[NBLUG/talk] using NTP to synchronize the clock

E Frank Ball frankb at frankb.us
Tue Aug 9 22:49:39 PDT 2005


On Tue, Aug 09, 2005 at 10:11:16PM -0700, Lincoln Peters wrote:
} 
} As for the issue of using NTP, I have my computers set up via cron to run the 
} following command at midnight every night:
} 
} rdate time.nist.gov

That will work, but NTP really is the *best* tool for the job.

NTP initially checks the time every minute, then as things
stabilize it reduces the rate to once every 17 minutes.

NTP compares several times sources, picks the best one, and
compensates for network delay.  Overkill for most
applications maybe, but it's pretty easy to setup and run.


time.nist.gov is a very high level source to be using for the average
computer.  If everybody did that time.nist.gov would be swamped.

time.nist.gov is fairly far away (Colorado?).  Choosing a source
with precise accuracy is wasted when it is too far away.

It is better to pick a time source that is more physically local, and
farther down the food chain.  It's considered bad form for everybody and
their brother to synchronize to top level (stratum 1) servers.  It's
also good to have multiple sources in case one drops out.

Stratum 1 NTP servers are synchronized to GPS clocks, atomic clocks. or
WWV radio clocks.  Stratum 2 servers are synchronized to stratum 1
servers. Stratum 3 synchronize to stratum 2, etc.

Here are 3 local stratum 2 servers that synchronize to three different
stratum 1 servers that make good NTP servers in Sonoma County.  I'd list
these three in /etc/ntp.conf:

time.sonic.net
ntp.nblug.org
ntp.frizzen.net

For more info see http://www.pool.ntp.org/
I know that the last two on this list are in the pool (I put them
there), and I think sonic's server is too.

-- 

   E Frank Ball                frankb at frankb.us



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