ISA Server Does Not Cache Responses That Contain the Location Header

Internet Security and Acceleration (ISA) Server does not cache responses that contain the Location header. (For example, in a Network Monitor trace, under the HTTP protocol in the headers section: Location:Http://domain.com).

Location headers are sometimes used in links that redirect a user to a site based on certain criteria. The link itself may contain only parameters for a query that is run on the Web server. The response to that query is an URL to which the user is being redirected. This URL is sent to the browser as a Location header, the browser then goes to that location.

With ISA Server, the problem can occur if the caching options are set to cache all content including dynamic content and a scheduled content download job is set to download and cache such a site; the links that return location headers are not cached, even though the sites that are returned by the links are cached (provided that the download job specifies the proper depth of links to follow). When such a site is later accessed, ISA Server needs to access the original link and gets the response (the Location header). The site that is referenced in the response is served from the cache.

It may be appropriate in certain situations for ISA Server never to contact the original site but only to serve content from cache. The hotfix that is listed in this article makes ISA Server cache responses that contain Location headers as well.

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next ISA Server service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone 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 typical 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  
   ------------------------------------------------------
   6/12/2001  13:14:32  3.0.1200.65  373,520  W3proxy.exe
				

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.