What is DNS ?
Every host that runs TCP/IP must have a unique IP address (ex: 203.115.0.64). That is used
when communicating with other computers in a network. Computers operate easily with IP
addresses, but people don't. Users would rather identify systems by a name. To facilitate
effective and efficient communication, users need to be able to refer to computers by name,
and still have their computers use IP addresses transparently. Domain Name System (DNS)
is the name service for Internet addresses that translates (resolves) friendly domain names
to numeric Internet Protocol (IP) addresses.

The Domain Name Service is the method by which Internet addresses in mnemonic form such
as sunc.scit.wlv.ac.uk. are converted into the equivalent numeric IP address such as
134.220.4.1. To the user and application process this translation is a service provided either
by the local host or from a remote host via the Internet. The DNS server (or resolver) may
communicate with other Internet DNS servers if it cannot translate the address itself.

DNS name structure
DNS names are constructed hierarchically. The highest level of the hierarchy being the last
component or label of the DNS address. Labels can be up to 63 characters long and are case
insensitive. A maximum length of 255 characters is allowed. Labels must start with a letter
and can only consist of letters, digits and hyphens.

DNS addresses can be relative or fully qualified. A fully qualified address includes all the labels
and is globally unique. A relative address can be converted by appending the local domain
information. For example sunc.scit.wlv.ac.uk is a fully qualified name for the host sunc in the
domain scit.wlv.ac.uk. Strictly there should be a stop at the end of a fully qualified name but
this is often overlooked.

The DNS was originally introduced in the United States of America and the final component of
an address was intended to indicate the type of organisation hosting the computer. Some of the
three letter final labels (edu, gov, mil) are still only used by organizations based in the USA,
others can be used anywhere in the world.

The three letter codes are

The final two letter codes indicate the country of origin and are defined in ISO 3166. For eg.,
lk for Sri Lanka, uk for United Kingdom, au for Australia, etc. The two letter code us is used
by some sites in the United States of America.

DNS Hosting
Domain Name Server (DNS) maintains a table of Host (Domain) Names and their IP addresses.
The DNS Server will resolve the name to IP addresses and release it to the requesting host.

One has to register the desired domain with an appropriate registartion authority (Internic,
Cintec, etc.) by paying the relevant charges to them. sltnet offers sub domains under
slt.lk free of charge.