Updating domain names
A FQDN is basically a DNS host name and it represents where to resolve this host name within the DNS hierarchy. The Domain Name Space The DNS is a hierarchical tree structure whose root node is known as the root domain.
A label in a DNS name directly corresponds with a node in the DNS tree structure.
A label is an alphanumeric string that uniquely identifies that node from its brothers.
The threats that surround the DNS are due in part to the lack of authenticity and integrity checking of the data held within the DNS and in part to other protocols that use host names as an access control mechanism.When the DNS is used to map an IP address back into a host name (i.e., inverse resolution), the DNS makes use of the same notion of labels from left to right (i.e., most specific to least specific) when writing the IP address.This is in contrast to the typical representation of an IP address whose dotted decimal notation from left to right is least specific to most specific.Even though four decimal numbers may be easier to remember than thirty-two 1s and 0s, as with phone numbers, there is a practical limit as to how many IP addresses a person can remember without the need for some sort of directory assistance.The directory essentially assigns host names to IP addresses.