[ntp:questions] Re: Best way to harness multiple stratum 1 servers

Richard B. Gilbert rgilbert88 at comcast.net
Wed Apr 5 22:02:03 UTC 2006

John Ackermann N8UR wrote:
> Hal Murray said the following on 04/05/2006 03:08 PM:
>>As a practcal matter, the best is probably the one that's that most
>>reliable.  Or the one that's most convenient.  Or the one with the
>>fastest CPU or best network connection.
>>The last few nano/micro seconds won't make much difference
>>after a network hop.
> You're probably right, but my problem (if you can call having too many
> time sources a problem!) is that it's not intuitively clear which one of
> the servers is the best, other than that the WWVB server is
> significantly worse than the GPS and Cs ones.  But the GPS and Cs ones
> have very similar performance.  To the outside world it doesn't matter
> because the internet and even my firewall performance will mask
> differences at this level, but as an academic exercise, and on the local
> wire, I'd like to see if I can wring the best possible performance out
> of the system.
> I'm probably asking NTP to perform at a level it's not really designed
> for, and that perhaps the OS/hardware can't even support (in terms of
> system clock stability and time resolution -- though a longer term goal
> is to replace the mobo clock with a source derived from the Cs to solve
> at least one problem).
> John
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I believe I have read the PHK has modified the ntpd PLL for use with 
refclocks such as GPS and Cesium.  I don't know PLL design from a hole 
in the ground but he might have improved the design for that specific 
purpose.  It's worth looking into!!

BTW, what hardware and O/S are you using for this project?  Solaris 
8/SPARC keeps time to a precision of one microsecond.  I don't know of 
any hardware/software that supports a higher precision but there may 
well be some.

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