[ntp:hackers] Re: NTP and leap-seconds

Tim Shoppa shoppa at trailing-edge.com
Tue Jul 4 15:56:54 UTC 2006

"todd glassey" <todd.glassey at worldnet.att.net> wrote:
> I have suggested that NIST and USNO and the other National Timing
> Laboratories submit secured notice - through signed emails, to the Satellite
> Timelords of the Non-Federally Operated leaves of the global NTP Services.
> I am a Professional Auditor, and as such assure you folks that the US
> Government already uses the exact same thing for Notices of Electronic Court
> Activities... So it does work.There is an entire practice model which if
> this group is interested, I can submit later this week.

All of this seems like extreme overkill considering that few of the
OS's that underly NTP, and very few syscalls/libraries/applications,
support the concept of leap seconds in a Good Way. Usually
we just want to supply non-leapsecond aware applications
with a monotonically increasing time that isn't off by more than 
a second or so in a leapsecond event.

There are a very few OS's that do support TAI-like timescales (e.g.
a base clock that always ticks forward one second every second no matter
what) and use OS-supplied tables to do leapsecond and timezone/calendar magic.
But as far as I know none of them use NTP nor do they support automagic
net propogation of leapsecond/timezone tables. An example is z/OS.
I could be wrong and maybe parallel sysplex operation now allows NTP supplied
time; I am not a Mainframe Guru although I do bump my horns up against
their horns at meetings :-) Last time I checked a refclock for a
parallel sysplex rang in in the $30000-$60000 price tag.

Of course a similar tick-forward-a-second-every-second-no-matter-what
timescale is the GPS timescale. And even there, there are a lot of
embedded timing devices that do NOT properly interpret the leapsecond
corrections distributed (e.g. Z3801A's) in all circumstances and
we end up with NTP drivers for those GPS refclocks that apply their
own correction to the leapsecond-pending flag correction!


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