Offset is Slowly Increasing Over Time - NTP

This is a discussion on Offset is Slowly Increasing Over Time - NTP ; If the dispersion on a client machine is spiking at 8 seconds does that indicate that my NTP server wants to be a rodeo cowboy? But seriously... I gathered up the loop and peer stats per the FAQ, posted here: ...

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Thread: Offset is Slowly Increasing Over Time

  1. Offset is Slowly Increasing Over Time

    If the dispersion on a client machine is spiking at 8 seconds does that
    indicate that my NTP server wants to be a rodeo cowboy? But seriously...

    I gathered up the loop and peer stats per the FAQ, posted here:

    http://www.stradamotorsports.com/~jcw/NTP_Stats.xls

    If I restart all the NTP processes on my network I can get my clocks to
    sync for a while. At some later time the offset creeps up to over one
    second and the clients will reject my server.

    The dispersion graph is interesting. The offset doesn't seem to
    misbehave in a pattern resembling dispersion.

    About the only thing that I can tell from the graphs is that they are
    pretty. I was hoping that some good natured soul would look at them and
    say, "Here's your problem."

    My local NTP server syncs with my ISP just fine.

    Thanks,
    Jason C. Wells

  2. Re: Offset is Slowly Increasing Over Time

    Jason C. Wells wrote:
    > If the dispersion on a client machine is spiking at 8 seconds does that
    > indicate that my NTP server wants to be a rodeo cowboy? But seriously...
    >
    > I gathered up the loop and peer stats per the FAQ, posted here:
    >
    > http://www.stradamotorsports.com/~jcw/NTP_Stats.xls
    >
    > If I restart all the NTP processes on my network I can get my clocks to
    > sync for a while. At some later time the offset creeps up to over one
    > second and the clients will reject my server.
    >
    > The dispersion graph is interesting. The offset doesn't seem to
    > misbehave in a pattern resembling dispersion.
    >
    > About the only thing that I can tell from the graphs is that they are
    > pretty. I was hoping that some good natured soul would look at them and
    > say, "Here's your problem."
    >
    > My local NTP server syncs with my ISP just fine.
    >
    > Thanks,
    > Jason C. Wells


    On the PC where you recorded your peerstats, did you reboot it and/or
    otherwise cause an intermittent connection with the NTP server(s) upstream?

    There's one period of nearly 18 days between syncs and two other gaps of
    nearly 2 days. The other spikes are where your offset exceeded a
    certain window, and ntpd stepped the clock instead of slewing it.
    That's why your offset goes, for instance, from -1.4 seconds to nearly
    zero in one step.

    The numbers in your dispersion column seem fine. If there's a big
    offset--such as the ones after rebooting--the number goes up, and ntpd
    whittles that down as it gets closer to the one correct time.

    You might post the server lines and maybe the filegen lines in your
    ntp.conf file. If I had to make one based on the results, it might look
    like this:

    server 192.168.1.204 minpoll 14 maxpoll 17 iburst

    But then again, maybe your data is a snippet from a longer file, and I
    didn't see where the local NTP server started with polling intervals
    like 32s and 64s.

    Michael

  3. Re: Offset is Slowly Increasing Over Time

    What command-line flags are you using when you start ntpd?

    What do your ntp.conf files look like?

    H

  4. Re: Offset is Slowly Increasing Over Time

    Jason C. Wells wrote:
    > If the dispersion on a client machine is spiking at 8 seconds does that
    > indicate that my NTP server wants to be a rodeo cowboy? But seriously...
    >
    > I gathered up the loop and peer stats per the FAQ, posted here:
    >
    > http://www.stradamotorsports.com/~jcw/NTP_Stats.xls
    >
    > If I restart all the NTP processes on my network I can get my clocks to
    > sync for a while. At some later time the offset creeps up to over one
    > second and the clients will reject my server.
    >
    > The dispersion graph is interesting. The offset doesn't seem to
    > misbehave in a pattern resembling dispersion.
    >
    > About the only thing that I can tell from the graphs is that they are
    > pretty. I was hoping that some good natured soul would look at them and
    > say, "Here's your problem."
    >
    > My local NTP server syncs with my ISP just fine.
    >
    > Thanks,
    > Jason C. Wells


    Dispersion is the accumulated error between the root (atomic clock
    somewhere) and your server. A value of eight seconds indicates a
    complete and total disaster! Eight milliseconds would be extremely
    worrisome! Eight microseconds maybe?

    If the graphs are pretty, how about if you draw them and post them on a
    web site somewhere. Downloading your loopstats file and graphing them
    locally is too much like work.


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