Background to the Domain Name Sysytem

What is a Domain Name?

A domain name is the user-friendly form of an Internet address. They are commonly used to find websites, for example, www.cabinet-office.gov.uk is used to find the Cabinet Office website. A domain name also forms the basis of other methods or applications on the Internet, for example, email addresses (naming@cabinet-office.x.gsi.gov.uk), and for file transfer – ftp addresses.

The Domain Name System

The Domain Name System (DNS) comes from the early days of the Internet when it was a small network for defence and academic research purposes. The DNS system that we use today was introduced in 1984. The system is essentially a global addressing system. It is the way that domain names are distributed, located and translated into Internet Protocol (IP) addresses and vice versa; a process known as ‘resolution’.

A domain name is a unique alias for an IP address (a number for example, IP 212.24.85.85), which is an actual physical point on the Internet. For example, your PC if you have an internet connection.

The DNS forms a hierarchy with Top Level Domains (TLDs), Second Level Domains (SLDs), Third Level Domains (3LDs) and so forth. The Top Level Domains (TLDs) are administered internationally by the Internet Corporation for Assigned Names and Numbers (ICANN) which is also the overall body for providing the Uniform Domain
Resolution Policy.

Country Code Top Level Domain Names (ccTLDs)

There are over 250 Top Level Domain names organised on a country-by-country basis and based upon ISO 3166-1.

For example:

.au (Australia) .ca (Canada)

.de (Germany) .uk (United Kingdom)

Some countries allow anyone to register a domain name in that country; others require a local connection, or if there is no such connection, that the domain name matches trademark registration within that country.

The design of the naming structure under a country code rests with the country manager (Registry). Some ccTLDs are only available with a second level domain (SLD) attached. For example, under the rules of the United Kingdom’s country code manager it is not routinely possible to register [sample].uk; we are more familiar with our domain names divided into three levels

top-level (ccTLD) -- .uk .uk

second-level (SLD) -- .gov.uk .co.uk

third-level (3rdLD) -- electronic.gov.uk electronic.co.uk

United Kingdom Second Level Domains (SLDs)

The following are examples of available Second Level Domains:

.co.uk - for commercial use
.org.uk - for non-commercial use
.plc.uk - for public companies under the Companies Acts
.ltd.uk - for limited companies under the Companies Acts
.net.uk - for networks and ISPs etc
.ac.uk - for academic organisations
.sch.uk - for schools

See www.nominet.uk.org.uk for further details on second level domains.

For information on the UK public sector SLDs see paragraphs 1.9.2 for .gov.uk and 1.9.2.5 for other public service SLDs.