DNS: Domain Name System

Mark Ciocco Chris Janik Networks Class Presentation Tuesday April 18, 2000

Presentation Outline

• • • • 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 January 1996 January 1993 29,670,000 14,352,000 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 A Network Solutions, Inc B C D E Information Sciences Institute, PSINet University of Maryland National Aeronautics and Space F G H I J K L M Internet Software Consortium Defense Information Systems Army Research Laboratory NORDUNet (TBD) RIPE-NCC (TBD) WIDE City, State/Province Herndon, VA Marina Del Rey, CA Herndon, VA College Park, MD Mountain View, CA Palo Alto, CA Vienna, VA Aberdeen, MD Stockholm Herndon, VA London Marina Del Rey, CA 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!