Source for good reference information..?

Jan 31, 2005 2 Replies
E

Hi,



Anyone know of a really good hard copy source (i.e., book) that is an excellent reference for wireless 802.11 network configurations? I'd really like something that shows various topologies and configurations to impliment them -- and also includes a nice glossary of definitions, IEEE standards, procedures, etc.



My googles have been leading mainly towards just very specific (and often, unrelated) material to manufacturer knowledge bases, which more than often lead to more confusion than answers.



I've been doing the home wireless network thing for several years now, but up until recently it was just a simple broadband cable modem --> 802.11a/b router/AP --> clients (and a couple wireless-ethernet bridges). Everything has been straight forward in the past and pretty much just "Plug n' Play" even with security considerations. Recently I just added a new AP (plugged into wireless router/AP) in order to get 802.11g into the loop as I'm starting to look at "stand-alone" products such as broadband phones and media players -- all of which seem to be primarily 802.11g. My experience with 802.11a (108 MBS Turbo) has proven to give vast superior performance over 802.11b. Thus, I would to take advantage of 802.11g for such "stand-alone" products.



Recently just picked up a second "AP" (same model as new one plugged into router/AP). Its also a 802.11a/b/g device. I bought it because one of the modes it supports is "repeater" and figured it should work beatifully with the AP since its the same exact piece of hardware. Here is where the headaches begin. I've been very pleased with D-Link products, but their documentation (and online "Knowledge Base") leaves a lot of unanswered questions. Getting this thing to repeat was an exercise in hair pulling. Couldn't find answers to questions that may be obvious (i.e., does the repeater need encryption on to repeat or is it just a "garbage in, garbage out" device in repeater mode, which modes such as Super/Turbo can be repeated, in "repeater mode" is DHCP still funneled from router, etc.) Eventually figured out answers to all those questions, but not until after hours of trial-and-error. I still haven't been able to figure out if both



802.11a and 802.11b/g can be simultaneously repeated. I can report one or other, but when I try both it locks up. In 20 years of using computers, I had to make my first ever calls to a technical support line -- and even they, althought I do have to say they were very friendly and commited to trying to help, didn't really know if both could be repeated. Get different answers depending on who you talk to. Crazy. If a function isn't capable in a certain situation, why didn't they have the configuration program just grey-it out? That would save headaches. From my deja searches, seems Linksys is not really much better off in this department as well.

Hence, why I would like such a book. Also would nice to see how PtP and PtMP bridging actually works. Documentation and KB leave much confusion on these as well.



Thanks!


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J

Most printed books are at least 1-2 years out of date.

See:

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topologies shown revolve around the YDI product line, but cover most (not all) possible configurations. Note that a mixed infrastructure/bridge WDS network is not shown, which is becoming all too common. Same with a mesh network and an ad-hoc network.

Mesh and ad-hoc network topologies are essentially similar and appear to be somewhat arbitrary and random. Well, actually, they are arbitrary and random. Kinda difficult to draw a sane topology diagram. See:

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a typical example. Any semblance to spaghetti is strictly coincidental. The major distinction is the mesh network routing protocol.

IEEE standards:

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that they do not post proposed standards and standards in progress.

802.11 Data frames and such:
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the various links for details.

There are many glossaries that include wireless terms, acronyms, and buzzwords on the web. However, most offer only one line definitions, with little detail. If you run into a non-obvious term, I suggest just using Google to search for an explanation.

Wireless Security:

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Some manufacturers databases, marketting hype, and buzzword manufacturing is intended to confuse rather than clarify. Do you get driving lessons from your autombile manufacturer or dealer? Your best sources are the various tutorials, white papers, product data sheets, and hated power point presentations by the various chip manufacturers (Broadcom, Atheros, etc) which are intended to educate the panic stricken neophyte engineer stuck with delivering a working product before the traditional unrealistic deadline.

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are web review and test web sites with advertising cluttered tutorials, but worth reading:
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My domain is LearnByDestroying.com for obvious reasons. Some things are best learned by experience.

What is "it"? What locks up? Can you ping the various boxes involved?

Simple economy. Tech support has become an entry level position years ago. If they knew what they were doing, they wouldn't be doing tech support. It's also difficult for anyone on the phone to answer questions about systems they've never seen or worked with. How much hands-on hardware time do you think they get in support. In my never humble opinion, experience is more important than access to the internal knowledge base. However, experience is expensive.

The reason you're getting different answers is not because of different individuals. It's because operation of the knowledgebase is dependent upon the selection of the appropriate buzzwords. Each person on the phone will tend to select a different assortment of buzzwords to pound into the search engine. Of course, results will vary. In addition, they are usually not allowed to guess, or offer advice which is not in the database.

It would also be nice if the useless and excessively over-simplified data sheets and product specifications detail such things. Yeah, you're correct. Now, imagine the multitude of configurations that one can assemble a wireless network using repeaters, WDS, bridging, and mixed mode radios? All the combinations and permuations should be tested, but often one is missed. More likely, the engineering specification indicated that it should be possible to do a mixed mode repeater (which is why it's not grayed out), but someone either forgot to test it or some manager decided that it wasn't important, or could be fixed in the next inevitable firmware release. Meanwhile, you fall into the trap.

DLink, Linksys, and Netgear are all bottom of the line vendors. One's expectations should generally follow the price tag.

Well, you'll find quite a bit on Point to Point and Point to Multipoint protocols in the various IEEE 802.11 specifications. It's rather rough reading. Pay attention to the contents of the management frames, which run the show. However, the IEEE 802.11 specs idea of point to point is NOT a transparent (workgroup) bridge, but a single MAC address wireless bridge. Point to mutlipoint is called infrastructure mode.

However, you'll find very little on proprietary implimentations such as Super-G, Turbo-G, and such. You will also have difficulty finding specifics on WDS (wireless distribution system), and repeater mode, which are similar, but proprietary to the chip manufacturers. I've found that reading the WDS code for the various open source WRT54G firmware to be the best source of detail. Also lacking in the 802.11 specifications is any protocol for transparent bridging, which also tends to be proprietary by chip manufactory. The thing to remember when reading all this stuff is that everything in 802.11 happens on the MAC layer (Layer 2) and the IP address features are just along for the ride.

Good luck...

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