60 ms cross-continent
nanog at ics-il.net
Sat Jun 20 17:02:55 UTC 2020
The speed of light in fiber is only about 2/3 the speed of light in a vacuum, so that 15 ms is really about 22.5 ms. That brings the total to about 45 ms.
Some would come from how many miles of extra glass in that 2,742 miles in the form of slack loops.
Some would come from fiber routes not being straight lines. Allied Fiber's formerly planned route from the Westin Building to Equinix Ashburn was about 4,464 miles. That's about 38% longer than your 2,742 miles. Add that 38% to the previous 45 ms and you're at 62.1 ms.
Intelligent Computing Solutions
----- Original Message -----
From: "William Herrin" <bill at herrin.us>
To: nanog at nanog.org
Sent: Saturday, June 20, 2020 11:24:11 AM
Subject: 60 ms cross-continent
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
2742 miles from Seattle to Washington DC mainly driving I-90
2742/186282 ~= 0.015 seconds
bill at herrin.us
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