KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q119644: Copying Files from Windows NT Using NBF Can Be Very Slow

Article: Q119644
Product(s): Microsoft Windows NT
Version(s): 3.1
Operating System(s): 
Keyword(s): 
Last Modified: 07-FEB-2002

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows NT Server version 3.1 
- Microsoft Windows NT Workstation version 3.1 
- Microsoft Windows NT Advanced Server, version 3.1 
-------------------------------------------------------------------------------

SYMPTOMS
========

When you connect to a Windows NT computer from a computer with a very slow
network card (for example, the 3Com 3c501 EtherLink card) installed, copying
files to the workstation from the server can be extremely slow when using
NetBEUI as the protocol.


CAUSE
=====

The 3Com 3c501 card can only cope with a send window size of one. Windows NT
dynamically adapts the send window size for a session to cope with the
performance of different network cards and differing network conditions, however
it does not set it to a value less than two. This means that the server always
sends at least two data packets before expecting an acknowledgment from the
workstation. Because the network card in the workstation can only cope with one
packet at a time, the second packet is lost and the workstation only
acknowledges receipt of the first packet. The server then has to resend the
second packet.

RESOLUTION
==========

A new Registry parameter called MinimumSendWindowLimit has been added for the
Windows NT NBF (NetBEUI) protocol to allow the configuration of the minimum send
window size that NBF will use. The default value is 2. To fix the above problem,
this parameter needs to be changed to 1.

Use the Registration Information Editor (REGEDT32.EXE) to add this entry, as
follows:

WARNING: Using Registry Editor incorrectly can cause serious, system-wide
problems that may require you to reinstall Windows NT to correct them. Microsoft
cannot guarantee that any problems resulting from the use of Registry Editor can
be solved. Use this tool at your own risk.

1. Start REGEDT32.EXE and locate the following Registry subkey:

  HKEY_LOCAL_MACHINE\CurrentControlSet\Services\NBF\Parameters

2. From the Edit menu, choose Add Value. Enter MinimumSendWindowLimit in the
  Value Name field. Select REG_DWORD for the Data Type. Enter 1 in the data
  field. Save your changes.

3. Quit REGEDT32.

4. Quit Windows NT and restart your computer.

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT and Windows NT
Advanced Server version 3.1. This problem has been corrected in the latest U.S.
Service Pack for Windows NT and Windows NT Advanced Server version 3.1. For
information on obtaining the Service Pack, query on the following word in the
Microsoft Knowledge Base (without the spaces):

S E R V P A C K

The 3Com product discussed here is manufactured by 3Com Corp., a vendor
independent of Microsoft; we make no warranty, implied or otherwise, regarding
this product's performance or reliability.

Additional query words: prodnt 3.10

======================================================================
Keywords          :  
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW310 kbWinNTSsearch kbWinNTS310 kbWinNTAdvSerSearch kbWinNTAdvServ310 kbWinNTS310search kbWinNT310Search kbWinNTW310Search
Version           : :3.1

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.