have you seen this before, 3 ms jumps every 6 hours - NTP

This is a discussion on have you seen this before, 3 ms jumps every 6 hours - NTP ; I'm seeing some funny behavior with NTP. My setup: I have an IRIG card feeding time source to a Symmetricon XLi time & frequency system box. The XLi is intended to be the NTP server for the rest of my ...

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Thread: have you seen this before, 3 ms jumps every 6 hours

  1. have you seen this before, 3 ms jumps every 6 hours

    I'm seeing some funny behavior with NTP.

    My setup: I have an IRIG card feeding time source to a Symmetricon XLi time
    & frequency system box. The XLi is intended to be the NTP server for the
    rest of my servers.

    The IRIG card is in one of the servers running Linux. As a test I had this
    server use the XLi as the NTP server, and they in a small program on the
    Linux box I compared the system time to the time on the IRIG card, to see
    how close the NTP can get to the IRIG reference.

    What I saw was very good performance of generally less than 1 ms match,
    however, at approximately 6 hour intervals, there was a 3 ms jump lasting
    about 10 minutes.

    I have a plot at http://home.twcny.rr.com/rkellog1/ntp5.jpg

    Does anyone have an explanation for this behavior?

    In this setup, the XLi is directly connected to the Linux server, and no one
    else is logged onto this isolated server.

    Thanks in advance.

    Rick



  2. Re: have you seen this before, 3 ms jumps every 6 hours

    RAK306 wrote:
    > I'm seeing some funny behavior with NTP.

    []
    > What I saw was very good performance of generally less than 1 ms
    > match, however, at approximately 6 hour intervals, there was a 3 ms
    > jump lasting about 10 minutes.

    []
    > Rick


    - what else happens every 6 hours?

    - does FreeBSD work better?

    David



  3. Re: have you seen this before, 3 ms jumps every 6 hours


    "David J Taylor"
    wrote in message news:Q1h1h.43861$r61.455@text.news.blueyonder.co.u k...
    > RAK306 wrote:
    >> I'm seeing some funny behavior with NTP.

    > []
    >> What I saw was very good performance of generally less than 1 ms
    >> match, however, at approximately 6 hour intervals, there was a 3 ms
    >> jump lasting about 10 minutes.

    > []
    >> Rick

    >
    > - what else happens every 6 hours?
    >

    Nothing as far as I can tell. This is a server running fedora core with no
    users acounts other than root, and no one using the machine. It was
    directly connected via crossover cable to XLi NTP server.

    > - does FreeBSD work better?

    This is not an option, unfortunately.


    Rick



  4. Re: have you seen this before, 3 ms jumps every 6 hours

    RAK306 wrote:
    > "David J Taylor"
    > wrote in
    > message news:Q1h1h.43861$r61.455@text.news.blueyonder.co.u k...
    >> RAK306 wrote:
    >>> I'm seeing some funny behavior with NTP.

    >> []
    >>> What I saw was very good performance of generally less than 1 ms
    >>> match, however, at approximately 6 hour intervals, there was a 3 ms
    >>> jump lasting about 10 minutes.

    >> []
    >>> Rick

    >>
    >> - what else happens every 6 hours?
    >>

    > Nothing as far as I can tell. This is a server running fedora core
    > with no users acounts other than root, and no one using the machine. It
    > was directly connected via crossover cable to XLi NTP server.
    >
    >> - does FreeBSD work better?

    > This is not an option, unfortunately.
    >
    >
    > Rick


    Then I can't help further, sorry.
    Perhaps you need to find a Fedora Core guru....

    David



  5. Re: have you seen this before, 3 ms jumps every 6 hours

    RAK306 wrote:

    > This is not an option, unfortunately.
    >
    >
    > Rick

    Have you had a look into the housekeeping stuff in cron.daily, cron.hourly ... ?

    look into /etc/cron* ;# some dirs, some files

    uwe

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