Settings for minimizing periodic WAN traffic

Your dial-on-demand link activates while the computer is idle if the following conditions are true:

• You are using a Microsoft Windows 2000 Professional-based computer or a Microsoft Windows XP-based computer on a remote network.
• The computer is a member of one of the following domains:
  • Microsoft Windows NT 4.0
  • Windows 2000
  • Microsoft Windows Server 2003
• You are connected to the domain controllers over a dial-on-demand link.

The following sections contain a comprehensive summary of registry settings and Group Policy settings that you can add or modify to minimize WAN traffic. Some of the settings depend on the operating system version that the computer is running.

Part 1: A description of the relevant registry settings

The following registry settings affect WAN traffic and ISDN costs. To minimize periodic WAN traffic and to reduce ISDN costs, configure these settings as appropriate.

The Browser service registry settings

The domain master browser periodicity

Note This setting also applies to Windows Server 2008.

Description: The primary domain controller (PDC) is always the domain master browser. Therefore, a master browser on a network that does not host the PDC for the domain activates dial-on-demand links when a server that participates as a master browser tries to locate the PDC. By default, the attempt interval is five minutes. You can create a MasterPeriodicity registry entry that instructs the Browser service to adjust its default interval for contacting a domain master browser. By default, the MasterPeriodicity entry is not present. The recommended default for dial-on-demand deployments is 86,400 seconds (one day).

Server list maintenance

Note This setting also applies to Windows Server 2008.

Description: If you enable a server to participate as a browser and to potentially be elected as a master browser for its network, the server will periodically contact the PDC for its domain. By default, the MaintainServerList registry entry is set to Auto. The recommended value is No unless you must have browser functionality on the network. If you must have browser functionality, set this value to Yes. However, make sure to configure the MasterPeriodicity interval to a large enough interval to reduce the number of PDC contacts.

The SAM replication registry settings

Security Accounts Manager (SAM) replication is controlled by the Net Logon service on the PDC.

The pulse frequency

Description: The Pulse entry defines the typical pulse frequency.

The maximum pulse frequency

Description: The PulseMaximum entry defines the maximum pulse frequency.

The dial-up latency registry settings

The expected dial-up delay

Description: The ExpectedDialupDelay entry specifies the time that is required for a dial-up router to dial when it sends a message from a client computer to a domain across a slow link. In this scenario, the domain is trusted by the client computer. Typically, the Net Logon service assumes that it can quickly reach a domain controller. By setting the ExpectedDialupDelay entry, you inform the Net Logon service to expect an additional delay. The recommended value for this setting is the average time in seconds that is required for the dial-on-demand link to be established, plus a constant of 5 seconds for variance.

The Net Logon service registry settings

The AvoidPdcOnWan entry

Description: The AvoidPdcOnWan entry instructs the server that is running the Net Logon service to avoid going to the PDC operations master roles as much as it can. (The operations master roles are also known as flexible single master operations or FSMO.) The AvoidPdcOnWan entry also instructs other components, such as the SAM, that use this information. For example, assume that this entry is enabled on a domain controller in a remote site. In this scenario, the remote domain controller will not try to verify a password with the PDC operations master roles if the client does not authenticate with the local domain controller. In Windows 2000 Service Pack 2 and in later Windows 2000 service packs, in Windows XP, and in Windows Server 2003, the Directory service client queries are issued one time per hour. You can adjust the following registry entries to extend this query time beyond one hour.

The negative cache period

Description: The NegativeCachePeriod entry specifies the time that a client will remember that a domain controller could not be found in a domain. If a program tries again within this time, the client call immediately fails without trying to find a domain controller again.

The background retry initial period

Description: Some programs periodically try to find a domain controller. If the domain controller is not available, these periodic retries can be costly in dial-on-demand scenarios. The BackgroundRetryInitialPeriod entry defines the minimum amount of elapsed time before the first retry occurs. If the value is smaller than the value set in the NegativeCachePeriod entry, the NegativeCachePeriod value is used.

The background retry back-off period

Description: The BackgroundRetryMaximumPeriod entry defines the maximum interval that the retries will be backed off. For example, if the first retry is after 10 minutes, the second retry will be after 20 minutes, and the next retry will be after 30 minutes. This continues until the value in the BackgroundRetryMaximumPeriod entry is reached. Then, the BackgroundRetryBackoffPeriod value is used for the retry interval until the value in the BackgroundRetryQuitTime entry is reached.

The background retry quit time

Description: When a program runs a periodic search for domain controllers and cannot find a domain controller, the value that is set in this entry determines when retries are no longer possible. For more information about these parameters, click the following article number to view the article in the Microsoft Knowledge Base:

DFS registry settings

The frequency of domain controller queries by DFS

Description: The DfsDcNameDelay entry can reduce the frequency of domain controller queries by Distributed File System (DFS). Modify this entry on the client computer. On Window XP-based computers, the default value is set to 60 minutes by using a Group Policy setting. This setting determines how frequently a DFS client discovers the domain controllers.

Windows XP-based client computers dynamically look for updates to the DFS discovery interval. The valid range for DfsDcNameDelay is from 15 minutes to 360 minutes. No restart is required for new settings to take effect.

For more information about the DfsDcNameDelay parameter, click the following article number to view the article in the Microsoft Knowledge Base:

The frequency of PDC queries by DFS

Every DFS server that has a domain-based DFS root polls the PDC for changes on the root object. You can control the interval between pollings by setting the SyncIntervalInSeconds registry entry on the DFS root server or servers. By setting this entry, you can control when DFS returns referrals that are based on cached data. If you increase this value, DFS caches namespaces and referrals for a longer duration.

The maximum password age

Description: Specifies how frequently the system changes the computer account password of the local computer. This entry is used only when the system is configured to change the computer password automatically at set intervals. That is, this entry is used only when the value of the DisablePasswordChange entry is 0. For more information, visit the following Microsoft Web site: For more information about the MaximumPasswordAge entry, click the following article number to view the article in the Microsoft Knowledge Base:

Intrasite domain controller replication

Description: The "Replicator notify pause after modify (secs)" entry defines the delay after a domain controller writes a change to its local copy of the Active Directory directory service and before the domain controller's replication partners are notified of the change. When this interval elapses, the domain controller initiates a notification to each intrasite replication partner that changes exist that must be propagated.

The Knowledge Consistency Checker (KCC) replication topology update period

Description: The "Repl topology update period (secs)" value defines the number of seconds between intervals.

Windows XP Group Policy settings

The following policy settings control the frequency of Net Logon-based traffic and of DFS-based traffic on Windows XP clients. To locate these settings, click Start, click Run, type gpedit.msc, and then click OK.

Computer Configuration/Administrative Templates/System/Net Logon

• Scavenge Interval
• Positive Periodic DC Cache Refresh for Non-Background Callers
• Positive Periodic DC Cache Refresh for Background Callers
• Final DC Discovery Retry Settings for Background Callers
• Maximum DC Discovery Retry Interval Settings for Background Callers
• Initial DC Discovery Retry Settings for Background Callers
• Negative DC Discovery Cache Settings
• Contact PDC on logon failure
• Expected dial-up delay on logon

Computer Configuration/Administrative Templates/Network

• Sets how often a DFS Client discovers DCs
  
  By default, a DFS client tries to discover domain controllers every 15 minutes. If you enable the Sets how often a DFS Client discovers DCs setting, you can change the interval. This value is specified in minutes. If you disable this setting or do not configure it, the default value of 15 minutes applies. The corresponding registry subkey is the following:
  HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\System\DFSClient\DfsDcNameDelay

"Group Policy domain controller selection" setting

By default, Group Policy reads and writes changes to the domain controller that is designated as the PDC operations master for the domain. We recommend that you change the Group Policy domain controller selection value on the domain controller that Active Directory Users and Computers or Active Directory Sites and Services uses. The corresponding registry subkey is the following:The DCOption entry stores the setting of the Group Policy domain controller selection Group Policy setting. Group Policy adds the DCOption entry to the registry when you enable the policy. If you disable the policy or set it to "Not configured," Group Policy deletes this entry from the registry, and the computer behaves as if the value is 1.

To change the value of the DCOption entry, configure the Group Policy domain controller selection policy in Group Policy Object Editor. To locate the Group Policy domain controller selection policy, see the following Group Policy object: The following table describes the settings.

Part 2: Default values

Default values for packet types

The following table shows the packet types and their default send intervals.Notes

• The Browse packet type in this table indicates network traffic between a Windows NT-based PDC and its backup domain controllers (BDCs).
• The Windows NT redirector echoes an SMB echo frame every 30 seconds or 32 seconds to each file server that has an associated long-term request that is outstanding. For example, a file server might have a NotifyChange request in Microsoft Internet Explorer. To avoid these packets, you can set the NoRemoteChangeNotify key.
  
  For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
  831129 Folder tree flickers when you view a mapped network drive in Microsoft Windows Explorer
  816375 Windows XP Explorer pane flickers on mapped network drives
• If there is no data transfer between the client and the server for the KeepAlive interval (120 seconds), the server sends the first keep-alive probe. After two minutes of inactivity (idle tree connects), the file server sends a 1-byte session message. The TCP payload is "02". The TCP sequence number starts with the last received acknowledgement (ACK) minus 1 and ends with the current acknowledgement.
• If the connection against the server is made by using named pipes, the server sends an "NetBT: SS - Session Keep Alive" message to the client approximately every 300 seconds.
  
  The NetBT SessionKeepAlive entry is in the following registry subkey:
  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetBT\Parameters
• A Common Internet File System (CIFS) TCP session keep-alive message includes a byte with an 0x85 value, followed by three bytes with a 0 (zero) value in the NetBT header. The keep-alive message may be sent if no messages have been sent for a client-configurable interval.

The default values for Microsoft Office Outlook 2003 and for Microsoft Exchange Server

By default, the client publishes free or busy information to the server for 15 minutes (900 seconds). In Outlook 2003, the default interval is 45 minutes. To change this interval, follow these steps:

1. Start Microsoft Outlook.
2. On the Tools menu, click Options.
3. On the Preferences tab, click Calendar Options.
4. In the Calendar Options dialog box, click Free/Busy Options.
5. In the Update free/busy information on the server box, type the number of minutes that you want to use as the interval.

The default values for Windows NT 4.0

Default values for Windows NT 4.0 and Windows 2000

Default values for Windows 2000

Default values for Windows XP and for Windows Server 2003

Microsoft Knowledge Base articles

For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

A Microsoft white paper

A white paper that is titled "Using Microsoft Windows XP Professional with Service Pack 1 in a Managed Environment" is available for download. This white paper provides information about the communication that flows between components in Windows XP Professional Service Pack 1 (SP1) and sites on the Internet.

The following file is available for download from the Microsoft Download Center:

Download the white paper package now.

Release Date: October 26, 2004

For more information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.

Specific problems and their associated Microsoft Knowledge Base articles

Windows NT 4.0 and Windows 2000 browsing and WINS replication

• Article:
  134985 Browsing and other traffic incur high costs over ISDN routers
  
  Cause: This problem may be caused by incorrect configuration of the default interval for the following components:
  • Domain browsing
  • WINS replication
  • Directory replication
  • User accounts database (SAM) replication
  • Printer browsing
  Occurrence: Varies depending on default interval parameters.
  Resolution: Increase appropriate intervals.

Windows NT 4.0

• Article:
  142692 Minimizing WAN traffic
  
  Cause: This problem may be caused by incorrect configuration of the default interval for the following components:
  • License Logging service
  • Browsing
  • SAM replication
  • Closing of SMB connections
  • NetBIOS node type
  • Trust relationships
  • Replicator service
  • WINS replication
  Occurrence: Varies depending on default interval parameters.
  Resolution: Change the appropriate intervals to greater values.

Windows NT 4.0 Service Pack 6a (SP6a)

• Article:
  271374 Windows NT 4.0 SP6 clients contact the PDC every 21 minutes
  Cause: Windows NT 4.0 may contact the PDC every 21 minutes to obtain a DFS referral.
  Occurrence: Every 21 minutes.
  Resolution: Install hotfix 271374.

Windows 2000

• Article:
  265395 Windows 2000 member runs discovery every 15 minutes with possible high dial-on-demand line costs
  Cause: This problem is caused by the DsGetDcName function that is used in Net Logon service domain controller discovery, DFS queries for the domain controller, or the GPO refresh interval.
  Occurrence: Varies depending on the default interval parameters.
  Resolution: Install Windows 2000 Service Pack 2 (SP2). Windows 2000 SP2 sets the default interval to one hour and enables configuration of longer intervals.
• Article:
  279117 The Distributed Link Tracking Server service may cause extra DNS queries in Windows 2000 Server
  Cause: This problem is caused by an additional DNS query for "_ldap._tcp.Site_Name._sites.dc._msdcs.Server_Name"
  Occurrence: Every four hours.
  Resolution: Install Windows 2000 SP2.
• Article:
  295165 Extraneous DNS queries generate network overhead
  Cause: This problem is caused by a bogus DNS query for "_ldap._tcp.Site-Site_Name._sites.dc_msdcs.Server_Name.Domain_Name
  Occurrence: Every time the Security section of the domain Group Policy setting on the DNS client domain controller is opened.
  Resolution: Install Windows 2000 Service Pack 3 (SP3).
• Article:
  311736 Reoccurring WAN traffic every five minutes may cause high line costs
  Cause: This problem occurs when the following conditions are true:
  • Remote procedure call (RPC) LsaLookupNames for "Authenticated Users" are forwarded to trusted domains.
  • Non-English versions of Windows 2000 are running DNS servers that have Active Directory integrated zones.
  Occurrence: Every 5 minutes or 300 seconds.
  Resolution: Install Windows 2000 SP3.

Windows XP

• Article:
  330929 Windows XP may cause extra SMB notify change traffic
  Cause: There is a bug in Windows XP that causes the client to send KeepAlive traffic even though the SessionKeepAlive setting has been modified.
  Occurrence: Every 32 seconds.
  Resolution: Apply hotfix 330929, and then set the NoRemoteRecursiveEvents registry entry to 1.
• Article: For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
  829104 The DFS client ignores the DfsDcNameDelay registry key setting
  Cause: The procedure that is described in Microsoft Knowledge Base article 291377 does not reduce the number of Distributed File System (DFS) queries that the computer issues after you add the DfsDcNameDelay registry key.
  Occurrence: Every 15 minutes.
  Resolution: Apply hotfix 829104, and then set the DfsDcNameDelay registry entry to a value between 15 and 360 minutes.
• Article:
  323713 Description of Universal Plug and Play features in Windows XP
  Cause: UPnP devices can automatically periodically announce their presence on a network subnet.
  Occurrence: The occurrence varies.
  Resolution: Disable the UPnP device host service, if you do not require it.