[ntp:questions] What happens if ntp server unavailable at start up?

Richard B. Gilbert rgilbert88 at comcast.net
Fri Sep 12 20:40:58 UTC 2008

Evandro Menezes wrote:
> On Sep 12, 8:31 am, Unruh <unruh-s... at physics.ubc.ca> wrote:
>> Sounds great. So, let me say I have pool.ntp.org as a server. when my
>> system comes up (a desktop) the network interface is there, but the dns
>> server is still dead, and the gateway is still dead. Ie, no address for
>> pool can be gotten from dns. Does the system keep trying or does it give up
>> on that server?
> Similarly, if a connection is dropped, will NTP query the DNS server
> about the IP of a specified server again or will it binds to an IP
> address and never give it up?

There is NO "connection"!!  UDP, which is what NTP uses is a 
connectionless protocol.  If a client receives no response to a query, 
it is supposed to wait and try again, double the wait time and try 
again, etc.  I believe that a conforming implementation is supposed keep 
doubling the retry time until it reaches 1024 seconds.

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