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Q191370: Slow Network Performance with Terminal Server

Article: Q191370
Product(s): Microsoft Windows NT
Version(s): winnt:4.0
Operating System(s): 
Keyword(s): 
Last Modified: 11-JUN-2002

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The information in this article applies to:

- Microsoft Windows NT Server version 4.0, Terminal Server Edition 
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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

Windows NT Terminal Server experiences difficulties communicating with another
Windows NT computer on the network. A network monitor trace reveals significant
delays between successive server message blocks (SMBs) sent from the Windows NT
Terminal Server client to the remote server.

This situation usually occurs when a high number of client sessions (RDP or ICA)
are connected and actively using the Terminal Server. This situation is more
likely to occur if every user has a drive mapped to a common server. Under
certain circumstances, this can cause the Terminal Server to stop responding on
all client sessions. When this occurs, console response is normal until
attempting to use the redirector. CPU usage will normally be very low.

You may experience the following error messages on the Terminal Server computer:

- Event ID: 5719
  Source: Netlogon
  Description: No Windows NT Domain Controller is available for domain
  domain_name. The following error occurred:
  There are currently no logon servers available to service the logon request.
- Error 1722: The RPC server is unavailable.
- Error 1723: The RPC server is too busy to complete this operation.
- Error 1721: Not enough resources are available to complete this operation.

User Manager, Server Manager, or other programs that require RPC and run on
Terminal Server may not work.


CAUSE
=====

The MaxMpxCt parameter allows a server to provide a suggested maximum number of
simultaneous outstanding client requests to a particular server.

During negotiation of the SMB dialect, this value is passed to the client's
redirector where the limit on outstanding requests is enforced.

When multiple RDP clients are connected to the Terminal Server, there is normally
one instance of the Windows shell, Explorer.exe, running for each client.

Explorer makes extensive use of directory notifications, resulting in a number of
NTNotifyDirectoryChange SMBs being posted to the server. Directory notifications
allow the server to notify the client when file or directory information
changes. The NTNotifyDirectoryChange SMB is classified as a long term request.
The SMB is received by the server but is not returned until a change occurs (or
until the SMB is cancelled by the client).

When several RDP clients connect to the Terminal Server, the number of
outstanding commands against the server can exceed the default maximum of 50. If
this situation arises, other SMB requests will wait in the redirector until
previous requests complete, timeout, or are cancelled.


RESOLUTION
==========

Increase the MaxMpxCt parameter on the remote server, not the Terminal Server
computer.


Although increasing this value can potentially increase server performance, it
may require a high use of server work items.

NOTE: For Windows NT 4.0 Service Pack 3 and later, the valid values for this
entry range from 1 to 65535 requests, with a default value of 50 requests. For
Windows 2000, the maximum value for this entry is limited to 125 requests to
assure that Windows 95 and Windows 98 clients can connect to the server.
WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

WARNING: Making a change to the MaxMpxCt registry entry may cause Windows 95/98
clients to not be able to connect to the server.

1. Use Registry Editor to locate the following registry key:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer \Parameters

2. Make the following changes:

  MaxMpxCt REG_DWORD

  Range: 1 to 65535 requests
  Default: 50

For additional information, click the article number below to view the article in
the Microsoft Knowledge Base:

  Q232890 Windows 98 Client Unable to Connect to Windows NT Share

Additional query words: semaphore lock freeze break transact tranceive

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Keywords          :  
Technology        : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400search kbNTTermServ400 kbNTTermServSearch
Version           : winnt:4.0
Issue type        : kbprb

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