Re: WGLC for HTTP Priorities

Hi Piers,

Thanks for the feedback! Responses in line

On Fri, Oct 15, 2021 at 4:39 PM Piers O'Hanlon <piers.ohanlon@bbc.co.uk>
wrote:

> Hi,
>
> I had a few comments on the draft, but in general it seems fine.
>
> Section 1:
> - It might be useful to mention something to the effect of 'Expressing
> priority is only a suggestion’ as is later detailed in section 10.
>

This has been raised by some others too. We can do a better job of making
that clear up front. Earlier today I already filed a PR to do that, please
take a look https://github.com/httpwg/http-extensions/pull/1752


> Section 4:
> "If intermediaries want to specify prioritization on a multiplexed HTTP
> connection, they SHOULD use a PRIORITY_UPDATE frame and SHOULD NOT
> change the Priority header field.”
> - So an intermediary not using multiplexed HTTP can change the Priority
> header field?
>

 This sounds related to the issue on
https://github.com/httpwg/http-extensions/issues/1715. Please take a look
at this PR which touches the text to let us know if it addresses your
question https://github.com/httpwg/http-extensions/pull/1735


> Section 10:
> - It could be useful to expand the PTO acronym
>

Agreed, I just made https://github.com/httpwg/http-extensions/pull/1753


>
> I was curious if there were any open implementations available of this in
> a server/proxy?
>

The cloudflare quiche library supports setting stream priorities as a local
transport layer API. We expose this up to the H3 layer so that it can set
response priorities. We delegate the parsing of HTTP request headers to
applications. The quiche example HTTP/3 server application [1] can read the
Priority header or a special (custom and non-standard) querystring format
(?u={val}&i={val}). I beleive nghttp3 [2] and h2o have support. Chrome has
some support on the client side, not sure about the status of Google's
server side though.

Cheers,
Lucas

[1] - https://github.com/cloudflare/quiche#command-line-apps
[2] -
https://github.com/ngtcp2/nghttp3/blob/cecc6791c7b1ffe8a1ddbc7c27cbea6c341afb89/README.rst#http3

>
>