[ntp:questions] stepping and slewing

Riccardo Castellani castellani.riccardo at tiscali.it
Tue May 1 10:42:30 UTC 2007

According to www.ntp.org in stanard Linux o.s. (adjtime(2) - http://www.ntp.org/ntpfaq/NTP-s-algo.htm#S-ALGO-BASIC) time adjusting has rate of 0.5ms per second to slew time but because do you speak about "maximum"  rate of 0.5 ms/sec. ? Does ntpd use always the same 0.5 as value or it's a variable parameter ?

I'm confused because "Rob MacGregor" said about step method (128ms < offset < 1000s) :
Stepping: Time changes in large units, quickly

With "Step" method (settimeofday), time is gradually changed with higher rate or time is changes immediately to correct time.
example for use step method : my local clock is 5:00 pm and real time is 5:05 pm, Ntpd set immediately local clock to 5:05 pm or it corrects time gradually ?

  ----- Original Message ----- 
  From: Richard B. Gilbert 
  Newsgroups: comp.protocols.time.ntp
  To: questions at lists.ntp.isc.org 
  Sent: Monday, April 30, 2007 9:02 PM
  Subject: Re: [ntp:questions] stepping and slewing

  Riccardo Castellani wrote:
  > but can I define slew rate and step rate ?
  > Pheraps these parameters are defined inside kernel of o.s. ?
  > slew rate is always 0.5 ms/sec ?

  No!  That is the maximum slew rate.  It's a limit built into most Unix 
  and Unix-like operating systems.

  What problem are you trying to solve?  ntpd works very well for most of 
  us, just as it is.

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