Even more mysterious Tx excessive retries - with solution?

Roger Larsson roger.larsson at norran.net
Sun Sep 22 00:16:22 EST 2002

On Wednesday 01 May 2002 08.34, David Gibson wrote:
> On Tue, Apr 23, 2002 at 10:44:34PM -0700, Jim Carter wrote:
> > The continuing saga of the Dell Truemobile 1150 (Agere firmware 6.16)
> > vs. Linksys WPC11 (Intersil firmware 1.03).  This is with driver 0.10.
> > 
> > I've had another thought.  Suppose the reason the Linksys card under Linux
> > cannot talk to the Cisco-Aironet access points is that it never acks
> > (at MAC level) any packets.  Suppose the reason the Dell card thinks it
> > has to retry so many times is that it never gets the acks.  Suppose the
> > Agere firmware does the obvious thing, and acks as soon as it has the
> > complete packet on the card with a correct checksum.  But the Linksys
> > firmware doesn't ack until the driver confirms that it has the packet.
> > The Windows driver would know how to do this, so the Linksys card works
> > fine under Windows.  But the Linux driver doesn't...
> Yes, this seems a very probably explanation.  What's weird, though, is
> that the we didn't use to have this problem and I'm not sure what's
> changed that might have made the firmware stop giving ACKs.

I have run into something similar.
Did you find a solution on this? I have searched the achieves but found none.

Lets describe my situation:

* Two stationary computers was connected Ad-Hoc with older kernels (I think it 
was 2.4.14..17) - this was working OK.

* Upgraded the client to SuSE 8.0 (2.4.18), had some problems to get it going.
SuSE includes several sets of wireless... but I finally get it working with 
the kernel set.
But it did not work as good as before. FTP gets were slower - did not think 
much about it...

* Noticed that my "server" disk was close to give up...
Bought a new disk. And did a fresh install of SuSE 8.0. Made the same 
modifications to get it going.

* The resulting communication speed was... slow... slow... slow...
Noticed those "Tx excessive retries". Searched my mail achieves,
found your messages.

* Since I had the problem and control over both the client and the server
I started to test a lot.

Several settings made the problem worse: like enabling RTS.
But when I did
  iwconfig eth0 rate 2M fixed
on both computers, it started to behave again.

My understanding of the problem is:

  The new driver version detects the "Tx excessive retries" and
  tries to do something about it - but it only makes it worse...

Roger Larsson

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