[ntp:questions] Is always T2 = T3 ?

Danny Mayer mayer at ntp.isc.org
Thu Apr 19 11:48:32 UTC 2007


Mastuac wrote:
> I've been looking for some NTP server responses and I have always seen
> that T3=T2.
> Is this always true.   Its a  bore to do  32 bit calcs and the
> fractional part in a small micro, so if  I can simplify the  formula
> it would be great
> 
> current Time = T4 +1/2 ( T2-T1 + T3-T4 )  =  T2 + 1/2(T4 - T1 )

T3 is *never* equal to T2. You cannot simplify the formula. It was
carefully designed and carefully implemented.  T1, T2, T3 and T4 are
large numbers implemented as 64-bit values in NTP format. It is *very*
necessary to subtract one large number from another large number *first*
in order to bring the result into a reasonable number range. These are
*not* 32-bit calculations.

Danny



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