Re: WGLC for Datagram Extension

Spencer Dawkins at IETF <spencerdawkins.ietf@gmail.com> Fri, 24 September 2021 01:08 UTC

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From: Spencer Dawkins at IETF <spencerdawkins.ietf@gmail.com>
Date: Thu, 23 Sep 2021 20:07:50 -0500
Message-ID: <CAKKJt-dG9inej0GU0ZWHJBORgzz35870Dhbm0EWQjjaFY7ig0g@mail.gmail.com>
Subject: Re: WGLC for Datagram Extension
To: David Schinazi <dschinazi.ietf@gmail.com>
Cc: Lucas Pardue <lucaspardue.24.7@gmail.com>, QUIC WG <quic@ietf.org>, QUIC WG Chairs <quic-chairs@ietf.org>
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Hi, David,

On Thu, Sep 23, 2021 at 6:53 PM David Schinazi <dschinazi.ietf@gmail.com>
wrote:

> Hi Spencer,
>
> Yes, your interpretation is correct. The language about whether it's
> interchangeably one frame type or two frame types mirrors RFC 9000's
> definition of the STREAM frame which is also one or eight frames depending
> on how you look at it <
> https://datatracker.ietf.org/doc/html/rfc9000#section-19.8>gt;.
>

Thank you for the background here (I was watching the base QUIC drafts, but
spent a lot of time looking at diffs, rather than re-reading carefully, so
your pointer was super helpful).

I did see a couple of places where the STREAM frame type was using plurals
(for example, https://www.rfc-editor.org/rfc/rfc9000.html#name-stream-frames,
plural,  versus
https://www.ietf.org/archive/id/draft-ietf-quic-datagram-04.html#name-datagram-frame-type,
singular), so I included that in the PR. I swear, if I wasn't looking for
the second datagram frame type in the second called "datagram frame type",
I wouldn't have noticed anything 🙂)

And it really was a couple of small changes. Thanks for considering my
comments.

Best,

SPencer


> Regarding your editorial comments, could I ask you to send them our way as
> a PR to <https://github.com/quicwg/datagram> ?
>
> Thanks,
> David
>
> On Thu, Sep 23, 2021 at 4:33 PM Spencer Dawkins at IETF <
> spencerdawkins.ietf@gmail.com> wrote:
>
>> Hi, Lucas,
>>
>> I'm top-posting to say that I'm not talking about multiplexing datagrames
>> now (except to thank you and Christian for your replies), but I'm still
>> looking at the datagram draft, and noticed something odd. Could you put
>> your working group chair hat back on for a moment?
>>
>> From the Introduction:
>>
>> *This document defines two new DATAGRAM QUIC frame types, which carry
>> application data without requiring retransmissions.*
>>
>>
>> And most of the document about "datagram frame types" (plural), but
>> pretty much all of
>> https://www.ietf.org/archive/id/draft-ietf-quic-datagram-04.html#name-datagram-frame-type
>> talks about "the datagram frame type" (singular) - even the section header
>> uses the singular phrasing, along with the caption to Figure 1.
>>
>> I understand what the document is saying, to be
>>
>>    - there are two datagram frame types, 0x30 and 0x31
>>    - the only difference between these two datagram frame types is that
>>    datagram frames with frame type 0x30 do not include a length field, while
>>    datagram frames with frame type 0x31 do contain a contain a length field,
>>    and
>>    - otherwise, whatever this document says about "datagrams" is true
>>    for both datagram frame types.
>>
>> Is that about right?
>>
>> I can dig that out from the document, but if that was clearer in Section
>> 4 - "Datagram Frame Types", and a couple of clarifying sentences, that
>> might be a bit easier for the reader (and, of course, for the various
>> review teams that will be looking at this document for the first time
>> during IETF Last Call).
>>
>> As long as I'm still typing, I might mention one other thing - I searched
>> for the string "reliabl" in the draft, and there are 24 occurrences, which
>> is fine, although perhaps repetitive, until you get down to
>> https://www.ietf.org/archive/id/draft-ietf-quic-datagram-04.html#name-behavior-and-usage,
>> which says
>>
>> When an application sends an unreliable datagram over a QUIC connection,
>> QUIC will generate a new DATAGRAM frame and send it in the first available
>> packet. This frame SHOULD be sent as soon as possible, and MAY be coalesced
>> with other frames.
>>
>>
>> Could "unreliable" be dropped from the first sentence? It would belong
>> there if reliable datagrams were an option, but (after 20 occurrences
>> explaining that all datagrams are unreliable), maybe this is just inviting
>> confusion.
>>
>> Thanks for considering my comments, of course. Do The Right Thing!
>>
>> Best,
>>
>> Spencer
>>
>> On Thu, Sep 23, 2021 at 1:12 PM Lucas Pardue <lucaspardue.24.7@gmail.com>
>> wrote:
>>
>>> Hi Spencer,
>>>
>>> On Thu, Sep 23, 2021 at 6:52 PM Spencer Dawkins at IETF <
>>> spencerdawkins.ietf@gmail.com> wrote:
>>>
>>>> Hi, Lucas and Matt,
>>>>
>>>> On Thu, Sep 16, 2021 at 3:35 PM Lucas Pardue <
>>>> lucaspardue.24.7@gmail.com> wrote:
>>>>
>>>>> Hello QUIC WG,
>>>>>
>>>>> This email starts the Working Group Last Call for "An Unreliable
>>>>> Datagram Extension to QUIC", located at:
>>>>>   https://www.ietf.org/archive/id/draft-ietf-quic-datagram-04.html
>>>>>
>>>>> Please take time to review it carefully and raise any remaining issues
>>>>> you see either on the GitHub repo issues list[1] or on this mailing list.
>>>>>
>>>>
>>>> I've re-read the discussion in
>>>> https://github.com/quicwg/datagram/issues/6, and now better understand
>>>> the points of view that resulted in the lack of datagram multiplexing in
>>>> this specification (I was following that discussion when it was happening,
>>>> but hindsight during re-reading helped a lot!)
>>>>
>>>> I especially appreciate the addition of the text in
>>>> https://www.ietf.org/archive/id/draft-ietf-quic-datagram-04.html#name-multiplexing-datagrams
>>>> .
>>>>
>>>> I accept the wisdom of getting more experience with various people
>>>> using application-defined multiplexing in various ways before adding any
>>>> flavor of multiplexing at the transport layer, and agree that holding this
>>>> specification up while that experience is gathered, would not be The Right
>>>> Thing To Do.
>>>>
>>>> I'm aware of at least two "RTP over QUIC" proposals that assume that
>>>> they'll need to multiplex datagrams, so I won't be surprised if we return
>>>> to this question in the future, but for now, the chairs are Doing The Right
>>>> Thing, and I support requesting publication of -04 (modulo any changes that
>>>> pop up in WGLC, of course).
>>>>
>>>
>>> Thanks for your comments.
>>>
>>> Chair hat off, speaking as an individual. To add to the examples, the
>>> MASQUE working group is working on a draft to define HTTP's use of QUIC
>>> DATAGRAM frames and it includes multiplexing [1]. The working group's 00
>>> draft started with a single variable-length integer multiplexing identifier
>>> called the Flow ID. After some fruitful WG implementation and discussion,
>>> in draft 01 it switched to an identifier tuple (Quarter Stream ID, Contenxt
>>> ID). I'd say that we're still figuring out exactly how the things the
>>> __use__ datagrams, want to use datagrams. I think it's too early to
>>> understand the right common transport solution at this time, and that
>>> leaving it undefined does not prevent people from using datagram frames for
>>> their own precise needs and purpose.
>>>
>>> Cheers,
>>> Lucas
>>>
>>> [1] - https://datatracker.ietf.org/doc/draft-ietf-masque-h3-datagram
>>>
>>