Slow Network Performance Using NetBEUI Across Bridges

ID: Q177654

The information in this article applies to:

Microsoft Windows NT Workstation version 4.0
Microsoft Windows NT Server version 4.0
Microsoft Windows NT Server version 4.0, Terminal Server Edition

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information on how to do this, view the "Restoring the Registry" online Help topic in Regedit.exe or the "Restoring a Registry Key" online Help topic in Regedt32.exe.

SYMPTOMS

Your network performance seems to slow down and may actually stop in some instances. You are using the NetBEUI protocol with your Windows NT computers.

CAUSE

Network performance can decrease because of the frequency and time interval the Logical Link Control (LLC) POLL frames are sent. When LLC POLL frames are not answered, NetBEUI starts resending these frames. Depending on the circumstances, the first LLC POLL frame is sent after +/- 400 ms (a hardcoded value for MinimumT1Timeout), thereafter increasing the time between LLC POLL frames.

RESOLUTION

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, please see the following article in the Microsoft Knowledge Base:

Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack

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

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

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

Start Registry Editor (Regedt32.exe or Regedit.exe).

Go to the following subkey:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Nbf\Parameters

Create a new value with the following information:

Value name: MinimumT1Timeout Data type : REG_DWORD Default: 8 (decimal) (which equals 400 milliseconds)

STATUS

Microsoft has confirmed this to be 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.

MORE INFORMATION

In the following trace you can see the time intervals (measured as seconds from previous frame):


1  0.000 LLC       RR DSAP=0xF0 SSAP=0xF1 R N(R) = 0x04 FINAL
2  1.772 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL
3  0.450 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL
4  0.651 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL
5  0.952 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL
6  1.402 LLC       RR DSAP=0xF0 SSAP=0xF0 C N(R) = 0x04 POLL

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

Keywords : kbnetwork NT4SP4Fix kbbug4.00 ntnetserv ntprotocol kbfix4.00.sp4 NTSrvWkst
Version : WinNT:4.0
Platform : winnt
Issue type : kbbug