Domain Name System
The Domain Name System (DNS) is the system used to translate alphanumeric domain names into Internet Protocol numbers. Simply put, the DNS converts the names typed in the Web browser address bar into IP addresses. 
The DNS is made up of many servers and databases which, through a series of lookups in various caches, configure Domain Names into IP Addresses. The Domain Name System is a distributed database arranged hierarchically; its purpose is to provide a layer of abstraction between Internet services (web, email, etc.) and the numeric addresses (IP addresses) used to uniquely identify any given machine on the Internet. The DNS associates a variety of information with the domain names assigned and, most importantly, translates the domain names meaningful to humans into the numerical identifiers that locate the desired destination.
How Does It Work?
The DNS makes it possible to assign domain names in a meaningful way to Internet resources as well as to users, regardless of the entity's location. As a result, the WWW hyperlinks remain consistent, even for mobile devices. A domain name is an easy way to remember an address, but that needs to be converted to its numerical, IP format. 
Coordination across the Internet is maintained by means of a complex authoritative root system known as the Top Level Domain (TLD), as well as the DNS and other smaller name servers responsible for hosting individual domain information.
DNS includes three types of top-level domains: generic (gTLD), country code (ccTLD), and sponsored (sTLD). gTLDs include domains that could be obtained by anyone (.com, .info, .net, and .org). Since 2014 many other gTLDs have been added like .pub, .ngo, .sucks. sTLDs are limited to a specific group e.g .aero (for air-transport industry).
For each domain, the DNS spreads the responsibility by mapping the domain names and assigning them into IP addresses, and vice-versa. This is accomplished through authoritative name servers which have been designated for each domain. Each authoritative name server is responsible for its own particular domain, but it has the authority to assign new authoritative name servers to any of its sub-domains. The DNS is able to store many types of information, even the mail server lists for a specific domain. The DNS is a core element which ensures the functionality of the Internet through its distributed keyword-based redirection service.
However, the DNS does not include security extensions, which was instead developed as DNSSEC.
==Domain Name System== dns illustration.
The Structure of a DNS
The Domain Name System presents the following structure:
- Domain space name: represented by tree of domain names with nodes and leaves 
- Domain name syntax: rules include in standards like RFC 1035, RFC 1123, and RFC 2181
- Name server
- Domain names Internationalized
- DNS resolver: initiates the queries will finally lead to the complete translation (resolution) of the information.
These types of services include:
- Managing the DNS
- By means of powerful, secure and complete tools and DNS administration options such as Manage A records or MX records
- By means of controlling and managing the traffic
- Hosting the DNS
- Efficient DNS resolution
- Location DNS services: to ease visitors' work, increase visitors' satisfaction and strengthen the relationship with all visitors.
In 2012, an IETF draft proposal, called "DNS Extension for Autonomous Internet (AIP)," was written by three Chinese technologists suggesting a method of operating alternate DNS root servers within national boundaries using gateways for translation. All DNS requests would carry an additional TLD, in order to designate that the requests were being sent to an alternate root.
Domain node “www.yahoo.com” in network B is expressed as “www.yahoo.com.B” for its external domain name.
The proposal would allow greater governmental control over the Internet.