[ntp:questions] The libntp resumee...

Richard B. Gilbert rgilbert88 at comcast.net
Fri Sep 5 18:42:32 UTC 2008


Kay Hayen wrote:
> Hello Richard,
> 
> you wrote:
> 
>> The "rules" about how often to query a daemon are not all that
>> complicated.  The fact that there ARE rules is due to some history;
>> google for "Netgear Wisconsin" for the sordid details.  For a "second
>> opinion" google for "DLink PHK".
> 
> Fascinating reads indeed, thanks for the pointers. 
> 
> What worried me more was how often we can query the local ntpd before it will 
> have an adverse effect. Meantime I somehow I sought to convince me I should 
> be able to convince myself that ntpq requests are served at a different 
> priority (other socket) than ntpd requests are. I didn't find 2 sockets 
> though.
> 
>> Briefly, you use the defaults for MINPOLL and MAXPOLL.  You may use the
>> "iburst" keyword in a server statement for fast startup.  You may use
>> the "burst" keyword ONLY with the permission of the the server's owner.
>> 99.99% of NTP installations will work very well using these rules".  If
>> yours does not, ask here for help!
> 
> Now speaking about our system, not the middleware, with connections as 
> follows: 
> 
> External NTPs <-> 2 entry hosts <-> 8 other hosts.
> 
What do you mean by "entry hosts"?

> And iburst and minpoll=maxpoll=5 to improve the results.

Use the default values of minpoll and maxpoll!  Ntpd will adjust the 
polling interval within those limits.  Ntpd is far smarter than you or 
I.  It will normally start by using minpoll and increase the interval 
after it has initial synchronization.  If network conditions deteriorate 
it will decrease the poll interval and increase it as conditions 
improve.  IOW it will use the optimum poll interval for the conditions 
then obtaining.  If you configured seven servers, you might observe ntpd 
using seven DIFFERENT poll intervals, one for each server because seven 
different servers will be reached by at least seven different network paths!
> 
> Currently we observe that both entry hosts can both become restricted due to 
> large offsets on other hosts, so they become restricted and that will make 
> the software refuse to go on. Ideally that would not happen.
> 
> I will try to formulate questions:
> 
> When the other hosts synchronize to the entry hosts of our system, don't the 
> other hosts ntpd know when and how much these entry hosts changed their time 
> due to input? 
> 
> Would NTP would be more robust if we would configure routing on the entry 
> hosts, so that they can all speak directly with the external NTPs on their 
> own?
> 
> Is the use of ntpdate before starting ntpd recommended and/or does the iburst 
> option replace it?
> 
> Best regards,
> Kay Hayen




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