Naming authority

In a flat network, all hosts in the network are administered by one central authority. This form of network requires that all hosts in the network have unique host names. In a large network, this requirement creates a large administrative burden on the central authority.

In a domain network, groups of hosts are administered separately within a tree-structured hierarchy of domains and subdomains. In this case, host names need to be unique only within the local domain, and only the root domain is administered by a central authority. This structure allows subdomains to be administered locally and reduces the burden on the central authority. For example, the root domain of the Internet consists of such domains as com (commercial organizations), edu (educational organizations), gov (governmental organizations), and mil (military groups). New top-level domains can only be added by the central authority. Naming at the second level is delegated to designated agents within the respective domains. For example, in the following figure, com has naming authority for all commercial organization subdomains beneath it. Likewise, naming at the third level (and so on) is delegated to agents within that level. For example, in the Domain Structure of the Internet figure, Century has naming authority for its subdomains Austin, Hopkins, and Charlotte.

This figure illustrates the hierarchical structure of the internet. It begins at the top with the root and branches to the next level containing the mil, com, and edu domains. Below the com domain is another level containing Charlotte, Austin, and Hopkins. Below Austin is Dev and Graphics.

Century's Austin subdomain might also be divided into zones, for example, Dev and Graphics. In this case, the zone austin.century.com has all the data contained in the domain austin.century.com, except that which was delegated to Dev and Graphics. The zone dev.century.com would contain only the data delegated to Dev; it would know nothing about Graphics, for example. The zone austin.century.com (as opposed to the domain of the same name) would contain only that data not delegated to other zones.