[ntp:questions] NTP under AIX?

Miroslav Lichvar mlichvar at redhat.com
Fri May 19 07:56:04 UTC 2017


On Thu, May 18, 2017 at 03:32:42PM -0400, Paul wrote:
> On Thu, May 18, 2017 at 3:06 PM, Brian Inglis <
> Brian.Inglis at systematicsw.ab.ca> wrote:
> > A lot of these types of boxes appear to be some type of SoC board with
> > some GPS module, some Linux distro, some NTP release, probably GPSd,
> > and with little in the way of docs, specs (typical: <1us!), guarantees,
> > or likely support and maintenance. They often feature pictures of fancy
> 
> I assume here you are referring to classic NTP appliances from folks like
> Spectracom, MicroSemi or EndRun (if they still exist).  I would expect the
> LeoNTP to be more like Tharp's Laureline (V2) (
> https://partiallystapled.com/pages/laureline-gps-ntp-server.html) and not
> actually run anything one would recognize as NTP -- except for network
> packets.  I think of these things as being network attached GNSS modules
> that use NTP compatible packets for time transfer.

Yes, it doesn't look like the LeoNTP runs a regular OS. From what I
hear it actually delivers what they promise. One issue I've heard
which may affect accuracy is that it doesn't support 1gbit ethernet
and the difference in link speed may create an asymmetric delay in
the network switch.

Does anyone sell an NTP appliance with sub-microsecond accuracy and
1gbit ethernet?

As modern NICs support hardware timestamping, it's possible to
synchronize computers to few tens or hundreds of nanoseconds, but the
choice of NTP servers with such accuracy is very limited. For people
who don't want to spend money on new switches with PTP support, it may
be better to buy a PTP grandmaster and connect it directly to a
machine with two NICs, which would be a PTP slave and an NTP server
for other machines in the network.

-- 
Miroslav Lichvar


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