Symptoms:Problems downloading .tar.gz files, issues with Linux package managers (apt/aptitude), or accessing the iTunes music store from behind Microsoft ISA Server 2004 with SP2.
Logging:ISA logs contain error 0x80004001 with reference to accessing a .gz file.Compression: client=No, server=No, cache=No, compress rate=0% decompress rate=0%Failed Connection Attempt via Web Proxy Filter
Details:KB 915045: Error 502 "The HTTP request includes a non-supported Header" when accessing certain web servers. This occurs when accessing certain Web servers that return headers that are incompatible with each other.KB 915421: Errors 11001 or 400 when accessing certain web servers. This is caused by a misinterpretation of spaces in headers provided by ISA Server, and results in a corrupted URL and failure to load the Web page.KB 915422: Event ID 23004 when accessing web sites that respond with compressed content. Some Web servers always return compressed content, which is denied by ISA Server when it did not request compressed content.KB 916573: Error 500 (Internal Server Error. Not implemented (-2147467263)) when trying to download zip attachments from an Outlook Web Access server. The header returned by Outlook Web Access causes ISA Server to deny the response.KB 917134: Grayed out checkbox “Enable caching of content received through the BITS service”
Cause:Missing the latest patches to handle HTTP issues - related to compressed files.
Resolution:ISA 2004 Standard:http://www.microsoft.com/downloads/details.aspx?familyid=2AA53EE6-527C-4398-AB7C-FCF8E8DDE8CEISA 2004 Enterprise:http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=EBC32D50-2E9F-4D55-AEFF-EEBA511827B0