On Thu, 2023-12-21 13:58:21 +0100, Johnny Billquist <bqt%softjar.se@localhost> wrote:
> On 2023-12-21 13:53, Jan-Benedict Glaw wrote:
> > On Thu, 2023-12-21 12:49:06 +0100, Johnny Billquist <bqt%softjar.se@localhost> wrote:
> > > On 2023-12-21 12:14, Jan-Benedict Glaw wrote:
> > > > Looking at the numbers, I wonder about multiple issues here. Why did
> > > > the jitter values rise up that much, while the delay keeps its value?
> > >
> > > Unless I remember wrong, delay is merely how long it takes for packets to
> > > travel back and forth to the ntp server. So it has no relation to jitter or
> > > offset. It would rather be weird if delay suddenly started changing.
> >
> > delay is ... "ping time". jitter is a measure of how much ping times
> > differ to each other.
>
> Right for delay. But no for jitter. Jitter is, unless I remember wrong,
> comparison between your local clock and the server clock, and how much they
> are shifting around compared to each other. It has nothing to do with ping
> times.
>
> And jitter have to get low for ntp to start syncing, since it's not possible
> to do any kind of syncing if local time is moving around too much compared
> to server time. It becomes impossible to tell how local time should be
> modified in such a case.
Referring to https://kb.meinbergglobal.com/kb/time_sync/ntp/ntp_basics
("Checking ntpd's Time Adjustment Performance"), it lists:
delay The mean packet delay, in milliseconds. This is the mean
execution time required to send a read request to the time
source, and receive the reply from that source.
offset The mean time offset, in milliseconds.
jitter The time jitter, in milliseconds. This indicates how much
packet delays from individual pollings vary from the mean
packet delay.
But to tell for sure, we'd have to dive in into ntpd's code to prepare
`ntpq`'s `peers` data.
MfG, JBG
--
Attachment:
signature.asc
Description: PGP signature