Subject: sub.dom with cached NXDOMAIN dom

From: "D. J. Bernstein" <[email-masked]>
Date: 8 Dec 1999 00:44:15 -0000

Here are three ways to use a recently cached NXDOMAIN foo.bar IN A:

   (1) Respond NXDOMAIN for any IN query within the foo.bar domain.
   (2) Respond NXDOMAIN for any IN query for the name foo.bar.
   (3) Respond NXDOMAIN for any IN A query for the name foo.bar.

RFC 2308 recommends #2. It doesn't mention #1 or #3. Is this choice
based on some unpublished statistics on caching effectiveness? Or did
RFC 2308 actually mean to recommend #1?

---Dan

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From: Paul A Vixie <[email-masked]>
Date: Tue, 07 Dec 1999 23:00:54 -0800

> RFC 2308 actually mean to recommend #1?

NXDOMAIN's scope is the {name,type}.  RFC 2308 implicitly outlawed BIND's
behaviour, which is to return NOERROR/ANCOUNT=0 for empty nonterminals.
After RFC 2308, empty nonterminals are signalled with NXDOMAIN.  Therefore
#1 would be incorrect.  #3, while correct, would waste information since
NXDOMAIN signals "no RRs of any type at this name".