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.
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.
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:
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.
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:
How to back up and restore the registry in Windows
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.
- Start Registry Editor (Regedit.exe).
- Go to the following subkey:
- Create a new value using the following information:
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.
If you are using the IntranetWare client from Novell, you will need
to follow these steps in addition to the procedures listed above:
- Run the registry editor (Regedt32.exe).
- Go to the following key:
Note The above registry key is one path; it has been wrapped for
- Click DeviceName, click Edit, and then click String.
- Change \Device\NetwareWorkstation to \Device\NetwareRedirector.
- Click OK, exit Registry Editor, and restart the computer.
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
The NetWare Redirector will be used as an example.
The following illustrates an initial UNC connection attempt:
- Application makes UNC request.
- Dfs is checked and the request is processed if Dfs is enabled.
- The MUP then checks the MUP cache for a recent connection.
- 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
- 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.
- 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.
- The handle to the resource is returned to the application based on the
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
- Run the Network tool in Control Panel.
- Click Services and click Network Access Order.
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.