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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