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Assessing Network Bandwidth Availability and Requirements

Updated: March 28, 2003

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

The availability of network bandwidth can affect how Group Policy settings are applied. By default, some policies do not process across a slow network connection. If the network link speeds between a client and the authenticating domain controller fall below the default slow-link threshold of 500 kilobits per second (Kbps), only the administrative template (registry-based) settings and security settings are applied. By default, all other Group Policy settings, including Software Installation and Folder Redirection, are not applied. When the available bandwidth between the client and the domain controller falls below this preset threshold, the client is said to be on a slow link.

If necessary, you can modify the default slow link behavior by using the Group Policy slow link detection policy setting for both the user and computer aspects of a GPO. The Group Policy slow link detection policy setting is available in both Computer Configuration and User Configuration, under the Administrative Templates\System node. You can also adjust the Group Policy extensions that are processed below the slow link threshold. However, depending on your situation, it might be more appropriate to place a local domain controller at a remote location to serve your management requirements.

For more information about slow links, see "Designing a Group Policy Infrastructure" in this book. For more information about Group Policy mechanics and infrastructure, see the Windows Security Collection of the Windows Server 2003 Technical Reference (or see the Windows Security Collection on the Web at http://www.microsoft.com/reskit).

Is it important to have sufficient network bandwidth available between servers and workstations when you deploy Roaming User Profiles, Offline Files, and Folder Redirection. It is also recommended that the servers to which workstations connect for this data are on a fast network link. Check your network configuration for ways to minimize network routing hops when accessing frequently needed data. Keeping the needed data and the user on the same subnet improves performance.

When evaluating network bandwidth for Folder Redirection, be aware that slow link detection is based on link speed between the workstation and the domain controller to which the workstation is connected. If the link to the domain controller is fast but the link to a shared folder that contains redirected folders is slow, users might experience slow performance when accessing redirected files. Selecting these redirected files for offline caching does not improve file access speed in this case because the slow link is not detected. As a result, the Offline Files cache is not brought online.

Logging on the first time after having a folder configured for redirection might be slow for the user because all the files are being copied from the user’s local drive to the shared folder on the network. The time this takes depends on the amount of data being copied, the local computer’s disk I/O speed, the available network bandwidth, and server performance. You can minimize logon time by doing the following:

  • Locate the validating domain controller in close proximity to the workstations that it needs to validate.

  • Simplify or remove existing user logon scripts. Group Policy can replace many conventional logon script settings. Group Policy creates additional download time at logon; however, this is insignificant if Group Policy objects (GPOs) are judiciously used (keeping in mind that the number of GPOs influences logon time). If Group Policy is used for new folder redirection or software installation, logon time for those actions increases.

  • Keep roaming user profiles as small as possible. Folder Redirection and profile quotas are common tools to manage roaming user profile size. For more information about managing roaming user profile size, see "Recommendations for Folder Redirection and "Setting Quotas on User Profiles," later in this chapter.

Understanding network traffic can help you design your network and servers to balance network loads. In some cases, it is cost effective to add another server or subnet to redistribute load; in other cases, making simple changes to server configuration can produce similar benefits.

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