[ntp:questions] Number of Stratum 1 & Stratum 2 Peers

William Unruh unruh at invalid.ca
Mon Dec 8 23:58:19 UTC 2014

On 2014-12-08, Brian Utterback <brian.utterback at oracle.com> wrote:
> On 12/4/2014 6:56 PM, William Unruh wrote:
>> One source is fine, unless it either dies or goes nuts.
>> Two are fine, unless on goes nuts.
> Define "goes nuts". Two are not fine if they don't agree on the time, 
> and in my experience the many of the admins that consider using only two 
> servers are unable to get those two servers to agree on the time.

By "go nuts" I mean that it does not deliver an approximation to UTC
within its jitter bounds. Eg, suddenly decides to deliver times a second
late because of GPS/NMEA/PPS problems. Or the server had "localclock"
set and all its sources died but it blithely kept delivering time to
anyone who asks. 

>> Three are fine, as long as only one dies or goes nuts.
> Again, define "goes nuts". You don't seem to like the term 
> "falseticker", so how do you define "goes nuts"? If one "goes nuts" or 
> even goes offline, if the remaining two do not agree then it is like 
> having no server at all.

No, it is like having two, with one being out. 
falseticker is a term with a very specific internal definition. Thus a
server whose time is right on UTC could be a falseticker, because the
other two servers were both exactly 3 days out, with tiny jitter estimates. 
I would say then that you had two servers going nuts, and one good, even
though ntpd would say there were two good and one falseticker. 

> Brian Utterback

More information about the questions mailing list