NTP question

William Herrin bill at herrin.us
Thu May 2 00:55:30 UTC 2019


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.

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

Regards,
Bill Herrin


-- 
William Herrin ................ herrin at dirtside.com  bill at herrin.us
Dirtside Systems ......... Web: <http://www.dirtside.com/>
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