[ntp:questions] stepping and slewing

Riccardo Castellani castellani.riccardo at tiscali.it
Mon Apr 30 18:48:48 UTC 2007


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 ?

Where can i find doc. about stepping and slewing ?
  ----- Original Message ----- 
  From: Richard B. Gilbert 
  Newsgroups: comp.protocols.time.ntp
  To: questions at lists.ntp.isc.org 
  Sent: Sunday, April 29, 2007 11:25 PM
  Subject: Re: [ntp:questions] stepping and slewing


  Riccardo Castellani wrote:
  > What is difference among stepping and slewing mode which are used by ntpd ?
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  Slewing means that ntpd adjusts the clock at a maximum rate of 500 
  microseconds per second.

  Stepping means that the clock jumps abruptly from some incorrect time to 
  some reasonable approximation of the correct time.  In normal operation 
  ntpd will not step the clock; any error less than 128 milliseonds will 
  be corrected by slewing the clock.  An error of more that 128 
  milliseconds in considered an abnormal condition!

  Since correcting large errors by slewing the clock could take days or 
  weeks to complete stepping is used but, as mentioned above, this is not 
  normal.

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