Domain Name System

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The Domain Name System (usually abbreviated to DNS) is a replicated distributed database which is used on the Internet to hold mappings from human-readable names (such as '.COM') to binary addresses. Before DNS, a file holding the mappings, the host table, was used, but that clearly was not going to scale.

The DNS is organized as a hierarchy; like file names in a hierarchical file system, a complete DNS name consists of a number of parts, each one of which selects one of the possible namespaces (sub-directories) at the next level down. The leaves of the tree usually name individual hosts.

Although the DNS has the capability to hold addresses for a number of different protocol suites using the concept of address classes, in general it now only hold addresses for the Internet Protocol. The CH class for Chaos fell in disuse and has sometimes been reused for other purposes, but is now in use again for a hobbyist Chaos network.

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