nanog mailing list archives

Re: ATM (was Re: too many routes)


From: Vadim Antonov <avg () pluris com>
Date: Thu, 11 Sep 1997 20:05:13 -0700

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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