SI networks) that there is no one- dimensional structure of layers/logical networks. Instead, logical networks are related to each other in a complicated, multidimensional structure of logical net- works, unique for each specific network concept. Logical nodes and protocols are defined for each logical network independently of other logical networks. The mapping of a logical network on a particular physical network model must also be specified separately for each logical network, and for each physical network solu- tion. One can say that a logical network structure substitutes the OSI RM seven- layer model, and logical networks replace the OSI RM layer concept. Note also that, contrary to OSI RM, each network concept defines its own logical network structure, i.e., there is not as fixed number of layers for all types of sysnets. Although we have already separated a network process controller into more primitive units, the remaining part of the NPC is still a very large and complex unit in implemented systems. It constitutes the major part of the several millions lines of code that realize a DNPC. The question is then: faced with describing or devel- oping a new network architecture, what principles can guide you in creating a suit- able logical network structure and logical networks? There are at least four well- known additional strategies for partitioning a process control system (PCS) into smaller parts: 1. Separate mobility control, such as locating, paging and hand-over, from other connection control functions. 2. Separate teleservice process control from connection process control. This prin- ciple is also often called call-connection separation. 3. Separate service handling into one part that handles distributable service aspects, and another part that handles service aspects that may very well be cen- tralized in a physical network. This distinction is often referred to as the intelli- gent network concept (IN). 4. Separate management from other process control functions. 3.5 Logical Network Structures Th