[ntp:questions] Issues trying to sync to NIST public servers

François Meyer fmeyer at obs-besancon.fr
Thu Feb 7 14:33:44 UTC 2019

On Mon, 4 Feb 2019, Greg.Dowd at microchip.com wrote:

> I'm not certain I understand the traceability concern as stated  since
> they are  both  traceable  to  UTC.  NIST  servers  are  traceable  to
> UTC(NIST) while

" GPS is traceable to UTC(USNO) "

Well, that's the point.

>From the BIPM's point of view about "Metrological traceability" :


"...the result can be  related  to  a  reference  through  a  documented
  unbroken chain of calibrations..."

The key word here is "documented" ; since the process of
building/steering/calibrating GPS time out of UTC(USNO) is not publicly
documented (ie you wont find that in the BIPM's circular T, nor any
otherpublicly available source), GPS Time is not a priori traceable to UTC, it
takes at least some afterwards steps/checks to possibly fill the gap.
François Meyer

> It is true that NIST is
> charged with distributing time to commercial entities in the  US  (via
> WWVB/NTP/Popcorn/etc) so that is probably where the legal  requirement
> comes in. But as you say, I think you can make good arguments for have
> a more diverse (and robust) synchronization network with NIST  servers
> being an element of it.  Then,  with  proper  logging,  it  should  be
> possible to show the clock  reference  as  validated  by  NIST  server
> queries while not having to always be directly synchronized  to  them.
> Most servers are in free fall  all  the  time  anyway  with  just  the
> occasional ping to the servers. At least from a sync point of view.
> Greg Dowd
> Principal Engineer, FTD
> Microsemi
> 3870 N. First St. | San Jose | CA 95134 | USA
> Office: 408.964.7643
> Email: greg.dowd at microchip.com
> Company Website:  www.microsemi.com
> -----Original Message-----
> From: questions [mailto:questions-bounces+greg.dowd=microsemi.com at lists.ntp.org] On Behalf Of François Meyer
> Sent: Saturday, February 2, 2019 3:40 PM
> To: questions at lists.ntp.org
> Subject: Re: [ntp:questions] Issues trying to sync to NIST public servers
> Yes, the main reason behind the requirement is probably the traceability to UTC of the stratum 0 used by the server : NIST servers are traceable to UTC, which is (formally) not the case for a server with a GNSS as stratum 0.
> In case NIST servers are hard to reach, a metrologically defendable fallback could be to use ntp servers from another national metrology institute which would provide the same traceability to UTC.
> From the US, servers operated by the NRC in Canada is the most sensible (geographically speaking) option, and those servers have the same traceability status as NIST servers.
> https://www.nrc-cnrc.gc.ca/eng/services/time/network_time.html
> Just log the reason why you pick a server outside the US, locate and log the page on the NRC site stating the traceability to UTC of their time servers and Bob's your uncle ; thats enough to prove that you have taken the issue seriously and have taken the appropriate steps to ensure both your requirements and the traceability concern.
> In Europe, picking a server operated by for example PTB in Germany, OP (Syrte) in France, NPL in the UK and so on would do the job.
> On Fri, 1 Feb 2019, Jason Rabel wrote:
>>> Yes, this is a common PITA. FINRA and/or SEC getting onto you?
>>> They are still "defining" the regulation, but the current idea is rather silly.
>>> Many of the NIST servers are run out of the University of Colorado
>>> and are single home with CenturyLink. Congestion and/or other network
>>> issues causes false alarms all the time.
>> I don't know anything about the financial regulations, but what about
>> having a local GNSS or cellular based S1 NTP (or PTP) server? You will
>> gain an order of magnitude in accuracy syncing to a LAN source vs
>> traversing the Internet. Or possibly using the USNO NTP servers? I
>> suppose if it *has* to be traceable to NIST (which operates
>> independently of USNO/GPS) you could get a WWVB based NTP server. NIST
>> & USNO are generally less than 10 ns difference from each other, which
>> for NTP over ethernet the best you are going to get is in the ms range
>> so it's technically a non-issue.
>>> IMHO, if FINRA is going to require something like that, then NIST
>>> should provide hardened NTP/PTP services at major peering/colocation facilities.
>> Or use existing facilities at other major universities around the
>> country that could also benefit from having extra local NIST-synced
>> atomic standards.
>> I've often wondered why they don't have multiple network providers at
>> their two existing facilities, having a single point of failure seems
>> awfully ironic seeing as how they have dozens of atomic clocks and
>> servers in the facility... lol.
>> Though one has to remember this is also a very tiny part of overall
>> NIST. IIRC last time I saw NIST's 2019 budget figures they were taking
>> a pretty sizable cut in funding across the board, so expanding
>> services is probably out of the question unless it's deemed critical
>> for national security or something (Which I would think would still
>> fall under USNO & GPS before NIST).
>> Jason
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