NTP Newbie, can anyone help out ? - NTP

This is a discussion on NTP Newbie, can anyone help out ? - NTP ; Hi All, I am currently at a site where we have workstations running an application program that requires accurate time. The application writes a date time stamp to a database, the dts is generated locally on the machine. Another applcation ...

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Thread: NTP Newbie, can anyone help out ?

  1. NTP Newbie, can anyone help out ?

    Hi All,

    I am currently at a site where we have workstations running an
    application program that requires accurate time. The application
    writes a date time stamp to a database, the dts is generated locally on
    the machine. Another applcation periodically copies data from the
    original database, to another database querying by the dts since it
    last ran. This is why the time needs to be accurate on all clients,
    please note though, that the dts resolution is only down to the second.

    All the client workstations currently use xntpd for time keeping, and
    we have a time server etc. all already configured, thing is we seem to
    still be getting issues where clients aren't having their time adjusted
    correctly, or maybe quickly enough ?

    I think NTP is just overkill for this site, I haven't done a full
    in-depth investigation into the NTP RFC's but it seems it is a very
    sophisticated time keeping protocol, and it has an algorithm that
    doesn't just slam the time back in line upon finding clock drift, also
    I have read that there maybe a maximum drift for which the protocol
    will adjust.

    We have hundreds of workstations and sometimes they may have been
    switched off for a peroid of time, or the CMOS battery may have died -
    does this affect NTP on the whole ?

    Basically, could someone give me a brief primer on NTP from a
    protocol/algorithm/operational point of view (if possible)

    I think we could be better with just a very basic SNTP ?, or just
    UDP/TIME implementation

    All we need is for the machine's time to be brought in line
    peroidically accurate to the second from a reference machine.

    Unfortunately we can't do this simply with login scripts because a) we
    don't have desktop permissions to change time, and b) users could be
    left logged in for days at a time, so we still need some sort of active
    time management.

    Sorry for the long post

    Cheers


  2. Re: NTP Newbie, can anyone help out ?

    There are costs and benefits everywhere.

    If it was me I'd figure out what the problems are on the few machines where
    you say you are having some problems syncing and just let ntp do its thing.

    Otherwise you have lots of machines and you are going to be bothered by
    different machines misbehaving on a fairly constant basis.

    H

  3. Re: NTP Newbie, can anyone help out ?

    apexi.200sx@hotmail.co.uk wrote:

    > Hi All,
    >
    > I am currently at a site where we have workstations running an
    > application program that requires accurate time. The application
    > writes a date time stamp to a database, the dts is generated locally on
    > the machine.



    > All the client workstations currently use xntpd for time keeping, and
    > we have a time server etc. all already configured, thing is we seem to
    > still be getting issues where clients aren't having their time adjusted
    > correctly, or maybe quickly enough ?


    Details please?? You can't fix it until you know what's happening!!
    Include the version of ntpd you are running. The name "xntpd" was
    changed to "ntpd" several years ago which suggests that you may be
    running a very old version.


    > We have hundreds of workstations and sometimes they may have been
    > switched off for a peroid of time, or the CMOS battery may have died -
    > does this affect NTP on the whole ?


    If you start ntpd in such a way as to ensure that the clock is correct
    or very close to correct initially it should not make much difference.
    With modern versions you use a -g switch to have it set the clock as it
    starts. With older versions you need to use ntpdate to set the clock
    before starting ntpd.

    Note that cold starting ntpd can require as much as thirty minutes to
    achieve tight synchronization. The frequency of the crystal oscillator
    that drives the clock is dependent on the temperature which tends to
    increase rapidly when the machine is started. It's best to leave the
    machines running if possible. If the electric bill is a problem, try to
    have someone turn on the machines thirty minutes before the work day starts.

    >
    > Basically, could someone give me a brief primer on NTP from a
    > protocol/algorithm/operational point of view (if possible)
    >

    There are links to a lot of documentation on the NTP web page:
    http://www.ntp.org/

    > I think we could be better with just a very basic SNTP ?, or just
    > UDP/TIME implementation


    SNTP is pretty crude! The times on two workstations could differ by as
    much as two seconds! With ntpd the difference between any two
    workstations should be less than one second; a lot less! With a
    properly designed and operated NTP subnet, it's possible keep a whole
    herd of machines within 10 to 20 milliseconds or better.
    >




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