What is DNS (Domain name server or system)? working of DNS, types of domain names?

Domain Name/Domain Name Space

·        Domain Name is a way to identify and locate computers connected to Internet.

·        No two organizations can have same domain name.

·        A domain name always consists of two or more components separated by periods called dots. For example : www.yahoo.co.in, www.facebook.com etc.

·        Once a domain has been established, subdomains can be created within the domain.               For example, the domain for a large company could be "uni.com" and within this domain, subdomains can be created for each of the company's regional office. For example: bombay.uni.com.

·        The structure for domain name is hostname.subdomain.second-level domain.top-level domain. For example, vijay.bombay.uni.com.

·        Not all domain names will have a hostname and subdomain.

·        The top level domains are classified into 3 categories

                                                 1. Organizational or generic domains

                                                2. Geographical or country domains

                                                3.Reverse domains

·        The organizational/generie domain consists of 3 character code which indicates the primary function of the organization or their generic behaviour.

·        The most country used top-level domains are:

                                                1. com-> for commercial organization >e.g. yahoo.com

                                                2. net- for networking organizations ->e.g. www.whois.net

                                                3. .gov- for governmental organizations e.g. www.newjersey gov

                                                4. edu for educational organizations- e.g. www.educause.edu

                                                5. org-> for non-commercial organizations -> e.g. www.eklavya.org .

      6       .mil-for military organizations- e.g. www.dod.mil

      7       .intfor international organizations -> e.g. www.itu.int .

·        Beside this, the Internet Corporation for Assigned Names & Numbers (ICANN) approved several new domain names in Nov. 2000. These are:

                                                biz->business

                                                info-information

                                                coop >cooperatives

                                                aero-> aeronautical industry

                                                name- for individuals

                                                pro >for certified professionals

·        The country domains consists of 2 characters which represents different countries/regions all round the world. (ISO).

·        These codes have been standardized by International Standard Organization .

·        For example :        in - india, cn-> china

.                                               au- australia, .it- italy, jp >japan

                                                 us-united states, .fr >france etc.

The Reverse domain is a special domain named in-addr.apra that is used to translate the IP address to Fully Qualified Domain Name.

For eg. : 14.220.134 in-addr.apra will return sunc.scit.wlv. Here 1.4.220.134 is the IP address that is mapped to its name sune.scit.wlv.at.uk with the help of in-addr.apra domain.

Thus each domain name has a corresponding IP address.

When a user types the domain name in address bar the corresponding IP address is supplied. Such a translation is possible with the help of system called DNA (Domain Name System)

Domáin Name System

The domain name system is a collection of databases that contain information about domain names and their corresponding IP address.

Domain name server is the computer that translates domain name to IP address.

Working of DNS

When an application program needs to communicate with other computer, it needs to translate the name of the other computer into its IP address. The application program that requests the service then becomes the client of DNS. It then sends the request to DNS server. The server looks up the name & then returns the correct IP address. A large number of DNS servers may be involved to get the right IP address. After receiving the correct IP address, the communication between two computers start Consider an example, where we want to access the IP address of www.yahoo.com. In this case following steps will take place:

1. When you type name www.yahoo.com into your browser it asks local DNS server (at ISPs end) for its IP address.

2. When local DNS server does not find the IP address of given name, it forwards request to root DNS server and again require about IP address of it.

3. The root DNS server replies "I do not know the IP address of www.yahoo.com but know the IP address of the dot com DNS server."

4. The local DNS server then asks the dot com DNS server for IP address.

5. The dot com DNIS server replies with same answer it does not know the IP address of www.yahoo.com. But know the IP address of yahoo.com which is then returned to local DNS server.

6. The local DNS server then ask the yahoo.com DNS server for IP address.

7. It then replies with the IP address corresponding to www.yahoo.com which it has

8. The local DNS server then send this IP address back to the client computer that send the request.