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Re: Satellite latency (fwd)
- From: Ukyo Kuonji
- Date: Wed Feb 27 09:11:22 2002
Is that 36000 km above the equator measures from the surface of the earth,
or the center of the earth? I would assume that most companies would use
the surface of the earth to determine the orbit, or sea level.
The radius of the earth is about 6400km. Geostationary orbit is, as
you note, 36000km above the equator. The path from the satellite to
the North Pole is the hypotenuse of a right triangle with legs of
6400km and (6400+36000)km. That gives a distance from the North Pole
to the satellite of 43000km. It's reasonable to conclude that the
distance from either New York or San Diego is less than that.
Looking at a spam I just received from satcast.com, it looks like they are
considering the distance from the dish to the satellite to be roughly 44000
miles. That's roughly 70000 km. Assuming that they are stating that from
the dish to the bird, that would account for the larger RTT times that
My real problem with these directpc type systems are two fold. The first is
that these systems use a USB connection. I use wireless at home since I
have a number of laptops. I certainly am not willing to tie myself down to
a usb cable.
The second problem is that the users are addressed using rfc1918 address
space and are translated via nat to the Internet. This may mess up any
number of applications that I use, including VPN software. Add to this the
first problem, and suddenly I have two levels of NAT that I have to contend
with, one on my windows machine connected to the USB cable (with Internet
sharing), and one at earthlink's edge.
Those are what's keeping me at dialup, even though I only get 28.8 at best.
Well... that and the fact that I can't get cable where I live, and the CO is
sonething like 15 miles away (not that they can spell DSL out here).
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