On 07-01-04 20:04 Jon Smirl wrote:

> > You should also now retest the vendor driver and see if you can
> > reproduce the vendor-driver-is-2x-faster thing.
> Linux version of the vendor driver is running about the same speed as
> zd1211rw. It it the Windows version of the vendor driver that is
> faster for the copies. About 50% right now.

Unless we start to reengineer the Windows driver, there is
nothing we can do about this. It might even be that the Windows
driver is using a different firmware.

As Daniel proposed it is worthwhile to check against the Linux
vendor driver. If our driver has a lower performance, than there
is something we can do about it.

> I'll try adding some more hints to the debug output. I wouldn't expect
> to retransmit enough times to cause a frame transmission error. If it
> is noise there would normally be only a single retransmission.
> Multiple retransmissions and then frame transmit failure implies a bug
> somewhere.

I have trouble to follow the logic here. There are several
retransmissions until the device gets the ACK. There is nothing
which guarantees, that the second transmission must succeed.

> When I was using kismet the traces looked more to me like the ACK was
> being transmitted by the AP and the zd1211rw wasn't listening.

Please recognize that the fact that you see the ACK elsewhere,
doesn't mean, that the packet can be seen at another point. There
are interferences. The other fact is that the ZD1211 devices are
cheap devices, the RF transceivers have low quality.

> BTW per packet low level synchronous ACKs is a terrible design for a
> MAC layer. I don't see that they needed any acks at all. UDP is
> unreliable and TCP will recover. TCP also piggybacks acks on return
> traffic which is much more efficient. Those acks waste a huge chunk of
> bandwidth.

This is the way the 802.11 standard has been designed. As far as I
know there is discussion about doing a single ACK for several
packets in 802.11n. There are some vendor based optimizations to
merge several packets into a single packet and so on, but they are
not interoperable.

Kind regards,


Uli Kunitz

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