HTTP/3 with strict priorities (PR #2700)

[Dmitri Tikhonov <[e-mail]>]

Hello Ian,

You opened a PR that proposes YAHPM (Yet Another HTTP Prioritization
Mechanism) -- HTTP/3 with Strict Priorities.  Having read through the
diff, I have several questions.  I am using this medium because your
PR does not have an associated bug.

1. What is a _strict priority_?

    There is no definition of strict priority that I could find
    in the diff.  Do strict priorities work outside of the
    dependency tree?  For example, which stream has higher priority
    in the following figure?

                (Root Node)
               /           \
              /             \
    (Placeholder A,     (Placeholder B,
     Weight 50)             Weight 100)
        |                    |
        V                    V
    (Stream P,          (Stream Q,
     Priority 100)       Priority 50)

2. Why require PRIORITY frames delivered on own streams?

    " In order to ensure that prioritization is processed in a
    " consistent order, any subsequent PRIORITY frames for that
    " request MUST be sent on the request stream.

    This requirement is unfortunate, as Lucas Pardue has already
    observed (see PR comments).  Is this done to avoid introducing
    false stream dependencies or is there another reason for this
    requirement?

3. What problem do all-or-nothing resources solve?

    " When [weight is] absent, indicates the resource should be
    " delivered all at once or not at all.

    This is new.  I don't believe I've seen it in other prioritization
    proposals.  Adding this dimension increases complexity.  What
    problem do these all-or-nothing resources solve?

Thank you,

  - Dmitri.