forget VoIP: use the Plain Old Telephone System for important relationships

Posted Feb 3, 2006 15:06 UTC (Fri) by zooko (guest, #2589)
Parent article: The Next Battleground for VoIP (O'Reilly)

I was excited about VoIP, like every other freedom-oriented hacker geek, but after working in the field for a year and experimenting extensively, I've come to realize that VoIP is unusuably bad for my purposes, and will continue to be unusably bad for the forseeable future.

It's because of latency. Here's how to get a feeling for the latency in VoIP that I recently learned from Brian Warner: the person on one end looks at a digital watch with a second count and counts off numbers one per second: "one... two... three...". The person on the other end tries to say the numbers *at the same time* as he hears them, speaking "four... five... six..." in unison with the first person.

Now the first person can hear the turnaround time as the different between when they say "seven" and when the person on the other end says "seven", which that person perceives as being said in unison.

Then do the same experiment the other way around so that the other person can hear the latency.

You can also set up a Plain Old Telephone System call and a VoIP call at the same time between the same two endpoints and you have easily hear how the words arrive a fraction of a second later by VoIP than it does by POTS.

The insidious thing about latency is that you don't detect in normal conversation, but it makes it sound like the other person is either interrupting you a lot, as though they don't care to let you finish your thoughts, or else they fall silent after you've finished speaking, as though they aren't paying attention or they can't think of anything to say. Of course, it sounds the same to *them* -- they perceive that you are interrupting them and being unresponsive to them.

For people with whom I want to preserve a good relationship, including my co-workers at my remote Internet startup, and my family, and my friends, I refuse to use VoIP (even though of course they are all excited about it) and instead insist on using the Plain Old Telephone System with its unbeatably low latency.

forget VoIP: use the Plain Old Telephone System for important relationships

Posted Feb 9, 2006 10:28 UTC (Thu) by ekj (guest, #1524) [Link] (1 responses)

Agreed. Latency needs to get down. That's a network-problem more than a voip problem though, and doesn't stop company-internal voip-solutions from being successful.

100ms is tolerable, anything under 50ms is close enough as makes no difference. Given that speed of ligth around half the globe gives a minimum latency for a call over that distance of around 66ms, it's a given we'll never reach 66ms globally, but then again, neither does POTS.

For calls within a continent sub-50ms should be possible. And optimally, sub-100-ms globally. (I doubt POTS manages that now btw)

I'm in Germany rigth now, and when talking to my dad in Norway, 1400 km away I had around 80ms roundtrip time. That's good enough, considering that that is only 40ms lag one-way, but it's still around 10 times the theoretical limit give by the ridicolously low speed of ligth. (who engineered that thing ? It's completely unscalable for a multi-planet civilization.)

forget VoIP: use the Plain Old Telephone System for important relationships

Posted Feb 9, 2006 14:03 UTC (Thu) by job (guest, #670) [Link]

When I toyed with VoIP back in the 90s we had 50ms as the limit of what is acceptable for voice. Today the networks are much faster so voice is easier, but the PSTN-gateways hasn't improved much, and they often introduce delays. The packetization itself has around 20ms delay to start with.

My brother lives 900km away here in Sweden. Our network roundtrip time is around 20ms which is acceptable. So it all depends on your network and puts very different demands on it than fast downloads.