[ntp:questions] ntpq -p "when"

Richard B. Gilbert rgilbert88 at comcast.net
Sat Nov 10 01:14:54 UTC 2007


lmr wrote:
> What does the "when" field from the ntpq -p output means?
> 
> The man pages say its seconds since the last packet was received but
> some documentation online say the it resets to 0 when is equal to the
> poll.
> 
> Is it set when a sync is requested or received?
> Is is possible for the "when" count to be greater that the polling
> interval in case no packet was received (server is unreachable)?  --
> Has anyone seen it going greater than the poll interval?
> 

I have seen the "When" field claim *days* since a server last responded.
It's rare to see something like that since most servers are available 
24x7 but a server may encounter serious problems, either hardware or 
software, that require days to fix.  If there were any NTP servers in 
New Orleans when hurricane Katrina struck, they might have gone down for 
days, weeks, months, or forever!

This suggests that a robust configuration should use a number and 
variety of servers that cannot all be wiped out in the same disaster.




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