WAN Minimization

For Windows networking to be able to span multiple network segments you need to be using an NT DOMAIN. In most cases its recommended you have at least a Backup Domain Controller on each subnet, although Windows NT Workstation can be used on smaller subnets.

The default configuration of domain controller traffic and network browsing will result in an ISDN line virtually never dropping. When using a dial-on-demand ISDN router for Windows networking you need to consider the following parameter modifications:-

The License Service May Generate Traffic Every 15 Minutes
The license service performs licensing replication. Data moves from BDCs and member servers to the PDCs, and then, optionally, from the PDCs to an enterprise server, which maintains licensing information across the whole network. This replication, by default, is performed one time every 24 hours. If, for some reason, the BDC cannot connect to the license service on the PDC, the BDC will continue to attempt replication one time every 15 minutes until it is successful. Check regularly that replication is occurring successfully.

Reducing Exchange of Browse Lists
Every MasterPeriodicity time interval (every 12 minutes, by default), the master browsers, try to contact the domain master browser, the PDC, to exchange their browse lists. This parameter can be changed in the registry of all the NT servers or workstations likely to be the master browser on a subnet.:

Key : HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Browser\Parameters
Value : MasterPeriodicity DWORD <number in seconds>
Default : 720

For additional information about this parameter, please see the following:-

Browsing & Other Traffic Incurs High Costs Over ISDN Routers
ARTICLE-ID: Q134985

To optimize the traffic on your WAN lines, increase the value above on all BDCs.

SAM Replication Between a PDC and Its BDCs
The SAM replication is controlled by NetLogon on the PDC. The following registry value defines the typical pulse frequency (in seconds):

Key : HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetLogon\Parameters
Value : Pulse
REG_DWORD 60 to 172800 seconds (48 hours)
Default : 300

For additional information, please see the following:-

ARTICLE-ID: Q150350NetLogon Maximum Value of Pulse Should Exceed 3600

All SAM/LSA changes made within this time are bundled together. After this period has elapsed, a pulse is sent to each BDC needing the changes. No pulse is sent to a BDC that is up-to-date. Increasing this value on the PDC reduces the number of replications between the PDC and the BDCs. Nevertheless, the SAM changes are propagated less quickly from the PDC to the BDCs. You must choose a balance between infrequent replication that may increase the number of connections to a PDC to validate changed passwords and frequent replication that may generate excessive ISDN traffic. The NetLogon PulseMaximum parameter has to be changed:

Key : HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetLogon\Parameters
Value : PulseMaximum
REG_DWORD 60 to 172800 seconds (48 hours)

It defines the maximum pulse frequency (in seconds). Every BDC will be sent at least one pulse at this frequency, whether its database is current or not. NOTE: The replication takes place immediately if a change is made in LSA secrets, for example, when adding a workstation to the domain or changing trusts relationships.

Close of SMB Connections Key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters
Value : KeepConn
REG_DWORD 1 to 65535 seconds
Default : 600 (10 minutes)

This value specifies the maximum amount of time that a connection can be left dormant. In a WAN environment, it is preferable to lower this value to 10 seconds on all the servers and the workstations, so that a new ISDN connection is not established just because of a SMB connection close. Changing KeepConn may generate significant SMB overhead. As connections are closed very quickly, each new connection implies the establishment of a new SMB connection.

NetBIOS Name Resolution Mode
When you use a domain spanning into multiple sites, the NetBIOS name resolution mode should be set to m-node (broadcasts followed by name server) on all servers and workstations. This setting ensures that a local (for example, on the same subnet) domain controller is always contacted first (for example, before trying to contact the PDC). On Windows NT systems, the NetBIOS name resolution mode can be set to m-node with the modification of the following key:

Key : HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetBt\Parameters
Value : NodeType
REG_DWORD 4 (4 is for M-NODE)

Trusts Relationships
Under certain circumstances, it is possible for 2 PDCs of 2 domains with a trust relationship to generate traffic every 15 minutes. For additional information, please see the following:-

ARTICLE-ID:Q152719 WAN and Trust: Traffic on the Wire

ARTICLE-ID: Q154355 How to Tune Trusts for Dialup Routers in a WAN Key:

HKEY_LOCAL_MACHINE\SYSTEM\CCS\Services\NetLogon\Parameters
Value : ScavengeInterval
REG_DWORD 60 to 172800 seconds (48 hours)
Default : 900 (15 minutes)

This parameter defines the time interval during which NetLogon does miscellaneous work (on the PDC and on the BDCs), for example, finding a domain controller. Other Services That Generate Traffic Check out the configuration of your WINS database renewal interval, and the replicator service as well. The replicator service may be modified as follows:

Key : HKEY_LOCAL_MACHINE\SYSTEM\CCS\Services\Replicator\Parameters
Value : Interval
REG_DWORD 60 (minutes)
Default : 5 (minutes)

Key : HKEY_LOCAL_MACHINE\SYSTEM\CCS\Services\Replicator\Parameters
Value : Pulse
REG_DWORD 6 (6 * 60 minutes = 6 hours)
Default : 3

For additional information on modifying the WINS settings, please see the following:-

ARTICLE-ID: Q142305
TITLE : Min. and Max. Interval Values for WINS Configuration

ARTICLE-ID:Q135922
TITLE : Windows NT Registry Parameters for WINS

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Last modified: 04 June 2005