Q. I have a very slow link between a location and a hub. Can I increase compression on the replication traffic?

A. By default, Windows Server 2003 and above use XPRESS compression. However, you can use Windows 2000 MS ZIP compression, which is recommended for links slower than 64 Kbps. To change to MS ZIP, make the following change on the domain controllers and read-only domain controllers (RODCs) in the location connected via the slow link.

  1. Start the registry editor on the RODC.

  2. Navigate to HKLM \SYSTEM\CurrentControlSet\Services\NTDS\Parameters.

  3. From the Edit menu select New then DWORD value.

  4. Enter the name Replication compression algorithm and press Enter.

  5. Double-click the new value and set it to 2 to use MS ZIP. A value of 3 says to use XPRESS, the default.

  6. You can optionally create a key named Replication compression level of type DWORD which controls the amount of compression, with 0 being no compression and 9 being the most. The default value is 3. The higher the compression, the more load on the hub bridgehead servers.

  7. Close the registry editor.

Remember that changing the compression algorithm and increasing the amount of compression both place extra load on the bridgehead servers, so you should monitor their CPU usage carefully when making these types of changes.

Related Reading:

Check out hundreds more useful Q&As like this in John Savill's FAQ for Windows. Also, watch instructional videos made by John at ITTV.net.
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