Windows 2003 Scalable Networking pack and its possible effects on Exchange - Part 2

Published Mar 12 2008 01:05 PM 2,958 Views

Note: Please see this blog post for the most updated recommendations on this subject.

I am sure many of you might have seen the issues that can be caused by the Windows Scalable Networking pack and incompatibilities with certain NIC drivers, as previously mentioned in

As of yesterday, there is a new High Priority Windows update available that will turn off of the Scalable Networking Pack features once it is installed. If you have Windows Update setup to receive updates automatically, this update will be downloaded and automatically installed.  If you need to manually apply the update, you can reference for more information as well as a link to the download. Note: Once this update is installed, you must reboot your server for these changes to take effect.

I would highly recommend applying this update to all Windows 2003 SP2 servers to help alleviate some of the connectivity issues that  can occur as a direct result of having the Scalable Networking Pack features enabled, and some incompatibilities with NIC drivers that we have seen.

In Windows 2008, these features are disabled by default and can be enabled if desired.

Have a great day!!

- Mike Lagase

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Thx for the heads up!  Does this affect E2K7 as well or only E2K3?
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Indeed - both E2003 and E2007 could be hit by symptoms of this problem.
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You have to question exactly what the point of the Scalable Network Pack is considering every blog or KB you read advises you to disable it!
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This issue is really a combination of enabled features and specific device drivers, rather than a general issue that impact all of the systems where W2003 SP2 was installed. On systems that are not affected, having SNP enabled can be a beautiful thing. There are measurable performance benefits.
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PoS scalable Network pack has given me grief for the last few months with Broadcom NetExtreme II nics; I have all the registry keys set to disable the tcp IP chimney features among other changes and still no luck. I am ripping out the problematic Broadcom NICs and replacing them with Intel's.
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prior to the release of 948496 we have multiple server where we had set the tcp chimney per the documentation.

We have cluster servers that are reverting back.  Are there other users out there having the problem of the settings reverting back to  enable the
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How can I verify that "netsh int ip set chimney DISABLED" actually changed anything?  If I run "netsh int ip show offload" on my W2K3R2 servers they come back with "TCP Chimney Offload" listed as one of the settings, but it doesn't say ON or OFF.  Is there a registry key I should look at?
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You can look in the registry under HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParameters

If EnableTCPChimney = 0  then it is disabled.

- Richard
M3 Postmasters
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I would encourage the readers of this blog not to give up on Scalable  Networking Pack because of these issues that have primarily to do with a single driver from a single vendor.  The fact that SP2 was released with SNP features enabled by default was accidental (just ask Microsoft, and witness that they are disabled by default in Server 2008).  TCP Chimney and RSS both potentially offer performance advantages in an Exchange environment if they are implemented correctly (though non-page pool memory usage may continue to be an issue).  

Disclaimer:  As an employee of a TOE vendor that is not Broadcom, I am certain to be biased.
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I've gone thru and checked settings as indicated but i'm still being disconnected from exchange.  Any other fix on this problem?

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Even with this hotfix applied, I am still getting Event ID: 9646.
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I have a Windows 2008 with Exchange 2007 SP1 that recorded event 9646, but it seems that Chimney isn't enable.

My roaming users, using Outlook Anywhere, have disconnections to Exchange. When this occurs, they don't have access to OWA too.

Is it related ? I'm searching for a few weeks but don't find any solution for this particular problem.
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Our HP Proliant NC371i NICs say they are fully capable of taking advantage of it so we'll see if the same symptoms appear as they did in an older box.  I'm hoping it works as planned though because it'd be nice.
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"On systems that are not affected, having SNP enabled can be a beautiful thing. There are measurable performance benefits."

Exchange Team:

Are you referring specifically to NICs that have drivers that support NDIS 5.2 or later? We're running Win2k3 with Exchange 2007 SP1 with the SNP features disabled, and we're experiencing the same issues as Petoulachi described above.
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Just adding some errors we saw after installing SP2 that may help people looking for this fix in the search engine.   The tcp chimney offload worked for us.

1. Mail messages stuck in the SMTP connector to the frontend server
2. When accessing Outlook receieved an error "No authority could be contacted for authentication"
3. Outlook is retreiving data from the Microsoft Exchange server_name(and the server was unresponsive to network activity such as viewing event logs, and opening shares.  this would come and go)
4. Outlook is disconnected from the server.

I hope this helps others in the search!
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Just a BIG detail on WINDOWS 2008 (RTM) servers:
- only "TCPChimney" is DISABLED by default
- RSS (Receive Side Scaling) is ENABLED by default
(but I don't know for TCPA)
unlike that you said in this post:
"In Windows 2008, these features are disabled by default and can be enabled if desired."

This activated RSS feature on a Windows 2008 can then affect Exchange 2007 Sp1 (for me it was the "SMTP Send Connector" with messages stuck in the queue - status 'connection dropped')...

And there is no windows 2008 version of the kb948496 to disable these feature.
Please could you talk more about the TOE default settings in Windows 2008 ?
Thank in advance
Jb Vernejoux
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Sorry, after many tests again , it seems that RSS isn't the source of my message errors in SMTP Queue. Even if RSS is disabled on W2008, the "connection dropped" errors are still here.

Anyway, it would be nice if you could tell us why "Receive Side Scaling" is by default enabled on W2008 rtm fresh installation unlike Chimney.
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