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Is there any way to get real-time voice connections over the modern internet? Is it just a matter of setting up VOIP and then mercilessly debugging latency iss

Is there any way to get real-time voice connections over the modern internet? Is it just a matter of setting up VOIP and then mercilessly debugging latency issues on both ends? Is FaceTime or any other commercial solution close to zero latency?

schoen 8y ago
Presumably a lot of the unavoidable latency (in any particular Internet path) compared to a dedicated switched circuit comes in when the routers examine packets, decode addresses, perform routing table lookups, execute routing algorithms, and then copy the packet into another interface. If you had a physically switched circuit you could imagine that the data would travel over it at the speed of electricity in wires, while for packet switching there's some kind of software step and "hesitation" as the router "thinks" about the routing problem posed by each packet. There are some Internet connections where the speed of light limitation dominates the routing issues, but I don't think this is the case most of the time when dealing with short-to-medium-distance connections involving multiple commercial ISPs. (Especially for peer-to-peer connections on residential broadband, you also don't have the latency benefit of a possible CDN node colocated with or direct CDN peering with your own ISP.) So I think the best answer to most of your questions is "not really", although it would be really interesting to see a detailed breakdown in a traceroute of speed-of-physical-medium vs. various router tasks for each hop. (Then you could imagine improving some of these by changing the physical medium, reducing the number of hops via better or different peering arrangements, and getting fancier routers in some places that contribute less latency per hop.) Periodically on HN we see pieces about the extreme lengths that people engaged in high-frequency trading will go to in order to get really low latency. Those folks know all the details of exactly where the latency comes in and exactly what could be done about it. But the huge expense and trouble that they have to go to in order to get some of these improvements suggests to me that we're probably not going to see the same improvements easily on the typical consumer broadband connection.
- kortilla 8y ago
  Decision time in the router usually isn’t an issue. That’s mostly a fixed cost that can easily be kept under a millisecond. Most of the time gets spent queueing for your turn to either come off of the interface or to go onto the egress interface. All of your jitter in a stable configuration router is going to be coming from those varying queue depths.
  - schoen 8y ago
    Thanks, I don't really have any intuition for the relative contribution of these factors!
- jimpudar 8y ago
  > people engaged in high-frequency trading These people pay to have their servers colocated with the trading servers they are communicating with. That would be like having a VoIP call with someone sitting next to you connected to the same switch.
  - cm2187 8y ago
    Though I doubt the difference between a 50ms vs 2ms latency would be perceivable for a phone communication.
uiri 8y ago
If by "modern internet", you mean TCP/IP, then no. You'd need a circuit-switched network to do that, and those are all obscure/niche networks except for the Public Switched Telephone Network. Real landlines work even if the power is out.
deleted 8y ago
[deleted]

schoen 8y ago

Presumably a lot of the unavoidable latency (in any particular Internet path) compared to a dedicated switched circuit comes in when the routers examine packets, decode addresses, perform routing table lookups, execute routing algorithms, and then copy the packet into another interface. If you had a physically switched circuit you could imagine that the data would travel over it at the speed of electricity in wires, while for packet switching there's some kind of software step and "hesitation" as the router "thinks" about the routing problem posed by each packet. There are some Internet connections where the speed of light limitation dominates the routing issues, but I don't think this is the case most of the time when dealing with short-to-medium-distance connections involving multiple commercial ISPs. (Especially for peer-to-peer connections on residential broadband, you also don't have the latency benefit of a possible CDN node colocated with or direct CDN peering with your own ISP.) So I think the best answer to most of your questions is "not really", although it would be really interesting to see a detailed breakdown in a traceroute of speed-of-physical-medium vs. various router tasks for each hop. (Then you could imagine improving some of these by changing the physical medium, reducing the number of hops via better or different peering arrangements, and getting fancier routers in some places that contribute less latency per hop.) Periodically on HN we see pieces about the extreme lengths that people engaged in high-frequency trading will go to in order to get really low latency. Those folks know all the details of exactly where the latency comes in and exactly what could be done about it. But the huge expense and trouble that they have to go to in order to get some of these improvements suggests to me that we're probably not going to see the same improvements easily on the typical consumer broadband connection.

kortilla 8y ago
Decision time in the router usually isn’t an issue. That’s mostly a fixed cost that can easily be kept under a millisecond. Most of the time gets spent queueing for your turn to either come off of the interface or to go onto the egress interface. All of your jitter in a stable configuration router is going to be coming from those varying queue depths.
- schoen 8y ago
  Thanks, I don't really have any intuition for the relative contribution of these factors!
jimpudar 8y ago
> people engaged in high-frequency trading These people pay to have their servers colocated with the trading servers they are communicating with. That would be like having a VoIP call with someone sitting next to you connected to the same switch.
- cm2187 8y ago
  Though I doubt the difference between a 50ms vs 2ms latency would be perceivable for a phone communication.

uiri 8y ago

If by "modern internet", you mean TCP/IP, then no. You'd need a circuit-switched network to do that, and those are all obscure/niche networks except for the Public Switched Telephone Network. Real landlines work even if the power is out.

deleted 8y ago

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