[ntp:questions] ntp stratum

Richard B. Gilbert rgilbert88 at comcast.net
Sat Sep 27 17:41:27 UTC 2008

stephaneguedon wrote:
> Hello
> I own a ubuntu 8.04 server, which provide a ntp service (not only, but 
> it's the thing we look at here...).
> I would like to know how I can tell the server he is in stratum 3.
> This is my /etc/ntp.conf :
> # /etc/ntp.conf, configuration for ntpd
> logfile /var/log/ntp
> #driftfile /var/lib/ntp/ntp.drift
> statsdir /var/log/ntpstats/
> statistics loopstats peerstats clockstats
> filegen loopstats file loopstats type day enable
> filegen peerstats file peerstats type day enable
> filegen clockstats file clockstats type day enable
> # You do need to talk to an NTP server or two (or three).
> #server ntp.your-provider.example
> # pool.ntp.org maps to more than 300 low-stratum NTP servers.
> # Your server will pick a different set every time it starts up.
> #  *** Please consider joining the pool! ***
> #  *** <http://www.pool.ntp.org/join.html> ***
> server ntp2.jussieu.fr
> server ntp.metas.ch
> server soleil.uvsq.fr
> server ntp.u-psud.fr
> server ntp.obspm.fr
> server ntp1.fau.de
> server audaxsystems.co.uk
> thanks for your answers.
> sincerly yours

Ntpd will compute the proper stratum! It simply adds 1 to the stratum of 
the source it is using.  If ntpd is synchronized with a stratum 1 source 
it will declare itself stratum 2.  If synchronized to a stratum 2 source 
it will declare stratum 3, etc.  In principle, you could get down to 
stratum 15 but if you do something is probably VERY wrong.  The stratum 
is simply the number of "hops" from the atomic clock at the root. 
Stratum 1 got it from atomic clock, stratum 2 got it from a stratum 1 
server, stratum 3 go its time from a stratum 2 server and so on.

If you are using the unsynchronized local clock as a clock of last 
resort it is customary to force a stratum of 10 to ensure that nobody 
will believe that clock if he can possibly find anything at a lower 
stratum number.

Stratum has nothing whatever to do with accuracy.  ISTR that the latest 
NTP server survey found a clock claiming stratum 1 that did not even 
have the correct year!!!!

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