nanog mailing list archives

Re: PAIX


From: "Stephen J. Wilcox" <steve () telecomplete co uk>
Date: Tue, 19 Nov 2002 10:21:45 +0000 (GMT)


On Mon, 18 Nov 2002, Jere Retzer wrote:

Stephen Sprunk wrote:

Any point in the US is within 25ms RTT (or less) of a major exchange;
eliminating this 25ms of latency will have no effect on VoIP unless you're
already near the 250ms RTT limit for other reasons.<<<


25 MS is assuming that the only delay is due to the speed of light. Add
equipment, especially routers or other gear that requires manipulating
packets and the delays add up quickly. I once read that the most people wil
tolerate on a regular basis is around 150-180 ms. I think that is much too
high for regular use

this is well studied and the numbers are not guessed they are empirical.. off
top of my head its -something like- local calls 80-100ms is fine and totally
unnoticable at that level, long distance people expect a little delay and
100-200ms is ok and slightly noticable and for long haul (satellite) etc people
will tolerate anything up to 600ms

so as you say 25ms even with extra ms for switching is fine..

Steve


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