[Dart] Open Issue: Guidance for RTCP

Ben Campbell <ben@nostrum.com> Mon, 25 August 2014 05:00 UTC

Return-Path: <ben@nostrum.com>
X-Original-To: dart@ietfa.amsl.com
Delivered-To: dart@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com []) by ietfa.amsl.com (Postfix) with ESMTP id 8B9071A8A0C for <dart@ietfa.amsl.com>; Sun, 24 Aug 2014 22:00:19 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -0.669
X-Spam-Status: No, score=-0.669 tagged_above=-999 required=5 tests=[BAYES_20=-0.001, RP_MATCHES_RCVD=-0.668] autolearn=ham
Received: from mail.ietf.org ([]) by localhost (ietfa.amsl.com []) (amavisd-new, port 10024) with ESMTP id j_XWWgZkZlyo for <dart@ietfa.amsl.com>; Sun, 24 Aug 2014 22:00:18 -0700 (PDT)
Received: from nostrum.com (raven-v6.nostrum.com [IPv6:2001:470:d:1130::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 03B661A8A09 for <dart@ietf.org>; Sun, 24 Aug 2014 22:00:17 -0700 (PDT)
Received: from [] (cpe-173-172-146-58.tx.res.rr.com []) (authenticated bits=0) by nostrum.com (8.14.9/8.14.7) with ESMTP id s7P50Fn9037421 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO) for <dart@ietf.org>; Mon, 25 Aug 2014 00:00:17 -0500 (CDT) (envelope-from ben@nostrum.com)
X-Authentication-Warning: raven.nostrum.com: Host cpe-173-172-146-58.tx.res.rr.com [] claimed to be []
From: Ben Campbell <ben@nostrum.com>
Content-Type: text/plain; charset=us-ascii
X-Mao-Original-Outgoing-Id: 430635615.389255-6e469708cff1a1c1abeb25760d4f4575
Content-Transfer-Encoding: quoted-printable
Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\))
Message-Id: <442BA084-2172-4251-BBD6-EF8280055854@nostrum.com>
Date: Mon, 25 Aug 2014 00:00:15 -0500
To: dart@ietf.org
X-Mailer: Apple Mail (2.1878.6)
Archived-At: http://mailarchive.ietf.org/arch/msg/dart/yyQjwRJmiYGU5nj2Ccc-bfhfv-8
Subject: [Dart] Open Issue: Guidance for RTCP
X-BeenThere: dart@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "\"DiffServ Applied to RTP Transports discussion list\"" <dart.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/dart>, <mailto:dart-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/dart/>
List-Post: <mailto:dart@ietf.org>
List-Help: <mailto:dart-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/dart>, <mailto:dart-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 25 Aug 2014 05:00:19 -0000

(as chair)

We have an open issue (Designated issue [B] by David) about what guidance to give about RTCP in draft-ietf-dart-dscp-rtp. We need to close this in order to progress the draft--meaning we need to do so ASAP.

Please look at the the following quoted text for background, and offer an opinion:

> (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.