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From Alexei Kosut <>
Subject Re: [PATCH] PR#39 (no "Vary: Host" in response)
Date Fri, 28 Feb 1997 21:59:16 GMT
On Fri, 28 Feb 1997, Rodent of Unusual Size wrote:

> >From the fingers of Dean Gaudet flowed the following:
> >
> >Didn't we decide this was a deficiency in HTTP/1.1?  That it would require
> >"Vary: Host" on all HTTP/1.1 requests and so we shouldn't bother...
>     Perhaps it's considered a deficiency, but we can't really claim
>     compliance with HTTP/1.1 if we're going to pick and choose the parts
>     we like.  If it says `MUST' we don't have much option..
>     In addition, as I read it we *don't* have to include "Vary: Host" on
>     all responses - only those that used the "Host:" header to narrow
>     the field as it were.  In other words, requests that fall through to
>     the default server configuration (the only one, for people not using
>     VirtualHost) don't need "Vary: Host" because the "Host:" header
>     wasn't used.  That's what I implemented in the patch.

Sorry, that's not how Apache works. Apache looks at the Host header in
*every* request. Any request can be transferred to any other server in
the configuration by the use of the Host header. Therefore, Apache
would have to include "Vary: Host" in *every* request (even if the
request did not contain a Host header, since lack of a header is the
same as presence of one as far as Vary is concerned).

Roy (who, if you may recall, wrote much the HTTP/1.1 spec) has assured
us that it is not neccessary to include Vary: Host, as this should be
assumed by HTTP/1.1 proxies. In addition, minimally HTTP/1.1 compliant
caches would then not cache any Apache response, since the HTTP/1.1
spec requires that caches not cache responses with Vary: headers
unless they are prepared to honor them (i.e. only send the response
to a request with the same content in the named headers).

Y'know, we've had this discussion at least twice in the last few
months. There is a mail archive ( and it
seems to me that if you are going to bring up a topic on the list, you
should check to see if it's been discussed recently first. It would
save us all a lot of effort.

Alexei Kosut <>      The Apache HTTP Server

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