FREE online courses on Internet Network of Networks - World wide Web - Domain Name System - DNS

This is a mechanism to associate domain names that the host names to their respective IP addresses. No two hosts have the same address on Internet. The names of the domain describes the organisational or geographic realities. They have a following form:

hostname.domain_name.type_of_service.geographical_area

A few examples are:

www.mcneer.com

mail.yahoo.com

www.w3c.org

www.bbc.co.uk

www.delhi.mtnl.net.in

www.yahoo.com.sg

First three addresses belong to the servers located physically in United States of America and hence the .us is omitted, whereas the next three servers are located in the United Kingdom, India and Singapore respectively.

In the first example, www refers to the name of the machine while mcneer.com is the domain and com refers to the nature of service, i.e., is a commercial service. It is also called as top level domain. Table below lists all the top level domains.

Table: Top Level Domains

                        Domain                                  Description

                   .co                                  company

                   .com                                commercial organization

                   .edu                                 Educational organization

                   .net                                 Network organization

                   .gov                                 Government organization

                   .mil                                  Military network

                   .org                                 Organisations which can not come under educational or commercial categories

                   .int                                  International organization

Geographic Domains

Geographic domains use two letters, such as .in for India and .sg for Singapore.

Table below lists a few geographic domains.

Table: Few Geographic Domains

                   Domain                                  Country

                   .af                                   Afghanistan

                   .al                                   Albania

                   .dz                                  Algeria

                   .as                                  American Samoa

                   .ad                                  Andorra

                   .ao                                  Angola

                   .at                                   Austria

                   .au                                  Australia

                   .ca                                  Canada

                   .de                                  Germany

                   .fr                                   France

                   .fi                                    Finland

                   .in                                   India

                   .it                                    Italy

                   .jp                                   Japan

                   .lk                                   Sri Lanka

                   .kr                                   Korea

                   .pk                                  Pakistan

                   .sg                                  Singapore

                   .se                                  Sweden

                   .uk                                  United Kingdom

                   .tw                                  Taiwan

                   .za                                  South Africa