[ntp:questions] Re: Ntp-4.1.2: tinker step 0;always slew and kernel time discipline

Nikolaev, Sergey snikolaev at ebs.com
Fri Feb 18 14:52:08 UTC 2005


Thanks for your replies. Actually, I have just got data from my tests
and this is what I am observing.
If "tinker step 0" but the "kernel" is not disabled explicitly, a
20-second offset 
(set manually via the date command) is corrected at a rate of about 0.5
millisecond/s as expected, 
but overshoots the right time by about the same absolute value of
offset. This happens repeatedly. 
For example, from -20 sec it goes all the way to 20 sec offset and then
back to -20 and so on many times. 
I did not wait for it to settle down. 

When the "kernel" is disabled, it overshooted only by less than 0.5s and
then slowly settled to the correct time.
Actually, it settled to the range of +-120ms around the peer's time.

It looks to me that "disable kernel" offers a saner behavior in this
Any comments?


-----Original Message-----
From: questions-bounces at lists.ntp.isc.org
[mailto:questions-bounces at lists.ntp.isc.org] On Behalf Of David L. Mills
Sent: Thursday, February 17, 2005 9:24 PM
To: questions at lists.ntp.isc.org
Subject: [ntp:questions] Re: Ntp-4.1.2: tinker step 0;always slew and
kernel time discipline


In truth, the kernel is disabled only if the actual correction is 
greater than 0.5 s no matter what the tinker. However, there could be 
grief if the discipline switches from one to the other. There are a 
rather large number of untested and probably dangerous things that might

happen with uncharted combinations of tinkers and I'm not thrilled when 
spending lots of time fixing the broken combinations. You are on your 
own, but a "diable kernel" command might be appropriate.


Nikolaev, Sergey wrote:
> We have a requirement to always slew the clock even if it means long 
> periods of time to correct the offset.
> The NTP documentation mentions this tinker option:
> step step
> The argument is the step threshold, by default 0.128 s. It can be set
to any positive number in seconds. If set to zero, step adjustments will
never occur. 
> Note: The kernel time discipline is disabled if the step threshold is
set to zero or greater than the default.
> However when I set "tinker step 0" and restart ntpd, I see in "ntpdc 
> -c sysinfo" that the kernel flag is still enabled. Obviously, it is 
> not disabled automaticly just by setting "tinker step 0".
> Do I need to disable it explicitly?
> Thanks in advance,
> Sergey

The information contained in this e-mail is confidential. This e-mail is intended only for the stated addressee.  If you are not an addressee, you must not disclose, copy, circulate or in any other way use or rely on the information contained in this e-mail. if you have received this e-mail in error, please inform us immediately and delete it and all copies from your system.

EBS Dealing Resources International Limited. Registered address: 10 Paternoster Square, London EC4M 7DY, United Kingdom. Registered number 2669861.

EBS Dealing Resources, Inc, registered in Delaware. Address: 535 Madison Avenue, 24th Floor, New York, NY 10022, USA, and One upper Pond road, Building F - Floor 3, Parsippany, NJ 07054, USA.

EBS Dealing Resources Japan Limited, a Japanese Corporation. Address: Asteer Kayabacho Bldg, 6th Floor, 1-6-1, Shinkawa, Chuo-Ku,  Tokyo 104-0033, Japan.

More information about the questions mailing list