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What is Domain Name System? Learn about DNS.

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In this article we will talk about what is domain name system and what exactly it does. So let us start.

Domain Name:

Domain name is an unique name used to identify website on internet. There rules and procedures are defined in Domain Name System i.e DNS. Any name registered in the DNS is a domain name. Domain names are case-insensitive, so com, Com, and COM mean the same thing. A full domain name is a sequence of labels separated by dots (.).

Domain Name System (DNS):

Domain Name System is an invention of a hierarchical, domain-based naming scheme and a distributed database system for implementing this naming scheme. It is primarily used for mapping host names to IP addresses but can also be used for other purposes. DNS Provides the protocol that allows the client and servers to communicate with each other.

Name Space:

In DNS Name Space is structured as a tree, with domain names referring to nodes in the tree. The tree has a root, and a fully-qualified domain name is identified by the components of the path form the domain name to the root. It has two types: Flat name space and Hierarchical names. Flat name spaces considered of sequence of characters with no further structure. Flat names are convenient and short. They cannot generalize to large sets of machines because of the single set of identification. The hierarchical name spaces provides a simple yet flexible naming structure. These name space is partitioned at the top level. Each domain is partitioned into subdomains, and these are further partitioned, and so on.All these domains can be represented by a tree, as shown in Figure.
A portion of the Internet domain name space.
A portion of the Internet domain name space.

The figure shows top level domains.
top-level domains
Top-level domains

Domain Name Space:

In DNS, names are defined in an inverted tree structure with the root at the top. The tree can have only 128 level: Level 0 to Level 127. Each node has a label, which is a string with a maximum of 63 characters. The root label is a null string, i.e. empty string. Each node has a domain name, they are separated by dot (.). Figure shows domain names & labels.
Domain name and labels.
Domain name and labels.

Name Servers:

A single name server could contain the entire DNS database and respond to all queries about it. In practice, this server would be so overloaded as to be useless. Furthermore, if it ever went down, the entire Internet would be crippled. To avoid the problems associated with having only a single source of information, the DNS name space is divided into nonoverlapping zones. Figure shows the zones.

Part of the DNS name space divided into zones (which are circled).
Part of the DNS name space divided into zones (which are circled).
In zone, a server is responsible and have some authority. The server makes database called zone file and keeps all the information for every node under that domain. Domain and zone are same if server accepts responsibility for domain and does not divide the domain into sub-domain. Domain and zones are different, if a server divides its domain into sub-domains and delegates part of its authority to other server. Figure shows zones and domain.
Zones and Domains
Zones and Domains

Domain Name Registrar:

It is an organization that reserves or manages internet domain name. They are accredited by a top-level domains and country-level domains. We will see how to register for domain in next article.

I hope you have got much detailed information about Domain Name System. If you have any query regarding to this article please post it below in the comment section. We will see how to apply domain name for your blog in next article.Thank you!
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