How a Slow Link Is Detected for Processing User Profiles and Group Policy

ID: Q227260

The information in this article applies to:
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Datacenter Server
  • Microsoft Windows 2000 Professional
  • Microsoft Windows 2000 Server

SUMMARY

This article describes how a slow link is detected in Windows 2000 for processing user profiles and Group Policy.


MORE INFORMATION

Windows 2000 includes a new method of determining whether a client computer is gaining access to a domain controller over a slow link to apply Group Policy or download a roaming user profile. This takes the form of a sequence of TCP/IP ping requests to the destination server. There is a greater reliance on the detection of slow links in Windows 2000 because this is used to determine the types of Group Policy that are applied.

The new mechanism takes the form of measuring the response time from a sequence of TCP/IP pings from the client computer to the server to determine the average transfer rate in kilobits per second (kbps). If the response time from any of the pings is less than 10 milliseconds (ms), the link is automatically considered to be fast. Otherwise, the average transfer rate is calculated (in kbps) from three ping requests to the server with 4 KB of data. If the transfer rate is slower than the default or a value defined by the administrator, the connection is considered slow.

Effects on Group Policy

When Group Policy is being applied to the computer or to the user, the IP slow link detection mechanism is always used. By default, if a slow link is detected, some forms of Group Policy are not applied. For more information about which Group Policy components do not apply by default and how to modify this behavior, see the following article in the Microsoft Knowledge Base:
Q227369 Default Behavior for Group Policy Extensions with Slow Link
The administrator can specify the connection speed independently for the application of Group Policy to computers and users:
  1. In the Active Directory Users and Computers Microsoft Management Console (MMC) snap-in, right-click the site, domain, or Organizational Unit in which the Group Policy Object (GPO) exists that will contain the policy for the connection speed, and then click Properties.


  2. Click the Group Policy tab, click the appropriate GPO, and then click Edit.


  3. To change the slow link detection speed for Windows 2000 when computer Group Policy is being applied, expand the Computer Configuration node and navigate to the Administrative Templates\System\Group Policy folder. Modify the Group Policy slow link detection policy.

    To change the slow link detection speed for Windows 2000 when user Group Policy is being applied, expand the User Configuration node and navigate to the Administrative Templates\System\Group Policy folder. Modify the Group Policy slow link detection policy.

    In either case, the value must be specified in kbps. To disable slow link detection, use 0 (zero) for this value. By default, the connection speed is set to 500 kbps.


  4. Close the Group Policy MMC snap-in.


Effects on Roaming User Profiles

Roaming user profiles are not required to be stored on a server on which TCP/IP is an installed protocol. However, when a user attempts to download a roaming user profile, the IP slow link detection mechanism is used first. If Windows 2000 detects that the server on which the roaming user profile is located does not support TCP/IP, it uses the method used by Microsoft Windows NT 4.0 and earlier versions, whereby the time it takes the server to respond to a request for the file attributes of the profile are timed and compared to the value determining a slow network.

The administrator can specify the connection speed that determines a slow network when user profiles are being downloaded:
  1. In the Active Directory Users and Computers Microsoft Management Console (MMC) snap-in, right-click the site, domain, or Organizational Unit in which the Group Policy Object (GPO) exists that will contain the policy for the connection speed, and then click Properties.


  2. Click the Group Policy tab, click the appropriate GPO, and then click Edit.


  3. To change the slow link detection speed for Windows 2000 when a user's roaming user profile is being downloaded, expand the Computer Configuration node and navigate to the Administrative Templates\System\Logon folder. Modify the Slow network connection timeout for user profiles policy. This policy uses two values, one in kbps for the TCP/IP slow network detection mechanism and one in ms (milliseconds) for the time to contact server. To disable slow link detection, use 0 (zero) for these values. By default, the connection speed is set to 500 (kbps) and the time is set to 120 (milliseconds).


  4. Close the Group Policy MMC snap-in.


Viewing the Slow Network Detection Data in the Debug Log

If debug logging is enabled on a Windows 2000-based computer, the result of the slow network detection mechanism is recorded in the Userenv.log file. An example of the entries recorded when a client is on a fast link (where the TCP/IP pings resulted in times of less than 10 ms) might look like the following:
USERENV(ac.150) 10:00:04:554 PingComputer: First time: 0
USERENV(ac.150) 10:00:04:554 PingComputer: Fast link. Exiting.

Additional query words:

Keywords : kbenv kbtool
Version : WINDOWS:2000
Platform : WINDOWS
Issue type : kbinfo


Last Reviewed: December 29, 1999
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