Using the Windows 2000 Compression Algorithm on Slow WAN Links

Applies To: Windows Server 2008

For slow wide area network (WAN) links, we recommend that you use the compression algorithm that creates .zip files. This algorithm generates more calculation effort on the bridgehead server, but it lowers the traffic on the network. The compression algorithm is controlled by registry entries under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NTDS\Parameters, as shown in the following table.

Registry entry


Default value


Replicator compression algorithm



Recommended value if the bandwidth is greater than 64 Kbps: 3

Recommended value if the bandwidth is less than 64 Kbps: 2

The default value of 3 means that the XPRESS compression algorithm is used. The value 2 switches the compression algorithm to the .zip file compression algorithm, which we recommend for a bandwidth that is less than or equal to 64 Kbps. Note that we do not recommend switching to the .zip file compression algorithm if a bridgehead server runs under heavy load (CPU usage is greater than or equal to 80 percent). If you change the value to 2, you should monitor CPU usage on your bridgehead servers to determine whether to revert to the previous setting or maintain the change.

Replicator compression level



A value of 0 means no compression. A value of 9 means the highest compression. Increasing the compression level increases the load on the CPU. Therefore, you should monitor the CPU load closely in case you want to change this value. It is generally recommended to keep the default value of 3.