Examining DNS Components
As previously mentioned, name servers, or DNS servers, are systems that store information about the domain namespace. Name servers can have either the entire domain namespace or just a portion of the namespace. When a name server only has a part of the domain namespace, the portion of the namespace is called a zone.
There is a subtle difference between zones and domains. All top-level domains, and many domains at the second and lower level, are broken into zones—smaller, more manageable units by delegation. A zone is the primary delegation mechanism in DNS over which a particular server can resolve requests. Any server that hosts a zone is said to be authoritative for that zone, with the exception of stub zones, ...