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
On Mon, Nov 18, 2002 at 10:13:48AM -0800, 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
True. As far as VoIP goes, take 2 (digital/pcs/gsm/whatnot) cell phones (preferably on different carriers, or even the same if you want to see it) and call the other phone. Check out the delay in there. People who think that VoIP needs low delay don't realize the [presumably compression and other dsp related] delays introduced that people will be able to withstand. - jared -- Jared Mauch | pgp key available via finger from jared@puck.nether.net clue++; | http://puck.nether.net/~jared/ My statements are only mine.
Jared Mauch wrote:
True.
As far as VoIP goes, take 2 (digital/pcs/gsm/whatnot) cell phones (preferably on different carriers, or even the same if you want to see it) and call the other phone. Check out the delay in there. People who think that VoIP needs low delay don't realize the [presumably compression and other dsp related] delays introduced that people will be able to withstand.
- jared
It's not compression only, at least GSM (which I'm familiar with) runs it's audio packetized. Or should we call them cells since they are all the same size? Pete
Well... remember it's speed of light THROUGH fiber which isnt the same, its actually a bit slower then "c" Coast to coast you should see 35 - 65ms depending on the route. We've all had this thread about router overhead. If there is a congestions point in the middle with buffering and traffic level priorities running, then you are right. Otherwise I dont think you should see 150-180ms. In the real world however, yes, off several dsl links Im seeing those levels to various sites, I think it's more a factor of congested peering links or traffic aggregation at a hub. People arent spending the money to upgrade links right now. At 10:13 -0800 11/18/02, Jere Retzer wrote: Content-Type: text/html Content-Description: HTML 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 -- David Diaz dave@smoton.net [Email] pagedave@smoton.net [Pager] Smotons (Smart Photons) trump dumb photons
On Mon, 18 Nov 2002, David Diaz wrote: In the real world however, yes, off several dsl links Im seeing those levels to various sites, I think it's more a factor of congested peering links or traffic aggregation at a hub. People arent spending the money to upgrade links right now. I should move to whichever shangri-la you reside in; How about 4 seconds from a sfba SBC dsl link to www.pbi.net: http://snark.net/~mrtg/www.pbi.net.html Correlating data to other points on the net seems to suggest the problem isn't congested peering :) http://snark.net/~mrtg/ matto Shame on you, pacbell. --mghali@snark.net------------------------------------------<darwin>< Flowers on the razor wire/I know you're here/We are few/And far between/I was thinking about her skin/Love is a many splintered thing/Don't be afraid now/Just walk on in. #include <disclaim.h>
Wow, well Im in the SE. Matter of fact, I did get adsl and sdsl from 2 different providers on the same line. Maybe I can multihome ;-) Telocity seems to be doing a decent job lately, however they seemed to be doing some maint yesterday as it was the 1st time I noticed any issues. Oh Telocity is dtv owned now. It would be curious to see how the cable/dsl providers are doing lately. I know cox has a buildout going to ashburn and will be doing peering. Wonder if that is going to help or hurt latency and packet loss. Depends if they decide not to continue upgrading their transit circuits (it would seem to me). I usually say more peering is a good thing. Hopefully the new broadband players will have a more open peering policy and KEEP it that way. Seems once people get close to tier1 they close it again. Like a 2yr window opening and closing. d At 11:29 -0800 11/18/02, just me wrote:
On Mon, 18 Nov 2002, David Diaz wrote:
In the real world however, yes, off several dsl links Im seeing those levels to various sites, I think it's more a factor of congested peering links or traffic aggregation at a hub. People arent spending the money to upgrade links right now.
I should move to whichever shangri-la you reside in; How about 4 seconds from a sfba SBC dsl link to www.pbi.net:
http://snark.net/~mrtg/www.pbi.net.html
Correlating data to other points on the net seems to suggest the problem isn't congested peering :)
matto Shame on you, pacbell.
--mghali@snark.net------------------------------------------<darwin>< Flowers on the razor wire/I know you're here/We are few/And far between/I was thinking about her skin/Love is a many splintered thing/Don't be afraid now/Just walk on in. #include <disclaim.h>
Thus spake "Jere Retzer" <retzerj@ohsu.edu>
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.<<<
Can you please upgrade to a MUA with standard quoting semantics?
25 MS is assuming that the only delay is due to the speed of light.
No. I'm asserting that every populated area in the U.S. is within 25ms ping time of a major exchange, absent congested pipes.
Add equipment, especially routers or other gear that requires manipulating packets and the delays add up quickly.
If your router(s), switch(es), or firewall(s) need more than 1ms to forward a packet, it's time to select a new vendor. It's 20 hops between my home and work box, including 2900mi of fiber, a couple firewalls, and a DSL link -- and that's only 80-90ms. We clearly don't need an exchange for every 100km2 to get acceptable RTT. What we need are uncongested pipes.
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
ITU G.113 says users won't even notice the latency until it his 250ms. Do you have scientific studies that show 150-180ms is problematic? I'm sure the ITU (and a few hundred telcos) will be interested. Business experience shows users will tolerate over 1000ms latency if there's an economic incentive. There are many companies doing voice-over-internet that operate networks this way, and they're making a lot of money doing it. S
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
participants (7)
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David Diaz -
Jared Mauch -
Jere Retzer -
just me -
Petri Helenius -
Stephen J. Wilcox -
Stephen Sprunk