[ntp:questions] Re: NTP does not sync when using pool.ntp.org

Brad Knowles brad.knowles at skynet.be
Thu Oct 9 17:32:08 UTC 2003

At 7:02 PM +0200 2003/10/09, Jan Ceuleers wrote:

>  Would it not be sufficient to do as Dale suggested and list the same
>  servers in each of the 3 pools?

	You'd have to make sure that the order of listing in each pool is 
totally different from the other two -- pseudo-random number 
generators may be helpful here.  Of course, you can't guarantee that 
the secondaries are going to serve out those records in the same 
order as the master.  ;-(

>                                   The probability that the queries would
>  return the same server twice or even three times would be remote (or
>  certainly more remote than is the case without the pool repetition
>  mechanism), and perhaps this probability could be reduced still further
>  by listing the servers in a different order in each of the pools.

	For the larger pools (i.e., pool.ntp.org), this would certainly 
be true.  For the smaller pools (i.e., ones with only a handful of 
addresses), it would be far too easy for them to get in sync.

	For this reason, it might actually be best to have country-level 
pools be CNAME aliases to region-level pools (e.g., 
europe.pool.ntp.org, na.pool.ntp.org, etc...), unless there are 
enough servers within a single country to ensure a reasonably low 
probability of getting in sync (i.e., at least ten or more).

	If there aren't enough region-level servers, then they could be 
further CNAME aliases to hemisphere-level (or other higher-level) 

>  (Note that I do not purport to be a DNS expert).

	I have specialized in the DNS for a number of years, and I was a 
technical reviewer of 2nd edition of the O'Reilly book _DNS and 
BIND_.  I'm working on a variety of ideas to try to help make this 
concept work better.

Brad Knowles, <brad.knowles at skynet.be>

"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
     -Benjamin Franklin, Historical Review of Pennsylvania.

GCS/IT d+(-) s:+(++)>: a C++(+++)$ UMBSHI++++$ P+>++ L+ !E-(---) W+++(--) N+
!w--- O- M++ V PS++(+++) PE- Y+(++) PGP>+++ t+(+++) 5++(+++) X++(+++) R+(+++)
tv+(+++) b+(++++) DI+(++++) D+(++) G+(++++) e++>++++ h--- r---(+++)* z(+++)

More information about the questions mailing list