[Question] Question about negative answers from the cache of BIND9

[Barry Margolin]

In article <dnve24$2p4n$1 at sf1.isc.org>,
 Kevin Darcy <kcd at daimlerchrysler.com> wrote:

> Hideshi Enokihara wrote:
> >RFC2308 6 - Negative answers from the cache says,
> >
> >   As with all answers coming from the cache, negative answers SHOULD
> >   have an implicit referral built into the answer.  This enables the
> >   resolver to locate an authoritative source.  An implicit referral is
> >   characterised by NS records in the authority section referring the
> >   resolver towards a authoritative source.
> >
> >This sentence means that DNS server should include NS record in the 
> >authority section
> >when DNS server send the negative answer from the cache, right?
> >
> >But, DNS Server1(BIND9) does not include NS record in the authority section 
> >at step6.
> >Why does not includ NS record in the authority section when BIND9 send the 
> >negative answer from the cache?
> >
> >I think this BIND9's behavior does not follow the RFC.
> >How do you think?
> >
> Well, a SHOULD is not the same as a MUST, so there is technically no RFC 
> violation here.
> 
> However, as the reference implementation for DNS, my curiosity is piqued 
> as to why BIND, of all implementations, would opt for default behavior 
> that contravenes a SHOULD from the relevant RFC.

I don't think it really matters.  In practice, clients that query a 
caching server will never query the authoritative servers directly.  So 
they would never use the NS records if they were sent.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
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