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On 09.04.2023 08:24, Harlan Stenn wrote:
> 4 is better than 3 because from time to time, one of them will be
> unreachable. If one uses 3 and this happens, there is nobody to break a
> tie.
>
> I recommend also having these top-tier time sources 'peer' with each other.
>
> What is your "interesting" issue with leap seconds?
>
> H
>
> On 4/8/2023 7:49 AM, MAYER Hans wrote:
> >
> > Dear All,
> >
> > I would say 3 ntp servers are also fine and good enough as there are never taken more than 3 servers.
> > If there are no stratum-1 server available I would define at least 4 pools for these 3 NTP servers.
> >
> > I can tell you what I have done. Without claim to be correct.
> > I have 3 stratum-1 server ( GPS, DCF77 and rubidium disciplined )
> > The GPS and DCF77 are peered with the same type of server with another organisation. In case the stratum-0 source would fail.
> > Below this I have 4 stratum-2 server which have also upstream servers from the Internet. Just in case all 3 internal stratum-1 would fail.
> > There I am using two different types of daemon software. And 3 of these 4 servers are public available as part of the AT-pool (Austrian) for IPv6.
> > And internally I use only 2 stratum-3 servers for all clients. Good enough as I manage and monitor complete NTP infrastructure.
> > These stratum-3 servers have defined all 4 of my stratum-2 servers I have and are not using any external time source.
> >
> > In my opinion it is not important to be accurate within a millisecond to the real time. It is more important that all devices have the same time.
> > This becomes interesting especially if there is a leap second.
> > Therefore all clients are not allowed to fetch the time from Internet and such traffic is prohibited by firewall.
> > To avoid that mis-configured clients have NO time I am using RPZ ( restricted policy zones ) in DNS where a lot of well known DNS names for NTP servers are rewritten to the internal IP address.
> >
> >
> > Kind regards
> > Hans
> >
> > —
> >
> >
> >
> >> On 08.04.2023, at 13:37, Terje Mathisen <terje.mathisen@tmsw.no> wrote:
> >>
> >> Renzo Marengo wrote:
> >>> Il giorno venerdì 7 aprile 2023 alle 13:44:59 UTC+2 David Woolley ha
> >>> scritto:
> >>>> On 07/04/2023 10:47, Renzo Marengo wrote:
> >>>>> I know NTP server numbers must be 1, 3 or 4,....
> >>>> I don't understand this. NTP servers don't have numbers. They do
> >>>> have a stratum, but that is determined automatically from the
> >>>> current time distribution tree.
> >>> I wanted to say... the number (quantity) of ntp server. Now I have 3
> >>> ntp server(NTP1, NTP2, NTP3), if I had had 2 servers it should be
> >>> always a good idea ? I remembered there was a reason to have a
> >>> similar quantity (that is 3)
> >>> Server A has stratum 2 Server NTP1, NTP2, NTP3 has stratum 3
> >>> What do you think if I destroyed the Server A and I converted the
> >>> NTP1, NTP2, NTP3 to stratum 2 ? I would link these 3 server to the to
> >>> same time source of server A.
> >> Your clients should all have at least 4 sources, so if you don't want them to talk to the outside world, that means having at least that many internal servers for them to reference.
> >>
> >> Terje
> >>
> >> --
> >> - <Terje.Mathisen at tmsw.no>
> >> "almost all programming can be viewed as an exercise in caching"
> >> --
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> >>
> >>
>
> --
> Harlan Stenn <stenn@nwtime.org>
> http://networktimefoundation.org - be a member!
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