[ntp:questions] NTP vs chrony comparison (Was: oscillations in ntp clock synchronization)

Richard B. Gilbert rgilbert88 at comcast.net
Fri Jan 25 20:09:26 UTC 2008


Unruh wrote:
> "David L. Mills" <mills at udel.edu> writes:
> 
> 
>>David,
> 
> 
>>1. I have explained in very gory detail in many places how the time 
>>constant is chosen for the best accuracy using typical computer 
>>oscillators and network paths. See the briefings on the NTP project page 
>>and especially the discussion about the Allan intercept. If you want the 
> 
> 
> The Allan intercept is predicated on a very specific model of the noise in
> a clock ( as I recall basically random gaussian noise at high frequencies,
> and 1/f noise at low). It is not at all clear that real computers comply
> with that. 
> 
> 
> 
>>best accuracy over the long term, you had better respect that. Proof 
>>positive is in my 1995 SIGCOMM paper, later IEEE Transactions on 
>>Networking paper and das Buch. I abvsolutely relish scientific critique, 
>>but see the briefings and read the papers first.
> 
> 
>>2. To reduce the convergence time, reduce the time constant, but only at 
>>the expense of long term accuracy. An extended treatise on that is in 
>>das Buch, especially Chaptera 4, 6 and 12. I would be delighted to hear 
>>critique of the material, but read the chapters first.
> 
> 
> While you may know what in the world Das Buch is (Hitlers Mein Kampf?) I do
> not. Nor do I know where to get it. 
> 

Computer Network Time Synchronization: The Network Time Protocol by 
David L. Mills (Hardcover - Mar 24, 2006)

Available from Amazon.com.   You may be able to find a copy at a 
University Book store.  Be prepared for "Sticker Shock".  It ain't 
cheap!  Publishing in small quantities is EXPENSIVE!!!  It's different 
when you can amortize your setup costs over 50,000 copies!

"Das Buch" is unlikely to become a best seller!




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