Re: NTP question

[Harlan Stenn <stenn () nwtime org>]

On 5/1/19 7:54 PM, Mel Beckman wrote:
> Harlan,
>
> Why? The GPS NTP Server is Stratum-1.  If it fails computer clocks will freewheel for hours or days before losing 
> significant time, during which period you can simply order a replacement unit. If that isn’t fast enough, buy two 
> $300 boxes. The “consensus” issue is moot, since a GPS server gets a consensus of clock time from the GPS satellite 
> constellation. 
>
> The “enough NTP peers” you speak of are simply not necessary. 

You might be right about the GPS server.  It depends on how your $300
box behaves if it loses the GPS signal.

The consensus issue isn't about the number of satellites the GPS
receiver sees, it's about the number of time sources your NTP servers see.

H
--
> -mel via cell
>
> > On May 1, 2019, at 6:49 PM, Harlan Stenn <stenn () nwtime org> wrote:
> >
> >
> >
> > > On 5/1/19 4:53 PM, Mel Beckman wrote:
> > > Ask,
> > >
> > > But with a small compact server like the DC-powered TimeMachines Inc unit, which costs something like $300, you 
> > > simply put the server where the visibility is and connect back to the nearest Ethernet port in your network, up to 
> > > 300’ away, or virtually any distance with fiber transceivers. We’ve installed these in Cantex boxes on a windy, 
> > > rainy tenth-story rooftop in upstate NY and it runs flawlessly, warmed by its own internal heat at sub-zero temps, 
> > > and perfectly happy at ambient temps of 110F. 
> > >
> > > It’s hard to consider messing with signal converters and pricey remotely-powered active antennas when you can solve 
> > > the problem for $300. :)
> >
> > I sure hope you have ntpd set up to peer or get time with enough other
> > servers.
> >
> > H
> > --
> > > -mel 
> > >
> > > > On May 1, 2019, at 4:44 PM, Ask Bjørn Hansen <ask () develooper com> wrote:
> > > >
> > > >
> > > >
> > > > > On May 1, 2019, at 12:22, Mehmet Akcin <mehmet () akcin net> wrote:
> > > > >
> > > > > I am trying to buy a GPS based NTP server like this one 
> > > > >
> > > > > https://timemachinescorp.com/product/gps-time-server-tm1000a/
> > > > >
> > > > > but I will be placing this inside a data center, do these need an actual view of a sky to be able to get signal 
> > > > > or will they work fine inside a data center building? if you have any other hardware requirements to be able to 
> > > > > provide stable time service for hundreds of customers, please let me know.
> > > >
> > > > [ with my hobby-hat on … ]
> > > >
> > > > tl;dr: if any of the below is too much work, just run reasonably well monitored NTP server syncing from other NTP 
> > > > servers. If you want more than that, you need to see the sky. Don’t do the CDMA thing.
> > > >
> > > > Depending on your requirements having the antenna in the window may or may not be satisfactory. If it’s fine you 
> > > > probably could just have done a regular NTP server in the first place.  For long swaths of the day you might not 
> > > > see too many satellites which will add to the uncertainty of the signal.
> > > >
> > > > Meinberg’s GPS antenna has a bit more smarts which helps it work on up to 300 meters on RG58 or 700 meters on 
> > > > RG213.  (They also have products that use regular L1 antennas with the limitations Bryan mentioned).
> > > >
> > > > https://www.meinbergglobal.com/english/products/gps-antenna-converter.htm
> > > >
> > > > They also have a multi-mode fiber box to have the antenna be up to 2km from the box or 20km with their single mode 
> > > > fiber box, if you have fiber to somewhere else where you can see the sky and place an antenna.
> > > >
> > > > It will be more than the one you linked to, but their systems are very reasonably priced, too. For “hundreds of 
> > > > customers” whatever is the smallest/cheapest box they have will work fine. Even their smallest models have decent 
> > > > oscillators (for keeping the ticks accurate between GPS signals).
> > > >
> > > > The Meinberg time server products (I am guessing all of them, but I’m not sure) also have a mode where they poll 
> > > > an upstream NTP server aggressively and then steer the oscillator after it. I haven’t used it in production, but 
> > > > it worked a lot better than it sounded like it would.  (In other words, even without GPS it’s a better time server 
> > > > than most systems).
> > > >
> > > >
> > > > Ask
> >
> > -- 
> > Harlan Stenn <stenn () nwtime org>
> > http://networktimefoundation.org - be a member!

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