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Re: NY ranks #1 in Internet b/w
- From: Iljitsch van Beijnum
- Date: Sun Nov 04 10:43:47 2001
On Sun, 4 Nov 2001, Alex Rubenstein wrote:
> > 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...
> That sounds somewhat erroneous. Geosynchronus orbit is about 22,500 miles;
> up+down+roundtrip makes that 22,500 * 4, or 90,000 miles;
> 90,000 / 186,000 miles/sec = 483 milliseconds, which, or course, due to
> routers inducing very measureable delay, and the fact that an IP Packet
> takes adds a little delay due to its lenght, is usually a bit more.
I'm afraid you're right. 240 ms is firmly burned into my mind, but this is
the ONE WAY delay.
> 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.