remote NTP server - NTP

This is a discussion on remote NTP server - NTP ; Is it possible, (even practical) to configure a server as part of an autonomous, system nothing more than a GPS receiver providing PPS but with no connection to any part of the global "network" and if so what is a ...

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  1. remote NTP server

    Is it possible, (even practical) to configure a server as part of an
    autonomous, system nothing more than a GPS receiver providing PPS but
    with no connection to any part of the global "network" and if so what
    is a minimally resourced single board computer up to the task of
    serving NTP to half a dozen other similar machines?

  2. Re: remote NTP server

    Depending on needed stability, if you're talking about "within a few
    milliseconds, give or take", pretty much any motherboard with an Ethernet
    port, memory, and some kind of disk looking storage. You could do it with
    nothing more than a Via ITX motherboard, stick of memory, power supply, and
    USB flash drive running FreeBSD.

    "kvdh" wrote in message
    news:ebcef7ae-c50c-40c3-9570-f45802e97202@34g2000hsh.googlegroups.com...
    > Is it possible, (even practical) to configure a server as part of an
    > autonomous, system nothing more than a GPS receiver providing PPS but
    > with no connection to any part of the global "network" and if so what
    > is a minimally resourced single board computer up to the task of
    > serving NTP to half a dozen other similar machines?




  3. Re: remote NTP server

    On 2008-06-25, kvdh wrote:

    > Is it possible, (even practical) to configure a server as part of an
    > autonomous, system nothing more than a GPS receiver providing PPS
    > but with no connection to any part of the global "network"


    Yes. I've done it with a Soekris NET4801 ($231) and a Garmin GPS-18LVC
    (~$70)

    > and if so what is a minimally resourced single board computer up to
    > the task of serving NTP to half a dozen other similar machines?


    The Soekris NET4501 ($173) ought to be up to the task:

    https://www.soekris.com/shop/product...products_id=75

    --
    Steve Kostecke
    NTP Public Services Project - http://support.ntp.org/

  4. Re: remote NTP server

    kvdh wrote:
    > Is it possible, (even practical) to configure a server as part of an
    > autonomous, system nothing more than a GPS receiver providing PPS but
    > with no connection to any part of the global "network" and if so what
    > is a minimally resourced single board computer up to the task of
    > serving NTP to half a dozen other similar machines?


    Poul Henning Kamp (PHK) has done just this. I don't recall the
    manufacturer & model of the SBC he used. Google might help.

  5. Re: remote NTP server

    On 2008-06-26, Richard B. Gilbert wrote:

    > kvdh wrote:
    >
    >> Is it possible, (even practical) to configure a server as part of an
    >> autonomous, system nothing more than a GPS receiver providing PPS
    >> but with no connection to any part of the global "network" and if so
    >> what is a minimally resourced single board computer up to the task of
    >> serving NTP to half a dozen other similar machines?

    >
    > Poul Henning Kamp (PHK) has done just this. I don't recall the
    > manufacturer & model of the SBC he used. Google might help.


    Soekris NET4501

    --
    Steve Kostecke
    NTP Public Services Project - http://support.ntp.org/

  6. Re: remote NTP server

    On Jun 25, 10:49 pm, Steve Kostecke wrote:
    > On 2008-06-25, kvdh wrote:
    >
    > > Is it possible, (even practical) to configure a server as part of an
    > > autonomous, system nothing more than a GPS receiver providing PPS
    > > but with no connection to any part of the global "network"

    >
    > Yes. I've done it with a Soekris NET4801 ($231) and a Garmin GPS-18LVC
    > (~$70)
    >
    > > and if so what is a minimally resourced single board computer up to
    > > the task of serving NTP to half a dozen other similar machines?

    >
    > The Soekris NET4501 ($173) ought to be up to the task:
    >
    > https://www.soekris.com/shop/product...products_id=75
    >
    > --
    > Steve Kostecke
    > NTP Public Services Project -http://support.ntp.org/


    RE: ntp serving. How exactly does the server sync to information
    provided by a GPS receiver? Does it simply read the RMC string or
    equivalent on a serial port
    or does it also use the PPS as in interrupt and if the later is
    necessary, is that received via an SBC's parallel port bit. Does
    the server then make time information available on request?

  7. Re: remote NTP server

    kvdh wrote:
    >
    > RE: ntp serving. How exactly does the server sync to information
    > provided by a GPS receiver? Does it simply read the RMC string or
    > equivalent on a serial port


    You generally need either the NMEA string or some other source of time
    to differentiate between seconds. You can use just NMEA, but, with most
    receivers, that has a lot of jitter, and you will have to configure a
    large correction for systematic error.

    > or does it also use the PPS as in interrupt and if the later is
    > necessary, is that received via an SBC's parallel port bit. Does


    Generally PPS is read using a modem control line on the serial port.

    Note that ntpd then phase locks the software clock to this information,
    so individual measurements will, typically, have a larger error than the
    time on the software clock (except for systematic errors).

    > the server then make time information available on request?


    Yes.

  8. Re: remote NTP server

    On 2008-06-27, kvdh wrote:

    > RE: ntp serving. How exactly does the server sync to information
    > provided by a GPS receiver? Does it simply read the RMC string
    > or equivalent on a serial port or does it also use the PPS as in
    > interrupt


    A timing GPS provides both an NMEA sentence (which labels the seconds)
    and a PPS signal (which marks to top of the second, usually within 1us
    of UTC).

    The ntpd on the server uses both of these pieces of information
    to discipline, or steer, the server clock.

    > and if the later is necessary, is that received via an SBC's parallel
    > port bit.


    The Generic NMEA driver reads the PPS signal on the serial port DCD
    line.

    Other configurations are possible.

    > Does the server then make time information available on request?


    The ntpd on the server answers polls from other ntpds, and sntp
    instances, on the "client" systems.

    --
    Steve Kostecke
    NTP Public Services Project - http://support.ntp.org/

  9. Re: remote NTP server

    It's also possible to buy NTP appliances, some of which are basically
    just what you describe: a GPS coupled to an SBC.

    See for example http://www.meinberg.de/english/produ...e-m300-gps.htm.

    Paul

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