Transcript DNS: Domain Name System

DNS:
Domain Name System
Mark Ciocco
Chris Janik
Networks Class Presentation
Tuesday April 18, 2000
Presentation Outline
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What it is and how it works
How the Internet worked before DNS
DNS through the years
How you can register for your own
domain name
Foreign Languages
• Humans:
– Words are easy to remember
– Numbers are confusing
• Machines:
– Numbers are easy to work with
– What are words?
• Would amazon.com be what it is today
if it were 208.202.218.15
What is it?
• Global network of servers that translate
host names such as www.villanova.edu
into numerical IP addresses like
153.104.1.200
• An internet protocol, distributed
database and software existing on
many different name servers around the
world allowing for almost unlimited
growth of the Internet
DNS History 101
• Pre - DNS
– A single file (host table) containing a table
of all the host names that was distributed
via FTP to all domain name servers
– Updated manually by SRI-NIC a couple
times a week
• worked fine but not efficient or practical
• Paul Mockapetris invents DNS in 1984
Explosion of the Internet
Number of hosts registered with the DNS
January 2000
72,398,092
January 1998
29,670,000
January 1996
14,352,000
January 1993
1,313,000
Naming History 102
• DNS
– Domain Name Space
How Does It Work?
1.) DNS Server
– a computer that runs DNS software
– mostly UNIX machines so most popular program
is BIND (can find software for Mac and PC)
– authoritative vs caching
2.) DNS Software Components
– The Name Server: responds to requests by
supplying name to address conversion
– The Resolver: in the case of Name Server failure
the Resolver looks for the information on another
name server
DNS LOOKUP EXAMPLE
• DNS
– Domain Name Space
Movin’ On Down The
Line
•Root Servers
•DNS server asks for master server for .edu
•Master Servers
•DNS server asks for domain server for
villanova.edu
•Domain Servers
•DNS server asks for server that holds villanova.edu
•Individual Servers
•Supplies DNS server with IP address for the
machine called www.villanova.edu
Root Server System
• Because of its basis as a singly rooted
hierarchical namespace, DNS is one of
the single points of failure within the
Internet
• More specifically, the root of this system
• It is held in 13 geographically distributed
root name servers operated by 9
independent organizations
Root Server System 2
Root Name Server Operators and Locations
Name Organization
City, State/Province
A Network Solutions, Inc
Herndon, VA
B Information Sciences Institute,
Marina Del Rey, CA
C PSINet
Herndon, VA
D University of Maryland
College Park, MD
E National Aeronautics and Space
Mountain View, CA
F Internet Software Consortium
Palo Alto, CA
G Defense Information Systems
Vienna, VA
H Army Research Laboratory
Aberdeen, MD
I
NORDUNet
Stockholm
J (TBD)
Herndon, VA
K RIPE-NCC
London
L (TBD)
Marina Del Rey, CA
M WIDE
Tokyo
Country
USA
USA
USA
USA
USA
USA
USA
USA
Sweden
USA
UK
USA
Japan
DNS Control
– Was controlled by Network
Solutions (NSI) and Internet
Assigned Numbers Authority
(IANA).
– IANA replaced by a non
governmental organization called
ICANN.
DNS Control (con’t)
– Internet Corporation for Assigned
Names as Numbers (ICANN)
• Comprised of a board of 19 people picked by
the US Department of Commerce.
• Non profit organization that oversees the
administrative needs of the internet in a fair and
impartial manner.
• They will distribute the remaining IP numbers to
regional registries who will pass them on to
ISPs. The ISP will then assign the addresses
to their individual customers.
New Registrars?
– NSI’s monopoly ended
– April 1999 - Test phase in which 5
additional registrars were permitted to use
the shared registration system.
– August 1999
• Test phase is extended
• now allows 52 additional registrars
• All additional registrars use NSI’s registration
system (for a fee!)
New Registration System
– December 1999
• Phasing out NSI’s registration system
• New Shared Registration System (SRS)
• SRS has some glitches, but it is a fair system
– NSI
• Still the dominant registration service
• Makes them tough to compete with
How do I get a domain
name for myself?
– Register with an accredited registrar to get
a .com, .net, or .org top level domain
• Registrars include: NSI, Register.com, and
AOL.
• $70 initial investment for 2 years
• $35 for each additional year
– Most ISPs offer domain name registration
services
Alternatives
• You can bypass the registrars and get a
country code top level domain such as
.us, .uk, .md, or .tv.
More Alternatives
• AlterNIC
– Another alternative that offers exotic top
level domains such as .ltd, .inc, .games
and the ever popular .xxx
– Not really a viable alternative because it
requires net users to set up their
computers to use AlterNICs DNS servers.
THE END
• Comments or questions?
• Thank you!