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

Richard B. Gilbert rgilbert88 at comcast.net
Sun May 30 20:40:02 UTC 2010


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?

This is the reason why four servers is the minimum recommended 
configuration.  One server can fail; either fail to respond at all or 
respond with an incorrect time and be voted out and you still have a 
working configuration.
> 
> I have told the customer to use more than two servers, but they insist
> that they want answers to the above scenario.
> 
> Any help welcome
> 
> //Fredrik

I hope you charge them extra for this!  You can't itemize it as a fine 
for stupidity but I bet you wish you could!





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