As mentioned, the DNS “phone book” looks like a hierarchical system. This is also reflected in how the actual database which holds the information is implemented. Instead of having a big database containing answers to all queries, DNS works by delegating the responsibility, or “authority”, for each hierarchical component (., a subtree of the DNS hierarchical tree, also called a “zone”) to the servers that should be responsible for that component. These servers can further sub-delegate authority, resulting in a distributed database based on a tree topology
