4 ms·

The trip is dominated by the speed of light (or more accurately, the speed of electricity, which is close to the speed of light, at about 300,000 kilometers per

by dmayle 8y ago

The trip is dominated by the speed of light (or more accurately, the speed of electricity, which is close to the speed of light, at about 300,000 kilometers per second) The circumference of the earth is about 40,000 kilometers. A round trip from CA to Netherlends and back will have electricity going roughly that distance. Speed of electricity times 150 milliseconds is 44,000 kilometers. That means that the number won't change over time.

e12e 8y ago
> (or more accurately, the speed of electricity, which is close to the speed of light, at about 300,000 kilometers per second) Surely, the dominant part of the path city to city is via fiber, so laser light? That doesn't mean that's were most of the time goes (but ideally it should) - for latency things like light-to-signal, buffers, switching, carrier grade nat, all takes its toll. Would be interesting to see a detailed breakdown of typical data center(... Cell phone, home broadband user) to same, though. Including every "point" in the path from ram, via cache, pci, network card, routers and switches, media converters and up again... For bonus something like USB keyboard touch to glyph on screen over udp or other low latency protocol...
- Hikikomori 8y ago
  Yes, it's more or less all fiber. And in that case the speed is 2/3 of the speed of light. Delay will in most part be because of distance, forwarding delay in routers are a few 10's of microseconds while switches are at the sub-microsecond level. Stuff like this is quick when they have to handle 100Gbit interfaces.
  - e12e 8y ago
    (I assume you mean 2/3 of light speed in vacuum - it's 100% the speed of light in acrylic (?))
hhmc 8y ago
Wont the majority of the trip be over the fibre optic medium - which would require the speed of light (albeit in a glass medium), rather than the speed of electricity? This also implies that you could materially change that rtt number if you used a faster medium - e.g via air by way of microwave towers.
- pkaye 8y ago
  Yup, speed of light in fiber is roughly 2/3*c.
- Xylakant 8y ago
  > This also implies that you could materially change that rtt number if you used a faster medium - e.g via air by way of microwave towers. Which is done for high-speed trading networks: https://arstechnica.com/information-technology/2016/11/private-microwave-networks-financial-hft/ https://arstechnica.com/information-technology/2016/11/priva...
- Hikikomori 8y ago
  Funnily enough signal speed in fiber and most copper cablea is the same, 2/3 of the speed of light in vacuum.
bufferoverflow 8y ago
It might change, if we figure out neutrino-based communications. In which case we reduce that timing to roughly 48ms.

by dmayle 8y ago

e12e 8y ago

> (or more accurately, the speed of electricity, which is close to the speed of light, at about 300,000 kilometers per second) Surely, the dominant part of the path city to city is via fiber, so laser light? That doesn't mean that's were most of the time goes (but ideally it should) - for latency things like light-to-signal, buffers, switching, carrier grade nat, all takes its toll. Would be interesting to see a detailed breakdown of typical data center(... Cell phone, home broadband user) to same, though. Including every "point" in the path from ram, via cache, pci, network card, routers and switches, media converters and up again... For bonus something like USB keyboard touch to glyph on screen over udp or other low latency protocol...

Hikikomori 8y ago
Yes, it's more or less all fiber. And in that case the speed is 2/3 of the speed of light. Delay will in most part be because of distance, forwarding delay in routers are a few 10's of microseconds while switches are at the sub-microsecond level. Stuff like this is quick when they have to handle 100Gbit interfaces.
- e12e 8y ago
  (I assume you mean 2/3 of light speed in vacuum - it's 100% the speed of light in acrylic (?))

hhmc 8y ago

Wont the majority of the trip be over the fibre optic medium - which would require the speed of light (albeit in a glass medium), rather than the speed of electricity? This also implies that you could materially change that rtt number if you used a faster medium - e.g via air by way of microwave towers.

pkaye 8y ago
Yup, speed of light in fiber is roughly 2/3*c.
Xylakant 8y ago
> This also implies that you could materially change that rtt number if you used a faster medium - e.g via air by way of microwave towers. Which is done for high-speed trading networks: https://arstechnica.com/information-technology/2016/11/private-microwave-networks-financial-hft/ https://arstechnica.com/information-technology/2016/11/priva...
Hikikomori 8y ago
Funnily enough signal speed in fiber and most copper cablea is the same, 2/3 of the speed of light in vacuum.

bufferoverflow 8y ago

It might change, if we figure out neutrino-based communications. In which case we reduce that timing to roughly 48ms.