New Netlogon Registry Entry for Dialup Routers

ID: Q151259

The information in this article applies to:

Microsoft Windows NT Workstation version 3.51
Microsoft Windows NT Server version 3.51

SYMPTOMS

A user who logs on to a network where the domain controller is across a dialup router sees the following message:


   Dialog box message title: Logon Message

   A domain controller for your domain could not be contacted. You have
   been logged on using cached account information. Changes made to your
   profile since you last logged on may not be available.

The user encounters this message unless the router happens to have an existing connection open, in which case the user is validated normally by the domain controller.

CAUSE

A dialup router takes longer to make a connection to the remote network than Netlogon will wait, so Netlogon assumes no domain controller is available on the network. A dialup router can take as long as 30 to 90 seconds to make a connection to the remote network. Netlogon by default will send out three broadcast/multicast <1C> frames looking for the domain controller at 5-second intervals. This is a total of approximately 15 seconds that the dialup router has to make the connection and pass the frame before Netlogon times out and uses cached credentials to validate the user.

RESOLUTION

Apply the hotfix mentioned below. The hotfix consists of a new Netlogon Registry entry that adds an additional delay to each of the Netlogon broadcast/multicast <1C> frames sent. The net formula for wait time is as follows:


   5 seconds + ( ExpectedDialupDelay / 3 ).

If the ExpectedDialupDelay is set to 90 seconds, the wait time would be:


   5 + ( 90 / 3 ) = 35,

thus, a 35-second interval between frames.

The Registry location for the new parameter is:


   Location: HKLM\System\CCS\Services\Netlogon\Parameters
   Value Name: ExpectedDialupDelay
   Data Type:  Reg_Dword
   Data Value is in seconds.

Note that you can also add this registry entry to a Windows NT 4.0-based server manually.

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 3.51. This problem was corrected in the latest Windows NT 3.51 U.S. Service Pack. 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

Additional query words:

Keywords : NTSrvWkst
Version : winnt:3.51
Platform : winnt
Issue type :