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. ICANNs
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 UKs 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 cant 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. Nameserver A 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.
About
The Author
Clare
Lawrence is CEO of Discount Domains Ltd A leading UK
provider of Domain name registration and Web Hosting
services. www.discountdomainsuk.com.
