A. To begin, let's define site costing. A client that accesses a DFS namespace begins by connecting DFS root targets and the client site's own link targets. If all the client site targets are unavailable, the client attempts to randomly connect to the rest of the DFS root targets. Giving preference to the client site's link targets is part of a process called site costing and it exists in Windows 2003 Dfs and Win2K Dfs. This functionality is always enabled.

Microsoft added to Windows 2003 Dfs a new feature called closest site selection that's very similar to site costing. With closest site selection mode enabled, a client that accesses a DFS namespace begins by trying to connect DFS root targets and the client site's own link targets. However, if all client site targets are unavailable, the client attempts to randomly connect to targets in the next closest site, and so on. For closest site selection to work on link targets, Intersite Topology Generator (ISTG) must be running on Windows 2003, and for closest site selection to work on link and root targets, all domain controllers (DCs) must be running Windows 2003.

To enable closest site selection in Windows 2003, you must use the version of the Dfsutil.exe command-line tool that will ship with Windows 2003. To enable closest site selection, type

Dfsutil /Root:\\<DfsServerName>\<DfsRootName> /SiteCosting /Enable

To enable closest site selection for SYSVOL, you must create a registry key on all DCs. To create the key, perform the following steps:

  1. Start a registry editor (e.g., regedit.exe).
  2. Navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dfs\Parameters registry subkey.
  3. From the Edit menu, select New, DWORD Value.
  4. Enter the name SiteCostedReferrals, then press Enter.
  5. Double-click the new value, set it to 1 to enable closest site selection, then click OK.
  6. Close the registry editor.
  7. Reboot the machine for the change to take effect.

If you move a Win2K DFS server to a new site, the Win2K server won't automatically refresh its site-related information. You can prevent this problem by removing the DFS server from the original site as a root target, then adding it to the new site as a root target. Windows 2003 can migrate from one site to another without experiencing the same problem because the OS can discover site information dynamically. Thanks to reader Atul for providing this information.