[181390] in North American Network Operators' Group
Re: REMINDER: LEAP SECOND
daemon@ATHENA.MIT.EDU (Harlan Stenn)
Mon Jun 22 19:09:22 2015
X-Original-To: nanog@nanog.org
From: Harlan Stenn <stenn@ntp.org>
To: Doug Barton <dougb@dougbarton.us>
In-reply-to: <558889A6.10704@dougbarton.us>
Date: Mon, 22 Jun 2015 23:06:54 +0000
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Doug Barton writes:
> This is an OpenPGP/MIME signed message (RFC 4880 and 3156)
> On 6/19/15 2:58 PM, Harlan Stenn wrote:
>> Bad idea.
>>
>> When restarting ntpd your clocks will likely be off by a second,
>> which will cause a backward step, which will force the problem you
>> claim to be avoiding.
>>
>> There are plenty of ways to solve this problem, and you just get to
>> choose what you want to risk/pay.
>
> You misunderstand the problem. :) The problem is not "clock skips
> backward one second," because most of the time that's not what
> happens. The problem is that most software does not handle it well
> when the clock ticks ... :59 :60 :00 instead of ticking directly from
> :59 to :00.
POSIX NEVER shows :60.
> THAT problem is avoided by temporarily turning off NTP and then
> turning it back on again when "the coast is clear." Most software can
> handle the "clock skips forward or backwards one second" problem
> fairly robustly,= and as Baldur pointed out by doing the reset in a
> controlled manner you greatly reduce your overall risk.
Time going backwards is deadly to a number of applications.
But apparently not to applications you care about.
You're also not doing anything where somebody is going to get sued
because a timestamp is off by a second. There are people for whom this
is a very real risk.
H
