Name System: A Non-Technical Explanation – Why Universal Resolvability
What is the Domain
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 126.96.36.199, 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
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.
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
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
Behind the scenes, the
story becomes a little more complicated.
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
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 download and copy the
information contained in 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 been "resolved"!
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 users down.
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
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
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 the
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
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 TLDs.
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.
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