Re: draft-ietf-httpbis-client-hints-02, "2.2.1 Advertising Support for Client Hints"

Julian Reschke <> Thu, 13 October 2016 13:25 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 6FDCC129742 for <>; Thu, 13 Oct 2016 06:25:52 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -9.917
X-Spam-Status: No, score=-9.917 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.001, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, RP_MATCHES_RCVD=-2.996, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id EYY9-BYdbe-Y for <>; Thu, 13 Oct 2016 06:25:50 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 7447E1296E6 for <>; Thu, 13 Oct 2016 06:25:49 -0700 (PDT)
Received: from lists by with local (Exim 4.80) (envelope-from <>) id 1bufx2-00081Z-2i for; Thu, 13 Oct 2016 13:21:36 +0000
Resent-Date: Thu, 13 Oct 2016 13:21:36 +0000
Resent-Message-Id: <>
Received: from ([]) by with esmtps (TLS1.2:DHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.80) (envelope-from <>) id 1bufwn-00080k-6S for; Thu, 13 Oct 2016 13:21:21 +0000
Received: from ([]) by with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from <>) id 1bufwb-0000Z2-2N for; Thu, 13 Oct 2016 13:21:20 +0000
Received: from [] ([]) by (mrgmx003) with ESMTPSA (Nemesis) id 0M0PdN-1b0EUv4BBN-00uZNX; Thu, 13 Oct 2016 15:20:41 +0200
To: Ilya Grigorik <>
References: <> <>
Cc: " Group" <>
From: Julian Reschke <>
Message-ID: <>
Date: Thu, 13 Oct 2016 15:20:40 +0200
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0
MIME-Version: 1.0
In-Reply-To: <>
Content-Type: text/plain; charset="utf-8"; format="flowed"
Content-Transfer-Encoding: 7bit
X-Provags-ID: V03:K0:V8PBDYqyNy2yQnsodS7T95trt3UisiImiDaqTksn/JHOBkXlJMr QMppZBE3L88RzGvTlNsuETSWmuUJVFB+8v7EmQDffdIoQeMPgWy0Dp1+5MHEKGJTqpGQLI2 7BWFkmP8a4mwmQ29n/Wg+pKlZFf+zQZUcZ3Cuot1F3oX1O87r8jgUIMhB3Kln2CNhW7KbmH ZlLRZGCEN2pJLcVyngrxA==
X-UI-Out-Filterresults: notjunk:1;V01:K0:f57ooN+0cGw=:AvNJIaXG42WTwWWCpzzfR3 YtMvroa97moNs/7vNRWGZGEIDoiid/dK0oJkoawzD6qMFbFaf6pyCUrVw8NTAHjLkfTwopLJ8 AnzGND+rBLSZzsgxU6m7qG1IHA6wR/stJ8jB3ze+rkxMf2T5zRDdaw54O6BBxfhFZJd42I9kn FC+fKN/88cX9B9smUOxOa3YqbEZmS8T8COkbLccFYIliBPpLMAfRMt7LcscBaT6UXXrzOCXnk Ba/uhHxmv9L5lBU6Q8CsnnlNIbIjAU/jdJMAqsjPKX/YJVSrDgp11dFXzJj5I9DiKh0yNMuHx 5UV3l7NQPy6pyDw2ldaFGAjMNeOsS8utvWlSrOwxW+bDrGZfij+8GdmmdtvTvhur5LShtCiyp 1cbalb+sdVD/1Acx+2/pq4wBTC+ZULA+nyam1ELUzhpBCZD1GxMjs9C6iV4R2HODb0+FZdAHM S1+tW2lXNot9XkGxSdCAlJrnVJMTHx6QabVveHMBxplXHjkF429Rf8xl5ssfQySfeub5VoGV6 aTIDDjhzOcVO4kd1NtL5O9Oj/j4FUwxZRer4UNVLQKHukGle6xLf9fx09XKUi18molDOZOjNl W1G0w9GNMUyorlWTD0v9XsHPOSRBGTTt6K+/y6z5U89ZN6CpVC//K7LobUuKyrrZYrX7WlBGA VECyJtLCjE4+1cIyIvQmzr9ba3WcdjKTTiy6I7imCBv6+SyP5z6s/QnzQiWbLvTg0Jv3nXD2G AJMMPlUUu/NQkQwFcOqvh28PJMllGT7T7ibmXX1ZlLl83r1O1C5TPEPiumA5UOY7KmCknJUBp hNnbJ1R
Received-SPF: pass client-ip=;;
X-W3C-Hub-Spam-Status: No, score=-8.2
X-W3C-Hub-Spam-Report: AWL=1.418, BAYES_00=-1.9, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_LOW=-0.7, SPF_PASS=-0.001, W3C_AA=-1, W3C_DB=-1, W3C_IRA=-1, W3C_IRR=-3, W3C_WL=-1
X-W3C-Scan-Sig: 1bufwb-0000Z2-2N 0952607a1f61095fa6d76274f5ab845f
Subject: Re: draft-ietf-httpbis-client-hints-02, "2.2.1 Advertising Support for Client Hints"
Archived-At: <>
X-Mailing-List: <> archive/latest/32577
Precedence: list
List-Id: <>
List-Help: <>
List-Post: <>
List-Unsubscribe: <>

On 2016-10-07 20:43, Ilya Grigorik wrote:
> On Fri, Oct 7, 2016 at 4:47 AM, Julian Reschke <
> <>> wrote:
>     "When a client receives Accept-CH, or if it is capable of processing
>     the HTML response and finds an equivalent HTML meta element, it
>     SHOULD append the Client-Hint header fields that match the
>     advertised field-values to the header list of all subsequent
>     requests. For example, based on Accept-CH example above, a user
>     agent could append DPR, Width, Viewport-Width, and Downlink header
>     fields to all subresource requests initiated by the page constructed
>     from the response. Alternatively, a client can treat advertised
>     support as a persistent origin preference and append same header
>     fields on all future requests initiated to and by the resources
>     associated with that origin."
>     The "SHOULD" IMHO is problematic, as it isn't clear from the
>     following text to what URIs it applies? All of the same origin? Only
>     the same resource? Subresources?
> It was left intentionally vague to allow for flexibility as different
> UAs/clients experiment with how and when to send these hints. Some
> additional context
> here:
> Open to suggestions for how to word it better though :-)

Well, we can't have a SHOULD without saying to what it applies to...

Maybe just say that getting Accept-CH for a URI implies that the server 
would like to see the listed client hints on all requests for 
subresources of that URI (with a proper definition of what that is), and 
then leave it at that.

Best regards, Julian