NY ranks #1 in Internet b/w
alex at nac.net
Sun Nov 4 17:39:27 UTC 2001
On Sun, 4 Nov 2001, Iljitsch van Beijnum wrote:
> > 90,000 / 186,000 miles/sec = 483 milliseconds, which, or course, due to
> I'm afraid you're right. 240 ms is firmly burned into my mind, but this is
> the ONE WAY delay.
> > > Over 300 ms for less than 10000 km (6000 miles) is not great. Even a good
> > > satellite should be able to provide better round trip times...
"round trip times"
> > But, to make my point, Geosync orbit could never, ever be less than 483
> > milliseconds, ever.
> Well, actually there is a caveat: the distance to the satellite is never
> exactly 22500 miles. Depending on whether the orbit is measured from the
> surface of the earth (which is obviously the case for regular
> non-geosynchronous satellites) or the center of the earth (which I think
> is done with the 22500 mi figure) the satellite is either farther away or
> closer, depending on the location of the observer and the orbit of the
> satellite. The difference is substantial: up to 4000 miles.
Negatory. Per my sources, geosync is 22,500 miles from mean sea level, or
somehwat synonymously, from the surface of the earth. Agreed, there could
be variations if the earth station is in the Alps, but even if it were on
Mt. Everest at 29,035 feet (5.499 miles high), that would remove perhaps
up to 21.996 miles from the round-trip path (thus assuming both earth
stations are on Mt. Everest), which would remove 0.182 milliseconds from
the RTT delay.
Even with all the above content, this horse has just called me and asked
me to stop beating him.
-- Alex Rubenstein, AR97, K2AHR, alex at nac.net, latency, Al Reuben --
-- Net Access Corporation, 800-NET-ME-36, http://www.nac.net --
More information about the NANOG