Presence and IntComm WG

[Jeremy George <>]

Guy,

>   I'd love to hear more from you and the others in wg-pic and wg-voip about 
> the specifics of how amount of queueing delay and stability of queueing 
> delay impinge on their work.

  ITU-T specifications cap mouth-to-ear delay at 150ms for toll quality
voice.  How much of that can be allocated to transmission depends on
the hardware being used for the terminal devices.  A guideline might be
100ms.

  Jitter is often noted as a culprit but RTP timestamps will smooth
over modest delivery variability.  The key is timely delivery within
the ~100ms window.  If that can't be accomplished, we are better off
(as Sally Floyd points out) not sending the bits in the first place.

- Jeremy

>   One quibble: I would not want to burden your effort too early, but I 
> would argue that congestion control will be needed if/when large-scale 
> deployment occurs.  The cute way of saying it is that you only need to do 
> it if your application succeeds.

  I agree that the congestion control elements of real time transmission
within our purview, the UAs, should be addressed within the PIC and
VoIP working groups.  And I don't think it's too early or too hard to
begin doing it now.

- Jeremy


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