Updating dns server
Remember that the Internet (or any network for that matter) works by allocating every point (host, server, router, interface etc.) a physical IP address (which may be locally unique or globally unique).
Without DNS every host (PC) which wanted to access a resource on the network (Internet), say a simple web page, for example, would need to know its physical IP address.
At the top of the tree is the root followed by the Top Level Domains (TLDs) then the domain-name and any number of lower levels each separated with a dot.
NOTE: The root of the tree is represented most of the time as a silent dot ('.') but there are times as we shall see later when it very important.
If the Primary Name Server does not respond a host can use the Secondary (or tertiary etc.).As our network grows we start to build up a serious number of Names in our Name Server (database). Which leads us nicely into the characteristics of the Internet's Domain Name System (DNS).