Did you not read my posting on Quora?
Tim
On 6/20/20 10:49 AM, Wayne Bouchard wrote:
And thus far, no one has mentioned switching speed and other
electronic overhead such as the transceivers (that's the big one,
IIRC.)
I also don't recall if anyone mentioned that the 30ms is as the
photon flies, not fiber distance.
-Wayne
On Sat, Jun 20, 2020 at 05:32:30PM +0000, Mel Beckman wrote:
An intriguing development in fiber optic media is hollow core optical fiber,
which achieves 99.7% of the speed of light in a vacuum.
https://www.extremetech.com/computing/151498-researchers-create-fiber-network-that-operates-at-99-7-speed-of-light-smashes-speed-and-latency-records
-mel
On Jun 20, 2020, at 10:14 AM, Dave Cohen <craetd...@gmail.com> wrote:
??? Doing some rough back of the napkin math, an ultra low-latency path from,
say, the Westin to 1275 K in Seattle will be in the 59 ms range. This is
considerably longer than the I-90 driving distance would suggest because:
- Best case optical distance is more like 5500 km, in part because the path
actually will go Chicago-NJ-WDC and in part because a distance of 5000 km by
right-of-way will be more like 5500 km when you account for things like
maintenance coils, in-building wiring, etc.
- You???ll need (at least) three OEO regens on that distance, since there???s
no value in spending 5x to deploy an optical system that wouldn???t need to
(like the ones that would manage that distance subsea). This is in addition to
~60 in-line amplification nodes, although that adds significantly less latency
even in aggregate
Some of that is simply due to cost savings. In theory, you could probably spend
a boatload of money to build a route that cuts off some of the distance
inefficiency and gets you closer to 4500 km optical distance with minimal slack
coil, and maybe no regens, so you get a real-world performance of 46 ms. But
there are no algo trading sites of importance in DC, and for everybody else
there???s not enough money in the difference between 46 and 59 ms for someone
to go invest in that type of deployment.
Dave Cohen
craetd...@gmail.com
On Jun 20, 2020, at 12:44 PM, Tim Durack <tdur...@gmail.com> wrote:
???
And of course in your more realistic example:
2742 miles = 4412 km ~ 44 ms optical rtt with no OEO in the path
On Sat, Jun 20, 2020 at 12:36 PM Tim Durack
<tdur...@gmail.com<mailto:tdur...@gmail.com>> wrote:
Speed of light in glass ~200 km/s
100 km rtt = 1ms
Coast-to-coast ~6000 km ~60ms
Tim:>
On Sat, Jun 20, 2020 at 12:27 PM William Herrin
<b...@herrin.us<mailto:b...@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
2742 miles from Seattle to Washington DC mainly driving I-90
2742/186282 ~= 0.015 seconds
Thanks,
Bill Herrin
--
William Herrin
b...@herrin.us<mailto:b...@herrin.us>
https://bill.herrin.us/
--
Tim:>
--
Tim:>
---
Wayne Bouchard
w...@typo.org
Network Dude
http://www.typo.org/~web/
