[dns-operations] extra records in resolver answer, any benefit?

Mark Andrews marka at isc.org
Tue Jan 27 10:40:42 UTC 2015

In message <20150127094526.GA20728 at xs.powerdns.com>, bert hubert writes:
> On Tue, Jan 27, 2015 at 10:07:33AM +0100, Marek Vavrua wrote:
> > Hi, I was wondering if there's any operational benefit in including
> > records other than direct answer in resolver responses 1?  For
> > example, some recursors return authoritative NS records, SOA, glue,
> > etc., and some servers scrub them. I have utterly failed in finding
> > anything in the related RFCs to back this up, so I guess it's up to
> > implementors.
> It is all optional, and nobody does anything with that data. In fact stub
> resolvers do very little with what they receive. So for example, even the
> additional processing for an MX record is completely ignored mostly.

That is really dependent on the application.
> > congested mobile networks, it makes sense to me to return only minimal
> > possible responses.
> > Or am I wrong?
> It also saves CPU for the resolver.

Named will save, validate and return additional data without
performing additional queries if it is signed (assuming the DNSKEY
records exist in the cache and have already been validated).

So even if the application ignores the additional data, named will
take advantage of it using lazy validation.

> 	Bert
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Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org

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