NTP question

Harlan Stenn stenn at nwtime.org
Thu May 2 02:02:49 UTC 2019


On 5/1/19 5:55 PM, William Herrin wrote:
> On Wed, May 1, 2019 at 5:48 PM Keith Medcalf <kmedcalf at dessus.com> wrote:
> 
>> If you have one such installation, then you really do not care about the
>> "accuracy" of the time.  However if you have multiple such installations
>> then you want them all to have the same time (if you will be comparing logs
>> between them, for example).  At some point it becomes "cheaper" to spend
>> thousands of dollars per site to have a single Stratum 0 timesource (for
>> example, the GPS system) at each site (and thus comparable time stamps)
>> than it is to pay someone to go though the rigamarole of computing offsets
>> and slew rates between sites to be able to do accurate comparison.  And if
>> you communicate any of that info to outsiders then being able to say "my
>> log timestamps are accurate to +/- 10 nanoseconds so it must be you who is
>> farked up" (and be able to prove it) has immense value.
>>
> 
> If your network is air gapped from the Internet then sure. If it's not, you
> can run NTP against a reasonably reliable set of time sources (not random
> picks from Pool) and be able to say, "my log timestamps are accurate to +/-
> 10 milliseconds so it must be you who is farked up." While my milliseconds
> loses the pecking order contest, it's just as good for practical purposes
> and a whole lot less expensive.

It's not clear to me that there's anything *wrong* with using the pool,
especially if you're using our 'pool' directive in your config file.

That directive will bring up ~10 associations and continuously evaluate
their quality, throwing out the poor performers and soliciting new
servers of currently-good quality to replace them.

This goes to "have _enough_ good-quality servers, and monitor your ntpd".

> If your system is Internet-connected. If you run an air gapped network then
> yeah, get your time out of band.
> 
> Regards,
> Bill Herrin
> 
> 

-- 
Harlan Stenn <stenn at nwtime.org>
http://networktimefoundation.org - be a member!



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