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Re: RE-VERSION

From: Roy T. Fielding <fielding@kiwi.ics.uci.edu>
Date: Tue, 12 Aug 1997 17:16:52 -0700
To: Klaus Weide <kweide@tezcat.com>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Message-Id: <9708121716.aa17371@paris.ics.uci.edu>
>According to the "New Features in Apache 1.2" page, 
>  Aside from the optional proxy module (which operates as HTTP/1.0),
>  Apache is conditionally compliant with the HTTP/1.1 [...]
>I am not sure what this means, i.e. does it still act as an HTTP/1.1
>server when the proxy is used, aside from the version number question,

Nope.  A client talking to it as a proxy will only see an HTTP/1.0
proxy (and that's all it gets in the way of functionality).  It always
sends HTTP/1.0 in requests, so receiving chunked is not a problem.
It will respond with 411 if it receives chunked from a client.

However, a properly functioning HTTP/1.0 proxy is going to behave
very much like an HTTP/1.1 proxy, aside from the lack of a Via field.
For example, the following is going through a local test proxy:

   OPTIONS http://www.apache.org/ HTTP/1.1
   Host: www.apache.org

   HTTP/1.0 200 OK
   Date: Tue, 12 Aug 1997 23:24:41 GMT
   Server: Apache/1.3a2-dev
   Cache-Control: max-age=86400
   Expires: Wed, 13 Aug 1997 23:24:41 GMT
   Content-Length: 0
   Allow: GET, HEAD, OPTIONS, TRACE
   Connection: close

That is an HTTP/1.1 UA talking to an HTTP/1.0 proxy, forwarding an
HTTP/1.0 request to an HTTP/1.1 server (www.apache.org), which returns
an HTTP/1.1 response, which is then downgraded to HTTP/1.0 when it goes
back through the proxy.  So, although the Apache proxy does not puke on
OPTIONS, it does return HTTP/1.0.

On the flip side, however, if the proxy has been configured to deny
the request for the URL, then the error response will be coming from
the origin server and not the proxy. :(   E.g., the same without perms:

   GET http://www.apache.org/ HTTP/1.1
   Host: www.apache.org

   HTTP/1.1 403 Forbidden
   Date: Tue, 12 Aug 1997 23:17:56 GMT
   Server: Apache/1.2.3-dev
   Transfer-Encoding: chunked
   Content-Type: text/html

Likewise, it is the origin server that answers requests for "*".

   OPTIONS * HTTP/1.1
   Host: www

   HTTP/1.1 200 OK
   Date: Tue, 12 Aug 1997 23:39:55 GMT
   Server: Apache/1.2.3-dev
   Content-Length: 0
   Allow: GET, HEAD, OPTIONS, TRACE

which is, ummm, kind of a bummer if you are using OPTIONS to determine
if the proxy is HTTP/1.1 compliant.

This brings up a general problem I hadn't thought about before, which
is how does the proxy indicate that it is answering as itself and not
on behalf of the origin server?  It would look like an HTTP/1.1
response, but without the last Via entry.  Perhaps we need a way to
indicate that using another field, or a special value for Via.

....Roy
Received on Tuesday, 12 August 1997 17:22:09 EDT

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