DNS (DOMAIN NAME SYSTEM)

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Real Life Analogy: Telephone Example

Telephone connection

Source: Child

Destination: Dad

Information Child Needs: Dad’s Phone #

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Dials 312-256-1212:

(What is University # ?)

operator

2

Dials 0: (what is Turkey’s area code?)

3(Ankara are code is 312)

Directory assist

45(University number: 312-256-1212)

Universityoperator

6

Dials 312-256-1212 :

(what is Dad phone #?)

7Dad’s phone is 312-256-1212

Calls dad

(What is Dad’s Phone#?)1

Older sister

Child

Dad’s phone is

312-256-1212

8

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DNS COMPONENTSThere are 3 components:

Name Space:

Specifications for a structured name space and data associated with the names

Resolvers:

Client programs that extract information from Name Servers.

Name Servers:

Server programs which hold information about the structure and the names.

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NAME SPACE

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RESOLVERSA Resolver maps a name to an address and vice versa.

Query

Response

Resolver Name Server

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ITERATIVE RESOLUTION

iterative response (referral)“I don't know. Try a3.nstld.com.”

2

a3.nstld.com

3

client

iterative request “What is the IP address of www.google.com?”

udel server

1

iterative response (referral)“I don't know. Try a.root-servers.net.”

4

a.root server

5

iterative response (referral)“I don't know. Try a.gtld-servers.net.”

6

a.gtld- server

7

iterative response (referral)“I don't know. Try ns1.google.com.”

8

ns1.google.com

9

iterative response“The IP address of www.google.com is 216.239.37.99.”10

RECURSIVE RESOLUTION

client

recursive request“What is the IP address of www.google.com?”

udel server

1

edu server

2

root server

3 com server

4googleserver5

recursive response“The IP address of www.google.com is 216.239.37.99.”

6

10

78

9

DNS The Domain Name System (DNS) is a system for naming sources of information on the internet. Each source of information has a domain name attached to it, with the domain name then being translated into IP addresses for location purposes.

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VIDEO TIME http://www.youtube.com/watch?v=2ZUxoi7YNgs

Betül ŞAHİN - 21001525