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

unruh unruh at wormhole.physics.ubc.ca
Mon May 31 21:07:14 UTC 2010

On 2010-05-31, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
> 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!

No it is not. It is the best estimate of the true time you have. 


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