DNS on Windows Server 2003, 3rd Edition

The Domain Namespace

DNS’s distributed database is indexed by domain names. Each domain name is essentially just a path in a large inverted tree, called the domain namespace. The tree’s hierarchical structure, shown in Figure 2-1, is similar to the structure of the Windows filesystem. The tree has a single root at the top.^[1] In the Windows filesystem, this is called the root directory and is represented by a backslash (\ ). DNS simply calls it “the root.” Like a filesystem, DNS’s tree can branch any number of ways at each intersection point, or node. The depth of the tree is limited to 127 levels (a limit you’re not likely to reach).

Figure 2-1. The structure of the DNS namespace

^[1] Clearly this is a computer scientist’s tree, not a botanist’s.