This document provides an overview of the Domain Name System (DNS). It describes how DNS uses domain names to map to IP addresses in a hierarchical structure. Key points include: - DNS allows users to use domain names like "example.com" instead of numeric IP addresses for easier identification of internet hosts. - DNS information is stored across multiple name servers to prevent a single point of failure. - The domain name space is divided into generic, country code, and inverse domains to organize names by usage and map addresses to names. - Domain names are read from right to left with the top-level domain at the far right, working left through more specific subdomains.

1. Domain Name System
(DNS)
Created By:
Kheradiya Bhavik A.
Dhingani Harshil P.

2. Contents
 Introduction
 Example Of Domain Name
 Name Server
 DNS in Internet
 Generic Domain
 Country Domain
 Inverse Domain

3. Introduction
 Domain name system is a client server application that identifies each host on
the internet, with a unique user friendly name.
 Domain name system is a method to identifying hosts with user friendly names
instead of ip addresses. Because to remember numeric addresses are difficult
compare to names.
 In Domain Name System names must be unique because the addresses are
unique.
 Each Domain is partitioned into sub domains.
 Once an Organization assigned domain name, the name is reserved for the
Organization, means no other Organization will be assigned the same name.

4.  To map a name into IP address, an application program calls a library
procedure called the Resolver, passing it the name as a Parameter. The
Resolver sends a UDP packet to local DNS server, which then looks up the
name and returns the IP address to the resolver, which then returns it to the
caller process.
 Domain names are always read from the bottom to top.

5. Example Of Domain Name
Lable
Edu
Fhda
Atc
Chalanger
Edu.
Fhda.edu
Atc.Fhda.edu
Challenger.Atc.Fhda.edu

6. Name Server
 Information contained in the domain name system must be stored. It is very
difficult and not reliable to have just one computer store such large information.
 To solve above problem, we have to distribute the information among many
computer called DNS servers.
 The hierarchy of servers shown beside:

7. DNS in Internet
 In the internet, domain name space is divided into 3 different section.
1. Generic domain
2. Country domain
3. Inverse domain

8. 1. Generic Domain
 Generic domain defines registered host according to their generic behavior.
Each node in the tree defines a domain.

9. Com Commercial Organization
Edu Educational Institutions
Gov Government Institutions
Int International Organization
Mil Military Groups
Net Network Organization
Org Non profit Organization

10. 2. Country Domain
 The Country domain uses a two-character abbreviation in place of three
character abbreviation at first level.

11. 3. Inverse Domain
 The inverse domain is used to map address to a name.
 When a server has received a request from a client to do a task,
server lists only the IP address of the client. To determine if the
client is on the authorized list, the server can send a query to the
inverse DNS server and ask for a mapping of address to name.
 The inverse domain is added to the domain name space with the
first-level node called arpa. (Advanced Research Projects Agency)
The second level is also one single node named in-addr.
(for inverse address) The rest of the domain defines IP address.
 An ip address such as 132.34.45.121(class B address) this
is read as 121.45.34.132 in-addr arpa.
 132.34 45 . 12 = ip address of class B
net id subnet id host id

12. Thank You