Re: [Dart] I-D Action: draft-york-dart-dscp-rtp-00.txt

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

Hi Ruediger,

> thanks, your team created a well written draft.

Great - thanks for taking a look.
 
> If a MediaStream is carried in a RTP session, the text may also explicitely
> say that (it says MediaStreamTrack == media flow, which is carried in an
> individual RTP packet stream)

As I read Section 11 of draft-ietf-rtcweb-rtp-usage-15, for RTCWEB,
that would happen only when the MediaStream contains exactly one
MediaStreamTrack.  The use of these terms in bullet item 1 in section 2
is intended to be specific to RTCWEB, but we could add text elsewhere to
point out that non-RTCWEB usage of MediaStreams could use an RTP packet
stream for each Media Stream, independent of how many MediaStreamTracks
each MediaStream contains.

Could you suggest a reference that could be cited for usage of an RTP
packet stream for each MediaStream independent of how many
MediaStreamTracks each MediaStream contains?

> 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.

> The question coming to my mind is, whether your team can add a statement how
> many AF classes are useful to carry different RTP sessions within one UDP
> flow.

See draft-ietf-tsvwg-rtcweb-qos-00, which proposes to make all four AF
classes available, so we can expect that someone will try to use all of
them (and everything else in that draft).

OTOH, we did put this warning text in at the end of Section 2.4 of draft-york:

   Backbone and other carrier networks may employ a small number of
   DSCPs (e.g., less than half a dozen) in order to manage a small
   number of traffic aggregates; hosts that use a larger number of DSCPs
   may find that much of the intended differentiation is removed by such
   networks.

What additional text would you suggest that we add?

Thanks,
--David

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]]
> Sent: Tuesday, June 10, 2014 4:18 AM
> To: Black, David
> Cc: [e-mail]
> Subject: AW: I-D Action: draft-york-dart-dscp-rtp-00.txt
> 
> Hi David,
> 
> thanks, your team created a well written draft.
> 
> If a MediaStream is carried in a RTP session, the text may also explicitely say that
> (it says MediaStreamTrack == media flow, which is carried in an individual RTP
> packet stream)
> 
> Is the following correct:
> 
> UDP_5-tuple-+--transport protocol 1-----
>             |
>             +--RTP session 1-----
>             |
>             +--RTP session 2-----+---RTP_stream_2.1
>                                  |
>                                  +---RTP_stream_2.2
>                                  |...
> 
> This is impressive on first sight for a non-application expert. If the number of RTP (and other
> transport) streams is high, I doubt that DiffServ is able to support more than rough
> differentiation. DiffServ is designed to aggregate traffic of similar requirements. Fine grained
> differentiation should be part of the application.
> 
> The question coming to my mind is, whether your team can add a statement how many AF classes are
> useful to carry different RTP sessions within one UDP flow. I'd be happier to live without a hen
> and egg problem (meaning app developers to wait for the transport guys to provide a set of
> defined classes and transport guys waiting for app developers to demand a number of defined
> classes).
> 
> Regards,
> 
> Ruediger
> 
> 
> -----Ursprüngliche Nachricht-----
> Von: Dart [mailto:[e-mail]] Im Auftrag von Black, David
> Gesendet: Samstag, 7. Juni 2014 03:05
> An: [e-mail]
> Betreff: [Dart] FW: I-D Action: draft-york-dart-dscp-rtp-00.txt
> 
> On behalf of the author team, here's an initial -00 draft for consideration by
> the dart WG.  Please keep in mind that this is a -00 draft, so it really is a
> "draft".
> 
> I should be embarrassed that it appeared to take a public nudge from a past
> IETF Chair (Harald) to get this draft to appear, (Aside: if you'd like that
> ability, send your name to the NomCom this year - they're always looking for
> interested candidates for all positions), but the fact of the matter is that
> more than one of us had the experience of life being what happens while one is
> busy making other plans.
> 
> Comments and feedback are welcome and encouraged.
> 
> Thanks,
> --David
> ----------------------------------------------------
> David L. Black, Distinguished Engineer
> EMC Corporation, 176 South St., Hopkinton, MA  01748
> [phone]             FAX: [phone]
> [e-mail]        Mobile: [phone]
> ----------------------------------------------------
> 
> -----Original Message-----
> From: I-D-Announce [mailto:[e-mail]] On Behalf Of
> [e-mail]
> Sent: Friday, June 06, 2014 8:49 PM
> To: [e-mail]
> Subject: I-D Action: draft-york-dart-dscp-rtp-00.txt
> 
> 
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> 
> 
>         Title           : Differentiated Services (DiffServ) and Real-time
> Communication
>         Authors         : Dan York
>                           David Black
>                           Cullen Jennings
>                           Paul Jones
> 	Filename        : draft-york-dart-dscp-rtp-00.txt
> 	Pages           : 13
> 	Date            : 2014-06-06
> 
> Abstract:
>    This document describes the interaction between Differentiated
>    Services (DiffServ) network quality of service (QoS) functionality
>    and real-time network communication, including communication based on
>    the Real-time Transport Protocol (RTP).  DiffServ is based on network
>    nodes applying different forwarding treatments to packets whose IP
>    headers are marked with different DiffServ Code Points (DSCPs).  As a
>    result, use of different DSCPs within a single traffic flow may cause
>    transport protocol interactions (e.g., due to reordering).  In
>    addition, DSCP markings may be changed or removed between the traffic
>    source and destination.  This document covers the implications of
>    these DiffServ aspects for real-time network communication, including
>    RTCWEB.
> 
> 
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-york-dart-dscp-rtp/
> 
> There's also a htmlized version available at:
> http://tools.ietf.org/html/draft-york-dart-dscp-rtp-00
> 
> 
> Please note that it may take a couple of minutes from the time of submission
> until the htmlized version and diff are available at tools.ietf.org.
> 
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
> 
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