Client/Server RPC compression is disabled

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at]  

Topic Last Modified: 2007-01-05

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine whether remote procedure call (RPC) compression is enabled:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem\ Rpc Compression Enabled

If the Exchange Server Analyzer finds that the value for Rpc Compression Minimum Size is present and configured with a value of 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:

  • Rpc Compression Minimum Size

  • Rpc Compression Enabled

  • Rpc Packing Enabled

The Rpc Compression Enabled registry value determines whether the RPC compression algorithms are used. If this key is not present, RPC compression is enabled and 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.

  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 Enabled key. If the Rpc Compression Minimum Size 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 Knowledge Base article 825371, "Modify Remote Procedure Call Compression in Exchange Server 2003" (


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