remember to use your powers for good and not evil.

The final 3 chapters address deployment, analysis and tuning of 802.11 networks. These chapters, combined with the first six are the heart of this book and the whole motivation for buying the book. The analysis chapter has a particularly wonderful section about gathering user requirements with respect to 802.11 specific issues (security requirements, roaming ...) and a very practical section about physical installation that clearly illustrates the author's mastery of integrating 802.11 technologies into an existing infrastructure.

So What's In It For Me?

If you're an sysadmin and implementing 802.11 technologies is on the horizon, this book is a solid reference of the current state of 802.11 solutions, both good and bad. It pulls no punches in presenting issues and weaknesses with the current solutions and documents forthcoming standards that are being proposed or developed to address them. If you're considering a smaller deployment at home, the security aspects of the text are still applicable, but the design/deployment sections are more rigorous than you will need. There is a bit of starch (repackaged vendor installation documentation) and unnecessary details (knowing that 802.11 frequency hopping uses Gaussian frequency shift keying is good for impressing women at parties, but doesn't really impact the design/deployment of an 802.11 network) but the other chapters redeem themselves and make this a very valuable text.

Table of Contents

1. Preface
2. Introduction to Wireless Networks
3. Overview of 802.11 Networks
4. The 802.11 MAC
5. 802.11 Framing in Detail
6. Wired Equivalent Privacy (WEP)
7. Security, Take 2: 802.1x
8. Management Operations
9. Contention-Free Service with the PCF
10. Physical Layer Overview
11. The ISM PHYs: FH, DS, and HR/DS
12. 802.11a: 5-GHz OFDM PHY
13. Using 802.11 on Windows
14. Using 802.11 on Linux
15. Using 802.11 Access Points
16. 802.11 Network Deployment
17. 802.11 Network Analysis
18. 802.11 Performance Tuning
19. The Future, at Least for 802.11
20. 802.11 MIB
21. 802.11 on the Macintosh
22. Glossary
23. Index

You can purchase 802.11 Wireless Networks : The Definitive Guide from bn.com. Slashdot welcomes readers' book reviews -- to submit yours, read the book review guidelines, then visit the submission page.

Comments

Not a party piece

[mccalli]

knowing that 802.11 frequency hopping uses Gaussian frequency shift keying is good for impressing women at parties

I can guarantee you that it isn't...

Cheers,
Ian

Re:Not a party piece

[Rupert]

You are obviously going to the wrong parties.

Re:Not a party piece

[j1mmy]

putting on a wig and sitting in front of a mirror is not a party.

Quite a Good Book

[peatbakke]

I would actually recommend this book to anyone who has more than a passing interest in wireless networks -- sure, there's a lot of nitty gritty details, but that's better than being short on information, right?

Anyhow, for those of you who are interested in setting up a public node, I definitely recommend you check out the NoCat project. It's an authentication/monitoring system for admins interested in having a little control over who accesses their wireless networks.

Another fun resource is the Personal Telco Project. There's lots of smart folks involved who can tell you everything you need to know about setting up wireless nodes with old abandoned computers and home built antennas. Yes. Wireless can be done cheaply.

Enjoy!

802.11 Throughput

[RiBread]

This is your ammunition when users come and ask
why the wireless network is slower than the wired network with fewer users (preventing contention adds more overhead in wireless)

The right answer is: wireless networks are just plain slower than wired ones. Wired networks claim 100Mb/s access and wireless ones claim ~1/10 of that at 11Mb/s.

Actually CSMACA (as opposed to CSMACD the medium contention handling mechanism wired 802.3 networks use) really plays only a small part in the speed of .11 networks. It's the format of .11 physical layer packets and quality of current PHY layer chips which limits the throughput of most solutions to around 4 Mb/s.

New cards coming out from US Robitics using TI 802.11 silicon get consistent throughput close to 7Mb/s. Linksys also uses the TI ACX100 chipset, but doesn't have quite the marketing machine USR does.

If you need more speed you ought to check them out. Still not like a wired network but a hell of a lot better than 4 Mb/s.

The author Matthew Gast...

[mattyohe]

also published two articles on wireless security...

Seven Security Problems of 802.11 Wireless
http://www.oreillynet.com/pub/a/wireless/2002/05/2 4/wlan.html
May 2002

Wireless LAN Security: A Short History
http://www.oreillynet.com/pub/a/wireless/2002/04/1 9/security.html
April 2002

The REAL definitive guide - free!

[morcheeba]

And all this time I thought that this was the definitive guide. Silly me. It's cool that 802 standards (which usually cost big bucks) are now available for a free download once they've been in print for 6 months. Way to go, IEEE! Now, if we can just convince ANSI to do the same... See also the main 802.11 homepage

Not really a con.

[sinserve]

Most of the book is right on the mark when it comes to the sysadmin audience, however chapters 8 (the PCF, for contention free service), 10 (the ISM PHYs) and 11 (802.11a overview) are only of interest to folks who are implementing 802.11 hardware, IMHO. These chapters contain very low-level material about the 802.11 transmission protocol, and will not be generally useful since equipment manufacturers do not provide access to this layer.

These are strong points dummy. One can always learn the surface material and interface rather quickly, a book the provides strong "internals" information about a given piece of computer system almost always beats the shallow publications. It is good to abstract yourself from the details of a given technology is you are just a casual user, but if you are the administrator, you are expect to know your protocol specs and header formats.

Re:So, WEP is insecure

[bergeron76]

Your best bet would be to treat the wireless stations as "untrusted" and VPN them into your network. As such, you'll get decent encryption over the wire(err, air rather) and you can lock them down nicely. It's the only real solution to wirelss security.