The Domain Name System (DNS) is a hierarchical distributed naming system that translates human-friendly domain names like www.google.com to IP addresses like 192.0.32.10. DNS serves as the phone book of the internet by mapping names to addresses. It uses a client-server query/response system to look up names and return addresses between DNS servers and clients.

1. Name: Vinay. A. Kahar
Guru Nanak College

2. Domain Name System (DNS)
The DNS is a hierarchical distributed naming system for computers,
services, or any resource connected to the Internet or a private network.
It associates various information with domain names assigned to each of
the participating entities. Most importantly, it translates domain names
meaningful to humans into the numerical identifiers associated with
networking equipment for the purpose of locating and addressing these
devices worldwide.
An often-used analogy to explain the Domain Name System is that it
serves as the phone book for the Internet by translating human-friendly
computer hostnames into IP addresses. For example, the domain name
www.Google.com translates to the addresses 192.0.32.10 (IPv4) and
2620:0:2d0:200::10 (IPv6).

3. NEED FOR DNS
To identify an entity, TCP/IP protocols use the IP
address, which uniquely identifies the connection of a
host to the Internet. However, people prefer to use
names instead of numeric addresses. Therefore, we
need a system that can map a name to an address or
an address to a name.
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DNS Messages
Messages
Query Response
DNS has two types of messages: query and response.
Both types have the same format. The query message
consists of a header and question records; the response
message consists of a header, question records, answer
records, authoritative records, and additional records

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NAME SPACE
To be unambiguous, the names assigned to machines
must be carefully selected from a name space with
complete control over the binding between the names
and IP addresses. In other words, the names must be
unique because the addresses are unique. A name
space that maps each address to a unique name can be
organized in two ways: flat or hierarchical.

6. Purpose of DNS
User
Host
name
1
IP address
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TCP/IP Protocol Suite 6
Host
name
2
3 Query
Response 4
IP address
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Transport layer

7. Domain name space
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9. Recursive resolution
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7
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8
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2
9
1
10
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10. REGISTRARS
How are new domains added to DNS? This is done
through a registrar, a commercial entity accredited by
Internet Corporation for Assigned Names and Numbers
(ICANN). A registrar first verifies that the requested
domain name is unique and then enters it into the DNS
database. A fee is charged.