#486: Requiring proxies to process warn-date

Mark Nottingham <mnot@mnot.net> Fri, 17 May 2013 01:43 UTC

Return-Path: <ietf-http-wg-request@listhub.w3.org>
X-Original-To: ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com
Delivered-To: ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com
Received: from localhost (localhost []) by ietfa.amsl.com (Postfix) with ESMTP id 0476011E8138 for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Thu, 16 May 2013 18:43:08 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -5.966
X-Spam-Status: No, score=-5.966 tagged_above=-999 required=5 tests=[AWL=4.633, BAYES_00=-2.599, RCVD_IN_DNSWL_HI=-8]
Received: from mail.ietf.org ([]) by localhost (ietfa.amsl.com []) (amavisd-new, port 10024) with ESMTP id 3JbJYLgmgVGm for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Thu, 16 May 2013 18:43:02 -0700 (PDT)
Received: from frink.w3.org (frink.w3.org []) by ietfa.amsl.com (Postfix) with ESMTP id AE55A11E80BA for <httpbisa-archive-bis2Juki@lists.ietf.org>; Thu, 16 May 2013 18:43:02 -0700 (PDT)
Received: from lists by frink.w3.org with local (Exim 4.72) (envelope-from <ietf-http-wg-request@listhub.w3.org>) id 1Ud9fY-0000y8-9X for ietf-http-wg-dist@listhub.w3.org; Fri, 17 May 2013 01:41:16 +0000
Resent-Date: Fri, 17 May 2013 01:41:16 +0000
Resent-Message-Id: <E1Ud9fY-0000y8-9X@frink.w3.org>
Received: from lisa.w3.org ([]) by frink.w3.org with esmtp (Exim 4.72) (envelope-from <mnot@mnot.net>) id 1Ud9fI-0000xG-Hp for ietf-http-wg@listhub.w3.org; Fri, 17 May 2013 01:41:00 +0000
Received: from mxout-07.mxes.net ([]) by lisa.w3.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from <mnot@mnot.net>) id 1Ud9fH-0006en-Ir for ietf-http-wg@w3.org; Fri, 17 May 2013 01:41:00 +0000
Received: from [] (unknown []) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by smtp.mxes.net (Postfix) with ESMTPSA id 1E1AD22E1F3; Thu, 16 May 2013 21:40:36 -0400 (EDT)
Content-Type: text/plain; charset=iso-8859-1
Mime-Version: 1.0 (Mac OS X Mail 6.3 \(1503\))
From: Mark Nottingham <mnot@mnot.net>
In-Reply-To: <519413CF.7010007@measurement-factory.com>
Date: Fri, 17 May 2013 11:40:31 +1000
Cc: "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
Content-Transfer-Encoding: quoted-printable
Message-Id: <A73CEF6C-EE77-462C-BA7E-80147A948D31@mnot.net>
References: <D528E812-45A0-426F-972F-3F4AC6F8DEA7@mnot.net> <519413CF.7010007@measurement-factory.com>
To: Alex Rousskov <rousskov@measurement-factory.com>
X-Mailer: Apple Mail (2.1503)
Received-SPF: pass client-ip=; envelope-from=mnot@mnot.net; helo=mxout-07.mxes.net
X-W3C-Hub-Spam-Status: No, score=-3.4
X-W3C-Hub-Spam-Report: AWL=-3.396, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001
X-W3C-Scan-Sig: lisa.w3.org 1Ud9fH-0006en-Ir 51148349fead49d23ac1348aba15bdab
X-Original-To: ietf-http-wg@w3.org
Subject: #486: Requiring proxies to process warn-date
Archived-At: <http://www.w3.org/mid/A73CEF6C-EE77-462C-BA7E-80147A948D31@mnot.net>
Resent-From: ietf-http-wg@w3.org
X-Mailing-List: <ietf-http-wg@w3.org> archive/latest/18015
X-Loop: ietf-http-wg@w3.org
Resent-Sender: ietf-http-wg-request@w3.org
Precedence: list
List-Id: <ietf-http-wg.w3.org>
List-Help: <http://www.w3.org/Mail/>
List-Post: <mailto:ietf-http-wg@w3.org>
List-Unsubscribe: <mailto:ietf-http-wg-request@w3.org?subject=unsubscribe>

On 16/05/2013, at 9:01 AM, Alex Rousskov <rousskov@measurement-factory.com> wrote:

> On 05/08/2013 07:14 AM, Mark Nottingham wrote:
>> In #480, Alex brought this text up in p6:
>>> If an implementation sends a message with one or more Warning
>>> header fields to a receiver whose version is HTTP/1.0 or lower,
>>> then the sender must include in each warning-value a warn-date that
>>> matches the Date header field in the message.
>>> If a system receives a message with a warning-value that includes a
>>> warn-date, and that warn-date is different from the Date value in
>>> the response, then that warning-value must be deleted from the
>>> message before storing, forwarding, or using it. (preventing the
>>> consequences of naive caching of Warning header fields.) If all of
>>> the warning-values are deleted for this reason, the Warning header
>>> field must be deleted as well.
>> My inclination here is to change the first paragraph to begin "If a
>> sender generates a message...",
> This would address my concern about the first paragraph, thank you.
>> and the second to be "If a recipient receives...", also removing
>> "forwarding" later down.
> This would not be sufficient because "using" may be interpreted to
> include "forwarding". How about this:
> "A response sender MUST NOT generate warning-value with a warn-date
> different from the Date value in the response. A cache MUST NOT send a
> warning-value with a warn-date different from the Date value in the
> from-cache response. A recipient MUST ignore a warning-value with a
> warn-date different from the Date value in the response."
> Would that cover all important cases without being too restrictive (like
> requiring the cache not to store something when there is no harm in
> storing, only in serving from the cache)?

I think so, although we should remove the first 'response'.

>> This is because IME proxies do not do any of this for messages that
>> they aren't caching, and moreover there are whole classes of
>> implementations that won't.
> You can also look at this from a different view point: Should every hop
> suffer implementing this MUST just to protect some "naive caches" down
> the road? Seems like the onus should be on those naive caches, 99.9% of
> which do not even know about Warning headers :-).


This is a non-editorial change, so I'm giving it a new issue number:

I think the path outlined above is a good resolution; if anyone has concerns, please say so.


Mark Nottingham   http://www.mnot.net/