David,
On 10/25/2012 07:03 AM, David J Taylor wrote:
Magnus,
If it helps, I have my own measurements of the Meinberg NTP port and
later versions running on Windows here:
http://www.satsignal.eu/mrtg/performance_ntp.php
Strategy:
1 - have one FreeBSD (not Linux) server, although this is now not
essential, but it's nice as a confirmation that the rest is working OK.
2 - Configure some Windows PCs as stratum-1 servers fed from GPS. On the
plots above, PCs Alta, Bacchus, Feenix and Stamsund are acting as
stratum-1 servers. These all have serial port connections, and cover the
OS range Windows 2000, XP, Win-7/32 and Win-7/64. All are using the
kernel-mode serial port driver patch developed by Dave Hart. PC Pixie is
the FreeBSD box.
3 - For the client PCs, use a fixed 32-second polling interval to the
local stratum-1 servers, with Internet servers as a backup polled at
1024 seconds, resulting in a configuration file something like:
_______________________________________________
# Use drift file
driftfile "C:\Tools\NTP\etc\ntp.drift"
# Use specific local NTP servers
server 192.168.0.3 iburst minpoll 5 maxpoll 5 prefer # Pixie
server 192.168.0.2 iburst minpoll 5 maxpoll 5 # Feenix
server 192.168.0.7 iburst minpoll 5 maxpoll 5 # Stamsund
# Use pool NTP servers
pool uk.pool.ntp.org iburst minpoll 10
_______________________________________________
The client performance varies, with some of the best results being on a
Windows-8 Wi-Fi connected PC which seems to have very good drivers (PC
Bergen). Jitter is 40 - 110 microseconds. Windows XP also shows low
jitter, but greater offset (within 250 microseconds).
Windows Vista was the worst performer I had, but that PC has now been
retired. There are discussions in progress at the moment about improving
Windows-Vista and Windows-7 as a Windows time interval setting and
reporting bug has been discovered, particularly affecting NTP.
Lovely! I'm impressed.
What's the reasons for the offsets? Can't your tool handle negative values?
It would be good to have min, max, max-min, avg, std.dev values without
offsets to help illustrate worst-case behaviour as well as average
performance and noise "energy". The more advanced plotter would show
MADEV, TDEV and MTIE plots. Ah well.
Would it be possible to set up so you could measure deviation on SNTP
and undisciplined machines?
PS. Have my summerhouse not to far away from the town Ystad.
Cheers,
Magnus
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
