DNS Negative Caching
Barry Margolin
barmar at alum.mit.edu
Sat Aug 29 00:27:46 UTC 2015
In article <mailman.2604.1440796547.26362.bind-users at lists.isc.org>,
"Darcy Kevin (FCA)" <kevin.darcy at fcagroup.com> wrote:
> Negative-caching TTL and regular TTL have little to do with each other; it's
> not a reasonable assumption that one should stand in as a default for the
> other.
True, but that's water long under the bridge.
Note that if a server is authoritative-only, caching is mostly
irrelevant, so the negative cache TTL doesn't much apply. In this case,
the SOA Minimum is just being used as the default TTL.
> My opinion: named on the master should reject illegal zone files.
As far as I can tell, nothing in RFC 2308 says that $TTL is required. I
don't even see a SHOULD, let alone a MUST. Is there a later RFC that
adds this requirement? If not, then a zone file without $TTL is legal.
And for backward compatibility, it should continue to use the SOA
Minimum field as the default TTL.
--
Barry Margolin
Arlington, MA
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