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.

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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.

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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 the Microsoft Knowledge Base:
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.

1.	Start Registry Editor (Regedt32.exe or Regedit.exe).
2.	Go to the following subkey: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Nbf\Paramete
3.	Create a new value with the following information: Value name: MinimumT1Timeout Data type : REG_DWORD Default: 8 (decimal) (which equals 400 millisecond

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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.

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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.

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