the domain name system donna bair-mundy. visiting the mit library website
TRANSCRIPT
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