[e2e] Re: crippled Internet

Randy Bush randy at psg.com
Thu Apr 26 04:49:07 PDT 2001

> ]    According to G.114, one-way delays up to 150 ms should cause no problems
> ] with typical voice communications.  From 150 to 400, loss/noise/etc. become
> ] a bigger issue and "long-delay" echo cancelers are needed.  (But some form
> ] of echo canceler/suppression is needed on ALL delays beyond 25 ms.)
> ] ...

i admit i am blind and stupid, but i just can't wrap my head around how this
applies to voip.  echo cancellation?

> ]   So I'd summarize by saying that human factors in dealing with one-way
> ] delay sets in at about 150-250 ms.

again, in my limited experience, the speed of light in fiber and copper are
dominate the mode of the measured delays.  though i could imagine that
codecs and the like will make their contribution.

> Given the sort of digital processing against echos that is now routinely
> done for good speakerphones and the CPU cycles available in modern
> personal computers, I wonder if the old worries about echo cancelers are
> irrelevant.  There's also the fact that everything is digital in VoIP.

it seems more relevant to me that voip is two *separated* one way paths.
what's to echo?


More information about the end2end-interest mailing list