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Re: HTTP 1.1 Server Available for Testing

From: Roy T. Fielding <fielding@liege.ICS.UCI.EDU>
Date: Thu, 15 Aug 1996 18:08:42 -0700
To: Klaus Weide <kweide@tezcat.com>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Message-Id: <9608151808.aa16645@paris.ics.uci.edu>
>> CL-HTTP responds to 1.0 clients with 1.0 responses.  1.1 responses are
>> reserved for clients or proxies that also advertise 1.1 functionality.
> 
> This brings up a question - How legitimate is it for the same server
> (identified ipaddress:port) to change personality between HTTP/1.1
> and HTTP/1.0?  If a server answers some requests with "HTTP/1.1 200 .."
> and others with "HTTP/1.0 200 .." (or any other response code), this
> may confuse HTTP/1.1-aware clients.  

Well, there's no requirement against it (because that particular confusion
is harmless -- if it ever understands HTTP/1.1 then it is safe to send
HTTP/1.1-only features to it).

The intention of the protocol is that the server should always respond
with the highest minor version of the protocol it understands within
the same major version of the client's request message.  The restriction
is that the server cannot use those optional features of the
higher-level protocol which are forbidden to be sent to such
an older-version client.  [BTW, there are no required features of
a protocol that cannot be used with all other minor versions within
that major version, since that would be an incompatible change and
thus require a change in the major version.]

It sounds confusing, but it works in terms of providing a safe mechanism
of indicating and deploying future protocol changes.

 ...Roy T. Fielding
    Department of Information & Computer Science    (fielding@ics.uci.edu)
    University of California, Irvine, CA 92697-3425    fax:+1(714)824-4056
    http://www.ics.uci.edu/~fielding/
Received on Thursday, 15 August 1996 18:16:50 EDT

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