30.1. Introduction to the Domain Name System
DNS is a protocol used primarily for converting hostnames like www.example.com into IP addresses like 192.168.1.10, and vice-versa. At the IP level, all hosts on the Internet refer to each other by IP addresses, not by the hostnames that users enter into programs like web browsers and telnet clients. This means that a system needs a way of finding out the IP address associated with a hostname before they can communicate. Although there are several ways this can be done (such as reading the /etc/hosts file or querying an NIS server), DNS is the most common.
As well as looking up IP addresses for hostnames, the DNS protocol can also be used to find the hostname associated with an IP address. This is ...
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