Ever wonder why DNS systems came into existence?
Efficiency. Every computer has a distinct IP address, and the
Internet needed an elite method for obtaining these addresses
and for managing the system as a whole. Enter ICANN.
The Internet Corporation for Assigned Names and Number manages
the DNS root of the Internet domain namespace. ICANN’s
role is to manage the assignment of identifiers, ensuring that
all users have unique names.
The DNS system is run by a series of servers called DNS servers.
ICANN manages the root DNS domains, under which are the top-level
domains.
It also manages:
Organizational domains
Geographical domains
Reverse domains
Beneath the top-level domains are other naming authorities
such as Nominet, the UK’s naming authority.
How does a DNS Query work?
The process occurs in two parts. Firstly, a name query begins
at a client computer and is passed to DNS client service for
resolution. When the query cannot be resolved locally, DNS
servers are queried.
For example, when a web browser calls the fully qualified domain
name www.discountdomainsuk.com, the request is passed on to
the DNS client service to resolve the name by using locally
cached information. If the query is held in the cache, then
the process is complete.
If, however, the query cannot be answered locally, the DNS
client service uses a server list (ordered in sequence) to
query external DNS servers. When a DNS server receives a query,
it first checks to see if it is authoritive for that domain
name. If it is authoritive, it resolves the name, and the process
is complete.
If the DNS server is unable to resolve the query, it in turns
queries other DNS servers, using a process known as recursion.
DNS servers make use of root hints to assist in locating DNS
servers, which are able to provide the required result. In
this way, DNS queries are minimised and the Internet is able
to operate quickly and effectively.
A typical query may run as follows:
Client contacts Nameserver A looking for www.discountdomainsuk.com.
Nameserver A checks its cache, but can’t answer, so it
queries a server authoritive for the Internet root.
The root server responds with a referral to a server authoritive
for the .com domains. NameserverA queries the the .com server
and gets referred to the server authoritive for www.discountdomainsuk.com.
Nameserver A queries this server and gets the IP address for
www.discountdomainsuk.com.
Nameserver A replies to the client with the IP address.
Queries can return answers that are authoritive, positive,
negative or referral in nature. In the event of a negative
answer, another DNS server is queried.
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Clare Lawrence is CEO of Discount Domains Ltd – A
leading UK provider of Domain
name registration and Web
Hosting services. Please feel free to re-publish
this article provided this reference box remains
together with a hyperlink to http://www.discountdomainsuk.com Clare
can also be contacted on clare@discountdomainsuk.com.
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