What does QD stand for in DNS RFC1035

Question

I was just curious about the nomenclature of certain variables part of DNS's RFC: https://www.ietf.org/rfc/rfc1035.txt

While I was able to find most other acronyms :

• AN in ANCOUNT seems stands for Answer
• NS in NSCOUNT stands for Name Server
• AR in ARCOUNT stands for Additional Record

I was wondering what does "QD" stand for in the "QDCOUNT"?

Answer 1

it wasn't an acronym. QDCOUNT just means what it's defined to mean. FWIW, i always think of it as Query Domain Count, because the query section has no RDATA's in it unlike the other sections, each query has just a Name, Class, and Type.

note that this field is useless now, because BIND has always rejected QDCOUNT != 1. there is no way to ask more than one question per transaction, and it's not an oversight, rather it's because there is only one AA bit to describe the entire answer section.

Answer 2

I think that the "rule" could be devised looking to the explanations in section 4.1.2 about the question section format, QD should be interpreted as Question Definition or better Query Definition, since every contained element is referred to as being a query.

Answer 3

Based on https://tools.ietf.org/html/rfc2929 I believe it likely stands for Query Data, but I don't believe that you will get an official answer outside of asking the people who designed DNS.

The unsigned fields query count (QDCOUNT), answer count (ANCOUNT),
   authority count (NSCOUNT), and additional information count (ARCOUNT)
   express the number of records in each section for all opcodes except
   Update.  These fields have the same structure and data type for
   Update but are instead the counts for the zone (ZOCOUNT),
   prerequisite (PRCOUNT), update (UPCOUNT), and additional information
   (ARCOUNT) sections. 

Other references: 1, 2

We could also just go with DNSRR iteration that says it means Query DNS Count. :)