Slow Network Performance Using NetBEUI Across Bridges

This article was previously published under Q177654
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IMPORTANT: This article contains information about editing the registry.Before you edit the registry, make sure you understand how to restore it ifa problem occurs. For information on how to do this, view the "Restoringthe Registry" online Help topic in Regedit.exe or the "Restoring a RegistryKey" online Help topic in Regedt32.exe.
Your network performance seems to slow down and may actually stop in someinstances. You are using the NetBEUI protocol with your Windows NTcomputers.
Network performance can decrease because of the frequency and time intervalthe Logical Link Control (LLC) POLL frames are sent. When LLC POLL framesare not answered, NetBEUI starts resending these frames. Depending on thecircumstances, the first LLC POLL frame is sent after +/- 400 ms (ahardcoded value for MinimumT1Timeout), thereafter increasing the timebetween LLC POLL frames.
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack

After obtaining the fix mentioned above, then you will need to edit theregistry using the following steps:

WARNING: Using Registry Editor incorrectly can cause serious problems thatmay require you to reinstall your operating system. Microsoft cannotguarantee that problems resulting from the incorrect use of Registry Editorcan be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys AndValues" online Help topic in Registry Editor (Regedit.exe) or the "Add andDelete Information in the Registry" and "Edit Registry Data" online Helptopics in Regedt32.exe. Note that you should back up the registry beforeyou edit it.

  1. Start Registry Editor (Regedt32.exe or Regedit.exe).
  2. Go to the following subkey:
  3. Create a new value with the following information:
    Value name: MinimumT1Timeout Data type : REG_DWORD Default: 8 (decimal) (which equals 400 millisecond
Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.
In the following trace you can see the time intervals (measured as secondsfrom previous frame):
1  0.000 LLC       RR DSAP=0xF0 SSAP=0xF1 R N(R) = 0x04 FINAL2  1.772 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL3  0.450 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL4  0.651 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL5  0.952 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL6  1.402 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL				

This causes increased network traffic and LLC POLL frames from otherStations could timeout (router overload) increasing the overall number ofLLC POLL frames, which can finally lead to severe bridge problems.

Article ID: 177654 - Last Review: 10/07/2013 16:11:52 - Revision: 2.2

Microsoft Windows NT Server 4.0, Terminal Server Edition, Microsoft Windows NT Workstation 4.0 Developer Edition, Microsoft Windows NT Server 4.0 Standard Edition

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