A client computer connection request fails, or the client takes a long time to connect to a secure Web site through a downstream ISA Server 2004 proxy server (909062)

SYMPTOMS

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.

CAUSE

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.

RESOLUTION

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

Hotfix Information

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Internet Security and Acceleration Server 2004 Service Pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites

No prerequisites are required.

Restart requirement

You do not have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

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