[ntp:questions] UK report on GPS vulnerabilities seems to overlook NTP

Chris Albertson albertson.chris at gmail.com
Tue Mar 8 19:28:39 UTC 2011

>> There is a big difference between keeping a computer's time of day clock
>> set to the current time (NTP) and maintaining timing or frequency control
>> in a telecom system.
> And exactly what is that difference? While ntp is perhaps too slow to
> respond to local frequency changes, how do you see the difference
> between keeping a computer's idea of local time accurate from keeping a
> telecom's idea of local time accurate?

The telecom equipment needs to know the time with less then one
microsecond error and to do that requires a clock that is at least 10X
better.   NTP typicaly works at the microsecond level and has error
1000X more than is required.

It's for the same reason a cloth tape measure is perfectly good for a
dress maker but useless to a machinist.

NTP simply is not good enough for use in a tower so it is not used.
And why would they use it when all towers by definition have a clear
view of the sky
Chris Albertson
Redondo Beach, California

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