Demystifying DNS

Let's take some time out to prep up on the Domain Name System and some of its lingo.

Resolving a web address

Locally, we type a uniform resource locator into a web browser, rather like this:

http://www.somesite.com/somefolder/somefile.html

Setting aside the tidy/separators, here's the breakdown of a URL:

• http – The protocol, in this case Hyper Text Transfer Protocol, that we want parsed. Alternative protocols include ftp, https, and mailto.

• www – The hostname or sub-domain that distinguishes one network element from another. You could equally use, say, mypc for a PC, dlink for a router, mail for webmail, or blog for a sub-site.

• somesite – This is the network or domain to which hosts belong. You could use an IP address instead.

• com – com is one of many top level domains to which we attach a domain.

Finally we have a file, somefile.html, buried in a directory tree and it is this that we are telling http, having resolved the journey, to bring home and parse.

So how does the Domain Name...