Domain Names

You do not remember your friends’ phone numbers; you tap their names and the phone finds the number. Websites work the same way. Every web server has a number — its IP address — but you type a name.

1What a domain name is

Domain name

A domain name is a text name given to a server’s IP address, so that people can reach it without remembering numbers. For example, ncert.nic.in.

Every website is stored on a web server connected to the Internet, so every web server has an IP address. Names are much easier to remember than numbers. Your NCERT book gives these examples:

Domain name	IP address
ncert.nic.in	164.100.60.233
cbse.nic.in	164.100.107.32
mhrd.gov.in	164.100.163.45
wikipedia.org	198.35.26.96

NCERT’s Table 10.1, as printed. A site can move to a different IP address, so today’s numbers may differ.

2DNS: from a name to a number

A browser cannot send a request to a name; it needs the IP address. Turning a domain name into its IP address is called domain name resolution, and it is done by a DNS server (DNS: Domain Name System).

From a name to an IP address

Play the story, or step through it. Drag sideways to turn.

Press ▶ Play to watch the browser turn a domain name into an IP address before it asks for the page.

164.100.60.233 is the address printed in NCERT’s Table 10.1. A real site’s IP address can change over time.

Think of the contacts on your phone

You tap “Aman”; the phone looks up Aman’s number and dials it. A DNS server is the Internet’s contact list: it keeps names and their IP addresses, and looks the number up for you.

3Reading a domain name

Domain names are arranged in levels, like a family tree, and a name is read from the right. In www.ncert.nic.in:

in is the top-level domain — India.
nic.in is inside it, and ncert.nic.in inside that: ncert.nic.in is the domain name.
www at the front is a subdomain.

Reading a domain name

Choose a name and follow its branch from the root. Drag sideways to turn.

Read from the right: in → nic.in → ncert.nic.in → www.ncert.nic.in.

Some top-level domains

Ends in	Usually for
.com	commercial — companies
.org	organisations
.net	network providers
.edu	education (mostly USA)
.in	India
.gov.in	the Government of India
.ac.in	Indian colleges and universities

DNS servers are arranged in the same levels. At the top are the root servers. A DNS server either knows the IP address for a name, or knows which DNS server lower down to ask.

About NCERT's note on root servers

NCERT says there are 13 root servers, ten of them in the USA. There are 13 root server names, A to M, but each is copied at hundreds of places around the world today — including several in India.

4From the board papers

What is a domain name? What does a DNS server do? (Practice)

2 marks

▶Show the answer

A domain name is a text name for a server’s IP address, such as ncert.nic.in. A DNS server keeps domain names with their IP addresses and converts a domain name into its IP address (domain name resolution), so the browser can reach the server.

CBSE asks about domain names by comparing them with URLs — those questions are on the URL page.

5Check yourself

Quick Check

What does a DNS server give the browser?

Quick Check

In www.cbse.gov.in, which part is the top-level domain?

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