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

[Julian Reschke <[e-mail]>]

On 2016-10-07 20:43, Ilya Grigorik wrote:
>
> On Fri, Oct 7, 2016 at 4:47 AM, Julian Reschke <[e-mail]
> <mailto:[e-mail]>> 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: https://greenbytes.de/tech/webdav/draft-ietf-httpbis-client-hints-02.html#security-considerations
>
> 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