[ntp:questions] what happens when sys.peer turns stratum 16?

Richard B. Gilbert rgilbert88 at comcast.net
Mon May 31 11:29:57 UTC 2010

unruh wrote:
> On 2010-05-30, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
>> bombjack wrote:
>>> Hi,
>>> I am fairly new to the ntp arena, but have to learn fast as part of my
>>> work is trying to fix ntp problems. Lately I had a customer that
>>> complained that there servers went bananas due to time being wrong.
>>> (The customer claims that ntp had changed the time 20 years ahead).
>> That is somewhere between highly improbable and impossible!  NTPD had to 
>> have some human "help" to do that.
>>> Looking at some wire shark logs it seems that sys.peer for some reason
>>> had turned into a stratum 16 server (i.e. unsynched) and had "leap"
>>> set to 3 -"Alarm condition (clock not synchronized"
>>> the setup: klient syncs to 2 servers, one stratum 1 (sys.peer) and one
>>> stratum 2 server. If sys.peer all of a sudden says it's a stratum 16
>>> server, how does ntp react to this? instant outvote of the sys.peer?
>>> or are these packets filtered for some time as being errornous? or
>>> anything else?
>> With only two servers nobody can outvote anybody else!!  Is it not 
>> written that a man with two clocks can never be certain what time it is?
> But if one clock tells you that it itself is completly nuts, it is not
> hard to tell which the right one is. 
> If you ask me and my friend what time it is, and he says it is 12 noone,
> and I say it is 5PM, but my watch is broken, is it hard for you to
> figure out what the time is?

Yup!  In that situation "noon" is just a wild ass guess!

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