On Mon, 4 Feb 2019, greg.d...@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" :
https://www.bipm.org/en/bipm-services/calibrations/traceability.html
"...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.d...@microchip.com
Company Website: www.microsemi.com
-----Original Message-----
From: questions
[mailto:questions-bounces+greg.dowd=microsemi....@lists.ntp.org] On Behalf Of
François Meyer
Sent: Saturday, February 2, 2019 3:40 PM
To: questions@lists.ntp.org
Subject: Re: [ntp:questions] Issues trying to sync to NIST public servers
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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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