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Re: ETags vs Variants, was: Revising RFC2616 - what's happening

From: Henrik Nordstrom <henrik@henriknordstrom.net>
Date: Fri, 20 Oct 2006 09:26:08 +0000
To: Jamie Lokier <jamie@shareable.org>
Cc: HTTP Working Group <ietf-http-wg@w3.org>
Message-Id: <1161336351.29399.82.camel@henriknordstrom.net>
tor 2006-10-19 klockan 22:56 +0100 skrev Jamie Lokier:

> While on the subject of Etag and variants, it's never been clear what
> a Vary header that names a header not in the original request means.

For me that never was a question. I immediately read Vary as the
complete list of headers the server looked for while selecting which
variant to send. But this may be just my reading of the RFC..

What isn't very clear to me was what change in Vary means on a URI.

> But (a) is that use of Vary allowed

I think so.

> (b) is it consistently interpreted that way by caches, and

Quite likely. I know at least Squid does it this way, and most others I
have seen caching Vary.

But many shared proxy caches still don't cache Vary responses at all.

> (c) it would be good for the improved RFC to clarify this.

Probably. Many get Vary wrong. But the most common error I have seen is
not sending Vary when it should have been sent and still expecting
caches to do the right thing.. But I have not seen this dependent on the
existence of the header in the request or not.

Regards
Henrik

Received on Friday, 20 October 2006 12:08:39 GMT

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