The Domain Name System: A Non-Technical
Explanation – Why Universal Resolvability Is Important
This page was taken by Rene Rojas from www.internic.net with the
unique aim of being used for academic purposes.
What is the Domain Name System?
The Domain Name System (DNS) helps users to find their way around the Internet.
Every computer on the Internet has a unique address – just like a telephone number –
which is a rather complicated string of numbers. It is called its "IP address" (IP stands
for "Internet Protocol").
But it is hard to remember everyone's IP address. The DNS makes it easier by allowing
a familiar string of letters (the "domain name") to be used instead of the arcane IP
address. So instead of typing 220.127.116.11, you can type www.icann.org. It is a
"mnemonic" device that makes addresses easier to remember.
Translating the name into the IP address is called "resolving the domain name." The
goal of the DNS is for any Internet user any place in the world to reach a specific
website IP address by entering its domain name. Domain names are also used for
reaching e-mail addresses and for other Internet applications.
What is universal resolvability and why is it important to users?
Think of the phone system . . . when you dial a number, it rings at a particular location
because there is a central numbering plan that ensures that each telephone number is
unique. The DNS works in a similar way. If telephone numbers or domain names were
not globally unique, phone calls or e-mail intended for one person might go to someone
else with the same number or domain name. Without uniqueness, both systems would
be unpredictable and therefore unreliable.
Ensuring predictable results from any place on the Internet is called "universal
resolvability." It is a critical design feature of the DNS, one that makes the Internet the
helpful, global resource that it is today. Without it, the same domain name might map to
different Internet locations under different circumstances, which would only cause
When you send an e-mail to your Aunt Sally, do you care who receives it?
Do you care if it goes to your Uncle Juan instead? Wait a minute…do you have an
Uncle Juan? Then whose Uncle Juan received it? Do you care if it reaches Aunt Sally if
you send it from work but my Uncle Juan if you send it from home?
Of course you care who receives it . . . that's why you wrote it in the first place.
Whether you're doing business or sending personal correspondence, you want to be
certain that your message gets to the intended addressee.
If at any point the DNS must make a choice between two identical domain names with
different IP addresses, the DNS would not function. It would not know how to resolve
the domain name. When a DNS computer queries another computer and asks, "are
you the intended recipient of this message?", "yes" and "no" are acceptable answers,
but "maybe" is not.
Where does ICANN come in?
This is where ICANN comes in . . . ICANN is responsible for managing and
coordinating the DNS to ensure universal resolvability.
ICANN is the global, non-profit, private-sector coordinating body acting in the public
interest. ICANN ensures that the DNS continues to function effectively – by overseeing
the distribution of unique numeric IP addresses and domain names. Among its other
responsibilities, ICANN oversees the processes and systems that ensure that each
domain name maps to the correct IP address.
What goes on behind the scenes?
Behind the scenes, the story becomes a little more complicated.
In an Internet address – such as icann.org – the .org part is known as a Top Level
Domain, or TLD. So-called "TLD registry" organizations house online databases that
contain information about the domain names in that TLD. The .org registry database,
for example, contains the Internet whereabouts – or IP address – of icann.org. So in
trying to find the Internet address of icann.org your computer must first find the .org
registry database. How is this done?
At the heart of the DNS are 13 special computers, called root servers. They are
coordinated by ICANN and are distributed around the world. All 13 contain the same
vital information – this is to spread the workload and back each other up.
Why are these root servers so important? The root servers contain the IP addresses of
all the TLD registries – both the global registries such as .com, .org, etc. and the 244
country-specific registries such as .fr (France), .cn (China), etc. This is critical
information. If the information is not 100% correct or if it is ambiguous, it might not be
possible to locate a key registry on the Internet. In DNS parlance, the information must
be unique and authentic. Let us look at how this information is used.
Scattered across the Internet are thousands of computers – called "Domain Name
Resolvers" or just plain "resolvers" - that routinely cache the information they receive
from queries to the root servers. These resolvers are located strategically with Internet
Service Providers (ISPs) or institutional networks. They are used to respond to a user's
request to resolve a domain name – that is, to find the corresponding IP address.
So what happens to a user's request to reach our familiar friend at icann.org? The
request is forwarded to a local resolver. The resolver splits the request into its
component parts. It knows where to find the .org registry – remember, it had copied
that information from a root server beforehand – so it forwards the request over to the
.org registry to find the IP address of icann.org. This answer is forwarded back to the
user's computer. And we're done. It's that simple! The domain name icann.org has
Why do we need the resolvers? Why not use the root servers directly? After all, they
contain essentially the same information. The answer is for reasons of performance.
The root servers could not handle hundreds of billions of requests a day! It would slow
If you are still with the story, you are already wondering about more complicated names
with more parts such as www.icann.org. Well, the DNS is a hierarchical system. First,
the resolver finds the IP address for the .org registry, queries that registry to find the IP
address for icann.org, then queries a local computer at that address to find the final IP
address for www.icann.org. Just what you would expect.
It is important to remember the central and critical role played by the root servers that
store information about the unique, authoritative root. Confusion would result if there
were two TLDs with the same name: which one did the user intend? The beauty of the
Internet architecture is that it ensures there is a unique, authoritative root, so that there
is no chance of ambiguity.
What about "alternate roots?" How do they fit into this picture?
Anyone can create a root system similar to the unique authoritative root managed by
ICANN. Many people and entities have. Some of these are purely private (inside a
single corporation, for example) and are insulated from having any effect on the DNS.
Some, however, overlap the authoritative global DNS root by incorporating the unique,
authoritative root information, and then adding new pseudo-TLDs that have not resulted
from the consensus-driven process by which official new TLDs are created through
ICANN. The alternate root operators persuade some users to have their resolvers
"point" to their alternate root instead of the authoritative root. Others (New.net is a
recent example) also create browser plug-ins and other software workarounds to
accomplish similar effects. The one uniform fact about all these efforts is that these
pseudo-TLDs are not included in the authoritative root managed by ICANN and, thus,
are not resolvable by the vast majority of Internet users.
Why do alternate roots create a problem?
There are many potential problems caused by these unofficial, alternate root efforts to
exploit the stability and reach of the authoritative root. These efforts are often promoted
by those unwilling to abide by the consensus policies established by the Internet
community, policies designed to ensure the continued stability and utility of the DNS.
• First, the names of some of these pseudo-TLDs could overlap TLD names in the
authoritative root or those that appear in other alternate roots. Our familiar friend
icann.org could appear in two different roots. Your e-mail to Aunt Sally could end
up with my Uncle Juan.
• Second, the unknowing users might not be linked to one of these alternate roots
and not be able to reach these pseudo-TLD addresses at all. Your e-mail to Aunt
Sally could end up as a dead-letter.
• Third, those purchasing domain names in these pseudo-TLDs may not be aware
of these and other consequences of the lack of universal resolvability. Or they
may be under the impression that they are experiencing universal resolvability
when in fact they are not. They may be very upset to learn that the names they
registered are also being used by others, or that a new TLD in the authoritative
root will not include those names.
These problems are not significant so long as these alternate roots remain very small,
that is, house few domain names with little potential for conflict. But if they should ever
attract many users, the problems would become much more serious, and could affect
the stability and reliability of the DNS itself. Users would lose confidence in the utility of
What is ICANN's role?
ICANN's mission is to protect and preserve the stability, integrity and utility – on behalf
of the global Internet community – of the DNS and the authoritative root ICANN was
established to manage. ICANN has no role to play with alternate roots so long as these
and other analogous efforts do not create instabilities in the DNS or otherwise impair
the stability of the authoritative root. But ICANN does have a role to play in educating
and informing about threats to the Internet's reliability and stability.
ICANN is a consensus development body for the global Internet community, and its
focus is the development of consensus policies relating to the single authoritative root
and the DNS. These policies include those that allow the orderly introduction of new
There are those–including operators of commercialized alternate roots–who pursue
unilateral actions outside the ICANN consensus-development process. Many hope to
circumvent these processes by claiming to establish some prior right to a top-level
domain name. ICANN, however, recognizes no such prior claim. ICANN will continue to
reflect the public policy consensus of the global Internet community over the private
claims of the few who try to bypass this consensus.
In Short . . . . . .
Just as there is a single root for telephone numbers internationally, there must be a
single authoritative root for the Internet, administered in the public interest.