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What is the logic behind the changing of NTP Client Pol Intervals?

Answered What is the logic behind the changing of NTP Client Pol Intervals?

  • Friday, October 05, 2012 2:43 AM
     
     
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    I wonder if anyone might be able to help explain why the NTP Pol Interval changes on Windows Clients/Servers, beyond what I currently understand.  If I understand correctly, the Polling Interval changes if there was "x" amount of drift in the client's clock since the last synchronization.  It seems to change within the Min and Max polling intervals of 10 and 15 log2.  If that understanding is correct, then can someone define the x?  Perhaps provide a link to an rfc or whitepaper?
     
    I assume there's logic somewhere along the lines of; if the drift is within 5000ms since the last synchronization, then increase the pol interval by 1 towards the max interval.  If the drift is more than 5000ms, decrease the pol interval.  
    If such logic exists, can someone provide details?
     

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  • Wednesday, October 03, 2012 6:39 PM
     
     
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    I wonder if anyone might be able to help explain why the NTP Pol Interval changes on Windows Clients/Servers, beyond what I currently understand.  If I understand correctly, the Polling Interval changes if there was "x" amount of drift in the client's clock since the last synchronization.  If that understanding is correct, then can someone define the x?  Perhaps provide a link to an rfc or whitepaper?
     
  • Wednesday, October 03, 2012 7:04 PM
     
     
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    Please refer below link on NTP,

    http://www.ntp.org/ntpfaq/NTP-s-algo.htm#Q-POLL-RANGE

    Thanks & Regards, Amit Katkar ------------------------------------------------------------ This posting is provided "AS IS" with no warranties or guarantees and confers no rights.

     
  • Wednesday, October 03, 2012 7:48 PM
     
     
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    Thank you for your response.  Was your link intended to raise my awareness of the Pol Range?  I am aware of the Min and Max pol intervals,which on Windows are of 10 and 15 log base 2.

    I have found pieces of information that seem to indicate that Windows will initially synchronize at the minimum pol interval and if everything is running well, it will stretch the pol interval out close to the Max.  It is that logic which changes the Pol Interval on windows systems that I'm looking for info on.  

    Or perhaps info that tells me that the above simply isn't true and that polling between the Min and Max, on Windows 7 and 2008 R2, is entirely random?

    If it's not random, then I assume there's logic somewhere along the lines of; if the drift is within 5000ms since the last synchronization, then increase the pol interval by 1 towards the max interval.  If the drift is more than 5000ms, decrease the pol interval.  

    If such logic exists, and I am under the impression that it does, then it is the definition of this logic that I seek.

     
  • Thursday, October 04, 2012 7:11 AM
     
     
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    Hello,

    as this doesn't belong to Directory services in detail please ask this in http://social.technet.microsoft.com/Forums/en/winservergen/threads

    Best regards

    Meinolf Weber
    MVP, MCP, MCTS
    Microsoft MVP - Directory Services
    My Blog: http://msmvps.com/blogs/mweber/

    Disclaimer: This posting is provided AS IS with no warranties or guarantees and confers no rights.

    • Proposed As Answer by AwinishMVP Thursday, October 04, 2012 9:29 AM
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  • Friday, October 05, 2012 2:45 AM
     
     
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    I thought it was odd to post the question here, but there was a technet article on NTP that said if there were any further questions, ask them in this forum.

    I've reposted the question in the general forum.

     
  • Friday, October 05, 2012 2:51 AM
     
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    Maybe these ones helps.

    http://blogs.msdn.com/b/w32time/archive/2008/02/26/configuring-the-time-service-ntpserver-and-specialpollinterval.aspx

    http://blogs.msdn.com/b/w32time/archive/2009/02/02/group-policy-settings-explained.aspx

     

     

     

    Regards, Dave Patrick ....
    Microsoft Certified Professional
    Microsoft MVP [Windows]

    Disclaimer: This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.

     
  • Friday, October 05, 2012 3:02 AM
     
     
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    Thanks for the response.  That article has one line that states it polls based on the quality of the time samples, which was the key phrasing.  A quick search on NTP Quality reveals it computes based on offset, jitter, frequency error, and stability.  And THAT discovery, helped me find THIS:  http://tools.ietf.org/html/draft-ietf-ntp-ntpv4-algorithms-01

    Which is the answer I was looking for.  THANKS!


     
  • Friday, October 05, 2012 3:05 AM
     
     
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    You're welcome.

     

     

    Regards, Dave Patrick ....
    Microsoft Certified Professional
    Microsoft MVP [Windows]

    Disclaimer: This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.