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Domain

Name Server

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Domain Name Server(DNS)

Why DNS

History of DNSDNS hierarchy

Architecture

Domain Name Resolution

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Why Domain Name Service?

Each computer ON Internet has two addresses a numericIP address (such as 241.111.4.142") and a host name suchas www.bsnl.co.in.

Computer in the Network understands only IP address.

IP address may change whenever hosts are relocated on anetwork or from one network to another

It is easy to remember common language names than IPbased name format .

It is required to translate the domain name entered by theend user into its IP address to enable the transporting of

packets over networks.

DNS performs this translation using a database of hostinformation

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Domain Name Server

It is a database holding the IP address against domain

name.

In the early days the DNS was stored as a simple textfile located on each computer on the internet.

It became impossible to administer this database as

the host on internet grew in fast manner.

Hence DNS become a distributed database.

Portions of DNS database are stored on local name

servers and updated local DNS administrators.

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History of DNS

Initially started by ARPANet

Host information collected and organized by

InterNIC.The information file is called Hosts file or

Phone Book.

In 1980 DARPA shifted its protocol platform to

TCP/IP

This made to grow the network abundantly.

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Due to the fast growing nature of Internet it become

impossible to have all the host names in a centrally

organized Host file.

ARPA adopted new method of maintaining Host

name The Domain Name Service.

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In this system eight numbers of top level domainsare defined.

Sites are categorized and grouped in to the top level

domains.Each domain in the network would maintain a

Domain Name Server.

This server would supply information about thespecific hosts with in the domain it served to otherservers.

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Advantages of the DNS

Same Domain Name can repeat on different

domains.

The Domain administrator can add new host

without prior intimation to other hosts.

Distributed administration.

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Top Level Domains

.com:-Commercial organizations.edu:-Educational organizations

.gov:-Government organizations

.mil:-Military organizations

.net:-Networking organizations

.org:-Non-Commercial organizations

.int:-International organizations

.arpa:-ARPA Domain*

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Control on DNS

IAB

Internet Architecture Board

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Geographical domains

In addition to the top level domains IAB decided

to have geographical domains.

Geographical domain name with two alphabet.

Eg: in:- India, uk:- Britain ,fr:-France

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Domain Name Hierarchy

Domain name can be up to 63 character in length.

May contain digits or hyphens.

Should start with an alphabet.

Not case sensitive.Each domain has a domain server.

The collection of hosts which the server can give a name or

IP address is called The Zone of authority

Zone of authority defines the boundary of the zone.

The entire collection of domains is called domain name

space.

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Domain Name Hierarchy

A domain name which can be identified uniquely in a

domain is called fully qualified domain name(FQD)

A domain can have sub domains.

Eg:www.yahoo.com,www.rttctvm.bsnl.co.in

www.ernakulam.sancharnet.in are

fully qualified domain names.

http://www.yahoo.com/http://www.yahoo.com/http://www.rttctvm.bsnl.co.in/http://www.rttctvm.bsnl.co.in/http://www.ernakulam.sancharnet.in/http://www.ernakulam.sancharnet.in/http://www.ernakulam.sancharnet.in/http://www.rttctvm.bsnl.co.in/http://www.yahoo.com/

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Domain Name Hierarchy

in

sancharnet vsnl satyam

ernakulam chni bgr

www.sancharnet.inwww.satyam.inwww.sancharnet.ernakulam.in

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Domain Name-space

.com

.edu.in

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.in -domain name space

sancharnet

satyam

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.sancharnet.in -domain name space

ernalulam chni

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How to resolve Domain Name query?

You are requesting www.yahoo.com from a sanchernet client

Query sent to sancharnet nameserver

Query sent to .com rootname server

Response from the root name server

Ask the guy w.x.y.z

Query to name server w.x.y.z

Response from name server w.x.y.z

The address of www.yahoo.com is r.s.t.u

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Architecture of DNS

There are two type of name servers Primary master and

secondary master.

Primary master contains the database for its zone of

authority.

Secondary master stores a copy of primary master.

Name servers with zone of authority a top level domain is

called root name server.

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DNS software

The server application developed for DNS function is

called BIND.

BIND Berkeley Internet Name Domain

BIND is developed in UNIX platform.

A ported version of BIND is developed later for Windows

NT platform.

Microsoft developed its own DNS software for working inWindows NT platform.

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InterNIC

Controls the Domain Name

registration

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Controls the Domain Name

Registration in Asia Pacific

APNIC

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Controls the Domain Name

registration in in domain

C-DAC(formerly NCST)Centre for Development of Advanced Computing,

Mumbai (formerly known as National Centre

forSoftware Technology)