[tz] Google moves beyond NTP

Phil Pennock tz-list+phil.pennock at spodhuis.org
Tue Nov 27 01:33:04 UTC 2012

On 2012-11-26 at 14:22 -0800, Steve Allen wrote:
> On Mon 2012-11-26T13:10:03 -0800, Eric Fischer hath writ:
> > I'm no NTP expert so I'm not sure what it does differently, but the more
> > detailed paper is at http://research.google.com/archive/spanner.html
> In which it looks as if google has taken on the task of creating its
> own global time scale (a task previously only attempted by national
> governments and international agencies) and that the "leap smear"
> is implemented as part of that time scale.

Leap smear was implemented while Google used NTP; Chris Pascoe described
it publicly in:

A while back, I patched up the OpenNTPd sources with code from FreeBSD
and wanted to get around to implementing leap seconds handling, which
OpenNTPd didn't do.  I didn't get time to do so, but did document my
understanding of the issues and the approaches:


Note though, as I describe in that document, smear only works in a
closed community of timeservers, because of the lie introduced on the
wire; for open Internet usage, something like UTC-SLS is needed instead.

In all this, the closest relationship there is to time _zones_ is that
there's a similar problem of distributing a file of offsets to be used
by all systems handling time.  Instead of the Olson TZ DB, it's the
IERS leap-second jumps.


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