Clock Synchronization Algorithm
To synchronize its clock with a remote server, the NTP client must compute the round-trip delay time and the offset. The round-trip delay is computed as, where is the time of the request packet transmission, is the time of the request packet reception, is the time of the response packet transmission and is the time of the response packet reception. is the time elapsed on the client side between the emission of the request packet and the reception of the response packet, while is the time the server waited before sending the answer. The offset is given by .
The NTP synchronization is correct when both the incoming and outgoing routes between the client and the server have symmetrical nominal delay. If the routes do not have a common nominal delay, the synchronization has a systematic bias of half the difference between the forward and backward travel times.
Read more about this topic: Network Time Protocol
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