[ath9k-devel] AR9280 issue @ 2.4 GHZ

[Helmut Schaa <helmut.schaa@googlemail.com>]

[CC'ing ath9k-devel again]

Am Mittwoch, 6. April 2011 schrieb rafael garrido:
> Yes , we have "direct probe  to 00:24:6c:ce:fb:40 timed out "after 3 tries
> in the kernel log , regarding the your question , the Aruba AP-125 are
> configured to force 5GHZ capable clients , because the AP can spread signal
> at 2,4 GHZ and 5GHZ ( they have 2 radio devices ) , but there is some places
> set as 2,4 GHZ and we need to be sure both , so our problem is why atheros
> AR9280 doesn?t connect where  there is 2,4 GHZ AP ?  For you information we
> have tested this issue with another AP as Ovislink 2,4 GHZ and Atheros
> AR9280 connects properly , Do you know why not with Aruba AP-125

AFAIK because the Aruba AP does not comply with 802.11-2007 (11.1.3.2.1) when
you enable the "force 5Ghz clients to 5Ghz"-feature:

<cite>
11.1.3.2.1 Sending a probe response

STAs, subject to criteria below, receiving Probe Request frames shall respond with a probe response only if

a) The SSID in the probe request is the wildcard SSID or the specific SSID of the STA,
b) The BSSID field in the probe request is the wildcard BSSID or the BSSID of the STA, and
c) The DA field in the probe request is the broadcast address or the specific MAC address of the STA.
</cite>

The linux wireless stack mac80211 sends a direct probe request to the AP prior
to connecting. In turn the AP should answer with a probe response (case b from
above). But the Aruba AP won't do this in your configuration. Hence, mac80211
thinks the AP is not in range anymore and won't even try to authenticate/
associate.

The same problem seems to appear with cisco APs as well, see [1].

Helmut

[1] http://www.spinics.net/lists/linux-wireless/msg59513.html