[ntp:questions] Question on loopstats and PPS

Mauro Fiacco Mauro.Fiacco at ipaccess.com
Wed Dec 14 14:27:27 UTC 2005


Hi to All,

I am tryng to evaluate how good is my NTP server. It runs freeBSD and
uses a rubidium PPS signal to discipline the frequency (no time
correction).

The following loopstats is typical:

53667 64119.201 0.000000000 32.241623 0.000000954 0.003332 6
53667 64184.203 0.000000000 32.233749 0.000000954 0.004881 6
53667 64248.196 0.000000000 32.233749 0.000000954 0.004227 6
53667 64311.199 0.000000000 32.233749 0.000000954 0.003661 6
53667 64377.202 0.000000000 32.233749 0.000000954 0.003170 6
53667 64443.205 0.000000000 32.223343 0.000000954 0.005883 6

The Time offset is 0, as it does not know any better; the stability is
reasonable... But why the frequency offset (4th field) is so high?

The status reported by ntptime, shows that the FLL and PPSSIGNAL are active.

Shouldn't the frequency be corrected within the capability of the PPS
signal? 

I understand that this value may be the frequency offset measured by
PPS. 

In this case my question is: how can I calculate the Allan deviation of
my server without knowing the actual frequency offset?

Thank you all,

Mauro

P.S.: I am running ntp 4.2.0

-- 
Mauro Fiacco 

ip.access Ltd                      
URL: www.ipaccess.com  




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