Disable TCP SACK in Windows 2008 R2...

NTDEV
1

My question is simple.

Can TCP SACK be disabled in Windows 2008 R2?

I am using a TOE device that does not support TCP SACK. Connection establishment occurs in host so the Windows network stack permits SACK but once the connection is offloaded, SACK is not supported. Previous testing on Windows 2003 showed improved recovery performance if the peer device was correctly informed that TCP SACK is not supported on the connection. Unfortunately I cannot find a way to disable just TCP SACK on Windows 2008.

Thanks in advance,
Adam

2

Did you explore the Windows Filtering Platform? WFP is supported in VISTA
and Win7 and I would think Server 2008, though I have had no reason to deal
with 2008.

Gary G. Little
H (952) 223-1349
C (952) 454-4629
xxxxx@comcast.net

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of xxxxx@gmail.com
Sent: Monday, October 18, 2010 9:09 AM
To: Windows System Software Devs Interest List
Subject: [ntdev] Disable TCP SACK in Windows 2008 R2…

My question is simple.

Can TCP SACK be disabled in Windows 2008 R2?

I am using a TOE device that does not support TCP SACK. Connection
establishment occurs in host so the Windows network stack permits SACK but
once the connection is offloaded, SACK is not supported. Previous testing on
Windows 2003 showed improved recovery performance if the peer device was
correctly informed that TCP SACK is not supported on the connection.
Unfortunately I cannot find a way to disable just TCP SACK on Windows 2008.

Thanks in advance,
Adam

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3

>

My question is simple.

Can TCP SACK be disabled in Windows 2008 R2?

I am using a TOE device that does not support TCP SACK. Connection
establishment occurs in host so the Windows network stack permits SACK
but
once the connection is offloaded, SACK is not supported. Previous
testing on
Windows 2003 showed improved recovery performance if the peer device
was
correctly informed that TCP SACK is not supported on the connection.
Unfortunately I cannot find a way to disable just TCP SACK on Windows

I’ve wondered about this as well. I’ve seen firewalls that fail in
curious ways when SACK is in play. Obviously the best solution is to fix
the firewall/TOE device, but sometimes you have to work with what you’ve
got. The best I have come up with is to strip out the SACK options in
the SYN packets so neither end is aware that the other end supports it.
I’m surprised that your TOE device doesn’t do this for you although
maybe it isn’t involved until after SACK is negotiated.

Be aware that high latency links (eg satellite) do benefit greatly from
SACK once you get even the slightest amount of packet loss.

James