You may experience a long delay when you try to use Internet Explorer to access a redirected Web page and Internet Explorer uses ISA Server 2004 as a Web proxy server

You configure Microsoft Internet Explorer to use Microsoft Internet Security and Acceleration (ISA) Server 2004 as a Web proxy server. When you try to use Internet Explorer to access a redirected Web page, you may experience a long delay.

This problem occurs when the ISA Server-based computer sends an HTTP GET request that spans two packets to a Web server that is running BEA WebLogic Server. In this situation, the Web server may respond to the HTTP GET request by sending an HTTP 302 Redirect message before the Web server receives the second packet. The Web server may not acknowledge the second packet for a long time. Therefore, the packet eventually times out.

By default, the EnablePMTUDiscovery registry entry is disabled after you install ISA Server 2004 on a computer that is running Microsoft Windows Server 2003. Therefore, the data is sent with a packet size of 576 bytes. In this situation, the HTTP GET request may span more than one packet.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To resolve this problem, enable the EnablePMTUDiscovery registry entry on the computer that is running ISA Server 2004. To do this, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. In Registry Editor, locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. Right-click the EnablePMTUDiscovery entry.
4. On the Edit menu, click Modify, and then type 1 in the Value date box.
5. Create an ICMP MTU access rule for ISA Server. For more information about how to do this, click the following article number to view the article in the Microsoft Knowledge Base:
   902347� CPU use may be more than 50 percent when an ISA Server 2004 computer is operating under heavy load conditions
6. Quit Registry Editor, and then restart the computer.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.