[dns-operations] NXDOMAIN vs NODATA for suffixes of existing name

[Florian Weimer]

Suppose we've got the following zone contents:

   example.net. 1728000 IN SOA ...
                1728000 IN NS ....
   a.b          1728000 IN A 192.0.2.1

A query with QNAME=b.example.net., QTYPE=A, QCLASS=IN returns NODATA
with some authoritative server implementations, and NXDOMAIN with
others.  IIRC, the former is more correct, but I can't find out why.
RFC 1034 is almost silent on this issue (although the algorithm in
section 4.3.2 does not require returning NXDOMAIN in this case).  I
used to think that RFC 2308 required NODATA, but after reading
section 2.1, it seems that it doesn't, either.

Could anybody please provide the definite reference in favor of
NODATA?