Domain Synchronization Over a Slow WAN Link

• Microsoft Windows NT Server versions 3.5 and 3.51
• Microsoft Windows NT Server version 4.0

SUMMARY

Windows NT Server has a parameter that can be used to increase performance of replication across slow links. The parameter is called the ReplicationGovernor.

A backup domain controller (BDC) uses the ReplicationGovernor registry value to increase the performance of domain synchronization over a slow WAN link.

IMPORTANT: The ReplicationGovernor parameter is supported only on Windows NT Server 3.5 or later.

MORE INFORMATION

The ReplicationGovernor defines both the size of the data transferred on each call to the primary domain controller (PDC) and the frequency of those calls. Adjusting the ReplicationGovernor parameter works in two ways:

• It reduces the size of the buffer used on each call from the BDC to the PDC, ensuring that a single call does not occupy the WAN link for too long.
• It causes NetLogon essentially to "sleep" between calls, allowing other applications to access the WAN link between calls to the PDC.

You can add the ReplicationGovernor parameter to the registry of a BDC under \HKEY_LOCAL_MACHINE subtree under the following subkey:

   \SYSTEM\CurrentControlSet\Services\Netlogon\Parameters

For example, if you set the ReplicationGovernor value to 50 percent, it will use a 64KB buffer rather than the default 128 KB buffer. In addition, the BDC will have an outstanding synchronization call on the net for only a maximum of 50 percent of the time.

CAUTION: Care must be taken in setting this value, because if the ReplicationGovernor is set too low, synchronization might never complete. A value of zero will cause NetLogon never to synchronize, and the user account database can become completely out of sync.

IMPORTANT: This parameter must be set individually on each BDC and should only be used when the PDC is a computer running Windows NT Server 3.5 or later.