Connectivity delay with multiple redirectors installed

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Article ID: 171386 - View products that this article applies to.
This article was previously published under Q171386
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SYMPTOMS

You may experience a delay when you attempt to connect to network resources from a system with multiple redirectors installed. This delay only happens the first time that you attempt the connection.

CAUSE

When a non-WNET API initial UNC connection attempt is made to a network resource from a system with multiple redirectors, the Windows NT system sends the request to the multiple UNC provider (MUP) to identify which redirector should handle the request.

RESOLUTION

Windows NT 4.0

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
152734 How to obtain the latest Windows NT 4.0 service pack

Windows 2000 and Windows XP

A modification to the MUP has been made such that, if the redirector with the highest priority is attempted first with a successful response, those redirectors with lower priorities are then bypassed and the connection is made through the redirector with the highest priority.

Enabling this capability requires an updated Mup.sys. The speed improvement can be increased by modifying the registry entry DisableDFS.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows

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 (Regedit.exe).
  2. Go to the following subkey:
          HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Mup
    						
  3. Create a new value using the following information:
          DisableDFS  REG_DWORD
          Range:  0 or 1
          Default:  0 (Enabled)
    						

    Set this key to 1.

    If you set the DisableDFS key to 1, the client can no longer access a Distributed File System Namespace. This includes the SYSVOL Namespace in Active Directory. Do not set this key to 1 if the client is a member of Active Directory.
Note If you are using the IntranetWare client from Novell, you will need to follow these steps in addition to the procedures listed above:
  1. Run the registry editor (Regedt32.exe).
  2. Go to the following key:
          HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
          \NetwareWorkstation\NetworkProvider
    						

    Note The above registry key is one path; it has been wrapped for readability.
  3. Click DeviceName, click Edit, and then click String.
  4. Change \Device\NetwareWorkstation to \Device\NetwareRedirector.
  5. Click OK, exit Registry Editor, and restart the computer.

MORE INFORMATION

The MUP first establishes whether Distributed File System (Dfs) is in use and passes the request to Dfs.

The MUP then checks its internal cache to see whether the connection had been made previously (entries in the MUP cache are held for 15 minutes). The MUP then sends the request to each redirector that handles each request synchronously and attempts to identify a resource on the network that matches the request. After all redirectors return, the MUP chooses (based on response and priority) which redirector the application will use.

The delays come from two locations: first, the attempt to access the resource through Dfs and, second, the MUP must wait and accept all responses from all redirectors before completing the request. Therefore, even if a resource is readily available and accessible over one redirector, the request must still be made over the other installed redirectors before the request completes.

Depending on the number of redirectors, protocols, and timer configurations for connectivity, these delays can exceed 13 seconds for each initial connection.

The NetWare Redirector will be used as an example.

The following illustrates an initial UNC connection attempt:
  1. Application makes UNC request.
  2. Dfs is checked and the request is processed if Dfs is enabled.
  3. The MUP then checks the MUP cache for a recent connection.
  4. The MUP then makes a query to the first redirector, NetWare in this example, and the redirector responds.

    Note The return is immediate as NetWare uses only IPX and the calls are fast.
  5. The MUP sends the request to the second redirector, Microsoft in this example, and the second redirector responds.

    Note The delay for the Microsoft redirector depends on the protocols installed. With TCP/IP, delays exists as the resource name is queried through WINS, broadcasts, LMHOSTS file, DNS, and so on. For example, the default delay for an h-node client is 13 seconds.
  6. A priority is assigned to each redirector queried so if both redirectors return successfully, the priority is used to designate which redirector takes the request.
  7. The handle to the resource is returned to the application based on the MUP's decision.
If the application's request was made for a NetWare resource, the application would have to wait for the Microsoft redirector to timeout before returning the handle to the resource.

The priority for the redirectors can be configured using the following steps:
  1. Run the Network tool in Control Panel.
  2. Click Services and click Network Access Order.

STATUS

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.

Properties

Article ID: 171386 - Last Review: April 14, 2009 - Revision: 5.1
APPLIES TO
  • Microsoft Windows NT Server 4.0, Terminal Server Edition
  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Server 4.0 Standard Edition
  • Microsoft Windows 2000 Professional Edition
  • Microsoft Windows 2000 Server
  • Microsoft Windows XP Professional
Keywords: 
kbhotfixserver kbqfe kbbug kbfix kbnetwork KB171386

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