[time-nuts] can of worms: time-of-day in a community radio station

[Steven Sommars]

You can't test a server for smearieness.  It wouldn't surprise me if some
of them turn out to be getting time from google servers or something
similar.

The last time I checked over 50 of the NTP pool stratum 2 servers used
Google, based on the Reference ID.  The NTP pool folks are aware of the
issue.

Several other NTP pool servers make use of AWS NTP.   This too is smeared,
see https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time.html.



On Sun, Oct 20, 2019 at 9:00 PM Hal Murray <hmurray at megapathdsl.net> wrote:

>
> themadbeaker at gmail.com said:
> > In reference to using the NTP Pool, someone mentioned they don't trust
> them
> > and the possibility of a "rogue" server. The NTP Pool has a monitor that
> is
> > constantly querying every server in the pool, if the time drifts too far
> it
> > is removed from the DNS rotation.
>
> There is a catch.  The pool code in ntpd never goes back to check to see
> if a
> server has been kicked out of the pool or resigned.  As long as the server
> keeps responding, it will be used but subject to the usual filtering
> rules.
> If it stops responding, ntpd will drop it and do another DNS query to get
> a
> replacement.  (There may be some hysteresis on how-many.)
>
> Note that there are 2 ways to use the pool.  You can say
>   server pool.ntp.org (or us.pool.ntp.org or 0.us.pool.ntp.org)
> That will latch on to one of the servers in the pool.
> It won't do the replacement dance I described above.
> Next time you boot or otherwise restart ntpd you will probably get a
> different
> server.
>
> In the old says, before ntpd supported the pool command in ntp.conf, it
> was
> common to see things like:
>   server 0.pool.ntp.org
>   server 1.pool.ntp.org
>   server 2.pool.ntp.org
>   server 3.pool.ntp.org
> (Slot 2 also returns IPv6 addresses.)
>
> You can also say:
>   pool us.pool.ntp.org
> That will take several servers from the DNS response and try again later
> if it
> needs more.
>
>
> > Also, none of the servers in the pool
> > should be using leap-smearing (a requirement you mentioned).
>
> You can't test a server for smearieness.  It wouldn't surprise me if some
> of
> them turn out to be getting time from google servers or something similar.
>
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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