[ntp:questions] Looking for a NTP stratum 2 appliance

François Meyer fmeyer at obs-besancon.fr
Mon May 29 08:24:50 UTC 2017


On Sat, 27 May 2017, Matthew Huff wrote:

> I'll pass this along to our auditors, but I doubt  it  will  make  any
> difference. For another  example,  we  had  to  block  all  access  to
> removable USB drives because  of  possible  transfer  of  unauthorized
> data, but DropBox was okay. We have to archive all  IM  messages,  but
> not phone calls. /boggle
>
> Again, the goal is to satisfy auditors, not do the  right  thing.  But
> either way, we are synced to two S1 clocks on all of our  ntp  clients
> which have their source as GPS. So we are correct, either way.

I jump in the discussion, you can probably get out of problems just
by adding some infos in your QMS, detailing why you need (or not)
to check the UTC(NIST) - GPSTime traceability, and how you achieve
that, if needed ; since NIST declares it provides this information (with a
24 hour delay), you can rely on this to setup a more or less automatic
online check from the NIST website (that would prove to be technically 
useless since offests will stubbornly be 0 as far as milliseconds are concerned).
Instead of useless equipment, it is a one time documentation job, a daily 
automated data retrieval and check with email alarm for example.

Arguing against possible objections to the 24 hour delay is left to the reader :)
If you do need a proven, real time access to UTC(whatever) <5ms, then it might get 
a bit muddier.

(The problem is not between UTC(NIST) and UTC(USNO), both are
equivalently traceable to SI ; the problem is with GPS Time, 
that is not UTC(USNO) and not traceable)

> ----
> Matthew Huff             | 1 Manhattanville Rd
> Director of Operations   | Purchase, NY 10577
> OTA Management LLC       | Phone: 914-460-4039
> aim: matthewbhuff        | Fax:   914-694-5669
>
>
>> -----Original Message-----
>> From: questions [mailto:questions-bounces+mhuff=ox.com at lists.ntp.org]
>> On Behalf Of Paul
>> Sent: Saturday, May 27, 2017 1:32 AM
>> To: Harlan Stenn <stenn at ntp.org>
>> Cc: NTP Questions <questions at lists.ntp.org>
>> Subject: Re: [ntp:questions] Looking for a NTP stratum 2 appliance
>>
>> On Fri, May 26, 2017 at 10:33 PM, Harlan Stenn <stenn at ntp.org> wrote:
>>
>>> NIST doesn't control GPS.  That's done by USNO and the USAF.
>>>
>>
>> This is true(ish)* but irrelevant.  NIST defines traceability to NIST
>> and
>> GPS can be a component of UTC(NIST) traceability.
>>
>> More importantly the premise of this issue is incorrect (if it has been
>> properly presented).  If I have an S2 clock peering both with a GPS
>> disciplined S1 clock and a NIST clock via NTP then "apparent" errors
>> ("drift") are measurements of network instability not variance from
>> UTC(NIST).  E.g. this line:
>>
>>  time-d.nist.gov .NIST.           1 u   35  512    7   48.037    1.714
>> 2.137
>>
>> does not mean this clock has a 1.7ms offset and 2.1ms of jitter with
>> respect to UTC(NIST).
>>
>> Since NIST specs the NTP error O(50ms) due to network issues it's
>> insufficient for the stated need in any case.
>>
>> *NIST publishes the delta and the two groups work to maintain
>> constrained
>> offset between UTC(NIST) and UTC(USNO) so they can be considered
>> equivalent
>> instances of UTC in the US.
>> _______________________________________________
>> questions mailing list
>> questions at lists.ntp.org
>> http://lists.ntp.org/listinfo/questions
> _______________________________________________
> questions mailing list
> questions at lists.ntp.org
> http://lists.ntp.org/listinfo/questions
>

-- 
François Meyer    Tel : (+33) 3 81 66 69 27   Mob : 6 27 28 56 83
Observatoire de Besancon - BP1615 - 25010 Besancon cedex - FRANCE
Institut UTINAM * Universite de Franche-Comte * CNRS UMR 6213 ***


More information about the questions mailing list