Anonymous
Posted January 10, 2006
I¿ve taken several active directory design and security seminars from Byron when he was with Learning Tree International. When he invited me to work with him on the beta test of the WLAN analysis book and course last summer in Portland I jumped at the chance. The first time I analyzed the capture of a failed client authentication due to a misconfigured WEP key, I knew that I¿d never attempt to troubleshoot or optimize a WLAN without a network monitor. I¿ve applied the knowledge from the book and capture files almost every week into my own consulting practice. The 90-day LinkFerret monitor program included with the book is clean and precise, as is all of Byron¿s explanations. The book has over 300 illustrations and screen shots of wireless capture files ¿ the analysis is done frame-by-frame, field-by-field and bit-by-bit. I¿ve outgrown LinkFerret and invested $1,000 in AiroPeek, but I would have been clueless without the tutorial nature of the book, capture files and filters. It¿s a lot of work and a lot of headaches, but if you want it badly enough, this is the book for you! A final suggestion, I¿d read the book completely before installing the bundled version of LinkFerret. Then you¿ve got 90-days to perfect your capture file analysis skills before deciding which wireless network monitor program is best for your company and applications.
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Posted January 12, 2006
As a CCSI (Cisco Certified Systems Instructor) at a world-wide technical seminars organization I¿m always on the lookout for new, challenging in-depth books. I¿ve worked with the author on several network consulting and seminar development projects. Having a minimal WLAN & Wi-Fi technical background I picked up the beta version 802.11 WLAN Hands-On Analysis with a bit of trepidation. The 90-day LinkFerret network monitor and distribution files installed without any fuss. Chapters 1 and 2 focus on the detailed physical and media access control issues of wireless networks. I found the explanation and flowcharts on CSMA/CA especially fascinating as they revealed why performance analysis and optimization of WLAN is so critical. Chapter 3 is a mind blower! How many frames do you think it takes for an 802.11g wireless node to exchange just one ping request and response with an 802.11b node in the same network? I will never again share files and printers from wireless computers because the performance issues are immense. Chapter 4 tackles what is mistakenly considered as a rather mundane process, how a wireless station finds the access point. The capture file analysis and two mini-case studies on phantom protection and SSID broadcasting were truly insightful. The field and bit-level analysis is amazing. LinkFerret is simple to use and its features are readily accessible. The capture files and filters make the analysis text and screen shots really hit home. Chapter 5 reveals the mysteries of Authentication and Association. Once again, the hands-on mini-case studies were insightful and relevant ¿ especially the information about disassociation and deauthentication. One of the best aspects of the book is analyzing captures that show a working system and then transitioning to capture analysis of a broken system. I'm a troubleshooter at heart and that approach is what every WLAN administrator and technical support person needs.I was disappointed that the author didn¿t include a section on advanced authentication using 802.1x port-based control and RADIUS, but I understand that he¿s currently working on a follow-up text dedicated to 802.11i security analysis. Chapter 6 addresses 802.11 fragmentation, RTS/CTS medium reservation and MTU. Using a capture, simple math and a little logic, the author proves that the IEEE definition of 802.11 maximum frame size has little to do with how the specification is implemented in production networks. This dovetails nicely with the performance and optimization theme of the chapter. I don¿t know of any other book that addresses the issues of why support of fragmentation and RTS/CTS medium reservation seems to have been dropped in most 802.11g products and why one would ever configure the RTS threshold on an access point. These are nuts and bolts issues that aren¿t addressed anywhere else. Finally, Chapter 7 addresses the bottom line of how much TCP-based data can be pushed through various 802.11b and 802.11g connections and how invoking CTS-to-Self protection has a disastrous affect on throughput. The last section is on 802.11 power save mode. Although I initially considered this to be esoteric, it soon becomes obvious while analyzing the captures that understanding how the access points buffer broadcast, multicast and unicast data is an extremely important issue, not just for optimization but also to help understand why the frames received in a wireless network capture may be duplicated or out of order. Without this last section I can imagine many situations where the PS-mode frames would confuse the analysis and add an insurmountable layer of complexity. Lastly I¿d like to mention the end of chapter summaries and reviews, they are compressed and comprehensive a great resource for renewing concepts that have slipped away and preparing for wireless certification. All-in-all the author delivers what he says, a text and hands-on WLAN troubleshooting and optimization
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