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

"Black, David" <david.black@emc.com> Tue, 10 June 2014 19:59 UTC

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From: "Black, David" <david.black@emc.com>
To: "dart@ietf.org" <dart@ietf.org>
Date: Tue, 10 Jun 2014 15:59:22 -0400
Thread-Topic: RTP and non-RTP traffic on same UDP 5-tuple
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Cc: "Black, David" <david.black@emc.com>
Subject: [Dart] RTP and non-RTP traffic on same UDP 5-tuple
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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

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).

David L. Black, Distinguished Engineer
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953             FAX: +1 (508) 293-7786
david.black@emc.com        Mobile: +1 (978) 394-7754