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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: ATM (was Re: too many routes)
Photons propagate at 0.65c in fibre - the exact speed does vary depending on whether its single or multimode fibre. As I dimly recall single mode fibre is every so slightly faster. The equivalent EMR propagation speed in coppr is 0.75c And the EMR propagation speed in a vacuum is c (and according to Einstein it doesn't matter how fast you are travelling at the time.) Of course this assumes that anyone wants to know... Quite frankly I was having a good time listening to everyone blame thost nasty horrible slow routers for the missing 30ms. :-) Geoff At 08:05 PM 9/11/97 -0700, Vadim Antonov wrote: >Richard Irving wrote: > >> Light can travel around the world 8 times in 1 second. This means it >> can travel >> once around the world (full trip) in ~ 120 ms. Milliseconds, not >> micro.... > >You've got faster light than anybody else. The speed of light >is about 300000 km/s _in vacuum_; that gives 134 ms arond the >planet's equator. > >> So, why does one trip across North america take 70ms... > >a) light is slower in dense media >b) fibers are not laid out in straight lines (in fact, i saw > a circuit going from Seattle to Vancouver via Fort Worth :) > >70 ms RTT = 35 ms one way. Given that U.S. is about 50 deg. wide, >it is abput 0.7ms/degree; or 250 ms around the world. > >Less than 2 times slower than light in vacuum. > >> Hint, it is not the speed of light. Time is incurred encoding, >> decoding, and routing. > >Hint: have a look at a telco's fiber map before spreading >nonsense. > >--vadim > > >
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