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On page 220, the "clear channel assessment" could just as easily been replaced by "CS/CCA" - we were trying to use it generically, but to use it as you suggested would work fine as well. Your assessment of the CS/CCA breakdown is correct though...

You're correct about figure 8.4 - it's MIA. We'll get it posted to the errata immediately.

Devinator Escribió:

On page 220, the "clear channel assessment" could just as easily been replaced by "CS/CCA" - we were trying to use it generically, but to use it as you suggested would work fine as well. Your assessment of the CS/CCA breakdown is correct though...

You're correct about figure 8.4 - it's MIA. We'll get it posted to the errata immediately.

Hey!! no fair foul how come that dave guy gets credit on the errata and I don't:)

just kidding looking forward to the updates, I will insert into the book. Heck maybe you can find it in your heart to send me a complimentary second edition guide when it comes out. These guides are part of my reference library now.

This statement can be confusing regarding AIDs

Pg 162. under the Reassociation Response Frame
If the reassociation Request is successful, the new access point will indicate this status in the status code element and include a unique AID for this station to use if operation in Power Save Poll Mode.

This leads one to think is the AID only generated for Power Save stations as apposed to any and all stations that associate will have an AID generated regardless if CAM or PS mode are present.

Page 227 Under the Length Field paragraph. Sentence:
Note that the length extensions bits in the Signal Field are not needed….
Shouldn’t that be Service Field???

Page 232 Under the ERP-OFDM PMD Sublayer section

Second paragraph

“enabling the DSSS PLCP to direct t he PMD…..”

Shouldn’t that be enabling the ERP-PLCP??? Just need some clarification on this a little confused…

One possible suggestion for the next revision. This book is very packet detailed and most books like this usually have a nice fold out sheet that is large with all the frame formats and sizes, structures and hierarchies etc outlined in one easy reference.

I recall some of my earlier protocol books like Laura Chapples Netware IPX/SPX LAN Analysis book from 1994. A very very good book and it came with a fold out of the Token-ring frame formats that were indispensable to the protocol analyst. I had them hung up in my office at the time, now they are in my home lab, but they were easy to read and reference with the text.

Since the cwap guide is chock full of nuts(and making me nuts in a positive way) a foldout with all the frame formats, headers what goes into what and relation ships/sizes in one large poster like foldout would be awesome in the back of the book.


Let me know if I am being a pain...

...mostly because he's one of our instructors, took an outrageous amount of time to banter back and forth with me over nit-picky changes to graphics, etc. :-D. You're not far from that scenario yourself I think!

Page 162: The AID is only used in the Beacon's TIM field to alert individual stations that they have traffic queued at the AP. Before this can happen, each station has to be assigned an AID whether it will be used or not. This happens during association or reassociation. Regardless of the power state (which could change), each station gets an AID.

Page 227: You're correct - "Service field" is correct -this will be updated immediately.

More to come in another post....

Page 232: You are correct, "DSSS PLCP" should be "OFDM PLCP"

The foldout idea is a good one, but I'm not sure how practical that's going to be for us. I'll check with some of the vendors to see if they want to provide that as "advertising" to our customers for free.

Devinator

Page 352. A possible typo??
Fragment Threshold section
Last sentence: "If the threshold is set to large,.."
should be "too"

Confused on page about the MIMO section. You have a sentence that states "MIMO uses multiple antennas to break a signle fast dignal into several slower signals at the same time. The slower signals are sent using a different antenna using the same frequency channel"

Is the fast to slow correct? I am not too familiar with 802.11n yet and this just seemd reversed. I just wanted to confirm.


Page 361 figure 11.12 protocol trace of capturing on an adjacent channel. The trace shows channel 3 but the text references channel 1 and 2.

Page 388 figure 12.5 Wireless Middlewar model.
on the far right of the diagram under the Host/Server boxes the lowes box has Wirless protocols. Shouldn't that be LAN/WAN protocols since most Host/Servrs will reside on a wired backbone or server farm??? Is this a typo also.


Well that is it from my second pass at this book. I will now play with traces and the practice tests plus review the cisco book and probably re-read this guide one more time.

Thanks...

On the third read and getting ready for the test. I do have some more finding but will post them at another time.I also have traces with some tips.

I do have one quick one.

On page 135 figure 5.3 for the overall 802.11 frame structure below the frame you have an arrow pointing in both directions(??) and over it you have MPDUMAXLength = 4095 (or 8191)

Can you clarify what exactly does 4095 (or 8191)refer too? max frame size in bytes, bits etc???? max size for information elements for mpdus only???

Please elaborate..

Regards...

MPDUMaxLength is a variable in the MIB for each PHY that says how long, in bytes, an MPDU can be. In 802.11 FHSS, it's 4095, in 802.11 DSSS, it's 8191, in 802.11b DSSS, it's 4095, in 802.11a OFDM, it's 4095, and in 802.11g ERP-OFDM, it's 4095. To find these values in the standard, you can search on "MPDUMaxLength"

Devinator

Page 59 third paragraph about the sizes of long and short retry limits in the wording.

First you have dot11shortretry limit and dot11longretrylimit as 7 and 4 respectively. Then in the last sentence of the paragraph you have “Default values for short and long try limits are 7 and 4. Are the numbers 7 and 4 in the correct order for short and long? Or is it 4 and 7? Just to clarify.

Page 86 review questions 3 and 4 did you mean bytes instead of bits??? Or do you want us to do the math from bytes to bits?

Page 101 about fragments says first fragment will be set to 0 in a series but airopeek sets first fragment to 1 in a set of fragments. Packetyzer sets first to 0 and second to 1. Maybe in the next print you could mention that some protocol analyzers interpreted this differently.

Page 175 sentence The format of the capability information field is illustrated in figure 6.25. which is wrong it should be figure 6.23

Page 199 last sentence at bottom of page, DIFS?? Or did you mean SIFS?

Pg 268 third paragraph starts with PTP did you mean PPTP?

Page 227 last paragraph you define CRC as Cyclic Redundancy Codes. On page 379 you define CRC as Cyclic Redundancy Check..

I hope this kind of stuff is not on the exam for I would hate to lose a point because of semantics. BTW I have always thought/read CRC as Check.



Tip about CTS to self mode.
I can see CTS to Self from a 802.11g mode about to transmit. But remember that an 802.11g mode AP will send a cts to itself as well when it has to transmit.. So the trick to see this easily is to see if the CTS to Self Address 1 field is a WS address or an AP address. I have a trace that shows this.

Reference is below. Note that in the study guide, we give you references in the standard. You can download the standards for free from ieee.org.

dot11ShortRetryLimit OBJECT-TYPE
SYNTAX INTEGER (1..255)
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"This attribute shall indicate the maximum number of
transmission attempts of a frame, the length of which is less than or equal to dot11RTSThreshold, that shall be made before a failure condition is indicated. The default value of this attribute shall be 7."
::= { dot11OperationEntry 3 }


dot11LongRetryLimit OBJECT-TYPE
SYNTAX INTEGER (1..255)
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"This attribute shall indicate the maximum number of
transmission attempts of a frame, the length of hich is greater than dot11RTSThreshold, that shall be made before a failure condition is indicated. The default value of this attribute shall be 4."
::= { dot11OperationEntry 4 }