draft-ietf-httpbis-client-hints-04; 2.2.2. The Accept-CH-Lifetime header field

[Kari Hurtta <[e-mail]>]

2.2.2.  The Accept-CH-Lifetime header field
https://tools.ietf.org/html/draft-ietf-httpbis-client-hints-04#section-2.2.2

|   Servers can ask the client to remember an origin-wide Accept-CH
|   preference for a specified period of time to enable delivery of
|   Client Hints on all subsequent requests to the origin, and on
|   subresource requests initiated as a result of processing a response
|   from the origin.
|
|     Accept-CH-Lifetime = #delta-seconds
|
|   The field-value indicates that the Accept-CH preference should be
|   considered stale after its age is greater than the specified number
|   of seconds.
|
|     Accept-CH: DPR, Viewport-Width
|     Accept-CH-Lifetime: 86400


It is not very clear why two header fields is needed to pass that information.

2.2.1.  Advertising Support via Accept-CH header field
https://tools.ietf.org/html/draft-ietf-httpbis-client-hints-04#section-2.2.1

|   Servers can advertise support for Client Hints using the Accept-CH
|   header field or an equivalent HTML meta element with http-equiv
|   attribute ([W3C.REC-html5-20141028]).

Is it assumed that "Accept-CH" is given in http-equiv
attribute, but "Accept-CH-Lifetime" on http response ?

Or is that needed so that "Accept-CH" can be given
on several times?


What happens if there is several "Accept-CH-Lifetime"
on response?

/ Kari Hurtta