[ntp:questions] Re: Setting Up NTP Subnet

Terje Mathisen terje.mathisen at hda.hydro.com
Wed Mar 8 18:08:09 UTC 2006

Harlan Stenn wrote:
> The best reason to have your S2 servers chat with different vendors of
> different technologies of refclocks is that sometimes they can go insane.
> It's one thing for the GPS system to go insane.
> It's something else for a vendor to discover a bug in one of their GPS
> products.  The odds are good that different GPS vendors will not have that
> same bug.
> I don't mean to pick on GPS here - feel free to choose whatever technology
> you prefer for that "slot".

This is exactly the reason why I am using multiple technologies as S1 
servers in our corporate network:

I started out with three different 'black box' NTP/GPS servers, from two 
different vendors, plus a home-made Motorola Oncore UT+ hosted on a 
FreeBSD machine.

Over the next ~5 years all the 'black box' systems failed badly at least 
once: I.e. they became falsetickers, claiming that the current time was 
something like 2034. :-(

Since the Oncore didn't do this, I've based the new infrastructure on 
4-5 of the last available Oncore's, plus one Garmin OEM 18 VLC, a 
Meinberg DFC-77 radio receiver located in a German office, the old boxes 
as backups, and a few internet peers as the last resort.

With same-LAN location as a S1 server, minpoll = maxpoll = 16 seconds, 
I'm seeing ~100 us precision on secondary servers.


- <Terje.Mathisen at hda.hydro.com>
"almost all programming can be viewed as an exercise in caching"

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