[time-nuts] clock-block any need ?
Attila Kinali
attila at kinali.ch
Sun Dec 30 10:03:29 UTC 2012
On Fri, 28 Dec 2012 19:18:06 -0800
Hal Murray <hmurray at megapathdsl.net> wrote:
>
> attila at kinali.ch said:
> > From the data ntp gives me in the networks i manage. I hardly get any
> > jitter number below 1ms, even with unloaded network and unloaded hosts. The
> > 200us comes from the "usual" rtt time measurements on PCs.
>
> What sort of networks are you talking about? Are you synchronizing over LAN
> or WAN? Do you have a local refclock?
LAN, mostly two switches inbetween machines, no local refclock.
> On LANs with non-ancient PCs, it's easy to get round trip times under 200
> usec. That makes it hard to get jitter over 1 ms. Or, if the jitter is that
> bad, how can you call the network unloaded?
>
> Here are a couple of ntpq printouts:
For me it usually looks like this:
# ntpq -pn
remote refid st t when poll reach delay offset jitter
==============================================================================
*192.168.0.100 192.33.96.102 2 u 348 1024 377 0.450 0.530 1.132
Some better, some worse.
On the other hand, it's enough when these machines are synced better
than to a fraction of a second. They don't do anything critical with
their relative timing. Thus i never bothered to decrease the jitter.
Attila Kinali
--
There is no secret ingredient
-- Po, Kung Fu Panda
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