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Consider the following scenario:
A client computer tries to connect to a secure Web site through a downstream proxy server that is chained to an upstream proxy server or array.
The downstream proxy server is a Microsoft Internet Security and Acceleration (ISA) Server 2004 computer.
The downstream ISA Server 2004 proxy server is configured not to request authentication from clients.
The upstream proxy server or array is configured to request authentication from clients.
The client computer uses the HTTP 1.0 protocol to send connection requests to the downstream ISA Server 2004 proxy server.
NoteWhen Microsoft Internet Explorer 6 is configured to use a proxy server, Internet Explorer uses the HTTP 1.0 protocol to form the proxy tunnel that is required to connect to Web sites that use the HTTPS protocol. This is true even if you configure Internet Explorer to use HTTP 1.1 by clicking to select the Use HTTP 1.1 through proxy connections check box.
In this scenario, the connection request fails, or the client computer takes a long time to connect to the secure Web site.
This issue occurs if the client computer sends CONNECT requests that contain a "Proxy-Connection: Keep-Alive" header. The ISA Server 2004 proxy server keeps the connection alive but sends a response that does not contain a PROXY-CONNECTION header. Internet Explorer interprets this response as a CLOSE response.
Note A CLOSE response is the default interpretation for HTTP 1.0.
Therefore, Internet Explorer waits for the ISA Server 2004 proxy server to close the connection. The ISA Web proxy service keeps the connection alive until the connection times out.
Service pack information
To resolve this problem, obtain the latest service pack for Internet Security and Acceleration Server 2004. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
891024 How to obtain the latest ISA Server 2004 service pack
A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.
If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.
Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:
Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.
No prerequisites are required.
You do not have to restart the computer after you apply this hotfix.
Hotfix replacement information
This hotfix does not replace any other hotfixes.
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.
Date Time Version Size File name -------------------------------------------------------------- 11-Oct-2005 15:58 4.0.2163.282 661,216 W3filter.dll
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Internet Security and Acceleration Server 2004 Service Pack 2.
For more information about how to install ISA Server 2004 hotfixes and updates, click the following article number to view the article in the Microsoft Knowledge Base:
885957 How to install ISA Server hotfixes and updates
Microsoft Internet Security and Acceleration Server 2004 Service Pack 1, Microsoft Internet Security and Acceleration Server 2004 Enterprise Edition, Microsoft Internet Security and Acceleration Server 2004 Standard Edition