Missing WME information element causes problems with 802.11n

[Alexander Egorenkov]

I have encountered a problem with a 802.11n router Belkin F5D8631au.
The beacon and association response frames sent by this router do not
contain
WME information element although 802.11n mode is enabled. These frames
contain
HT capability IE and HT info. Because WME IE is missing in association
responses,
the net80211 stack does not set IEEE80211_NODE_QOS flag
(See ieee80211_sta.c:sta_recv_mgmt:IEEE80211_FC0_SUBTYPE_ASSOC_RESP).
But the flag IEEE80211_NODE_HT is set because the frame contains HT
capability and HT info.

So, because IEEE80211_NODE_QOS is not set, all outgoing DATA frames sent to
the Belkin AP
do not contain QoS field in the 802.11 frame header. And it causes problems
with the Belkin AP.

Is the QoS not mandatory for 802.11n mode ?
Why is QoS enabled only if an WME IE is found in association response ?
Would it be not right to enable QoS also if HT mode is enabled but no WME IE
was found ?

Thanks.