Re: Sub-millisecond NTP synchronization for local network

Unruh wrote:
"Richard B. Gilbert" <rgilbert88@xxxxxxxxxxx> writes:

Unruh wrote:
"Richard B. Gilbert" <rgilbert88@xxxxxxxxxxx> writes:

Unruh wrote:
"Richard B. Gilbert" <rgilbert88@xxxxxxxxxxx> writes:


There are other tools than NTPD. One called "chrony" MAY meet your needs, or may not. NTPD is very good at working over the Internet with its unpredictable queuing delays. Chrony, as I understand it, is not so good at working over the internet.
No idea where you get this from. chrony works over the internet at least as
well as does ntpd. Its philosophy of dealing with different delays is
different than ntp's( although it can be set up to be virtually identical)


If you can't keep your machines up 24x7, chrony MAY be a better tool. It's possible that you will need something else entirely.
Possibly true.


You may find that a hardware reference clock; e.g. a GPS timing receiver, will help. With a GPS timing receiver, you will not be dependent on the internet for time sources. NTPD will still need about thirty minutes to gain really tight synchronization. Once gained, synchronization should be stable as long as the machine is up.
Actually it is much worse than that. On my system, on bootup the clock
frequency can very by up to about 50PPM due to a Linux bug. In general it
takes ntp about 10 hours to regain tight synchronisation. (In that case it
is microsecond since it is synching to a GPS, but it is also on poll level
4 so it has lots of data and should converge faster than some other system
on poll level 6-10). David Mills has always insisted that ntpd is designed
for stable long time operation, and rapidity of response is a distant 49th
or so in priority.

My Solaris 8 SPARC system seems to be able to synch with the GPS receiver in about 30 minutes. I may reboot that system once a year
IF the frequency after reboot is very close to the frequency before (<1PPM
say) and the clock has not drifter far out ( 1ms say) then sure. Otherwise
it is a disaster.

unless we have a power outrage that lasts longer than the UPS battery!
Absent something like a power failure there's no real reason to reboot it at all.
Well, no. Power supply intermittent failure can have you rebooting 10 times
a week. (Yes, that is experience talking-- three weeks ago)


Your power quality seems to be a LOT worse than mine. It has been

Not my power quality, my power supply quality. I put in a new power supply
and so far no more reboots.

almost a year since the last time power went off here. A guy a couple of blocks from here trimmed the trees that were in contact with the power lines and that has made a HUGE difference.

I have UPS for most of the machines in the house. They never notice the brownouts and most of the blackouts!

They do notice it if a capacitor in the computer power supply fries however.


Who made that machine?? How old was it?

I've owned personal computers of one sort or another for a bit more than 20 years! I had only ONE power supply failure and that was a "white box" PC clone. It was so many years ago that I have almost forgotten it. For the last several years I've been using Compaq/HP machines which have been free from HARDWARE problems. Wish I could say the same for the software!!

I do use some "power conditioning" boxes from a company called "Zero Surge" which were highly recommended to me by a friend. Basically it's a low pass filter that eats "spikes" in the line voltage and protects both the UPS and the computer.
.

Relevant Pages

  • Re: Sub-millisecond NTP synchronization for local network
    ... Chrony, as I understand it, is not so ... good at working over the internet. ... well as does ntpd. ... IF the frequency after reboot is very close to the frequency before (<1PPM ...
    (comp.protocols.time.ntp)
  • Re: Sub-millisecond NTP synchronization for local network
    ... Chrony, as I understand it, is not so ... good at working over the internet. ... well as does ntpd. ... IF the frequency after reboot is very close to the frequency before (<1PPM ...
    (comp.protocols.time.ntp)
  • Re: Sub-millisecond NTP synchronization for local network
    ... NTPD is very good at working over the Internet with its unpredictable queuing delays. ... Chrony, as I understand it, is not so good at working over the internet. ... Absent something like a power failure there's no real reason to reboot it at all. ...
    (comp.protocols.time.ntp)
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    ... get email but could not access the internet. ... I would say reboot the network equipment. ... I lose internet connection if my network equipment goes awol. ... Power out will cause problems if the power out is not long enough. ...
    (microsoft.public.windows.mediacenter)
  • Re: XP SP2 reboots when PC2 is switched on
    ... there is no event log. ... It goes down as if you had cut the power, ... The reboot is normal without any problems ... >> internet, ...
    (microsoft.public.windowsxp.network_web)