Gorgy Timing LEDI NETWORK IN Mode D'emploi page 56

Dérive nulle
To perform this synchronization, the NTP client software permanently compares the two
clocks and computes the following information:
Evolution dans le temps
► Offset:
It's the difference between the time of the server clock and the time of the client
clock. For example, if the server clock indicates 2:10:13 and the client clock indica-
tes 2:11:14, the offset is –1:01.
► Drift:
Dérive constante
It's the frequency difference between the two clocks. When drift is not null and
without clock correction, the offset between the two clock increase or decrease
depending on the drift sign.
The following figure shows how the evolution of the two clocks with or without drift:
Drift is null :
Evolution during time
Drift is constant :
The objective of the synchronization of a NTP client to a NTP server is to reduce as
much as possible the drift and the offset. The accuracy and stability of the client clock
is tightly coupled to the efficiency of the reduction process.
3/ There are several reasons for the presence of a drift between two clocks: generally the drift is due to the tempe-
rature difference between the two clocks.
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MDE-LEDI-NETWORK-IN-4065V1.0
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