Leap second tonight

Kevin Oberman oberman at es.net
Tue Mar 17 10:06:51 CDT 2009


> From: =?ISO-8859-1?Q?Ask_Bj=F8rn_Hansen?= <ask at develooper.com>
> Date: Mon, 16 Mar 2009 23:07:42 -0700
> 
> 
> On Dec 31, 2008, at 15:28, Kevin Oberman wrote:
> 
> > We use CDMA clocks and last leap second it took weeks for all of the
> > cell sites to adjust the last one. As a result, I have set all of our
> > clocks for manual leap second and set them to adjust tonight at  
> > midnight
> > (UTC).I'll take a look in about 35 minutes and see how it worked.
> 
> Chiming in a little late here ...
> 
> Over at the NTP Pool we had about 9% of the servers not handle the  
> leap second accurately; starting at midnight UTC.  After an hour (so  
> between 01:00 and 02:00) it was down to about 3%; a couple hours later  
> down to about 1% of our servers (a few dozen)[1].  Most of those got  
> in order within 24-48 hours.    Interestingly the few who didn't get  
> corrected within a few days were, tada: CDMA clocks.
> 
> To stay vaguely NANOG on-topic: I believe at least some of our ~1700  
> NTP servers are routers; so I'm guessing they handled the leap second  
> alright.

Routers as ntp servers. Yuck! Routers route well, but they treat time as
a low priority job and jitter on Cisco routers is simply terrible.
Junipers do better, but are still a poor time server.

> Sounds like a "RISKS" lesson: Don't use side-effects of a tool for  
> something critical.  (If I understand it right then CDMA uses accurate  
> time because it needs accurate frequency; not because it cares what  
> time it is).

As I understand it, they need both time and frequency to do cell
hand-offs cleanly, but, as long as all towers in a carrier's market are
showing the same time, it really does not matter if they do the leap
second.

Endrun Technologies, who make our clocks, ship them configured for
manual leap seconds because so many cell operators are pretty casual
about the leap second thing, but that means that the people using the
clocks need to be aware that they need to be told when a leap second is
coming and that, in turn, means the they must know a bit about leap
seconds and must have read the manual. No surprise that a lot of CDMA
clocks missed the leap second.




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