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

William Unruh unruh at invalid.ca
Wed Dec 3 22:33:05 UTC 2014

On 2014-12-03, Jan Ceuleers <jan.ceuleers at computer.org> wrote:
> On 12/03/2014 02:58 PM, Brian Utterback wrote:
>> I still think that it takes four to
>> guarantee a majority but I don't have proof of that. Someday I will
>> spend some time to either prove or disprove it, but alas, time is
>> something I don't generally have extra to spend. But you are better off
>> with one than two from an operational standpoint.
> It takes three servers *at all times* to enable clients to use majority
> voting. So if you want to guard against a single failure (i.e. not a
> single falseticker, a single server that goes offline), then you need four.

Offline IS a false ticker. And no, you need three. In fact to gaurd
against offline, you only need two. Guarding against falseticking is
harder than guarding against offline. Just as it is harder to guard
against a liar than a dead man. 

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