The Domain Name System is one way to resolve host names in a TCP/IP environment. In non-Microsoft environments, host names are typically resolved through host files or DNS. In a Microsoft environment, WINS and broadcasts are also used. DNS is the primary system used to resolve host names on the Internet. In fact, DNS had its beginning in the early days of the Internet.In its early days, the Internet was a small network established by the Department of Defense for research purposes. This network linked computers at several government agencies with a few universities. The host names of the computers in this network were registered in a single HOSTS file located on a centrally administered server. Each site that needed to resolve host names downloaded this file. Few computers were being added to this network, so the HOSTS file wasn’t updated too often and the different sites only had to download this file periodically to update their own copies.

As the number of hosts on the Internet grew, it became more and more difficult to manage all the names through a central HOSTS file. The number of entries was increasing rapidly, changes were being made frequently, and the server with the central HOSTS file was being accessed more and more often by the different Internet sites trying to download a new copy.

DNS was introduced in 1984 as a way to resolve host names without relying on one central HOSTS file. With DNS, the host names reside in a database that can be distributed among multiple servers, decreasing the load on any one server and also allowing more than one point of administration for this naming system. The name system is based on hierarchical names in a tree-type directory structure. DNS allows more types of registration than the simple host-name-to-TCP/IP-address mapping used in HOSTS files and allows room for future defined types. Because the database is distributed, it can support a much larger database than can be stored in a single HOSTS file. In fact, the database size is virtually unlimited because more servers can be added to handle additional parts of the database. The Domain Name System was first introduced in 1984.