[130407] in North American Network Operators' Group
Re: A New TransAtlantic Cable System
daemon@ATHENA.MIT.EDU (Jon Meek)
Sat Oct 2 10:32:07 2010
In-Reply-To: <AANLkTi=CZH_QREwaLTdfJpsbbG30gAkzsj0G8WAzYjP8@mail.gmail.com>
Date: Sat, 2 Oct 2010 10:31:33 -0400
From: Jon Meek <meekjt@gmail.com>
To: Heath Jones <hj1980@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
One of the ways that I have tormented WAN vendors over the years is
with a plot of RTT vs. great circle distance between the end points of
a circuit. Most RTTs usually sit at some constant offset above that
Physics limit straight line. Circuits taking a less than ideal have
their RTT far above the Physics limit line and we have used that
information to get routes fixed.
Using my great circle program that accounts for the non-spherical
Earth for locations we have West of London and North of NYC, assuming
a 1.5 index of refraction I get:
One way distance: 5520.6 km Round Trip Delay: 55.2 ms
So Heath's estimate is right on, although depending on where he got
the distance maybe it does account for the shape of the Earth.
Jon
On Sat, Oct 2, 2010 at 6:17 AM, Heath Jones <hj1980@gmail.com> wrote:
> On 2 October 2010 10:52, Rod Beck <Rod.Beck@hiberniaatlantic.com> wrote:
>> Is that a straight line calculation or did you take into account that a
>> straight line is not the shortest path on a curved surface?
>
> Well that is pretty obvious to most, but no - I didn't go to the
> effort of factoring in curvature of the earth - especially given that
> 1.5 is very rough figure anyway for RI of glass. If anything, my
> comment was compliment to your network being close to minimum possible
> latency!
>
>
