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

[Marek Vavruša]

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.

My reasoning is that the end user rarely needs anything but the direct
answer, maybe additional address records for MX, NS and such. But
presuming that most of the resolver traffic is 'IN A
www.populardomain.com'-like, and a lot of traffic originates from
congested mobile networks, it makes sense to me to return only minimal
possible responses.
Or am I wrong?

 - Marek

[1] With the exception of SOA for NODATA and DNSSEC-related data.