Re: [Masque] Prioritizing QUIC DATAGRAMs (was: Re: Prioritizing HTTP DATAGRAMs)

[Martin Duke <[e-mail]>]

This is an argument against punting, I think. If there are additional
semantics required to specify priorities on a sub-stream basis, it will be
somewhat more painful to have this be an extension than something native.

Which is not to say we shouldn't punt.

On Wed, Jun 23, 2021, 13:25 Lucas Pardue <[e-mail]> wrote:

> Hey Martin,
>
> On Wed, Jun 23, 2021 at 9:13 PM Martin Duke <[e-mail]>
> wrote:
>
>> Lucas,
>>
>> Assuming that we have the necessary language about QUIC APIs, as I've
>> just proposed, to enable something in future, then I personally have no use
>> cases or strong objection to punting. It is somewhat annoying to have a
>> draft for priorities, datagrams, and then priorities-with-datagrams, but if
>> writing the last bit will be a struggle (which I have no informed opinion
>> on) deferring it is probably the right decision.
>>
>> Now descending into the weeds:
>>
>> > It's easy to say this. The difficulty comes, as an implementer, with
>> knowing what to actually do with the information. Concrete example, if a
>> client signals "incremental false" does a server send all streams as FIFO
>> and then all DATAGRAMS as FIFO, or does it look at DATAGRAM flow creation
>> order
>>
>> No, I think the DATAGRAMs correspond to a stream and they go with the
>> STREAM frames in with priority. Whether one delivers STREAM or DATAGRAM
>> first within a particular stream maybe doesn't need tight specification; if
>> we do, I'd say STREAM (if for no other reason than to deliver the headers)
>> and then DATAGRAM, unless STREAM is being flow-controlled. As datagram
>> flows don't have a 1-to-1 mapping with requests and responses, I think
>> streams are the correct abstraction for datagram priority, not flows. If
>> there are multiple Flow-IDs associated with the same stream, they all get
>> grouped together for priority purposes.
>>
>
> I think this model breaks down entirely for something like WebTransport
> where the session is created with a single stream and then there'll
> potentially be multiple datagram flows in either direction all vying for a
> slice of the pie.
>
> Cheers,
> Lucas
>