[ntp:questions] Order of servers in ntp.conf

unruh unruh at invalid.ca
Wed Aug 14 13:43:40 UTC 2013

On 2013-08-13, Nils Brubaker <ncb at us.ibm.com> wrote:
> For ntpd 4.2.4p6 running on Linux, is there any significance to the order 
> of servers in the ntp.conf file?  Will ntpd synchronize with the first 
> available/good time server in the list?

No, no.
ntp gets the data from all the servers. It then looks at the times it
gets from each server, and groups them into "classes" according to its
estimate of the max time error from the server-- ie whether the error
intervals overlap or not. It then looks for the largest group of servers
all of whose error intervals overlap and uses the average of those times
as the time to send on the the ntp engine. The others are "false
tickers". It estimates the error by looking at the round trip time and
the other machine's estimate of its own max error.

> Thanks,
> Nils Brubaker

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