Poll stations from AP transparently

Victor Aleo victor.aleo at estudiant.upc.es
Tue Oct 22 06:38:31 EDT 2002


Hi everybody!

I already know, from multiple emails with this list and especially with 
Jouni, that is not possible to know from the AP side if a station 
(client) can reach other APs in the same ESS. The reason to get this 
knowledge is very simple: if an AP knows that a STA can reach other APs 
it will be potentially possible to reject this station "safely". Thus, 
with the security that the station will be able to reassociate with at 
least another AP.

However, I still think that this can be implemented without the aid of 
any special software in the station side (transparent to the clients). 
Thus, only the AP will be "modified". The key question is how? It is 
clear to me that there are not specific methods to perform this task 
(mainly because the standard specified mobile based handoff but not 
network based). But I think there are "indirect" methods to find out the 
answer:

1) If the AP can poll, by means of beacon frames for instance, the 
stations. In this case, the APs in the  same ESS send beacon frames to a 
specified STA. If the STA answer to this beacon frames, it means that 
can be associated to more than one AP. Therefore, if it is rejected by 
its current AP it will not have problems to reassociate with  another.

My questions are: is this feasible with Prism2? Have you thought about 
other mechanisms to find out this information?

Sorry to write such a long email, but I think this is a key issue to 
implement load balancing algorithms in WLAN networks and I am working in 
it :)

Thanks a lot for your comments or suggestions,

Victor





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