[ntp:questions] frequency adjusting only

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Tue Apr 22 18:34:32 UTC 2008

>                          If you compensate for cable
>delays you can probably get to within 50-100 usec.

Do the arithmetic.  Cable delay is interesting for ns, not microseconds.

The speed of light is 1 ft/ns.  That's in vacuum.  It's slower in cable.
Inexpensive cable is about 1/2 c.  Good cable is faster than that.
The conversion from miles to km is about right.  5 microseconds
per mile (in vacuum) is 5 microseconds per km in cable.  So 100 meters
would be 0.5 microsecond.

So if we are discussing a handful of machines within ethernet/CAT5
distances, you don't have to correct for cable lengths unless your
target is better than a few microseconds.

These are my opinions, not necessarily my employer's.  I hate spam.

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