DNS as a Tree
With what you know now, it should be easier to see the tree data structure in DNS. Figure 1.3 shows the few names you have seen in this chapter in a series of zones that are nodes in the tree connected by edges in the form of NS and A records.
Figure 1.3. Nodes and edges in a DNS tree.
When a DNS server must find an RR that goes with a domain name, it first checks its own cache to see whether it has a match or how good a match it has. It might already know the nameserver for the zone or a zone closer to the root even if it doesn't have the answer. If nothing is found then a root server is queried. Each NS record returned leads ...
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