Each device connected to the public internet has a unique numeric address called IP address. An IP address is like a phone number which is difficult to remember. To simplify the identification of device on internet, the DNS was invented. Domain Name System translates IP address to alphanumeric names known as domain name. The domain name is human readable form of IP address. For example, IP address google.com is 220.127.116.11. Thus it is easy to remember google.com then its IP address 18.104.22.168.
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A namespace is a grouping in which names can be used to symbolically represent another type of information, such as an IP address, and in which specific rules are established that determine how names can be created and used
Before the implementation of DNS, the use of names to locate resources on TCP/IP networks was supported by a file called Hosts. Network administrators entered names and IP addresses into Hosts, and computers used the file for name resolution.
Hosts file posed a problem for network administrators. As the number of computers and users on the Internet grew, the task of updating and distributing the Hosts file became unmanageable. Thus DNS was introduces to rescue the internet.
Domain Name System (DNS) is a distributed database that implements a hierarchical naming system. DNS is based on hierarchical and logical tree structure known as domain namespace. A domain namespace consists of tree structure of domain names with root domain at the top. Immediately below the root, there are major domains such as .in, .net, .com, .org etc. From these domains, the name space can branch into multiple paths, with each intersection point called a node and labeled with a simple name.
Each node in DNS tree represents a DNS name. a DNS name can be DNS domains, computers and services.
For example, refer to the below DNS tree. Here google.com is a DNS domain. The domain google.com is further divided to create sub-domain mail.google.com.
Every node in the DNS domain tree can be identified by a fully qualified domain name (FQDN). An FQDN is a domain name that contains the full name of a host. It contains all labels, from the most specific to the most general, that uniquely define the name of the host. For example, the FQDN for the news server in the yahoo.com DNS domain is constructed as news.reskit.com. The dot is a standard separator between two labels in the tree.
Here are some of the common top level domains used widely over the internet.
Internet Corporation for Assigned Names and Numbers (ICANN) is responsible for managing domain names. It is responsible for management of root name servers.
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