To have a hierarchical name space, a domain name space was designed. In this design the names are defined in an inverted-tree structure with the root at the top. The tree can have only 128 levels: level 0 (root) to level 127.


                                                                         Fig: Domain Name Space

Domain Name

Each node in the tree has a domain name. A full domain name is a sequence of labels separated by dots (.). The domain names are always read from the node   up to the   root. The last label is the label of the root (null). This means that a full domain name always ends in a null   label,   which   means   the   last character is a dot because the null string is nothing. Figure shows some domain names.