svn commit: r320242 - head/etc/ntp

[Cy Schubert]

In message <2caa5927-9919-ce19-93f4-1005a5257295 at freebsd.org>, Allan Jude 
write
s:
> On 2017-06-22 21:04, Cy Schubert wrote:
> > In message <1498161747.66489.10.camel at freebsd.org>, Ian Lepore writes:
> >> On Thu, 2017-06-22 at 19:25 +0000, Cy Schubert wrote:
> >>> Author: cy
> >>> Date: Thu Jun 22 19:25:17 2017
> >>> New Revision: 320242
> >>> URL: https://svnweb.freebsd.org/changeset/base/320242
> >>>
> >>> Log:
> >>> Â  Update leap-seconds to leap-seconds.3701462400.
> >>> Â 
> >>>
> >>> Modified: head/etc/ntp/leap-seconds
> >>> =====================================================================
> >>> =========
> >>> --- head/etc/ntp/leap-seconds	Thu Jun 22 18:40:34 2017	
> >>> (r320241)
> >>> +++ head/etc/ntp/leap-seconds	Thu Jun 22 19:25:17 2017	
> >>> (r320242)
> >>> @@ -128,7 +128,7 @@
> >>> Â #		Washington, DC
> >>> Â #		jeffrey.prillaman at usno.navy.mil
> >>> Â #
> >>> -#	Last Update of leap second values:Â Â Â 6 Jul 2016
> >>> +#	Last Update of leap second values:Â Â 18 Apr 2017
> >>> Â #
> >> Â #	The following line shows this last update date in NTP
> >>> timestamp 
> >>> Â #	format. This is the date on which the most recent change to
> >>> @@ -136,7 +136,7 @@
> >>> Â #	be identified by the unique pair of characters in the first
> >>> two 
> >>> Â #	columns as shown below.
> >>> Â #
> >>> -#$	Â 3676752000
> >>> +#$	Â 3701462400
> >>> Â #
> >>
> >> Where did this leapfile come from? Â The last update of leap second
> >> values is supposed to change only when the actual list of offsets
> >> changes, not when the file is updated to just change an expiration
> >> date. Â This is actually very explicitly documented in the file itself,
> >> just a few lines down from this change:
> > 
> > The source of the leapfile is in the commit message. Here it is again:
> > 
> > Obtained from:  ftp://tycho.usno.navy.mil/pub/ntp/leap-seconds.3701462400
> > 
> >>
> >>   If an announcement by the IERS specifies that no leap second is 
> >>   scheduled, then only the expiration date of the file will 
> >> Â  be advanced to show that the information in the file is still
> >>   current -- the update time stamp, the data and the name of the file 
> >> Â  will not change.
> >>
> >>
> >>> -#	File expires on:Â Â 1 Jun 2017
> >>> +#	Updated through IERS Bulletin C 53
> >>> +#	File expires on:Â Â 1 Dec 2017
> >>> Â #
> >>> -#@	3705264000
> >>> +#@	3721075200
> >>> Â #
> >>
> >> This expiration is wrong too, dangerously so IMO. Â The data in the file
> >> is good through 12-31-2017-23:59:59, although historical practice has
> >> been to make the file expire a couple days before that. Â Making it
> >> expire 31 days early is about the worst possible choice... some systems
> >> for notifying clients/consumers of an impending leap second (or the
> >> lack thereof) only do so during the last month before the leap
> >> opportunity -- this has the file expire just at the point such software
> >> would consider it authoratative for dissemination. 
> > 
> > My guess is that USNO may have had reason to do so. I'll keep an eye on 
> > their next release of the file.
> > Â 
> >>
> >> I will note however, unlike the update date, there is no formal written
> >> description of how expiration date is determined, so the previous
> >> paragraph is just my opinion and experience working in the timing
> >> field.
> >>
> >> A leapfile without these problems can be found at
> >>
> >> Â Â ftp://time.nist.gov/pub/leap-seconds.list
> > 
> > We can use that instead. Attached is the diff between the USNO and NIST 
> > versions of the file.
> > 
> > One would think that two groups within the US Government might be able to 
> > produce a consistent leapfile. I suspect the real reason is that the USNO 
> > might have a different bureaucratic process than the NIST does.
> > 
> >>
> >>
> >> -- Ian
> >>
> >>> Â 2272060800	10	# 1 Jan 1972
> >>> Â 2287785600	11	# 1 Jul 1972
> >>> @@ -216,5 +216,5 @@
> >>> Â #	the hash line is also ignored in the
> >>> Â #	computation.
> >>> Â #
> >>> -#h	63f8fea8 587c099d abcf130a ad525eae 3e105052
> >>> +#h	3f004255 91f969f7 252361e5 27aa6754 eb6b7c72
> >>> Â #
> >>>
> >>
> > 
> > I'll update to the NIST version of the file.
> > 
> > 
> > 
> > 
> > 
> > 
> > Cheers,
> > Cy Schubert <Cy.Schubert at cschubert.com>
> > FreeBSD UNIX:  <cy at FreeBSD.org>   Web:  http://www.FreeBSD.org
> > 
> > 	The need of the many outweighs the greed of the few.
> > 
> 
> The NIST version does seem to have a number of improvements, like
> corrected typos etc, but:
> 
> -#	Last Update of leap second values:  18 Apr 2017
> +#	Last Update of leap second values:   8 July 2016
> 
> The USNO one seems newer. A bit strange.

That was Ian's issue. I think the following explanation makes sense: The 
leap second itself wasn't updated in the NIST version file cine July 8, 
2016, even though the file itself had been updated since then. I think  
USNO sees that date as the date the file itself was updated, not the leap 
second value, like NIST would appear it does. It sees like a fair 
hypothesis.


-- 
Cheers,
Cy Schubert <Cy.Schubert at cschubert.com>
FreeBSD UNIX:  <cy at FreeBSD.org>   Web:  http://www.FreeBSD.org

	The need of the many outweighs the greed of the few.