Re: Extension headers and caching

Eric Lawrence wrote:
>> IE has lots of issues with Vary
> 
> To be more specific, the WinINET networking stack does not cache outbound request headers, preventing IE and other applications from reusing resources that Vary without validation (except in narrow cases).  See http://www.fiddler2.com/fiddler/Perf/AboutVary.asp for more information.
> 
> Revalidation ensures cache-correctness but entails a performance cost.
> 
> -Eric

As far as I recall it also means that you can't pass content with Vary: 
to an external application, such as an *ics file (IE invokes the 
application with a filename of a temp file that does not exist). This is 
as of IE6, maybe it has been fixed since.

BR, Julian