[time-nuts] How does NTP's local clock estimation work in detail?

Magnus Danielson magnus at rubidium.dyndns.org
Sun Mar 8 18:38:40 EDT 2015


Do get the Dave Mills book.

You can strip away a number of methods under certain assumptions to make 
the system simpler to understand, and then add them back in.

The NTP packet exchange get's you a two-way hand-shake with time-stamps, 
which provides you with a offset (time error against the remote node). 
This is first processed for a FLL style lock-in which then swaps over to 
a PLL mode. Then it is a pretty simple PLL, with the capability of reset 
the time offset which is rarely used.

Things like the cluster algorithm weighs many sources etc.


On 03/06/2015 05:23 PM, Attila Kinali wrote:
> Moin,
> I am a little bit stuck here. I am trying to work out the math behind
> a synchronization of clocks problem. It shouldn't be too difficult,
> but every couple of minutes I'm getting stuck at some details and it
> takes me always a lot of time to get around it. I'm pretty sure that
> what I am doing is similar to what NTP does locally after it got an
> estimate on it's time difference. I tried to look up what NTP does
> but I got lost in the huge amount of papers/presentations.
> Could someone point me to some papers that explain what NTP
> does locally? If possible in compact form.
> Thanks in advance
> 				Attila Kinali

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