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Re: Geo location to IP mapping
On May 16, 2006, at 2:00 PM, Charles Cala wrote:
Oh, I am well aware of that, but you are making my point for me.--- Marshall Eubanks <[email protected]> wrote:I seriously doubt this would work to better than the regional area. My zip code (20124) region is about 5 km across, which would be 15 microseconds in vacuum, and maybe at most 50 micro seconds in glass. So, you would need accuracies at the 10's of microsecond level to specify zip codes.don't forget, cable paths are not direct, and each bend in the cable increases the distance that the light must travel within the fiber. optical repeaters, optical switches and other equipment can add distance, (thus time) to the signal. Please see http://www.fiber-optics.info/fiber-history.htm
I have seen nothing to make me change my conclusion -
You can't do geolocation using network timing to much better than about 10 milliseconds because
you don't control either paths or the routers etc. in those paths. (This requires absolute timing;
differential measurements can be better and useful for some things, but they won't give you location.)
In glass, at 1/2 c, 10 msec is ~ 1500 km.
If you had an unlimited budget, lots and lots of measurement points with known locations, etc., and used other info (such as traceroutes) you might do a little better, but even a factor of ten better means 100 km error.
I am not saying you can't do geolocation, at least in some cases, but just that network timing won't get you anything very precise.