TCP/IP name resolution
Although 32-bit Internet addresses provide machines an efficient means of identifying the source and destination of datagrams sent across an internetwork, users prefer meaningful, easily remembered names. Transmission Control Protocol/Internet Protocol (TCP/IP) provides a naming system that supports both flat and hierarchical network organizations.
Naming in flat networks is very simple. Host names consist of a single set of characters and generally are administered locally. 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. The administrative burden of keeping each machine naming file current grows as the TCP/IP network grows. WhenTCP/IP networks become very large, as on the Internet, naming is divided hierarchically. Typically, the divisions follow the network 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.
As in naming for flat networks, the domain name hierarchy provides for the assignment of symbolic names to networks and hosts that are meaningful and easy for users to remember. However, instead of each machine on the network keeping a file containing the name-to-address mapping for all other hosts on the network, one or more hosts are selected to function as name servers. Name servers translate (resolve) symbolic names assigned to networks and hosts into the efficient Internet addresses used by machines. A name server has complete information about some part of the domain, referred to as a zone, and it has authority for its zone.