[Dart] RTP and non-RTP traffic on same UDP 5-tuple

["Black, David" <[e-mail]>]

In another message, Ruediger Geib asked (>), and I responded:

--------------------

> Is the following correct:
> 
> UDP_5-tuple-+--transport protocol 1-----
>             |
>             +--RTP session 1-----
>             |
>             +--RTP session 2-----+---RTP_stream_2.1
>                                  |
>                                  +---RTP_stream_2.2
>                                  |...

Yes, that matches my understanding, although the author team would like to
see discussion of whether it's a good idea to mix RTP and non-RTP protocols
on the same 5-tuple - I'll copy your useful diagram into a separate message
to start that discussion.

--------------------

This is that message, and I want to thank Ruediger for drawing that useful
diagram.

The author team for draft-york would like input on whether the draft should
discuss mixing of RTP and non-RTP traffic on the same UDP 5-tuple, vs. using
separate 5-tuples (probably separate UDP ports) for RTP and non-RTP traffic.

RTCWEB clearly intends to mix SCTP (via DTLS) and RTP traffic on the same
5-tuple see the last paragraph of Section 3.5 of draft-ietf-rtcweb-transports-04:

   RTCWEB implementations MUST support multiplexing of DTLS and RTP over
   the same port pair, as described in the DTLS_SRTP specification
   [RFC5764], section 5.1.2.  All application layer protocol payloads
   over this DTLS connection are SCTP packets.

OTOH, concerns have been expressed about whether the not-exactly-elegant
demux processing specified in the reference (RFC 5764, Section 5.1.2) ought
to be recommended as a good way of doing this multiplexing.

Please comment, including whether mixing SCTP and RTP on the same UDP
5-tuple is a good idea (some rationale for doing this sort of multiplexing
onto a single 5-tuple can be found in Section 3 of draft-york-dart-dscp-rtp-00).

Thanks,
--David
----------------------------------------------------
David L. Black, Distinguished Engineer
EMC Corporation, 176 South St., Hopkinton, MA  01748
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