Transcript The Domain Name System donna Bair-Mundy Visiting the MIT Library Website http://libraries.mit.edu Visiting the MIT Library Website http://libraries.mit.edu.

The Domain Name
System
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
protocol
machine
Human-readable address
Getting the IP (numerical) address
What is numerical address of
libraries.mit.edu?
Where does the local
Domain Name Server
get the
numerical address?
Our
Computer
Address:
18.51.0.23
Local
Domain
Name
Server
Domain Name System Hierarchy
libraries.mit.edu?
.com
Our
Local
DNS
.org
Root
.edu .gov
.af
Top-Level Domains
.al ...
The DNS hierarchy
Root
.com
.org
.edu .gov
.af
.al ...
Generic
Country-Code
Top-Level Domains Top-Level Domains
(gTLDs)
(ccTLDs)
http://www.iana.org/domains/root/db/
The DNS hierarchy
Root
.com
.org
.edu .gov
.af
.al ...
United States
Generic Top-Level Domains
(also .mil)
The DNS hierarchy
address for .edu
server
.com
Our
Local
DNS
.org
Root
.edu .gov
.af
.al ...
The DNS hierarchy
Root
.com
.org
.edu .gov
libraries.mit.edu?
Our
Local
DNS
.af
.al ...
The DNS hierarchy
Root
address for
mit.edu server
.com
.org
mit.edu
Our
Local
DNS
.edu .gov
hawaii.edu
stanford.edu
.af
.al ...
ucsd.edu
yale.edu
The DNS hierarchy
Root
.com
.org
.edu .gov
.af
.al ...
libraries.mit.edu?
mit.edu
hawaii.edu
Our
18.51.0.23
Local
ucsd.edu
DNS
ucsd.edu
ucsd.edu
Getting the IP (numerical) address
What is numerical address of
libraries.mit.edu?
Our
Computer
Address:
18.51.0.23
Local
Domain
Name
Server
The DNS hierarchy
Root
.com
.org
mit.edu
Our
Local
DNS
.edu .gov
hawaii.edu
.af
.al ...
ucsd.edu
18.51.0.23
ucsd.edu
ucsd.edu
(authoritative answer)
Using the nslookup command
% nslookup www.google.com
Server:
Address:
128.171.3.13
128.171.3.13#53
Non-authoritative answer:
www.google.com canonical name = www.l.google.com.
Name: www.l.google.com
Address: 74.125.53.103
Name: www.l.google.com
Address: 74.125.53.104
Name: www.l.google.com
Address: 74.125.53.105
%
Caching DNS
www.google.com?
Non-authoritative
answer:
74.125.53.103
74.125.53.104
74.125.53.105
Cache
Our Local
DNS
The DNS hierarchy
Root
.com
.org
mit.edu
.edu .gov
hawaii.edu
ucsd.edu
.af
.al ...
ucsd.edu
ucsd.edu
The DNS hierarchy
Root
.edu Top-Level Domain
hawaii.edu
UH
DNS
Second-Level
Domain
UH IP Addresses
% nslookup www.hawaii.edu
Server:
Address:
128.171.3.13
128.171.3.13#53
www.hawaii.edu canonical name = web00.its.hawaii.edu.
Name: web00.its.hawaii.edu
Address: 128.171.224.100
%
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
The DNS hierarchy
Root
.edu Top-Level Domain
hawaii.edu
128.171.x.x
Second-Level
Domain
The IPv4 Address
Range: 0-255
(256 possibilites)
128.171.224.100
Fixed
for
UH
256
256
possible possible
nos.
nos.
256 x 256 = 66,536
addresses
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
The DNS hierarchy
Root
.edu
hawaii.edu
Subnets
ICS Dept.
128.171.10.x
128.171.x.x
Coll. of Engin.
128.171.60.x
Physics Dept.
128.171.30.x
Subnet Addresses
hawaii.edu
Subnets
128.171.x.x
ICS Dept.
128.171.10.x
Coll. of Engin. Physics Dept.
128.171.60.x
256
possible128.171.30.x
addresses
128.171.10.x
UH
ICS machine
Domain Name System Hierarchy
Root
.com
.org
.edu .gov
.af
.al ...
Root servers
Hidden Master
Root Server
Root
Root
Root
Root
Root
Root
Root
Problem
Tower of Babel
Standards - IETF
Problem
Every business or institution
on the Internet needs unique server
names to be registered in the DNS
www.hawaii.edu
Every entity
on the Internet
needs a unique address
128.171.224.100
ICANN
DNS History
History of DNS
(YouTube video)
http://www.youtube.com/watch?v=9ilYrY9iBhk&feature=related