Topic Last Modified: 2007-01-08

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine the minimum packet size for remote procedure call (RPC) compression:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem\Rpc Compression Minimum Size

If the Exchange Server Analyzer finds that the value for Rpc Compression Minimum Size is greater than 0, a non-default configuration message is displayed.

By default, all RPC data that moves between Microsoft Office Outlook® 2003 or Outlook 2007 and Exchange Server 2003 or Exchange Server 2007 is compressed, regardless of its size. In some scenarios, you may want to control RPC compression. For example, if you are trying to troubleshoot connectivity problems by viewing the packets that are being sent over the network, RPC compression may make analysis difficult because you see only the compressed data in the trace.

To configure RPC compression settings, you can add three registry key values to the system settings:

The Rpc Compression Minimum Size registry value determines the minimum number of bytes required in the RPC packet before compression is activated. If this key is not present, a default value of 1,024 bytes is used.

This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

To revert to the default configuration

  1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

  2. Navigate to: HKLM\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem

  3. Delete the Rpc Compression Minimum Size key. If the Rpc Compression Enabled and Rpc Packing Enabled keys are present, delete those also.

  4. Close the registry editor, and restart the Exchange server for the change to take effect.

Before you edit the registry, and for information about how to edit the registry, see the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (

For more information about controlling RPC compression, see the Knowledge Base article 825371, "Modify Remote Procedure Call Compression in Exchange Server 2003" (