On Thu, Nov 06, 2014 at 11:33:49AM +0100, Martin Burnicki wrote: > In his posting Dave Hart mentions the > > tos minclock 3 maxclock 6 > > directive which could be used to configure the limits. However, a quick test > with client running 4.2.7p470 always mobilized exactly 4 pool associations, > so this doesn't seem to work (anymore) as expected, or I may be missing > something.
The pool now returns 4 addresses, if all are reachable it probably didn't need to make a second DNS query. However, in a test using the suggested configuration and blocked NTP traffic it sends a DNS request every ~4 minutes and sends an NTP request once per minute. The NTP request rate doesn't meet the requirements listed on the pool vendors page. As for DNS, I have no idea. I was hoping Ask or someone else familiar with the pool DNS servers would be able to make a suggestion. > > - how should the client find IPv6 servers? they are currently returned > > only for the 2*pool.ntp.org name (4 IPv4 + 4 IPv6 addresses) Any comments on this? It would be nice if it was possible to have a configuration that works well on IPv4 only and IPv6 only systems. Would it be ok if the clients used just the 2* name? I suspect this would generate too much of IPv6 traffic. If the client was configured with all four names and used only one address per name, that would be close to the current recommended configuration. > > - should the client also check if reachable servers are still in > > the pool and replace them if not? any recommendations on that? > > How could a client be able to do this? From my understanding it just gets > gets a (more or less) random IP address from the pool's DNS server, and a > reverse lookup of the IP address should yield the "real" hostname of the > server. It could try to track all pool servers in its location. At least from my address I don't see that many different addresses (I'm not using the country specific name). If the client made a DNS request once per day, I guess over few weeks it would get all or most of its servers again. If not, it would just be slowly rotating the servers. > A possible way to do this which comes to my mind would be to introduce DNS > names like aa.bb.cc.dd.pool.dns.org, so once a client has received > aa.bb.cc.dd as a pool server address it could check if > aa.bb.cc.dd.pool.dns.org still resolves, and if not assume this server has > been removed from the pool. Yes, that would be a much better solution, but it would be specific to the pool.ntp.org pool. > Since most of these points are more related to how NTP clients should/could > behave vs. how this is actually implemented maybe a good location to discuss > this would be the NTP hackers list. I think we need to get the requirements first and then see if there is anything that needs to be fixed in the NTP implementations. -- Miroslav Lichvar _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
