Association Protocol Supported Rates

[Anand S. Katti]

Jouni,

>>That configuration is likely to not work with any normal AP. IEEE 802.11

>> Now I fixed the rate to 5.5 Mbps at the client side and then observed
>>the
>> Probe req,res, Asso REq and Asso res. Then i observed the above packets
>> for the supported rates. The probe req contained 5.5 Mbps in
>> supported rates field since i forced it. But no Asso Req went from the
>> client side.

>That configuration is likely to not work with any normal AP. IEEE 802.11
>requires that the station supports all basic rates of the AP. In most
>IEEE 802.11b APs the basic rate set is {1}, {1, 2}, or {1, 2, 5.5, 11}.
>In other words, if you remove 1 Mbps from the support rate set of the
>station, it will not associate with any of the APs with the basic rate
>sets listed above.

Does this mean that "supported rates" field is just & must field inthe
requests/response to make sure that standard "basic rate set"
{1},{1,2},{1,2,5,5,11} are supported by the Access Card and Access Point ?

And is it mandatory that all the Acccess Cards and Access Points must and
should support all the above set of rates ?

Since most of the cards hardware(if the card is 802.11b compliant) does
support these supported rates, then
what is point in having that field in the Prob req/ers Asso req/res
Beacon frames ?


Please correct me if im wrong.

I was in the notion that, the client who is sending "Assocaition
Request" to the AP will mention the "supported rates" as 1 or 2 or 5.5 or
11 Mbps, out of this which one he is capable of using. (and this decesion
is taken after sensing the signal strength of the heard beacon frame
from a AP) ?


Then after exchnage of Association Req and Response, What rate is allotted
to client ? by default does the client choose 11Mbps ? or the AP allotes
11Mbps ?

Your precious answers creates more questions in me..

Thanking You,
Anand