NS records for authoritative answer: necessary?

[Gonzalo HIGUERA DÍAZ]

Hello,

Given a (SOA) query to an authoritative server of that zone, is it
necessary for it to include NS records in the answer (in the authority
section)? BIND seems to do so but no so (some) servers, notably
Windows ones. I was wondering if Windows whether behaves wrongly or if
BIND is simply being verbose. (From my understanding of the algorithm
described in RFC 1034 there is no need for NS records because the
answer is authoritative, but I might be missinterpreting it.)

This question arises from the behaviour of the zone file timestamp
when refreshing a zone in BIND (e.g. forcibly through "rndc refresh"
under version 9.2.4 in GNU/Linux). In most cases, the timestamp is
updated even if there is no need for update (i.e. the zone's serial
number has not changed). For some servers however, notably (all?)
Windows servers, this is not the case. The only obvious difference I
is the absence of  NS entries in the authority section of the answer.
Is this the same for other other BIND versions? Are there any concerns
I should be aware of?

Thank you for any upcoming responeses.

-- 
Gonzalo HIGUERA DÍAZ <gonhidi at gmail.com>