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

Danny Mayer mayer at ntp.isc.org
Sun Jan 27 04:24:32 UTC 2008

Brian Utterback wrote:
> Danny, I agree with everything you said except:
> Danny Mayer wrote:
>> I agree. I don't see how it can be a specification violation. The 
>> biggest factor is how well it keeps time. A caesium clock keeps good 
>> time but you wouldn't say that it violates the specification.
> When we first started looking at the V4 spec for the ntp-wg, my first
> thought was the same as yours, namely that what happens inside a system
> shouldn't matter, the algorithms don't matter, only what it chimes
> matters. And strictly speaking, this is true. However, after reading
> Dave's book (Das Buch as he calls it), I realized that an important
> factor to the stability of the NTP network is the actual speed at
> which the clocks slew, i.e. the 500 PPM limit. This is largely
> ignored in the spec. I sent in some comments about how I thought it
> should be addressed but alas, my changes didn't make it in the latest
> versions.

I'm not sure what it was you were trying to modify, the NTP v4 draft, 
the book, something else.

I never said that you can consider ntpd in isolation. It's part of a 
network of ntpd servers and each is interacting with others. That's a 
very important part of the specification and each is affected by the others.


> Brian Utterback
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