[Dart] Open Issue: Guidance for RTCP

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

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From: Ben Campbell <ben@nostrum.com>
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Date: Mon, 25 Aug 2014 00:00:15 -0500
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Subject: [Dart] Open Issue: Guidance for RTCP
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(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.
> 
>