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Re: HTTP/3 Prioritization Proposal

From: Patrick McManus <mcmanus@ducksong.com>
Date: Tue, 29 Jan 2019 15:09:22 -0500
Message-ID: <CAOdDvNoKhWJmzf83NUrzzTjM8Rtaa9GHYjdNzEG10m29EMhWKQ@mail.gmail.com>
To: Patrick Meenan <patmeenan@gmail.com>
Cc: Lucas Pardue <lucaspardue.24.7@gmail.com>, Amos Jeffries <squid3@treenet.co.nz>, HTTP Working Group <ietf-http-wg@w3.org>
On Tue, Jan 29, 2019 at 2:56 PM Patrick Meenan <patmeenan@gmail.com> wrote:

> As far as I can tell, the placeholder streams serve to handle the Firefox
> use case of using idle streams for groupings,
>

 yes.. and you can probably solve for that in a simpler way by having an
explicit set of groups with simple ways to share between them.

But what I think you really need to do with your proposal is address what
you're giving up by removing the tree structure because it was an explicit
choice to include it.

That structure exists because Google convinced the WG that it was important
to be able to combine an arbitrarily large number of sets of streams
together fairly. (and the solution allowed generalized sharing, not just
fairness).

In short, if you've got a set of streams from tabs A, B, and C you cannot
really expect them to be coordinated in an absolute priority sense - but if
they were all rooted at the same level in a tree they could share fairly
and then the streams within the tab could locally coordinate their priority.

This is a much more important property in an aggregator like a CDN who
might be bringing different front end connections into a single backend
connection.. the priority expressed by the client should exist in some ways
e2e (css before imgs!), but in other ways hop to hop (you don't want every
css to stall every browser's images).. the tree allows that.
Received on Tuesday, 29 January 2019 20:09:58 UTC

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