Re: [Moq] Agenda topics for side meeting on Tuesday

[Justin Uberti <[e-mail]>]

On Mon, Nov 8, 2021 at 2:17 PM Luke Curley <[e-mail]> wrote:

> Twitch is using WebTransport and QUIC streams for live video distribution
> (Warp). I gave a presentation at Demuxed about it recently (including
> plugging this ML) and would love to start the conversation here too. I've
> got a draft and I'm just working on getting approval to publish it now.
>
> I don't think there's a good way to map RTP to QUIC. It's tempting because
> there's a lot of standards behind RTP, but any approach involves disabling
> huge swaths of functionality on either front. QUIC and RTP have
> incompatible ideas on how to perform fragmentation, congestion control,
> flow control, reliability, feedback, etc. My project briefly used RTP over
> QUIC but we abandoned it when it became too cumbersome.
>
>
Yeah, this is the real meat of the discussion. At Google we built something
called QRTP that basically used QUIC as a secure RTP packet transport, and
I think this sort of thing would have a lot of value in terms of making RTP
apps easier to deploy. But you're not getting any new functionality in the
protocol, and you're still mostly in RTP-land (which can be a positive or a
negative depending on where you are coming from).

IOW, we may need to choose between:
1) Adapting RTP to QUIC so that RTP can be sent to 'normal' QUIC servers,
making it easier to deploy RTP-based applications
2) Building RTP-like things on top of QUIC (e.g., RUSH) so that you can get
basic realtime functionality without having to use RTP

My own sentiment is that both may have value, especially if 2) is focused
on a different use case than traditional RTP. We tried a couple attempts at
2) and eventually concluded we were simply rebuilding RTP with a new name,
which led to the final QRTP direction.


> There are some compelling ways to map live media to QUIC and fully
> utilizing QUIC's functionality. For example, sending each frame as its own
> stream, which is how Facebook's RUSH works. I think we have enough
> non-video people on this list that we should discuss how video works and
> what we're trying to accomplish, instead of focusing on how we can port RTP.
>
>
>
> On Mon, Nov 8, 2021, 1:05 PM Spencer Dawkins at IETF <
> [e-mail]> wrote:
>
>> So, full disclosure -
>>
>> On Mon, Nov 8, 2021 at 1:23 PM Suhas Nandakumar <[e-mail]>
>> wrote:
>>
>>>
>>>
>>> On Mon, Nov 8, 2021 at 10:11 AM Spencer Dawkins at IETF <
>>> [e-mail]> wrote:
>>>
>>>> Hi, Ian,
>>>>
>>>> On Mon, Nov 8, 2021 at 11:38 AM Ian Swett <[e-mail]> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> I've looked at the following uses cases fairly closely for QUIC in the
>>>>> past.
>>>>>
>>>>>    - Live Video Ingestion - Existing protocols don't fully meet our
>>>>>    needs (ie: performance vs reliability, standardization, etc), and this is
>>>>>    becoming a real problem.
>>>>>    - Live Video Delivery - Currently we're pushing the edge of what
>>>>>    HTTP can do efficiently, including some non-standard extensions.  This is
>>>>>    also not optimized for QUIC or HTTP/3, which could improve performance.
>>>>>    - WebRTC over QUIC, ie: RTP over QUIC + Datachannels over QUIC -
>>>>>    There could be a number of benefits of WebRTC over QUIC.  A number of
>>>>>    people who were interested in this are now focused on WebTransport, but
>>>>>    there's still the matter of what you send over WebTransport, so I think
>>>>>    there's some work to be done in addition to finishing WebTransport.
>>>>>
>>>>>
>>>> Thanks for this - it's very helpful, and it will definitely be on the
>>>> list for tomorrow's meeting.
>>>>
>>>>
>>>>> As with QUIC, I see we have a number of different working groups
>>>>> different parts or applications could land in.  I worry that could cause
>>>>> fragmentation if each sub-domain solves their problem without collaborating
>>>>> closely with others.  I'm not sure if a new WG(ie: QUIC-style) is necessary
>>>>> here, but I do think caution should be taken to ensure we don't reinvent
>>>>> the wheel 3+ different ways.
>>>>>
>>>>
>>>> Yes, exactly. It's sad when three people working in isolation solve a
>>>> similar problem in three different ways that have to be implemented three
>>>> times, but it's doubly sad when they all show up in QUIC either asking for
>>>> advice on three similar solutions, or even proposing three similar but
>>>> incompatible extensions! 😈
>>>>
>>>
>>> One common theme that might needs addressing is : what sort of API knobs
>>> can be exposed by transport (QUIC) to help apps know about losses/recovery
>>> and influence the choice of congestion control . If some aspects of this
>>> can be done in a standard way, it would definitely help
>>> streaming/interactive use-cases.
>>>
>>
>> Yes, exactly (it's listed as a consideration in
>> https://www.rfc-editor.org/rfc/rfc9049.html#name-support-in-endpoint-protoco
>> .
>>
>> Having said that, I fully expect that we're going to end up with at least
>> some pain points that are outside the typical IETF working group's charter.
>> The ones I'm especially aware of, are
>>
>>    - The kind of tight integration between codec operation and awareness
>>    of path characteristics we've been talking about at length, in the thread
>>    Christian started at
>>    https://mailarchive.ietf.org/arch/msg/moq/jk9eDELqs_gyg1kSGAmhhzJ-_ts/.
>>    What I think is normal, is that we tend to have ICCRG looking at congestion
>>    control mechanisms (quoting today's ICCRG session) "until they're ready to
>>    come to the IETF. So I think this is worth pursuing, but chartering it in
>>    the IETF will probably be more complicated than adopting a draft i(say)
>>    encapsulating RTP in QUIC.
>>    - I'll say more about this in a reply to another note in this
>>    (increasingly awesome) thread, but there are things we've been talking
>>    about that are likely required in order to build a product, but aren't
>>    candidates for standardization, for various reasons.
>>
>> But I still think they're worth talking about during our meeting
>> tomorrow, because if we can agree on a strategy for them, we can take them
>> off the "media over QUIC" table without dropping them on the floor.
>>
>> Best,
>>
>> Spencer, who isn't even the MOQ list admin, and so is definitely not
>> running anything for the rest of the MOQ fans!
>>
>>
>>> Best,
>>>>
>>>> Spencer, who should be apologizing to Lucas for even thinking such a
>>>> thing!
>>>>
>>>>
>>>>>
>>>>> Thanks, Ian
>>>>>
>>>>> On Mon, Nov 8, 2021 at 7:13 AM Spencer Dawkins at IETF <
>>>>> [e-mail]> wrote:
>>>>>
>>>>>> So, three things I should say before the Tuesday side meeting.
>>>>>>
>>>>>> First - this side meeting will be under Notewell, because it's
>>>>>> focused on input to the IETF.
>>>>>>
>>>>>> Second - I'm planning to record the session, just so I can verify
>>>>>> what we said, so that I can produce decent minutes. If anyone objects,
>>>>>> please also volunteer to take excellent notes!
>>>>>>
>>>>>> Third - James and I are most familiar with the RTP over QUIC
>>>>>> proposals, but we recognize that there will be commonalities between
>>>>>> various proposals, so  we're perfectly happy to talk about other use cases
>>>>>> and requirement sets. So, letting us know what you're thinking about, as
>>>>>> requested below, will be super useful.
>>>>>>
>>>>>> Please Do The Right Thing.
>>>>>>
>>>>>> Best,
>>>>>>
>>>>>> Spencer
>>>>>>
>>>>>> On Sun, Nov 7, 2021 at 12:36 PM Spencer Dawkins at IETF <
>>>>>> [e-mail]> wrote:
>>>>>>
>>>>>>> Dear MOQ fans,
>>>>>>>
>>>>>>> It's time to put together an agenda for the Tuesday meeting. I'd
>>>>>>> like for this meeting to be a working session, not a forum for
>>>>>>> presentations, so please keep that in mind.
>>>>>>>
>>>>>>> As a high-order bit, I think we've spent a lot of time thinking
>>>>>>> about use cases here, and I'd like to push down another level, and make
>>>>>>> sure we understand what the work for the IETF (and possibly for the IRTF)
>>>>>>> is.
>>>>>>>
>>>>>>> I know what the protocol work is for my use cases:
>>>>>>>
>>>>>>>    - Mapping RTP onto QUIC (many options exist, so picking one or
>>>>>>>    more would be helpful) This is squarely in scope for AVTCORE
>>>>>>>    - Mapping RTCP onto QUIC (which may be the same approach as used
>>>>>>>    for RTP, or may include things like using QUIC facilities instead of RTCP
>>>>>>>    facilities, where those QUIC facilities exist).. Again, this is squarely in
>>>>>>>    scope for AVTCORE
>>>>>>>    - SDP description for RTP/RTCP over QUIC. This is squarely in
>>>>>>>    scope for MMUSIC, as soon as we figure out the details in AVTCORE.
>>>>>>>
>>>>>>> What is the IETF/IRTF work for your use cases?
>>>>>>>
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