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Re: Variants and Client Hints

From: Mark Nottingham <mnot@mnot.net>
Date: Mon, 4 Jun 2018 14:31:32 +0200
Cc: HTTP Working Group <ietf-http-wg@w3.org>, Ilya Grigorik <igrigorik@google.com>
Message-Id: <2DA552F8-076A-486E-8C52-26DEEA658731@mnot.net>
To: Jeffrey Yasskin <jyasskin@google.com>
Hi Jeffrey,

> On 2 Jun 2018, at 1:21 am, Jeffrey Yasskin <jyasskin@google.com> wrote:
> Hey Mark,
> I'm working on a matching algorithm for bundled exchanges (https://github.com/WICG/webpackage/issues/201), and I realized that a CDN's use of variants will need a similar algorithm. https://httpwg.org/http-extensions/draft-ietf-httpbis-variants.html#cache is fairly clear about how to pick a "best" Variant-Key for the Accept-* headers, but the introduction also mentions Client Hints, where matching is less about string equality.
> For example, if the client sends Viewport-Width: 350, and the server has images that are ideal for Viewport-Widths of 320 or 400, which one gets sent? I can imagine a couple options:
> 	• Only certain kinds of clients are supported efficiently. 🤢
> 	• The available-values are single numbers, and the spec says that a request for 350 matches the next smaller number.

This is kind of what I anticipated, but maybe Ilya has some thoughts?


> 	• The syntax of available-values defines ranges in some way, maybe using a syntax like CSS Media Queries or inventing a new syntax.
> What do folks think this should look like?
> Thanks,
> Jeffrey
> On Wed, May 2, 2018 at 12:14 AM <internet-drafts@ietf.org> wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the Hypertext Transfer Protocol WG of the IETF.
>         Title           : HTTP Representation Variants
>         Author          : Mark Nottingham
>         Filename        : draft-ietf-httpbis-variants-01.txt
>         Pages           : 19
>         Date            : 2018-05-02
> Abstract:
>    This specification introduces an alternative way to communicate a
>    secondary cache key for a HTTP resource, using the HTTP "Variants"
>    and "Variant-Key" response header fields.  Its aim is to make HTTP
>    proactive content negotiation more cache-friendly.
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-httpbis-variants/
> There are also htmlized versions available at:
> https://tools.ietf.org/html/draft-ietf-httpbis-variants-01
> https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-variants-01
> A diff from the previous version is available at:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-httpbis-variants-01
> Please note that it may take a couple of minutes from the time of submission
> until the htmlized version and diff are available at tools.ietf.org.
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/

Mark Nottingham   https://www.mnot.net/
Received on Monday, 4 June 2018 12:32:02 UTC

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