Proxy Server 2.0 May Return Old Expires Header from Cache

Article translations Article translations
Article ID: 307740 - View products that this article applies to.
This article was previously published under Q307740
Expand all | Collapse all


If a client requests Web content that is cached on Proxy Server 2.0, the content that Proxy Server returns may include old header information.

In addition, an updated expiration date/time may not be sent back to the client when Proxy Server receives a NOT-MODIFIED response from a Web server.


This is a limitation of Proxy Server 2.0. When Proxy Server returns content from its cache, the proxy headers and the header that arrived with the file are returned to the client as long as the Time-To-Live (TTL) value has not expired. Proxy Server does not update the headers that are contained in the cached file.

In addition, incorrect processing may occur when Proxy Server handles a NOT-MODIFIED response from a Web server for content that has not yet expired. This may prevent an updated expiration date/time from being sent to the client.


Microsoft Internet Security and Acceleration (ISA) Server 2000 cache management is redesigned to work around this problem. Microsoft recommends that you upgrade the service to Internet Security and Acceleration Server 2000. To obtain Internet Security and Acceleration Server 2000, refer to the following Microsoft Web site:


A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, 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:
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.

The English version of this fix should have the following file attributes or later:
   Date        Time   Version        Size    File name     Platform
   11-Dec-2001 13:19  2.0.390.16     43,280  W3PCache.dll  x86
   11-Dec-2001 13:21  2.0.390.16    192,272  W3Proxy.dll   x86
IMPORTANT: The format of the content that is maintained in the URLCACHE folder changes with this fix. To prevent previously cached content from being returned to the client with multiple headers, follow these steps before you install the hotfix:
  1. Stop the Web Proxy service.
  2. Delete the \URLCACHE folder and all of its contents from the drive that is configured to hold your cache.
  3. Install the above-mentioned hotfix.
  4. Reboot your system. Notice that the \URLCACHE folder is re-created as the service restarts.


Microsoft has confirmed that this is a problem in Proxy Server 2.0.


Article ID: 307740 - Last Review: October 17, 2005 - Revision: 1.3
  • Microsoft Proxy Server 2.0 Standard Edition
kbhotfixserver kbqfe kbbug kbfix kbqfe KB307740
Retired KB Content Disclaimer
This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.

Give Feedback


Contact us for more help

Contact us for more help
Connect with Answer Desk for expert help.
Get more support from