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

Danny Mayer mayer at ntp.isc.org
Tue Jan 22 03:36:29 UTC 2008

Unruh wrote:
>> correction applied on that sample.
> No, this is offset as measured by the ntp procedure ( (t1+t4-t2-t3)/2 )

No, that's wrong. It is very carefully described in the NTPv4 draft 
section 8 (p27):

theta = T(B) - T(A) = 1/2 * [(T2-T1) + (T3-T4)]

Not only do you have the wrong sign, the differences must be calculated 
first, otherwise the errors in the calculation overwhelm the resulting 
value. That's why it's written the way it is.


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