If you are using pool servers, best practice is to specify at least four
(that's the reason for having 1., 2., etc., so that you can select four
different ones). That way, if one of the them goes rogue it will be
exlcuded from the time solution but you will still have enough for a
correct time (there is a theory as to why three isn't enough). I
believe that Windows supports the use of multiple servers and the NTP
mitigation rules for deciding which ones are good, but you will probably
have to go to the registry.
If you want to use a single server, almost always the best one to use is
the one run by your ISP. More ISPs run these than advertise the fact,
and they are almost always time.<isp> or time1.<isp>, time2.<ips> etc.
Note that time server addresses are normally resolved at start up. The
latest reference implementations of ntpd will re-resolve pool servers
that stop responding, but I don't think that w32time has any specific
pool server support.
However, if you are radio amateur, and serious about time, you should be
using a local radio clock. The NTP reference version supports this,
even on Windows, although you are likely to need a non-USB serial port
for best performance. GPS receivers with pulse per second outputs are
available for a few tens of USD.
<http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html>
Times accurate to single figure microseconds are possible on Linux, but
one should really expect Windows to do better than single figure
milliseconds. (The figures in the article are likely to be for an
unloaded system and applications programmes can't normally read the time
to that high a resolution. They are also really repeatability, rather
than absolute accuracy, measurements. You need an even more accurate
clock to measure those.)
The GPS L1 Coarse/Acquisition signal should be able to obtain time
transfer accuracies of around 50ns, so GPS itself is not the weak link.
--
David Woolley
Owner K2 06123
On 28/06/15 00:02, Lynn W. Taylor, WB6UUT wrote:
The "pool" has a whole bunch of time servers, run by different
organizations. The people who run them can add them to the pool, or
remove them from the pool when they're about to be shut down.
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