Re: [AVTCORE] Last question about AVP profiles for RTP over QUIC (was: Re: Registering AVP Profiles for RTP over QUIC)

[Roman Shpount <[e-mail]>]

As the person who proposed this, I am for this.

You would probably need to register TCP/QUIC/RTP/AVPF as well, which would
be RTP over QUICK over TCP with RFC4571 framing. See
https://datatracker.ietf.org/doc/html/rfc8841#section-8 for a similar
definition for SCTP. The main reason for this definition is ice-tcp
support. If you do a session update once the ice-tcp candidate is
nominated, the protocol in the m= line should match the protocol for the
only remaining candidate, so TCP/QUIC/RTP/AVPF would be used.

Best,
_____________
Roman Shpount


On Sun, May 22, 2022 at 7:41 PM Spencer Dawkins at IETF <
[e-mail]> wrote:

> So, we had a spirited discussion about a few things in this thread, but
> I'd like to reset back to my original question.
>
> On Wed, May 11, 2022 at 3:46 PM Spencer Dawkins at IETF <
> [e-mail]> wrote:
>
>> Dear AVTCORE,
>>
>> I've had an open PR in
>> https://github.com/SpencerDawkins/sdp-rtp-quic/pull/9 for a while,so I
>> could get a sense of how AVT profiles are supposed to work, and I'd like to
>> push on that now (with a virtual interim meeting coming up next week)..
>>
>> The high-level summary of discussion in
>> https://github.com/SpencerDawkins/sdp-rtp-quic-issues/issues/5 (note
>> that this discussion is in a different repo, because reasons) has been
>> roughly,"what's the difference between QUIC/RTP/AVPF and QUIC/RTP/SAVPF"?
>>
>> The arguments about not registering secure AVP profiles involve
>>
>>    -  the computational overhead of double encryption for all packets,
>>    plus
>>    - the payload overhead of 10 bytes per packet since you have 2 HMACs.
>>
>> The arguments about registering secure AVP profiles seem to revolve
>> around
>>
>>    - Minimizing the impact of added QUIC support in existing
>>    implementations that are using /RTP/SAVPF now.
>>    - QUIC encryption protects payloads between QUIC endpoints, but there
>>    are many multi-endpoint RTP topologies (
>>    https://www.rfc-editor.org/rfc/rfc7667 has about 50 pages of them),
>>    and when a middlebox receives  QUIC/RTP/AVPF, it's not obvious whether the
>>    middlebox should
>>       - forward the RTP payload using  RTP/AVPF (where the outgoing AVPF
>>       matches the incoming AVPF), or
>>       - forward the RTP payload using RTP/SAVPF, where the outgoing SRTP
>>       encryption matches the incoming QUIC
>>
>> It seems to me that there are three choices:
>>
>>    - Use only QUIC/RTP/AVPF, and and require middleboxes receiving
>>    QUIC/RTP/AVPF traffic to always forward that traffic over RTP/SAVPF
>>    - Use only QUIC/RTP/AVPF, and and require senders to signal
>>    middleboxes whether they should forward that traffic over RTP/AVPF or
>>    RTP/SAVPF
>>    - Register both QUIC/RTP/AVPF and QUIC/RTP/SAVPF, and if you have to
>>    do double encryption on the QUIC/RTP paths to get RTP/SAVPF on the other
>>    side of a middlebox, too bad
>>
>> So, my questions are,
>>
>>    - What am I missing here?
>>    - Are any of the choices I'm listing obviously the *BEST* choice?
>>
>> My recommendation for what I was registering now, in sdp-rtp-quic, in my
> way-too-quick talk at the interim meeting last week, was that I was only
> registering QUIC/RTP/AVPF (if we ever figure out what SAVP and SAVPF mean
> when RTP is carried over QUIC, we can register them later).
>
> We didn't have time for Q&A after my talk, but in Jabber, this happened:
>
> 11:50:08 Roman Shpount It should be UDP/QUIC/RTP/AVPF
> 11:50:26 Sergio Garcia Murillo +1 to UDP/QUIC/RTP/AVPF
>
>
> So, we haven't talked about this, and if I'm making commits
> to sdp-rtp-quic, I should ask about it now.
>
> After a quick spin through
> https://www.iana.org/assignments/sdp-parameters/sdp-parameters.xhtml#sdp-parameters-2,
> I think this is reasonable and correct.
>
> So, that would give me one proto registration for UDP/QUIC/RTP/AVPF.
>
> I'll make this change before IETF 114.
>
> Any obvious objections? Please reply here, if so.
>
> Best,
>
> Spencer
>
>
>> Best,
>>
>> Spencer
>>
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