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

[Spencer Dawkins at IETF <[e-mail]>]

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
>