How to Disable HTTP Connection Reuse on a Microsoft Exchange Server 2003 Front-End Server (832749)

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

This article describes how to disable Hypertext Transfer Protocol (HTTP) connection reuse on a Microsoft Exchange Server 2003 front-end server.

You can use Exchange front-end servers to give Microsoft Outlook Web Access (OWA) users a single location that the users can connect to. The users can also use this single location to obtain mailbox data and public folder data.

Additionally, you can use front-end servers to transfer the HTTP encryption and compression processing load between servers. This article describes a server-side registry modification that you can make to prevent a front-end server from reusing an HTTP connection. When you prevent a front-end server from reusing an HTTP connection, a new HTTP connection is initiated every time that a request is made to the Exchange back-end server. Typically, an Exchange front-end server pools and reuses connections to deliver optimum performance. Therefore, when you disable HTTP connection reuse on the Exchange front-end server, users may experience a small degradation in response time when the users connect to programs such as OWA.

Note You may want to prevent Exchange front-end servers from reusing connections to Exchange back-end servers when a firewall or a proxy server (such as Microsoft Internet Security and Acceleration [ISA] Server 2000) is set to aggressively close unused TCP connections between the front-end servers and the back-end servers. Front-end servers typically try to reuse TCP connections to the back-end server. However, a firewall or a proxy server may silently close the TCP session. To work around this, the front-end server verifies that the socket is still active and retries connections that failed because the socket was closed. If you have a firewall that aggressively closes unused connections, you may find that it is more efficient for the front-end server not to try to reuse a connection.

MORE INFORMATION

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.

To disable HTTP connection reuse, follow these steps:

On the Exchange Server 2003 front-end server, start Registry Editor. To do this, click Start, click Run, type regedit in the Open box, and then click OK.
Locate and click the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeWEB\DAV
Note If the DAV registry key does not exist, create it. To do this, follow these steps:
1. Right-click MSExchangeWEB, point to New, and then click Key.
2. Name the new key DAV.
Right-click DAV, point to New, and then click DWORD Value.
Name the new value ReuseConnections.

Note This value is only valid for Exchange front-end servers.
Right-click ReuseConnections, and then click Modify.

Important The default value of 0 (zero) disables HTTP connection reuse. If you want to enable HTTP connection reuse, set the ReuseConnections registry value to 1. If you remove the ReuseConnections registry value, Exchange Server again reuses HTTP connections.
Click OK, and then quit Registry Editor.
Restart World Wide Web Publishing Service.

Note This registry change does not take effect until you restart World Wide Web Publishing Service.