y confined to the distribution and the communication dimensions, i.e. the DC-plane. The processing dimension and its effect on logical networks is discussed in the next chapter. In relation to the integration hierarchy, logical network modelling is con- fined to integration level 3. It was shown that any sysnet that provides some type of communication service can be modelled as a CSP. The CSP is a black box abstraction of all functional units that exist in a sysnet. The CSP does not describe the structure of units, it only spec- ifies the network service interfaces that are made available to users. It was also shown that any CSP can be modelled as a structure of logical net- works and (internal) CSPs. This view of the functionality of a sysnet lends itself describing the recursive functional structure of real communication networks. Each sysnet (or network concept) must define its own logical network structure. However, a unified, high-level picture of logical network structures appears, where there are four major parts in the structure: a teleservice system, a connectivity sys- tem, a logical network management system and network application systems. The trend in network architecture is towards service specialization in networks, frequently referred to as "horizontal integration". It has been shown that this is an aspect of network design that primarily concerns the architecture of the physical network, while logical networks and structures remain basically intact. This is a major argument for logical network modelling It also was demonstrated how the processing system paradigm (major functional separation into a resource system and a process control system) can be applied to the architecture of any telecom system. It is equally applicable to management sys- tems and traffic systems. It can be applied to any type of traffic systems, whether circuit-switched, packet-switched, a sysnet that provides connectivity only or a sysnet that provides teleservices. Primitive, composed and abstract resources, as well as gen