Any idea why we cannot disable /b rates?

Yeoh Chun-Yeow yeohchunyeow at
Wed Feb 25 02:30:01 PST 2015

On Wed, Feb 25, 2015 at 1:02 PM, Ben Greear <greearb at> wrote:
> On 02/24/2015 06:45 PM, Yeoh Chun-Yeow wrote:
>> On Wed, Feb 25, 2015 at 3:44 AM, Ben Greear <greearb at>
>> wrote:
>>> Ok, so I found the problem.  Appears that the firmware uses two different
>>> fixed rate-ctrl settings, one for non-data (bcast, mgt-frames, etc) and
>>> another
>>> for data frames.  The non-data one was not being set when user configured
>>> fixed rates, so beacons went out at 1Mbps.
>>> I updated CT firmware (beta-14) to set both data and non-data to the same
>>> value when the driver specifies the rates...  Seems to work...any idea
>>> if this is a bad idea in practice?
>> Rate control is applicable to unicast frame whether it is
>> management/data. Broadcast/Multicast rate is required for
>> management/data (usually the lowest transmission rate 5GHz is 6Mbps).
>> So it is more sensible if we can configure the broadcast/multicast
>> rate and also disable the rate control for unicast frame by using
>> fixed rate.
> User-space API doesn't give the ability to set different fixed rates for
> different packet types, as far as I know.
> So, the current firmware just ignores the fixed rate for management and
> broadcast
> frames.
> My firmware change makes the fixed rate apply equally to all types of
> frames.
> Should I make my change optional for mgt/bcast , or should it always set
> mgt/bcast rates to the
> same fixed rates as data packets use?

In iw, we have the following:
dev <devname> set mcast_rate <rate in Mbps>
dev <devname> set bitrates [legacy-<2.4|5> <legacy rate in Mbps>*]
[mcs-<2.4|5> <MCS index>*]

mcast-rate should be something set for broadcast/multicast frame
including the management and data frame. This allows us to have in
example beacon frame to be transmitted with higher rate from 1Mbps at
2.4GHz and 6Mbps at 5GHz.


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