What is DNS [Domain Name System]

Domain Name System

The addressing system on the Internet generates IP addresses, which are usually indicated by numbers such as 128.201.86.290. Since such numbers are difficult to remember, a convenient system has been created known as the Domain Name System (DNS). This system provides the mnemonic equivalent of a numeric IP address and further ensures that every site on the Internet has a unique address. For example, an Internet address might appear as dauniv.ac.in. If this address is accessed through a Web browser, it is referred to as a URL (Uniform Resource Locator), and the full URL will appear as:

http://www.techxio.com

The Domain Name System divides the Internet into a series of component networks called domains. Domain name system is a hierarchical system where we have a top level domain serving sub domain and clients with names. Each site attached to the Internet belongs to one of the domains. Universities, for example, belong to the "Edu" domain. Other domains are gov (government), com (commercial organizations), mil (military), net (network service providers), and org (non-profit organizations). These are called as generic domains.

Another category is known as country wise domain represents country. Country domains generally uses two letter from country name, some examples are:

Ae      United Arab Emirates

Au       Australia

Ca        Canada

Ch.       Switzerland

Cn        China

Gb        Great Britain

in          India

 om      Oman

 jp         Japan

 uk         United Kingdom

 

URL

A Uniform Resource Locator (URL) or Web address, is a standardized address for some resource (such as a document or image) on the Internet. It was first created by Tim Berners-Lee for use on the World Wide Web. Following is example of URL:

http://www.techxio.com

The typical URL is divided into three parts separated slashes (0) and periods (.). First part specifies the method (the protocol) used to access the resource and is followed by': 'and separated by two slashes ('//). In above example http: is denoting method. Second part is the name of the host computer on which resource is located, www.yahoo.com in above example. Third part is the path of the resource on host computer. The above example can be interpreted as a request for resource login.html, located on server www.techxio.com and it will be requested. using hypertext transfer protocol (http).

We can write generalized syntax of URL as

 method://hostname/path

In URL different methods are used for different protocols. These are:

Protocol	Method	Example
Hypertext Transfer Protocol	http:	http://www.techxio.com/login.html
File Transfer Protocol	ftp:	ftp://192.168.1.100/file.txt
Mail Servers	mailto:	mail:info@microsoft.com
Gopher	gopher:	gopher://debate.uvm.edu/
Telnet	telnet:	telnet: myserver.com