Top Level Domain Servers

Hostnames are presented in a hierarchical format. Each dot in a hostname indicates another level in the hierarchy. For example, www.ucsc.edu is the host www in the domain ucsc within the top level domain (TLD) edu. The final extension on any fully qualified hostname-the individual host with full domain-indicates the TLD. On the Internet, all fully qualified hostnames contain a TLD from a limited selection. The type of TLD usually determines to type of domain.

As with the root-level servers, TLD servers do not store individual hostnames. Instead, these servers maintain pointers to the official primary name servers for a domain. The primary name servers are the authoritative source for specific hostname resolution. The root and TLD servers provide the means for an arbitrary host on the Internet to identify a specific primary name server. RFC2240 defines three types of TLD servers: gTLD, ccTLD, and SLD.