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

[Dan Wing <[e-mail]>]

On Jun 11, 2014, at 5:58 PM, Black, David <[e-mail]> wrote:

>> 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.

Is the problem lack of color awareness in the AF remarker, or that AF remarkers assume all packets in the 5-tuple have the same color?

-d


> 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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