• Hello,

    Regarding review question #5 in chapter 7 - shouldn't the answer be A, [u]B[/u], D and not A, [u]C[/u], D? I'm pretty sure Opportunistic PKM caching has nothing to do with an 802.11k-2008 compliant client's decision to roam. Am I correct in saying this? Actually, I'm pretty sure Opportunistic PKM caching isn't even the proper term - it's OKC, correct?

  • I agree with you, stevea. The answers should be (A), (B), and (D) instead of (A), (C), and (D).

    Such a typo may be corrected in the next print, I think.

  • Greetings fellow wireless aficionados. I know this discussion is 3 months old but I came across the same Q & A. Opportunistic PMK caching does not register - Opportunistic Key Caching is the accurate term yet the Sybex Practice test engine picks C. as correct instead of B. Channel load reports. Should be A,B,D.

    Wireless Maestro - CWTS, CWNA

  • IEEE 802.11k is a highly interactive protocol in the sense that requests can be made of other STAs to say:

    "Right guys, I need to build up some information about how "busy" you all are, etc ". "I'm going to ask you to send me some information, and I'll use that information to help with roaming decisions etc"

    That information can be a large number of pieces of data compiled into reports, for example. Information such as signal strength, noise levels, even location information etc can be compiled and sent.

    This data will help STAs make more intelligent roaming decisions....e.g. "Ok, I'm getting really good signal strength values from AP X, but he seems to be pretty busy with a large number of associations right now".

    "AP Y is being received by me at a lower signal strength, but he only has a couple of associations....I think I'll go with him"

    Remember that as the number of associations go up, not only are more resources consumed on the AP, but because of the CSMA/CA mechanism, throughput can go down drastically as this happens.

    Complex, and often proprietary algorithms are used to figure out what to do and how to make use of all the data brought in by the various reports etc.

    Although the algorithms themselves may be proprietary, the actual requests and report formats are standardized under .11k.

    This means that an STA made by manufacturer A should be able to request data in an understandable ( to both parties ) format of an AP made by manufacturer B.


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