http://www.rfc-editor.org/rfc/rfc6195.txt
RFC 6195: Domain Name System (DNS) IANA Considerations, D. Eastlake 3rd2011-03-01T23:00:00-00:00This document specifies Internet Assigned Number Authority (IANA) parameter assignment considerations for the allocation of Domain Name System (DNS) resource record types, CLASSes, operation codes, error codes, DNS protocol message header bits, and AFSDB resource record subtypes. This memo documents an Internet Best Current Practice.