Domain names, URLs, DNSs and hosts
For the world wide web to work each website must have a unique name that is recognised everywhere. Wherever in the world you type www.bbc.co.uk into a browser address bar you must end up on the BBC site.
Obviously, then, the world needs an authority for dealing with domain names. In the absence of a suitable government (except perhaps the United Nations) to impose such a body, the countries of the world agreed to set up ICANN – the Internet Corporation for Assigned Names and Numbers. This does seem to be a truly international body – www.icann.com
ICANN delegates its authority for generic top level domains (gTLDs see below) such as the suffix ".com" to various bodies and the country-code top-level-domains (ccTLD see below) to government appointed registrars. In the UK the registrar for domain names ending in ".uk" is Nominet (www.nominet.org.uk) which lays down and administer the system in the UK.
gTLDs are supposed to be non-national but found themselves hijacked by Americans; ".gov" definitely "belongs" the United States legislature. However, gTLDs like .com are available world-wide.
ccTLDs lay down the rules for the domain name structure and meaning to the left of .uk and Nominet make available any name you like as long as it ends in the prescribed form which are currently .co, .org, .net, .me, .ltd, .plc, and .sch. Because all names registered by Nominet have to end with .uk these become .co.uk, .org.uk, .net.uk, .me.uk, .ltd.uk, .plc.uk, and .sch.uk. It delegates the control of more name endings such as .gov (which then becomes .gov.uk), .ac (for universities), .police, .nhs, . and .mod and .mil (both for the armed forces). Ultimate control of a name remains with Nominet but most registration of .uk names is done by authorised registration service companies who act as a link between would-be domain name owners and themselves.
The chosen domain name follows to the left of the chosen suffix and, of course, it must be unique. When, for instance, we registered plannedsites.co the agent’s computer will have looked at Nominet’s database to check. If there is a further full stop and name to the left of this domain name it is known as a sub-domain.
Strictly, plannedsites.co.uk (and plannedsites.com which is what we usually use – registering plannedsites.co.uk was a defensive move to prevent someone else trying to steal our thunder) is known as the registered name and www.plannedsites.co.uk as the domain name.
Information about UK domains is available from the Nominet site and on generic names from www.whois.net.
URL stands for Uniform Resource Locator and is what the internet needs to translate your page request into the page for which you are looking.
(Contrary to much argument, URLs are not case sensitive.)
This is what a complete URL looks like:
http://www.yourcompany.co.uk
Every website in the world is on a server. Each server on the internet has a unique indentifier called an IP address. (IP stands for Internet Protocol.) IP addresses are in the format nnn.nnn.nnn.nnn. where nnn is a number between 0 and 255. Apart from the fact that a server may host more than one site, numbers in this form are difficult to remember so a naming system is used. The best known site in the UK is the BBC’s (www.bbc.co.uk). If you type in 212.58.226.75, the IP of the server on which the BBC site sits, instead of the name, you’ll get a page of the BBC site. Domain names are converted to IP addresses at Domain Name Servers (DNSs) which are set up round the country and are a database of every domain name in the world together with the IP address of every server.
Requests for pages, typed into the address bar of a browser, arrive first at your ISP – internet service provider. Here the ISP looks up the IP address of the requested name in a nearby DNS and sends the request to the relevant server that is hosting the site. The host looks at the request and sends back the requested page.
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