[154408] in North American Network Operators' Group
Re: F-ckin Leap Seconds, how do they work?
daemon@ATHENA.MIT.EDU (Jay Ashworth)
Tue Jul 3 16:28:07 2012
Date: Tue, 3 Jul 2012 16:26:57 -0400 (EDT)
From: Jay Ashworth <jra@baylink.com>
To: NANOG <nanog@nanog.org>
In-Reply-To: <34ebe2600b91d04f9c049d59eb7e13da@mail.dessus.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
----- Original Message -----
> From: "Keith Medcalf" <kmedcalf@dessus.com>
> > Are you suggesting that NTP timekeeping should be based on UT1?
>
> The system clock should be based on UT1 and should be monotonically
> increasing since this matches the common concept of time. Calculations
> done with this value are all based on it being UT1 and using the
> "common" notion of UT1 rules. The root cause of the difficulties is
> that someone decided that the system clock would not maintain "wall
> clock" time (UT1) but rather some other timebase and then "step" that
> time to keep it in sync with UT1.
UTC is monotonic, and is based on UT1. Just not deterministically. :-)
The root cause *is* that someone made a bad decision about kernel
timekeeping, but it wasn't the choice of timescale. Non-monotonic time
is not a feature of UTC *either*.
> NTP can keep time in UTC (or anything else) if it wants, but it should
> discipline the system clock to monotonically increasing UT1.
As I undertstand it, the problem is not how NTP disciplined the kernel,
it's what the kernel does itself.
Cheers,
-- jra
--
Jay R. Ashworth Baylink jra@baylink.com
Designer The Things I Think RFC 2100
Ashworth & Associates http://baylink.pitas.com 2000 Land Rover DII
St Petersburg FL USA http://photo.imageinc.us +1 727 647 1274
