Fwd: New Version Notification for draft-nottingham-variants-01.txt

FYI, an update of Variants.

This one removes the requirement for conneg mechanisms to identify their own response header ("Content-*"), in favour of a central one -- Variant-Key.

Doing so avoids the big problem with Variants-00, where the semantics of a header like Content-Encoding could clash with variants' needs.

So, you now have a response that looks something like:

Vary: Accept-Encoding, Accept-Language
Variants: Accept-Encoding;gzip;br, Accept-Language;fr;en;jp
Variant-Key: gzip,en

... which roughly translates to "There are gzip, brotli and identity representations of this resource, in French, English and Japanese; THIS representation is the gzip'd English one."

Variant-Key is required to have the same number of members in the same order as Variants. Some space could be saved by using the same trick with Variants and Vary, but I don't think the overhead is that bad, and if support for this gets good, it'd be very tempting to send Vary:* sometimes.

A nice side benefit of this approach is that the definition of specific conneg mechanisms is much simpler, and it might be possible to put in some cool optimisations/tricks (TBD).

Comments welcome. Pretty version at:
  https://mnot.github.io/I-D/variants/



> Begin forwarded message:
> 
> From: internet-drafts@ietf.org
> Subject: New Version Notification for draft-nottingham-variants-01.txt
> Date: 30 October 2017 at 3:34:59 pm AEDT
> To: "Mark Nottingham" <mnot@mnot.net>
> 
> 
> A new version of I-D, draft-nottingham-variants-01.txt
> has been successfully submitted by Mark Nottingham and posted to the
> IETF repository.
> 
> Name:		draft-nottingham-variants
> Revision:	01
> Title:		HTTP Representation Variants
> Document date:	2017-10-30
> Group:		Individual Submission
> Pages:		15
> URL:            https://www.ietf.org/internet-drafts/draft-nottingham-variants-01.txt
> Status:         https://datatracker.ietf.org/doc/draft-nottingham-variants/
> Htmlized:       https://tools.ietf.org/html/draft-nottingham-variants-01
> Htmlized:       https://datatracker.ietf.org/doc/html/draft-nottingham-variants-01
> Diff:           https://www.ietf.org/rfcdiff?url2=draft-nottingham-variants-01
> 
> Abstract:
>   This specification introduces the HTTP "Variants" response header
>   field to communicate what representations are available for a given
>   resource, and the companion "Variant-Key" response header field to
>   indicate which representation was selected.  It is an augmentation of
>   the "Vary" mechanism in HTTP caching.
> 
> 
> 
> 
> 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.
> 
> The IETF Secretariat
> 

--
Mark Nottingham   https://www.mnot.net/