Basic DNS Concepts

This page provides brief definitions of DNS concepts, which are described in more detail in the following sections of this page.

What is DNS ?

The Domain Name System (DNS), is a naming protocol that is used for converting hostnames like into numeric IP addresses like, and vice-versa. DNS is connected to Internet or Private Network and converts human-friendly domains or website names to its unique numeric host IP address.

Domain Name

Any name registred in DNS with rules and procedures of domain name system (DNS) is a domain name. For example, and so on.

Domains are divided into 3 standard parts: [] where sub-domain can be any name like www (represents world wide web sub-domain), mail, ftp, etc. Top-level domains are the Authoritative domain extension, like .com, .in, .net, .gov, etc.

Domain Name constitute URL, example of valid URL: The URL is then accessed by browses or web program.

Top-Level Domain

A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. The top-level domain names are installed in the DNS root zone of the name server. The last lable of a fully qualified domain name is the top-level domain. For example, in the domain name, the top-level domain is com.

Responsibility for management of most top-level domains is delegated to specific organizations by the Internet Corporation for Assigned Names and Numbers (ICANN), which operates the Internet Assigned Numbers Authority (IANA), and is in charge of maintaining the DNS root zone.

IP Address

An Internet Protocol (IP), is the address of any network. Each IP address must be unique within its network. Each website domain-name is mapped with an unique IP address, this network is the entire Internet and are bind with unique Public IP address.

IPv4, the most common form of addresses, are written as four sets of numbers, each set having up to three digits, with each set separated by a dot. For example, "888.222.777.222" could be a valid IPv4 IP address.

With DNS, we bind a human friendly name to that numeric address so that it becomes easy to remember a complicated set of numbers for each place you wish to visit on a network.

Name Server

A name server is a computers that run DNS server programs containing DNS database information about the DNS domain tree structure. DNS servers also attempt to resolve client queries. When queried, DNS servers can provide the requested information, provide a pointer to another server that can help resolve the query, or respond that it does not have the information or that the information does not exist.

The most important function of Name servers is locating and translating (resolution) human-memorable domain names and hostnames into the corresponding numeric Internet Protocol (IP) addresses.

DNS resolvers

DNS resolvers are the client side of the DNS, responsible for initiating and sequencing the queries that lead to a full resolution of the domain name into an IP address.

DNS resolver are programs that use DNS queries to query for information from servers. Resolvers can communicate with either remote DNS servers or the DNS server program running on the local computer.

DNS Resource records

DNS Resource records are set of information in the DNS database or zone that can be used to process client queries. Each DNS server contains the resource records it needs to answer queries for the portion of the DNS namespace for which it is authoritative.

A DNS server is authoritative for translating queries of the DNS namespace if it contains information about that portion of the namespace.


A zone is a contiguous portion of the DNS namespace. It contains a series of records stored on a DNS server that binds domain names with IP addresses. Each zone is anchored at a specific domain node.

Using the zone, the DNS server answers queries about hosts in its zone, and is authoritative for that zone. Zones can be primary or secondary. A primary zone is the copy of the zone to which the updates are made, whereas a secondary zone is a copy of the zone that is replicated from a master server.

Zones can be stored in different ways. For example, they can be stored as zone files or as relational database.

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