The area which comprises all the nodes of a network corresponds to Level 0 of a hierarchical network structure

An area defines all the nodes of a network including its sub-networks (see also definition of hierarchical node numbers). The area number defines the area for administration purposes. A Level 0 area includes all the networked nodes of that level, and all the sub-networks at sub-network levels 1 and 2 which are accessible through the nodes of the level 0 area. A Level1 area includes all the networked nodes of the sub-network accessible through a particular node in a Level 0 area as well as any sub-networks at sub-network level 2 which are accessible through the nodes of the level 1 area.