[e2e] Re: crippled Internet

Randy Bush randy at psg.com
Wed Apr 25 21:32:11 PDT 2001

> There are ITU specs for jitter and delay in voice that have been used for
> years in standard telco system design.  I should think these would be easily
> accessible, but I only have a couple of graphs on paper.  The basic idea is
> that 50mS or so of frequent variation in sample arrival time is hard for
> listeners, and 100mS roundtrip delay becomes annoying in conversations.

in our universe, the modal delay is pretty much governed by the speed of
light in fiber and copper plus a few forwarding delays.  not a lot we can
do about it.  and i do not understand the meaning of round-trip delay in
the context of voip, as the phone calls i am on are simultaneous but non-
correlated one way chanels.

so the jitter characterization, "50ms or so of frequent variation," would
seem to be the interesting issue.  what is "frequent variation," and how
should it be measured?  i.e. if 3% of the samples are outliers, how they
are distributed in time would seem to be critical.


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