Re: [Dart] [AVTCORE] WGLC: draft-ietf-dart-dscp-rtp-02

"Black, David" <david.black@emc.com> Fri, 22 August 2014 01:06 UTC

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From: "Black, David" <david.black@emc.com>
To: Ben Campbell <ben@nostrum.com>, Colin Perkins <csp@csperkins.org>
Date: Thu, 21 Aug 2014 21:06:14 -0400
Thread-Topic: [Dart] [AVTCORE] WGLC: draft-ietf-dart-dscp-rtp-02
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Subject: Re: [Dart] [AVTCORE] WGLC: draft-ietf-dart-dscp-rtp-02
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Colin - many thanks for the review.  I'll pick up your proposed changes, perhaps
with minor edits.

Ben,

> >>   3.  The RTP and RTCP traffic can be multiplexed with other protocols
> >>       via UDP encapsulation over a common pair of UDP ports as described
> >>       in [RFC5764] as updated by
> >>       [I-D.petithuguenin-avtcore-rfc5764-mux-fixes]; and
> 
> Can we clarify what "other protocols" are expected? Are we just talking about
> WebRTC data-channels over SCTP/DTLS, or other things? If the latter, are we
> talking things we expect to do today, or in immediate futures, or extensions
> that might happen someday?

WebRTC will only multiplex its data channels, and this numbered list is about
WebRTC, so this text should focus on those data channels - I'll revise the draft
accordingly.

Other text elsewhere in the draft is broader (e.g., SCTP/UDP without DTLS, which
is of interest, even though WebRTC always uses DTLS).

Thanks,
--David

> -----Original Message-----
> From: Dart [mailto:dart-bounces@ietf.org] On Behalf Of Ben Campbell
> Sent: Monday, August 18, 2014 4:48 PM
> To: Colin Perkins
> Cc: draft-ietf-dart-dscp-rtp.all@tools.ietf.org; dart@ietf.org; avt@ietf.org
> WG
> Subject: Re: [Dart] [AVTCORE] WGLC: draft-ietf-dart-dscp-rtp-02
> 
> Hi,
> 
> I concur with all of Colin's comments, save one question below:
> 
> On Aug 18, 2014, at 10:17 AM, Colin Perkins <csp@csperkins.org> wrote:
> 
> > Hi,
> >
> > [I'm not on the DART list, so please cc me in replies]
> >
> > This draft looks good overall, but I did have some comments, primarily about
> the discussion of RTP multiplexing.
> >
> > The four bullet points in Section 2.1 that follow "The RTCWEB protocol suit
> encompasses a number of forms of multiplexing" seem to confuse RTP sessions,
> > RTCP, and transport-layer flows. I suggest they be changed to:
> > 
> >>   The RTP streams that comprise a WebRTC session can be multiplexed
> >>   together in a number of ways:
> >>
> >>   1.  Individual source streams are carried in one or more individual
> >>       RTP streams. These RTP streams can be multiplexed onto a single
> >>       transport-layer flow or sent as separate transport-layer flows.
> >>       This memo only considers the case where the RTP streams are to be
> >>       multiplexed onto a single transport-layer flow, forming a single
> >>       RTP session;
> >>
> >>   2.  The RTP Control Protocol (RTCP) [RFC3550] may be multiplexed onto
> >>       the same transport-layer flow as the RTP stream with which it is
> >>       associated, as described in [RFC5761], or it may be sent on a
> >>       separate transport-layer flow;
> >>
> >>   3.  The RTP and RTCP traffic can be multiplexed with other protocols
> >>       via UDP encapsulation over a common pair of UDP ports as described
> >>       in [RFC5764] as updated by
> >>       [I-D.petithuguenin-avtcore-rfc5764-mux-fixes]; and
> 
> Can we clarify what "other protocols" are expected? Are we just talking about
> WebRTC data-channels over SCTP/DTLS, or other things? If the latter, are we
> talking things we expect to do today, or in immediate futures, or extensions
> that might happen someday?
> 
> >>
> >>   4.  The data may be further encapsulated via STUN [RFC5389] and TURN
> >>       [RFC5766] for NAT (Network Address Translator) traversal.
> >
> > In the following paragraph (penultimate paragraph in Section 2.1), I suggest
> changing "unidirectional UDP packet flow" to "transport-layer flow" since it
> will not be unidirectional (since RTCP also flows in the reverse direction),
> and might not use UDP.
> >
> > In the first paragraph of section 2.2, I suggest changing "multiplexed over
> RTP sessions" to "multiplexed in a single RTP session" and "multiplexing of
> source streams in RTP sessions" to "multiplexing of source streams in a single
> RTP session".
> >
> > In Section 6, the second bullet point refers to "an RTCP session". There is
> no such thing. Rather, within a single RTP session there are RTCP packets sent
> that give information about the RTP streams that are being sent, and that
> report on the reception quality of RTP streams being received. Using a single
> PHB and DSCP for all RTCP packets within an RTP session might make sense, but
> it's important to note that one role of RTCP is to provide an estimate of the
> round-trip time seen by the media, so the PHB/DSCP will have to be chosen with
> care to avoid biasing that estimate too much.
> >
> > Editorial: the protocol is called WebRTC, but the working group is RTCWEB.
> Accordingly, I think all instances of "RTCWEB" in this draft need to change to
> "WebRTC".
> >
> > Cheers,
> > Colin
> >
> >
> >
> >
> >
> > On 9 Aug 2014, at 19:48, Ben Campbell <ben@nostrum.com> wrote:
> >> Hi,
> >>
> >> The DART working group has started a last call for draft-ietf-dart-dscp-
> rtp-02, ending on August 22. This informational draft describes considerations
> for the use of DiffServ code points in situations where one multiplexes
> multiple RTP packet streams, and potentially other protocol streams, that
> share the same 5-tuple.
> >>
> >> Since this draft is likely of interest to several working groups, I would
> like to solicit additional reviews from participants of TSVWG, AVTCORE,
> MMUSIC, CLUE, RTCWEB, and RMCAT. Please send any feedback (including feedback
> to the effect of "this is ready to progress") to the DART working group
> mailing list.
> >>
> >> Thanks!
> >>
> >> Ben.
> >>
> >> Begin forwarded message:
> >>
> >>> Resent-From: draft-alias-bounces@tools.ietf.org
> >>> From: Ben Campbell <ben@nostrum.com>
> >>> Subject: WGLC: draft-ietf-dart-dscp-rtp-02
> >>> Date: August 9, 2014 at 12:50:16 PM CDT
> >>> Resent-To: ben@nostrum.com, david.black@emc.com, paulej@packetizer.com
> >>> To: dart@ietf.org
> >>> Cc: draft-ietf-dart-dscp-rtp.all@tools.ietf.org, mls.ietf@gmail.com,
> Richard Barnes <rlb@ipv.sx>
> >>>
> >>> This is a DART Working Group Last Call of draft-ietf-dart-dscp-rtp-02.
> It's available on the data tracker at the following URL:
> >>>
> >>> https://datatracker.ietf.org/doc/draft-ietf-dart-dscp-rtp/
> >>>
> >>> The WGLC will conclude on 22 August, 2014. Please send your comments to
> the authors and the DART mailing list. If you've reviewed it and think it's
> good to go, please say so.
> >>>
> >>> Thanks!
> >>>
> >>> Ben.
> >>>
> >>
> >> _______________________________________________
> >> Audio/Video Transport Core Maintenance
> >> avt@ietf.org
> >> https://www.ietf.org/mailman/listinfo/avt
> >
> >
> >
> > --
> > Colin Perkins
> > http://csperkins.org/
> >
> >
> >
> 
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