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

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

> What do you mean by 'all the packets would be classified the same'?  If you
> mean all the packets in a 5-tuple would get the same differentiated treatment,
> that is not desirable, because there are lots of folks wanting to send video
> i-frames or packets with FEC or other stuff with lower drop precedence than
> other packets.

That would most likely be within an AF class; the entire set of packets marked
w/different drop precedences within an AF class should be classified the same.

Beyond that, one can hope that any AF remarker (e.g., for traffic shaping) is
running in Color-Aware mode and hence tries to preserve source drop precedence
distinctions, but this cannot be relied upon.

Thanks,
--David

> -----Original Message-----
> From: Dan Wing [mailto:[e-mail]]
> Sent: Wednesday, June 11, 2014 8:32 PM
> To: Brian E Carpenter
> Cc: Black, David; [e-mail]
> Subject: Re: [Dart] RTP and non-RTP traffic on same UDP 5-tuple
> 
> 
> On Jun 11, 2014, at 1:42 PM, Brian E Carpenter <[e-mail]>
> wrote:
> 
> > On 11/06/2014 07:59, Black, David wrote:
> >> 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.
> >
> > One observation is that we should be thinking about a 6-tuple these
> > days (see RFC 6437). I don't think it makes much difference to the argument.
> >
> > Another observation is when load balancing is in play, things get a bit
> > more complicated, but to a first approximation using the same 5-tuple
> > or 6-tuple will usually ensure that all the packets reach the same
> > load-balanced destination, which is probably a good thing.
> >
> > Third, reverting to the diffserv discussion, the same 5-tuple
> > should ensure that all the packets would be classified the same
> > (if they cross a diffserv domain boundary and get reclassified).
> 
> What do you mean by 'all the packets would be classified the same'?  If you
> mean all the packets in a 5-tuple would get the same differentiated treatment,
> that is not desirable, because there are lots of folks wanting to send video
> i-frames or packets with FEC or other stuff with lower drop precedence than
> other packets.
> 
> -d
> 
> 
> >
> >    Brian
> >
> >>
> >> 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
> >> [phone]             FAX: [phone]
> >> [e-mail]        Mobile: [phone]
> >> ----------------------------------------------------
> >>
> >>
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