Microsoft KB Archive/825371

= Modify Remote Procedure Call Compression in Exchange Server 2003 =

Article ID: 825371

Article Last Modified on 10/25/2007

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APPLIES TO


 * Microsoft Exchange Server 2003 Enterprise Edition
 * Microsoft Exchange Server 2003 Standard Edition

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Important This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry



SUMMARY
By default, all remote procedure call (RPC) data that moves between Microsoft Outlook 2003 and Exchange Server 2003 is compressed, regardless of its size. The algorithms that are used by the Exchange 2003 RPC compression code produce very little overhead on the server, and at the same time, they greatly reduce the number of bytes that are sent. The algorithms therefore help to speed up communication between the client and the server. Even though there are advantages, you may want to control RPC compression. To give you this flexibility, you can add three new registry key values to the system settings:
 * Rpc Compression Minimum Size
 * Rpc Compression Enabled
 * Rpc Packing Enabled



MORE INFORMATION
Even though the compression algorithms that are used by Exchange make compression cheap in terms of processor cycles when you compare them to other compression schemes, compression is still an expensive operation. Therefore, packets that are under a specific size do not justify the high cost to compress the data. Because the relationship between the cost to compress and the level of compression is not a linear relationship, it is more expensive to compress the first byte than it is to compress any subsequent bytes. Because Transmission Control Protocol (TCP) packets have a limit of 1.4 kilobytes, the cost to compress a packet that is less than 1 kilobyte outweighs any benefits of making a single packet smaller. By not compressing packets that are 1 kilobyte or smaller, you can regain some processor cycles.

Sometimes you may not want to use any compression at all. If you are trying to troubleshoot connectivity problems and you are using Network Monitor to view the packets that are being sent over the network, RPC compression may make analysis difficult because you only see the compressed data in the trace.

By using these registry keys to modify RPC compression, you can control Exchange 2003 RPC to your advantage.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

You can use the following registry keys control RPC compression on your Exchange Server:
 * Location:

Parameter: Rpc Compression Enabled

Type: REG_DWORD

Value: 0x00000001 means enabled (default)
 * Location:

Parameter: Rpc Compression Minimum Size

Type: REG_DWORD

Value: Minimum number of bytes required in the RPC packet before compression is activated (defaults to 1024)
 * Location:

Parameter: Rpc Packing Enabled

Type: REG_DWORD

Value: 1 is enabled (default), 0 is disabled

Keywords: kbinfo KB825371

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