Hi Georg,

thanks for your answer.

I now think that the ACKs the ap is sending could be NACKs, because the only sta in the setup repeats the frame. The weird thing is that in a point-to-point connection the sta can send at 54M without any problems and they are literally only a few feets apart. So if the sta sends at 6M the ap should get every single frame.
If the ap sends group frames I do not see any (N)ACKs. I will try changing the MCAST rate as advised and see what is happening. I could not find any documentation on this.

Thanks,
Tom

Georg Lukas <georg@boerde.de> wrote:
* Mad Wifi [2007-03-21 13:16]:
> I am using MadWifi NG 0.9.4.5 r2119 with a CM9 AR5212 abg card.
>
> I need to send group frames (Broad/Multicast) in 11a and can see that
> they are acknowledged. According to the standard they shouldn't be. Is
> that a setup issue or is Atheros s/w responsible rather than MadWifi?
> Or do I need to switch to monitor mode to avoid acks entirely?

Can you provide a monitor tcpdump trace from your setup? What station is
sending the ACKs? This really should not happen.

> The second issue is that those frames are being sent at 6Mbps, the
> lowest rate of the Basic Rate Set. I do not know why it is choosing
> the lowest one but I'd like to change the rates in the set. Is that
> possible at all? In another thread the bsr was referred to as default
> which sort of implies that it can be changed but unfortunately I do
> not know how.

The lowest rate is set to extend the transmission range and increase the
chance that the packet will be received - because mcast/bcast can not
implement retransmissions, this is a means to increase the reliability.

You can try setting the rate using "iwpriv ath0 mcast_rate XX", but I'm
not 100% sure if it will work as expected.

Cheers,

Georg
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