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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Satellite latency (fwd)
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 people see. 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). _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com
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