Introduction to Domain Name - GeeksforGeeks

22 Dec, 2020
Every computer on the Internet has an address which is unique in nature. It is a string of numbers and is referred to as IP address. To communicate with each other, computers identify another computer via its IP address. It is represented in either dotted decimal notation or in binary decimal notation. Example: The address 172.16.122.204 when represented like these in dotted-decimal notation and it can be converted into binary notation. After conversion, it becomes 10101100 00010000 01111010 11001100.But it is difficult for humans to remember this IP address. Thus to find the location on the Internet easily, DNS was invented. DNS stands for Domain Name Server. It implements a distributed database which translates IP address into a unique alphanumeric address which is referred to as Domain Names. Basically, a domain name is the sequence of letters and or numbers separated by one or more period (“.”). It is just like a pointer to a unique IP address on the computer network. As an analogy one can consider Domain name as address and DNS as address book of the Internet.
Example-1:Lets us consider an example for domain name;
www.google.com, www.yahoo.com 
In this “yahoo.com” is called domain name.“www.” tells the browser to look for World Wide Web Interface for that domain.
As from the above example, it is clear that domain names are easy to remember than an IP address.
Example-2:Assume that the IP address of www.yahoo.com is 69.147.76.15. It is easy to remember www.yahoo.com as compared to IP address 69.147.76.15.
Thus, we can say like these; domain name refers to the string of letters associated with an IP address and DNS is a mechanism used to convert an IP address to the domain name.Types of Domain Names :DNS has organized all the domain names in a hierarchical structure. At the top of this hierarchy come various Top-level domains followed by second and third-level domains and sub-domains. All these types of domain names are listed as follows –
Top Level Domains (TLD) :The Top Level Domains are at the highest level in DNS structure of the Internet. It is sometimes also referred to as an extension. It is further categorized into- country code TLDs and generic TLDs which Country is described as follows –
Country code Top Level Domain (ccDLDs) :It consists of two-letter domains that include one entry for every country. Example – .in for India, .au for Australia, .us for United Nations, .jp for Japan etc. To target the local audience it is used by companies and organizations . Only the residents of the country are allowed to is their specified ccTLD but now some countries allowed the users outside their country to register their corresponding ccTLDs.
Generic Top Level Domains (gTLDs) :These are open for registration to all the users regardless of their citizenship, residence or age. Some of the gTLD s are .com for commercial sites, .net for network companies, .biz for business, .org for organizations, .edu for education.
There are various other levels which are below TLDs –Second Level :It is just below the TLD in the DNS hierarchy. It is also named as the label. Example: in .co.in, .co is the second-level domain under the .in in ccTLD.
Third Level :It is directly below the second level. Example: in yahoo.co.in, .yahoo is the third level domain under the second level domain .co which is under the .in ccTLD.
Sub-domain :It is the part of a higher domain name in DNS hierarchy. Example: yahoo.com comprises a subdomain of the .com domain, and login.yahoo.com comprises a subdomain of the domain .yahoo.com.
Advantages of Domain Name :
User not need to remember the IP address.
More reliable and secure.
Disadvantages of Domain Name :
IP address changes due to several reasons, due to this IP address of the computer get changed but DNS may have cached previous IP which will lead to give us wrong information.
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