Microsoft Scalable Network Pack. Good or bad?

Filed under: Sametime, Technical Support, Technology

Recently our support center has received a flurry of calls regarding performance of Sametime Meetings.  After some in-depth investigations by our development team and network engineer, we have found something can really boost performance.  Windows 2003 SP1 introduced the scalable network pack.  Sound impressive doesn’t it?  Actually this feature can reduce the performance of the network to a point where network apps will run slower and meetings may sporatically disconnect.  We have found that after disabling this feature, network app performance improves dramatically. 

So how do you disable it?

To Disable TCP Chimney, navigate to the following registry key and set the value to 0. (Note: You have to reboot the server after this registry change)
      [HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParameters]
      ”EnableTCPChimney”=dword:00000000

If that does help with the situation, you could also try disabling the following offloading keys under the above registry hive to disable the RSS features.
      ”EnableTCPA”= dword:00000000
      ”EnableRSS”= dword:00000000

4 Responses to “Microsoft Scalable Network Pack. Good or bad?”

1. Chuck Hauble Says:
   February 9th, 2008 at 7:01 am

   Hi Andy,

   two questions:
   Have you seen issues with this running Windows 2003 SP2?
   Does the same issue apply to Domino email and application servers? (you talk about sametime servers)

   Thanks

2. Andy Yiu Says:
   February 9th, 2008 at 8:03 am

   This is definitely part of Windows 2003 SP2. The same issue does apply to other applications servers outside of the Sametime. One customer reported that they spent several weeks trying to track down the performance bottleneck with a non-IBM application and after they disable the scalable network pack, they saw a dramatic improvement.

3. Fred Mandeville Says:
   February 14th, 2008 at 2:23 pm

   Hey Andy. We have been seeing some intermittant meeting room issues since going to 7.5.1 cf1. But also at that time we went to from 2000 to 2003 sp2. How many servers have you removed from? How long has these servers have pack been disabled? Do I lose anything by disabling the scalable network pack?

   Thanks,
   Fred

4. Andy Yiu Says:
   February 14th, 2008 at 8:30 pm

   Fred, I do not have an exact count of the number of servers or customer environment where we have removed this from. However I have asked about 10 customers to remove this with favorable results. At least three of the customers whom I’ve informed have had the SNP disabled for at least two months.

   You will not lose anything by disabling the SNP if you do not have one of the supported network cards. Otherwise you have nothing to lose and a lot more to gain.

   This Microsoft article outlines the devices which are supported:
   http://support.microsoft.com/kb/912222

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