The Domain Name The Domain Name SystemSystem

donna Bair-Mundy

Visiting the MIT Library Website

http://libraries.mit.edu

Visiting the MIT Library Website

http://libraries.mit.edu

Universal Resource Locator (URL)

http://libraries.mit.edu

machineprotocol

Human-readable address

Getting the IP (numerical) address

What is numerical address of libraries.mit.edu?

Address: 18.51.0.23

Local Domain Name Server

Our Computer

Where does the local Domain Name Server

get the numerical address?

Root

Domain Name System Hierarchy

Our Local DNS

.com .org .edu .gov .af .al ...

libraries.mit.edu?

Top-Level Domains

Root

The DNS hierarchy

.com .org .edu .gov .af .al ...

GenericTop-Level Domains

(gTLDs)

Country-CodeTop-Level Domains

(ccTLDs)

http://www.iana.org/domains/root/db/

Root

The DNS hierarchy

.com .org .edu .gov .af .al ...

United StatesGeneric Top-Level Domains

(also .mil)

Root

The DNS hierarchy

Our Local DNS

.com .org .edu .gov .af .al ...

address for .edu server

Root

The DNS hierarchy

Our Local DNS

.com .org .edu .gov .af .al ...

libraries.mit.edu?

Root

The DNS hierarchy

Our Local DNS

.com .org .edu .gov .af .al ...

hawaii.edumit.edu ucsd.edu

stanford.edu yale.edu

address for mit.edu server

Root

The DNS hierarchy

Our Local DNS

.com .org .edu .gov .af .al ...

hawaii.edumit.edu ucsd.edu

ucsd.edu ucsd.edu

libraries.mit.edu?

18.51.0.23

Getting the IP (numerical) address

What is numerical address of libraries.mit.edu?

Address: 18.51.0.23

Local Domain Name Server

Our Computer

Root

The DNS hierarchy

Our Local DNS

.com .org .edu .gov .af .al ...

hawaii.edumit.edu ucsd.edu

ucsd.edu ucsd.edu18.51.0.23

(authoritative answer)

%Server: 128.171.3.13Address: 128.171.3.13#53

Non-authoritative answer:www.google.com canonical name = www.l.google.com.Name: www.l.google.comAddress: 74.125.53.103Name: www.l.google.comAddress: 74.125.53.104Name: www.l.google.comAddress: 74.125.53.105%

Using the nslookup command

nslookup www.google.com

Caching DNS

Our Local DNS

Cache

www.google.com?

Non-authoritative answer:74.125.53.10374.125.53.10474.125.53.105

Root

The DNS hierarchy

.com .org .edu .gov .af .al ...

hawaii.edumit.edu ucsd.edu

ucsd.edu ucsd.edu

Root

The DNS hierarchy

.edu

hawaii.edu

Top-Level Domain

Second-LevelDomain

UHDNS

www.hawaii.edu?

128.171.224.100

%Server: 128.171.3.13Address: 128.171.3.13#53

www.hawaii.edu canonical name = web00.its.hawaii.edu.Name: web00.its.hawaii.eduAddress: 128.171.224.100

%

UH IP Addresses

nslookup www.hawaii.edu

128.171.224.100 www.hawaii.edu

128.171.224.150 www2.hawaii.edu

128.171.57.17 library.manoa.hawaii.edu

128.171.10.76 www.ics.hawaii.edu

128.171.60.178 www.eng.hawaii.edu

Root

The DNS hierarchy

.edu

hawaii.edu

Top-Level Domain

Second-LevelDomain

128.171.x.x

The IPv4 Address

128.171.224.100

Range: 0-255(256 possibilites)

FixedforUH

256possible

nos.

256possible

nos.

256 x 256 = 66,536addresses

UH IP Addresses

128.171.224.100 www.hawaii.edu

128.171.224.150 www2.hawaii.edu

128.171.57.17 library.manoa.hawaii.edu

128.171.10.76 www.ics.hawaii.edu

128.171.60.178 www.eng.hawaii.edu

Root

The DNS hierarchy

.edu

hawaii.edu

128.171.x.x

ICS Dept.128.171.10.x

Coll. of Engin.128.171.60.x

Physics Dept.128.171.30.x

Subnets

Subnet Addresses

hawaii.edu

128.171.x.x

ICS Dept.128.171.10.x

Coll. of Engin.128.171.60.x

Physics Dept.128.171.30.x

Subnets

128.171.10.x

UH ICS machine

256 possible addresses

Root

Domain Name System Hierarchy

.com .org .edu .gov .af .al ...

Root

Root servers

Hidden Master Root Server

Root

RootRoot

Root

Root Root

Tower of Babel

Problem

Standards - IETF

Every business or institution on the Internet needs unique server names to be registered in the DNS

Problem

www.hawaii.edu

Every entityon the Internet

needs a unique address

128.171.224.100

ICANN

History of DNS(YouTube video)

DNS History

http://www.youtube.com/watch?v=9ilYrY9iBhk&feature=related