[ntp:questions] Strange server behaviour

Mauro Fiacco Mauro.Fiacco at ipaccess.com
Mon Jan 9 14:26:54 UTC 2006


I have a stand-alone NTP server (ntp-v4.2.0), it is a freeBSD PC, with
Rubidium PPS source. The server does not synchronize with higher stratum
servers (although I monitor other servers with noselect).

Only one client uses it for synchronisation, over a private subnet.

When I start NTP the server measures its stability of about 5-10ppm 
(as reported by ntpdc -c sysinfo), which converges to 2-5ppb within few
hours.

Once the server has converged to ppb stability, I start my client, a
run lasts for several days with the server maintaining good stability.

As I am testing with different client configurations, I need to stop and
start the client every so often. When I do it, the stability of the
server worsen instantaneously to ppm, before re-converge to lower
values. As shown in the loopstats below:

... very much stable to ppb range before this....
53744 42322.684 0.000000000 27.103912 0.000000954 0.001390 6
53744 42387.686 0.000000000 27.103912 0.000000954 0.001204 6
53744 42452.689 0.000000000 27.103912 0.000000954 0.001043 6
... here the client was killed ...
53744 42516.691 0.000000000 38.240784 0.000000954 5.568436 6
53744 42579.684 0.000000000 38.240784 0.000000954 4.822407 6
53744 42644.688 0.000000000 38.240784 0.000000954 4.176327 6
53744 42708.691 0.000000000 38.240784 0.000000954 3.616805 6
53744 42771.684 0.000000000 38.240784 0.000000954 3.132245 6
53744 42837.686 0.000000000 27.094574 0.000000954 6.198203 6
53744 42902.689 0.000000000 27.094574 0.000000954 5.367801 6
53744 42966.691 0.000000000 27.094574 0.000000954 4.648652 6
53744 43030.684 0.000000000 27.098007 0.000000954 4.025851 6
53744 43094.686 0.000000000 27.098007 0.000000954 3.486489 6
53744 43158.689 0.000000000 27.098007 0.000000954 3.019388 6
53744 43223.691 0.000000000 27.098007 0.000000954 2.614867 6
53744 43287.684 0.000000000 27.094116 0.000000954 2.264542 6
... slowly converging to ppb....

(Note that 0 offset and 0 network jitter are due to the fact that the
server is not disciplined to any other server)

The problem is repeatable. I know it does make little sense... I am just
at a loss with it. Any suggestions on why this is happening?

Thank you.

Mauro

PS:
ntp.conf main parameters:

keys ./ntp.keys
requestkey 1
controlkey 1

driftfile /etc/ntp.drift

enable stats
statistics loopstats peerstats clockstats rawstats sysstats
filegen loopstats file loopstats type none enable
filegen peerstats file peerstats type none enable
filegen clockstats file clockstats type none enable
filegen rawstats file rawstats type none enable
filegen sysstats file sysstats type none enable

enable pps
server 127.127.22.0
fudge 127.127.22.0 stratum 1
fudge 127.127.22.0 refid RBDM
fudge 127.127.22.0 flag3 1

server zzzz.yyyy.net noselect

server 127.127.1.0
fudge 127.127.1.0 stratum 1

restrict default kod notrap nomodify nopeer noquery
restrict 127.0.0.1



-- 
Mauro Fiacco 

ip.access Ltd                      
URL: www.ipaccess.com  




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