[Dart] Colin Perkins comments - WGLC: draft-ietf-dart-dscp-rtp-02
"Black, David" <david.black@emc.com> Fri, 22 August 2014 20:12 UTC
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From: "Black, David" <david.black@emc.com>
To: Colin Perkins <csp@csperkins.org>, "dart@ietf.org" <dart@ietf.org>
Date: Fri, 22 Aug 2014 16:12:11 -0400
Thread-Topic: Colin Perkins comments - WGLC: draft-ietf-dart-dscp-rtp-02
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Cc: Ben Campbell <ben@nostrum.com>, "avt@ietf.org WG" <avt@ietf.org>, "Paul E. Jones (paulej@packetizer.com)" <paulej@packetizer.com>, "draft-ietf-dart-dscp-rtp.all@tools.ietf.org" <draft-ietf-dart-dscp-rtp.all@tools.ietf.org>
Subject: [Dart] Colin Perkins comments - WGLC: draft-ietf-dart-dscp-rtp-02
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Hi Colin, I've picked up your changes (including RTCWEB -> WebRTC globally) in my working draft, with two exceptions: (1) Items 3 and 4 in the list of what can be multiplexed. I don't think you suggested any changes to these two items, but they need significant attention for other reasons: - Ben's comment that item 3 ought to focus on the WebRTC data channel - STUN doesn't encapsulate WebRTC traffic (TURN does). I plan to merge these items 3 and 4 as part of revising them, and intend to move the topic of TURN encapsulation out to be discussed elsewhere, as it's independent of multiplexing. I'll propose specific text in a separate message. (2) PHBs and DSCPs for RTCP. I'm not sure what to say about this, as it looks like I need to set off a discussion (debate?) between you and my co-author, Paul Jones. Colin (from WGLC comments): > 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. Paul (from shortly after the Toronto meeting: > During the meeting, there was discussion of marking RTCP packets. Some > notes I received on this topic suggested that it was proposed that RTCP > should be marked the same as for RTP. The argument was that this is used > for RTT calculations. If that is what was said, I'd like to state my > disagreement. :-) > > The forward and reverse paths are not necessarily the same and there is > nothing one should assume about the reverse path to provide guidance about > the forward path (or vice versa). As perhaps a gross example, I have the > ability to download far faster on my home Internet connection than I can > upload. Other important traffic characteristics differ in each direction. > > Further, an RTCP packet might provide information related to several different > RTP packets. I certainly would not want to see one RTCP packet per RTP packet. I'll watch where that discussion goes before proposing text. Thanks, --David > -----Original Message----- > From: Colin Perkins [mailto:csp@csperkins.org] > Sent: Monday, August 18, 2014 11:18 AM > To: dart@ietf.org > Cc: avt@ietf.org WG; Ben Campbell; draft-ietf-dart-dscp-rtp.all@tools.ietf.org > Subject: Re: [AVTCORE] WGLC: draft-ietf-dart-dscp-rtp-02 > > 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 > > > > 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/ > >
- [Dart] Colin Perkins comments - WGLC: draft-ietf-… Black, David
- Re: [Dart] Colin Perkins comments - WGLC: draft-i… Colin Perkins
- Re: [Dart] Colin Perkins comments - WGLC: draft-i… Ben Campbell
- Re: [Dart] Colin Perkins comments - WGLC: draft-i… Paul E. Jones
- Re: [Dart] Colin Perkins comments - WGLC: draft-i… Ben Campbell
- Re: [Dart] Colin Perkins comments - WGLC: draft-i… Paul E. Jones
- Re: [Dart] Colin Perkins comments - WGLC: draft-i… Colin Perkins
- Re: [Dart] [AVTCORE] Colin Perkins comments - WGL… Ali C. Begen (abegen)
- [Dart] Treatment of RTCP (was Re: Colin Perkins c… Ben Campbell
- Re: [Dart] Treatment of RTCP (was Re: Colin Perki… Black, David
- Re: [Dart] Treatment of RTCP (was Re: Colin Perki… Paul E. Jones
- Re: [Dart] Treatment of RTCP (was Re: Colin Perki… Colin Perkins
- Re: [Dart] Treatment of RTCP (was Re: Colin Perki… Colin Perkins
- Re: [Dart] Treatment of RTCP (was Re: Colin Perki… Black, David
- Re: [Dart] Treatment of RTCP (was Re: Colin Perki… Paul E. Jones
- Re: [Dart] Treatment of RTCP (was Re: Colin Perki… Colin Perkins
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Colin Perkins
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Michael Welzl
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Colin Perkins
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Michael Welzl
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Colin Perkins
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Ben Campbell
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Michael Welzl
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Ben Campbell
- Re: [Dart] Treatment of RTCP (was Re: Colin Perki… Paul E. Jones
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Paul E. Jones
- Re: [Dart] Treatment of RTCP (was Re: Colin Perki… Colin Perkins
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Colin Perkins
- Re: [Dart] [AVTCORE] Treatment of RTCP (was Re: C… Colin Perkins