[ntp:questions] Best practice: re-resolve server IP address beforeeach poll/query

Danny Mayer mayer at ntp.isc.org
Thu Jun 14 17:27:04 UTC 2007

James Cloos wrote:
> Wolfgang> DNS refresh and expire are two SOA entities that are meant to be
> Wolfgang> looked at by the secondaries of a domain.
> I'm sure he was thinking of the Time To Live (TTL) values for the
> individual RRs, rather than the values in the SOA.

Those are of course not the ones you need to look at since those have to
 do with the zone itself and not the zone records each of which has its
own TTL.

> I'm not aware of any universal way to get that at the application level,
> using the system resolvers.  Adns, however, can do so.  Cf:
> http://www.chiark.greenend.org.uk/~ian/adns/
> -JimC

I took a quick look at this and it's a non-starter. First of all because
it doesn't support AAAA records and we require IPv6 support and second
because of the GNU Licensing. My preference would be for ISC to provide
a new api which will provide among other things the TTL information
about the answers returned. It could be done as part of a DNSSEC
resolver api effort which would also encourage implementation of DNSSEC.


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