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

[Dan Wing <[e-mail]>]

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]
>> ----------------------------------------------------
>> 
>> 
>> _______________________________________________
>> Dart mailing list
>> [e-mail]
>> https://www.ietf.org/mailman/listinfo/dart
>> 
> 
> _______________________________________________
> Dart mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/dart