60 ms cross-continent

Joel Jaeggli joelja at bogus.com
Sat Jun 20 17:07:48 UTC 2020


Sent from my iPhone

> On Jun 20, 2020, at 9:27 AM, William Herrin <bill at herrin.us> wrote:
> 
> Howdy,
> 
> Why is latency between the east and west coasts so bad? Speed of light
> accounts for about 15ms each direction for a 30ms round trip. Where
> does the other 30ms come from and why haven't we gotten rid of it?
> 
> c = 186,282 miles/second

This is c in a vacuum. Light transmission through a medium is slower. In the case of an optical fiber about 31% slower.

My lowest latency transit paths Palo Alto to the ashburn area are around 58ms.  the great circle route for the two dcs involved is a distance 2408 miles which gives you a 39.6ms Lower bound.
 
The path isn’t quite a straight as that, but if you  eliminate the 6 routers in the path and count up the oeo regens I’m sure you can account most of the extra in the form of distance.

> 2742 miles from Seattle to Washington DC mainly driving I-90
> 
> 2742/186282 ~= 0.015 seconds
> 
> Thanks,
> Bill Herrin
> 
> -- 
> William Herrin
> bill at herrin.us
> https://bill.herrin.us/
> 



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