Introduction to the Domain Name System
Although TCP/IP uses IP addresses to locate and connect to hosts (computers and other TCP/IP network devices), users typically prefer to use friendly names. For example, users prefer the friendly name ftp.reskit.com, instead of its IP address, 172.16.23.55. The Domain Name System (DNS), defined in RFCs 1034 and 1035, is used on the Internet to provide a standard naming convention for locating IP-based computers.
On the Internet, before the implementation of DNS, the use of names to locate resources on TCP/IP networks was supported by a file called Hosts. Network administrators entered names and IP addresses into Hosts, and computers used the file for name resolution.
Both the Hosts file and DNS use a namespace. A namespace is a grouping in which names can be used to symbolically represent another type of information, such as an IP address, and in which specific rules are established that determine how names can be created and used. Some namespaces, such as DNS, are hierarchically structured and provide rules that allow for the namespace to be divided into subsets of names for distributing and delegating parts of the namespace. Other namespaces, such as the Hosts namespace cannot be divided and must be distributed in their entirety. Because of this, using the Hosts file posed a problem for network administrators. As the number of computers and users on the Internet grew, the task of updating and distributing the Hosts file became unmanageable.
DNS replaces the Hosts file with a distributed database that implements a hierarchical naming system. This naming system allows for growth on the Internet and the creation of names that are unique throughout the Internet and private TCP/IP-based intranets.