[time-nuts] OT: NTP server questions

Robert Darlington rdarlington at gmail.com
Wed Dec 1 01:10:14 UTC 2010


Hi Greg (and everyone!)

The environment will be dusty and hot and cold and hot and cold...   There
will be air conditioning but probably not much in the way of filtering.
Diesel and gas generators run out of fuel, UPS's are probably not going to
be going along with our stuff since they're too heavy.  I'm actually pretty
concerned about the heat issue getting out of control and we were kidding at
work about spontaneous fusion reactions due to the power density.  Our #1
problem with this project has been time synchronization.  Most of the big
issues were worked out but sometimes still crop up.  The really big issue we
see over and over is when people timestamp data and send that data into our
server, the timestamp doesn't meet our spec.  We require time in "UNIX time"
in whole numbers of seconds and assume UTC.  You'd be surprised at how many
months have passed since we first realized people were sending us time in
miliseconds so all dates looked like they were 40,000 years in the future.
Our computers are good but we don't have anywhere near that kind of
predictive capability.  The next big issue was when a sensor or some other
device sends the data to an intermediary that sends the data to us.  More
times than not there is a timezone correction done twice.  The sensor will
send in UTC and somebody will subtract 7 hours to put it into UTC again.
They're still doing this from time to time.  I recommended we modify our
message protocol to include a timezone offset to force people to think about
it but that opens a whole other can of worms.  Do you do it in seconds or
minutes or hours and introduce a whole other potential where people send in
the wrong format?

Guys, I think I have everything I need now -at least when it comes to mobile
time serving.  I really appreciate the responses.   Thank you.

-Bob

On Tue, Nov 30, 2010 at 5:35 PM, Greg Dowd <GDowd at symmetricom.com> wrote:

> Rob, you wound me :-)  Actually, the Meinberg unit is a great box.  The
> commercial devices pretty much all fit the need that you describe.  One
> caution I would make about them is the note about the environmentals.
> From experience I can tell you that a HV is a very harsh environment for
> shock and vib that could, and probably does, sometimes exceed the spec
> on these boxes.  For a box that has to survive repeated power cycles,
> dusty conditions with limited airflow and unmanned operation, the
> commercial boxes are optimal but can still have issues.  For OP, Rb in
> these devices is primarily targeted at holdover, providing extended
> periods of NTP service when the input time source (e.g. GPS) is lost.
> It doesn't sound like this is a requirement for your application.
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Rob Kimberley
> Sent: Tuesday, November 30, 2010 7:55 AM
> To: 'Discussion of precise time and frequency measurement'
> Subject: Re: [time-nuts] OT: NTP server questions
>
> FWIW, you can't go wrong with Meinberg.
>
> Several  versions to choose from, reliable, and priced well.
>
> Rob Kimberley
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Robert Darlington
> Sent: 30 November 2010 2:47 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] OT: NTP server questions
>
> Basically I need something to provide time within one second.  I can't
> roll
> my own in this case.  At home I have a Soekris box with a custom built
> gps
> board for my normal level of time-nuttery but this is not for home.  I'm
> looking for commercially made rack mount servers that will not have
> Internet
> access for reference and will need to rely on gps.   The system will
> need to
> serve time to less than 100 systems but it will live in a nasty
> environment
> in the back of a humvee (or something like an S-250 electronics
> enclosure)
> with no air conditioning of any sort.  I'm currently looking at
> Symmetricom,
> Trimble NetRS, EndRun, and Meinberg.
>
> Also, I apologize if I'm breaching protocol with this thread.  This is
> just
> about the first post I ever saw on this list that didn't get a steady
> stream
> of replies.  I was actually questioning if this even made it into the
> list
> till I saw this reply.  Yes this is for work and I could really use some
> opinions on this stuff since dropping $4-6k isn't in my nature to do at
> home
> for a network clock so I never gave this thought before.
>
> Thanks again,
> Bob
>
>
> On Mon, Nov 29, 2010 at 11:39 PM, Chris Albertson
> <albertson.chris at gmail.com
> > wrote:
>
> > What do you need to do?  What precision is required and how many
> > clients will
> > you be serving.   For most "normal" uses you don't need a special
> purpose
> > server system.  A $600 notebook PC and any GPS unit with a serial
> > connection and a copy of Linux or BSD.
> >
> > On Mon, Nov 29, 2010 at 11:36 AM, Robert Darlington
> > <rdarlington at gmail.com> wrote:
> > > Hi guys,
> > >
> > > I'm looking to buy an NTP server for a field deployable server
> > > system.  I currently have a Symmetricom SyncServer S250 which does
> more
> than I need.
> >  I
> > > am considering buying an S200 (same as the S250 but without the
> > > ability
> > to
> > > connect to an external frequency standard).  My gut feeling is I
> > > don't
> > need
> > > a rubidium oscillator or even an OCXO internally since we'd be going
>
> > > from
> > a
> > > power on to being used state in under an hour, outside of any kind
> > > of temperature controlled environment.  Are there any manufacturers
> > > out
> > there
> > > besides Symmetricom that I should be looking at for something like
> this?
> > > The unit we're considering buying is about $4k new and is inside of
> > > our budget.
> > >
> > > Thanks,
> > > Bob
> > > _______________________________________________
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> > > and follow the instructions there.
> > >
> >
> >
> >
> > --
> > =====
> > Chris Albertson
> > Redondo Beach, California
> >
> > _______________________________________________
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> >
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