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