Because DECnet-Plus software has so many manageable components, these
   entities must be organized into a logical structure.  The organization
   defined is a hierarchical one where there are top-level entities and
   subordinate entities.

   Each computer system in a DECnet-Plus network is a global entity
   which is represented by the node entity.  Each computer is given a name
   that is unique throughout the network.  That name is then represented in
   NCL commands as the "node node-id".  (The default node-id is 0, which
   represents the local node.)

   Below the node entity are modules, or entity classes, such as CSMA-CD,
   OSI Transport, Routing, etc.  You may type HELP ENTITY_HIERARCHY for a
   diagram of the modules beneath the node entity.  To obtain a description
   of any of those modules, you may use the HELP ENTITY <module_name>
   command.  For example, to obtain a description of the Routing module,
   type:

   ncl> help entity routing

   To obtain a diagram of the subentities beneath a module, use the
   HELP ENTITY <module_name> SUBENTITIES command.  For example, to see a
   diagram and descriptions of the Routing subentities, type:

   ncl> help entity routing subentities