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802.11 Wireless Networks: The Definitive Guide: The Definitive Guide [Kindle Edition]

Matthew S. Gast
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  • Länge: 654 Seiten
  • Sprache: Englisch
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Among network designers and administrators, wired Ethernet is a known quantity. Plenty is known about how to build good twisted-pair network infrastructures, how to keep them secure, and how to monitor their excess capacity. Not so for the wireless Ethernet networks (built around the IEEE 802.11x standards)--these hold much more mystery for even experienced network designers. 802.11 Wireless Networks: The Definitive Guide aims to codify the body of knowledge needed to design and maintain wireless local area networks (LANs). The authors succeed admirably in this, covering what installation and administration teams need to know and digging into information of use to driver writers and others working at lower levels.

The only significant detail that's been excluded has to do with security--a notorious weak point of 802.11x LANs. The authors cover the feeble but widely used Wired Equivalent Privacy (WEP) authentication protocol in detail and devote another whole chapter to 802.1x, which is an emerging authentication scheme based on Extensible Authentication Protocol (EAP). The author has considerable skill in communicating information graphically and does a great job of using graphs to show how communications frequencies shift over time and how conversations among access points and network nodes progress over time. This is indeed an authoritative document. --David Wall

Topics covered: How IEEE 802.11a and 802.11b wireless networks (also known as WiFi networks) work, and how to configure your own. The framing specification is covered well, as are authentication protocols and (in detail) the physical phenomena that affect IEEE 802.11x radio transmissions. There's advice on how to design a wireless network topology, and how to go about network traffic analysis and performance improvement.


'Building Wireless Community Networks is an enthusiastic introductory guide to a technology which can really be put to use to change people's lives. Wireless gives the power of the network back to the people, and this book helps to demystify the technology and enable any community to take control.' Linux User, March/April (Classic Title)


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13 von 13 Kunden fanden die folgende Rezension hilfreich
4.0 von 5 Sternen WLAN voll ins Eingemachte 7. Oktober 2002
Format:Taschenbuch|Verifizierter Kauf
Dieses Buch ist ein Spezialbuch für WLAN Administratoren und solche, die es werden wollen. Es geht in diesem Buch in einer Reihe von Kapiteln um die Details des 802.11b Protokolls, was bei Fehlersuche und Performance Problemen sicherlich hilfreich sein kann.
Der Stand der Informationen in diesem Buch ist meiner Meinung nach ca. Ende 2001. Es handelt sich um ein Amerikanisches Buch, was man bei der Auswahl der Komponenten sehen kann (APs von Lucent ORINOCO und Nokia sind recht aussergewöhnlich). Da der Hauptteil des Buches 2001 entstanden ist, sind die meisten Low End Hersteller oder EU Hersteller (noch) nicht erwähnt (Netgear, Elsa/Lancom usw.).
Sehr gut fand ich die Kapitel über die WLAN Integration in Linux. Da die Entwicklung in diesem Bereich rasant fortschreitet, sollte man die Online Informationsquellen besuchen, bevor man nur anhand des Buches zur Tat schreitet.
Einzelne Erkenntnisse:
- WEP ist noch unsicherer als befürchtet (Kapitel über airsnort)
- Ich werde WEP trotzdem einsetzten und zusätzlich auf IPSec migrieren
- WLAN ist super komplex im Vergleich zum einfachen Ethernet
- WLAN Technologie entwickelt sich so schnell, dass ein langsames Medium, wie ein Buch nicht super aktuell sein kann (so ein Buch kann nur der Einstieg sein und nicht alle aktuellen Informationen enthalten)
Ich würde dieses Buch wieder kaufen, da ich sicher bin, dass ich mit diesem Werk einen guten Helfer bei echten Problemen mit meinem WLAN haben werde. Bis dahin habe ich durch ein Querlesen zumindest die Zuversicht gewonnen, dass ich in der Lage sein werde meine im Schrank liegenden WLAN Komponenten in Betrieb nehmen zu können (Hersteller 3COM). Leider ist WLAN nicht so einfach wie Ethernet.
Wenn man nur einen groben Überblick über WLANs bekommen möchte, ist dieses Buch vielleicht zu viel des Guten.
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31 von 33 Kunden fanden die folgende Rezension hilfreich
5.0 von 5 Sternen Very Comprehensive; Valiant Effort. 9. Juli 2003
Von Donald Gillies - Veröffentlicht auf
Recently I've been designing a system to run atop 802.11b radios and this book has served as an excellent introduction to the 802.11b standard. For example, Gast's description of spread-spectrum radios, chipping, and OFDMA radio systems is a broad overview without going into excessive mathematical formulas and it gives a non-RF engineer a basic understanding of what are the issues underlying each of the 802.11 radios of today.
I found myself reading a chapter of this book, and then looking at the 802.11b standard itself (now available free on the website for more detailed information. I found only a couple of minor errors in this book. This book serves as an outstanding introduction to the protocol standard, which is large and which contains little or no practical information for the practitioner. However, I did also use Radia Perlman's book on Routing in conjunction with this book to help me understand IEEE 802.1 issues.
Gast attempts to be a be-all and end-all book for everyone. For example, he attempts to describe all 802.11 RF modulation schemes. He attempts to give a full description of all the packet formats. He attempts to describe which cards are based on which baseband (Intersil or Orinoco). This stuff is changing very fast but he gave it his best shot, and its very important to people installing *NIX drivers. He attempts to tell you how to set up an 802.11 Ethereal packet sniffer. All of his information is invaluable to anyone setting up 802.11b on any flavor of UNIX or Linux. Anyway, he makes a really valiant effort and I've never seen a networking book try to play in all 4 spaces at once - RF Theory, Network Protocols, Hardware Selection, and Practicum - all at the same time. He should be applauded for this attempt.
I have not found a book that is nearly as comprehensive (6/2003) and I've lent this book to at least 5 other people, most of them PhD's or VP's in EE or CS and/or wireless communications.
37 von 42 Kunden fanden die folgende Rezension hilfreich
5.0 von 5 Sternen Everything you need to know about 802.11 and wireless networ 29. Juli 2002
Von Ben Rothke - Veröffentlicht auf
802.11 Wireless Networks: The Definitive Guide lives up to its title and provides virtually everything you could need to know about 802.11 networks.
802.11 is a family of specifications for wireless networks developed by the Institute of Electrical and Electronics Engineers (IEEE). There are currently four specifications in the family: 802.11, 802.11a, 802.11b, and 802.11g, all of which use the basic Ethernet protocols.
Within the last few years, wireless networks have become extremely popular. No longer must a physical cable be run (at both a time and monetary expense) to each network host. With wireless technology, impromptu meetings can be set up just about anywhere, from conference rooms to airplanes, hotel rooms, and more.
Anyone who has looked at network standards can attest to how boring they are to read. However, Gast does a wonderful job writing about wireless Ethernet in a way that is not only "not boring," but actually interesting. This is due to his expertise with the subject matter and the many real-world scenarios that he shares.
Gast acknowledges that most readers who simply want a methodical, but not all-inclusive, overview of 802.11 can skip chapters 3 through 11, as they deal with the low level details of 802.11. He clearly states that just as it is quite possible to build a wired network without a thorough and detailed understanding of the protocols, the same is true for wireless networks. Nonetheless, there are a number of situations where one may need a deeper knowledge of the underpinnings of 802.11, and those underpinning are exhaustively detailed in chapters 3 through 11.
Chapters 3 and 4 address the MAC layer and 802.11 framing. Chapter 5 deals with the greatest weakness of 802.11 -- namely its lack of security. Chapter 5 clearly states the problems and inadequacies associated with 802.11 security and use of the WEP (Wired Equivalent Privacy) authentication protocol. However, despite all of the security weaknesses in 802.11, Gast never directly advises security conscious organizations to stay clear of 802.11. He does provide information on a possible successor to WEP, the Extensible Authentication Protocol (EAP).
WEP has numerous public security flaws. The first critical weakness was detailed in the now seminal paper, "Weaknesses in the Key Scheduling Algorithm of RC4." One of the paper's authors is Adi Shamir (Shamir is the S in RSA). Shamir's findings were considered somewhat of a death blow to WEP.
Chapter 8 deals with an unimplemented aspect of 802.11 -- the PCF (Point Coordination Function). Like PCF itself, much of chapters 3 through 11 are quite dry. The book includes relevant diversions into such topics as RF physics and issues such as the nonexistent microwave absorption peak of water.
Chapter 11 concludes the theory portion of the book, and chapters 12 and 13 deal with the very real issue of using 802.11 on Windows and Linux. Although most 802.11 installations are fairly straightforward, there are a number of specific configuration parameters that must be set correctly if the wireless network is to operate at peak efficiency.
Perhaps the most important chapter of the book is Chapter 15, "802.11 Network Deployment." As a security professional, I have seen many companies hastily deploy wireless technology, oblivious to the many wireless security weaknesses. The ease with which 802.11 can be deployed has allowed many organizations to overlook such critical issues as eavesdropping, scaling, radio interference, stability, and topology. Gast points out that proper deployment of a wireless LAN is a considerable undertaking, and that significant planning is required before one should even start thinking about the hardware.
Chapters 16 and 17 deal with network analysis and performance tuning. Gast describes what to look for when using a protocol analyzer on an 802.11 network and how to ensure its effective use. Chapter 16 includes three case studies using actual output from a sniffer. This chapter is quite valuable and also covers the use of AirSnort. AirSnort ([...]) is a wireless network tool used to recover WEP encryption keys. It works by passively monitoring network transmissions and then computing the WEP encryption key. AirSnort was one of the first publicly available tools to implement the attack described in the "Weaknesses in the Key Scheduling Algorithm of RC4" paper.
Overall, 802.11 Wireless Networks: The Definitive Guide is an excellent guide for any network administrator or architect who needs to understand the ins and outs of 802.11 networking. It has all the necessary information for design and deployment of wireless networks in an easy to read and enjoyable style.
19 von 20 Kunden fanden die folgende Rezension hilfreich
5.0 von 5 Sternen Comprehensive, clear: other reviews misstate quality 25. Januar 2003
Von Glenn Fleishman - Veröffentlicht auf
I'm not sure what book two other [] reviewers were reading, but Matthew Gast's does not suffer from the flaws they state: it's a comprehensive book with a laser-beam focus, and they're criticizing a book this isn't. Why no Ethernet primer? Because it's a focused 802.11 book. Why no reporting of security flaws discovered in mid-2001? Because the book was being printed then -- but the book delves deeply into the security model underlying 802.11, which is what it's about.
I recommend this book highly for anyone who needs a protocol level on up view of 802.11 for planning, deploying, or understanding 802.11 networks. It's a constant reference guide for me, and it's never steered me wrong.
If you read the critical reviews carefully, the first (Kevin) complains about when it was published, and the second (anonymous) complains about the book but then admits he or she hasn't read other 802.11 books and doesn't explain whether he or she has relevant knowledge.
Because most systems deployed are 802.11b based, this book retains its utility. At some point, probably within the next six months, another edition will be needed to deal with the current draft 802.11g standard, the new WPA security protocol, and the coming 802.11i, h, e, and f protocols. But as long as you're dealing with 802.11b, this is the ultimate guide for network administrators and software developers.
49 von 59 Kunden fanden die folgende Rezension hilfreich
2.0 von 5 Sternen Lots of Substance Poorly Written 28. August 2002
Von Ein Kunde - Veröffentlicht auf
The author, Matthew Gast, seems to have a dearth of relevant experience on 802.11. His bio in the back of the book (and on O'Reilly's website) gives no single specific experience - academic, professional, or otherwise - he had relating to 802.11. The bio instead is left to boast that Gast is a "renaissance technologist" and a "voracious reader on science and economics". I find it telling that the publishers spent more space discussing the design of the book's cover than on Gast's bio. If you don't know a subject well, you'll have a difficult time teaching it to others, and that appears to be the case here.
I noticed that Gast wrote other networking books for O'Reilly, so I assume he's their go-to guy on networking. Why they would do that on a hot subject like 802.11 is a mystery, and it produced a poorly written mess.
As for the book, it appears that he researched as much substance on 802.11 and haphazardly threw it together. The flow of the book is atrocious and seems poorly planned. For example, he advises readers to skip more than half the middle of the book and come back to it later if necessary since he feels it may be too complicated for most. Why not put that portion of the book at the end, or better yet, write clearly enough so that it's not too complicated? This is an 802.11 book, after all.
He also spends the first two chapters explaining the most rudimentary details of wireless networks, yet expects the reader to be well versed in Ethernet. If Ethernet is so vital to understanding 802.11, why didn't Gast devote a chapter as an Ethernet primer, especially since he found it compelling to include two chapters of the most basic of wireless network primers?
His clarity is also awful. The book is very dense with acronyms and technical terms. This isn't a problem in itself, but the glossary only defines acronyms. You're left searching the text for the definition to other terms, if they're even defined therein. Even if they are defined, don't expect a clear definition.
For example, "atomic operation" (granted, it's a simple term, but that makes for an even better example) should have been defined with something like "an atomic operation is a unitary action that is essentially indivisible, unchangeable, whole, and irreducible." Gast never says anything of the sort and chooses instead to give an example of two nodes in a network communicating an acknowledgement of a received frame to each other and then says "[The example] is an atomic operation". The index then refers to atomic operation as being defined by the above line. The reader is therefore forced back to the bad example. What aspect of the communication does atomic operation refer to for the naive reader? I already knew what "atomic operation" referred to yet I was still thoroughly confused by his definition. Poorly defined terms like that pollute Gast's text. Further, he repeatedly uses these poorly defined terms, so knowledge of their meaning is essential to understanding the substance.
He also does a rather poor job discussing 802.11 security, particularly regarding the future of 802.11 security. I know it's a fast-developing subject, but this book is copyright 2002 and it's already outdated on this aspect of 802.11 in August of the same year. He could have done a bit more forecasting and research on this topic.
This was the first 802.11 book I've read, but not my first technical book. It definitely goes into the bottom quarter of the latter category. There must surely be a better 802.11 book out there.
9 von 9 Kunden fanden die folgende Rezension hilfreich
5.0 von 5 Sternen Incredible 802.11 book 28. August 2006
Von Richard Bejtlich - Veröffentlicht auf
I tend not to read and review books on as broad a subject as "wireless networking." I've read and reviewed wireless security books like Real 802.11 Security and Wi-Foo, but 802.11 Wireless Networks: The Definitive Guide, 2nd Ed (8WN2E) was a departure for me. Thankfully, 8WN2E is an incredible book. It exceeded my expectations and definitely earned its "Definitive Guide" status.

8WN2E is exceptionally thorough and exceedingly informative. Everything is presented in a well-organized manner. (Note to reviewer G. Bailey -- I'm guessing you are indeed "not smart enough for this book" if you gave it 2 stars.) The diagrams clearly communicate various aspects of 802.11 networking. I even added tabs to certain pages for future reference. For example, the Ethereal/Wireshark display fields on p 562 is a great resource.

8WN2E is more than just a reference for 802.11. Author Matthew Gast brings insights and recommendations to this complex world. He even dispels myths often heard elsewhere. On p 303 he says "Only the protection frames are required to be transmitted at the 802.11b-compatible data rates. Protection does not require 802.11g stations to use a slower data rate for the payload data, as is commonly asserted." This means the introduction of 802.11b stations into an 802.11g network does not mean all stations run at 802.11b speeds.

8WN2E covers all of the subjects I would expect in an 802.11 book. Security, site surveys, architecture -- it's all here. The wireless world is rapidly changing, but this book provides solid fundamentals that still apply today. 802.11n, which is not yet standardized, is the main area where 8WN2E is not current. 8WN2E was published in the spring of 2005, so expect the third edition to include definitive 802.11n discussions. Overseas readers will also appreciate inclusion of standards which apply outside the US.

I believe one of the best ways to read 8WN2E is to capture some wireless traffic and analyze it in Ethereal/Wireshark. The framing chapters (3 and 4) will mean more to you if you inspect real traffic while reading them. Ch 24 will explain how to use Ethereal/Wireshark effectively.

If you really want to understand 802.11 wireless, definitely buy and read 8WN2E. You will not be disappointed.
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