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Q177654: Slow Network Performance Using NetBEUI Across Bridges

Article: Q177654
Product(s): Microsoft Windows NT
Version(s): WinNT:4.0
Operating System(s): 
Keyword(s): kbnetwork kbWinNT400sp4fix
Last Modified: 09-AUG-2001

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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 
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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 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.

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

2. Go to the following subkey:

  HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Nbf\Parameters

3. 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 kbWinNT400sp4fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch
Version           : WinNT:4.0
Issue type        : kbbug
Solution Type     : kbfix

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