[ntp:questions] how did ntp service set the maxallowphaseoffset

xiaoniao112233 at gmail.com xiaoniao112233 at gmail.com
Tue Nov 19 03:22:17 UTC 2013

在 2013年11月19日星期二UTC+8上午10时45分44秒,Brian Inglis写道:
> On 2013-11-18 01:30, xiaoniao112233 at gmail.com wrote:
> > hello :
> >     I had recently start a work about ntp service ,my friends and me use windows and linux to sync time in ntp.we could use w32time service to sync linux in ntp.In windows we could I found that in the registry:
> > HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config\ MaxAllowedPhaseOffset may be could set the offset time between the local time and the server that they will be synchronize. If out of range of MaxAllowedPhaseOffset in seconds ,they synchronize,otherwise not.
> > But I have a question that Is there a paremeter in ntp service that control the offset like in registry above in windows.
> W32tm is an SNTP service intended to synchronize time on
> workstations in a domain to a domain controller at intervals.
> NTP service is intended to maintain accurate time on clients
> and servers across the internet, where the accuracy willdepend
> on your budget and effort, from <100ms with poolservers to
> <1us with reference clock hardware and kernel PPS support.
> W32tm service parameters documented at
> http://technet.microsoft.com/en-us/library/cc773263%28v=ws.10%29.aspx,
> may be compared to options from NTP docs @ doc.ntp.org:
> e.g.
> Configuration Commands and Options
> Miscellaneous Commands
> tinker - modify sacred system parameters (dangerous)
> http://doc.ntp.org/4.2.6p5/miscopt.html#tinker
> for current stable release 4.2.6p5
> tinker...
> ... panic panic
>          Specifies the panic threshold in seconds with default 1000 s.
> If set to zero, the panic sanity check is disabled and a clock offset
> of any value will be accepted.
> ... step step
>          Specifies the step threshold in seconds.
> The default without this command is 0.128 s.
> 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 0.5 s.
> ... stepout stepout
>          Specifies the stepout threshold in seconds.
> The default without this command is 900 s.
> If set to zero, popcorn spikes will not be suppressed.
> So tinker step is similar to W32tm MaxAllowedPhaseOffset except for
> different service levels:
> The default value for domain members is 300.
> The default value for stand-alone clients and servers is 1.
> and the W32tm slew requirement:
> |CurrentTimeOffset| / (PhaseCorrectRate*UpdateInterval) < SystemClockRate / 2
> -- 
> -- 
> Take care. Thanks, Brian Inglis
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Thanks a lot,your analysis is very  helpful for me,I have understand NTP deeper with your help ,I will try it as you said.Thank you very much.

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