10.7. Host name resolution
TCP/IP provides a naming system that supports both flat and hierarchical network organizations so that users can use meaningful, easily remembered names instead of Internet addresses.
In flat TCP/IP networks, each machine on the network has a file (/etc/hosts) containing the name-to-Internet-address mapping information for every host on the network.
When TCP/IP networks become very large, as on the Internet, naming is divided hierarchically. Typically, the divisions follow the network’s organization. In TCP/IP, hierarchical naming is known as the domain name system (DNS) and uses the DOMAIN protocol. The DOMAIN protocol is implemented by the named daemon in TCP/IP.
The default order in resolving host names is: