NS

NS RRs appear in two places. Within the zone file, in which case they are authoritative records for the zone's name servers. At the point of delegation for either a subdomain of the zone or in the zone's parent in which case they are non-authoritative. Thus, the zone example.com's parent zone (.com) will contain non-authoritative NS RRs for the zone example.com at its point of delegation (point of delegation is the term frequently used to describe the NS RRs in the parent that delegate a zone of subdomain) and subdomain.example.com will have non-authoritative NS RRS in the zone example.com at its point of delegation. NS RRs at a point of delegation are never authoritative only NS RRs within the zone are regarded as authoritative. While this may look a fairly trivial point, is has important implications for DNSSEC