Clarifications to the DNS Specification

This document considers some areas that have been identified as problems with the specification of the Domain Name System, and proposes remedies for the defects identified. Eight separate issues are considered: (1) IP packet header address usage from multi-homed servers, (2) TTLs in sets of records with the same name, class, and type, (3) correct handling of zone cuts, (4) three minor issues concerning SOA records and their use, (5) the precise definition of the Time to Live (TTL) (6) Use of the TC (truncated) header bit (7) the issue of what is an authoritative, or canonical, name, (8) and the issue of what makes a valid DNS label. The first six of these are areas where the correct behaviour has been somewhat unclear, we seek to rectify that. The other two are already adequately specified, however the specifications seem to be sometimes ignored. We seek to reinforce the existing specifications.