Sent from my iPhone
On Jun 20, 2020, at 9:27 AM, William Herrin <bill@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@herrin.us https://bill.herrin.us/