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Q110136: Default Settings and Behavior or NbtKeepAlive and TcpKeepCnt

Article: Q110136
Product(s): Microsoft Windows NT
Version(s): 3.1
Operating System(s): 
Keyword(s): kbother
Last Modified: 15-DEC-2000

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The information in this article applies to:

- MSPRESS Microsoft Windows NT Resource Kit, version 3.1 
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SUMMARY
=======

The Windows NT Resource Kit Volume 1 incorrectly documents the default settings
and behavior for NbtKeepAlive and TcpKeepCnt parameters.

MORE INFORMATION
================

According to the Windows NT Resource Kit Volume 1, the following are default
values for keepalive parameters:

  NbtKeepAlive = 0 (disabled)
  TcpKeepCnt = 120 seconds

However, the actual defaults are the following:

  NbtKeepAlive = 60 seconds
  TcpKeepCnt = 120 seconds

Any frame sent by NBT (including a NetBIOS keep-alive) is considered to be data
by TCP. Because the NbtKeepAlive parameter is set lower than TcpKeepCnt, on an
idle NetBIOS session there will be one NBT keep-alive sent per minute, and no
TCP keep-alives sent. On an idle non-NetBIOS TCP session, such as that used by a
Windows Sockets program, TCP keep-alives will be sent, with their frequency
controlled by the TcpKeepCnt parameter.


As documented in the Windows Resource Kit, these parameters can be modified to
produce different behavior. To change these parameters, use the following
procedure:

WARNING: Using the 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. Open the Registry Editor (REGEDT32.EXE).

2. For NbtKeepAlive, use the following path:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Nbt\Parameters

3. Add a value for the NbtKeepAlive parameter as a REG_DWORD with the desired
  value in seconds. "0" disables NBT keepalives.

4. For TcpKeepCnt use the following path:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

5. Add a value for the TcpKeepCnt parameter as a REG_DWORD with the desired
  value in seconds. "0" disables TCP keepalives.

For example, if you want to send one TCP keep-alive every five minutes, and no
NetBIOS keep-alives, use the following values:

  NbtKeepAlive = 0
  TcpKeepCnt = 300

Additional query words: prodnt

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Keywords          : kbother 
Technology        : kbMSPressSearch kbZNotKeyword6 kbZNotKeyword2
Version           : 3.1

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