[cisco-voip] Silly question...

[Calvin, Martin]

People (including me) confuse RTT with one way.  Client server
application response times are all measured in RTT, but RTP is peer to
peer and it makes no sense to talk in terms of RTT.  In fact, using RTT
is a bad idea because you could very well have voice in one direction
take 75ms but in the opposite direction between the same peers, it could
be 200ms depending on whether or not the packets are taking the same
routed path.  If you added these, you are at 275ms which you might
consider acceptable, but yet you've broken the 150ms rule in one
direction and you'll have one user who is disgruntled while the other is
not.


> -----Original Message-----
> From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-
> bounces at puck.nether.net] On Behalf Of Jonathan Charles
> Sent: Friday, February 29, 2008 3:11 PM
> To: Bill Woodcock
> Cc: cisco-voip at puck.nether.net
> Subject: Re: [cisco-voip] Silly question...
> 
> Maybe I should be more clear.
> 
> What is the Cisco-recommended best-practice for maximum round trip
> delay for a Cisco IP Telephony deployment.
> 
> And the answer is apparently 150ms each way... that is still nuts.
> 
> I am wondering why most of us think it was 150ms round trip... this
> isn't isolated to a few of us, I asked all of the engineers I work
> with and every one of them (including two CCIEs) told me it was 150ms
> round trip....
> 
> Now, I found a doc on Cisco's website saying 150ms each way... so,
> 300ms...
> 
> 
> 
> Jonathan
> 
> On Fri, Feb 29, 2008 at 5:05 PM, Bill Woodcock <woody at pch.net> wrote:
> >     > OK, here's the thing.
> >     > This morning, if you had asked me this question, I would have
> bet
> >     > serious amounts of cash that the MAXIMUM ROUND TRIP DELAY was
> 150ms.
> >     > Now, I am seeing that it is ONE WAY, with a maximum of 300ms
> round
> >     > trip... that is insane.
> >
> >  I've been on triple-satellite-hop calls with more than four seconds
> of
> >  delay.  And obviously, astronauts and cosmonauts have no trouble
> phoning
> >  home.  It's all a matter of conversational turn-taking.  People who
> are
> >  good at it have no problem, while people who are nervous or
> impatient
> >  can't usually deal with it.
> >
> >                                 -Bill
> >
> >
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