 points (CSPM) for autonomous management functions (AMF). The planes define functions of the traffic system and management system which are described separately. The "values" associated to the layer dimension (L) and the node dimension (N) denote some kind of elements or interfaces ( CP and SP). The L and N dimensions are applicable on all types of layers, including OSI layers. Fig. 1.36 Main modeling dimensions. L=layer dimension; M=management dimension; N=node dimension When we work on an AMLn model we normally work only in one or sometimes in two dimensions. For example, taking the OSI RM model as a reference, we can either model it separately in the L and N dimensions, or apply a node structure on the L dimension and create a model in the L-N plane, as shown in Fig. 1.37. 1 Introduction to Network System Modeling Application Session & presentation Transport Network Physical Physical media stratum Application Session & presentation Transport Network Physical Physical media stratum Fig. 1.37 Creating models in two dimensions Through the AMLn definitions of the actor-agent separation principle and the definition of logical-network structure, each of the L and N dimensions become separated into two lower level dimensions. A layer structure resolves into two layer dimensions: one for control structures (Lac) and one for connectivity structures (Lco). Figure 1.38 exemplifies this for the ISDN network-system model. This model shows: Control structures consisting of actors that communicate over resource control points. Connectivity structures consist of agent layers and connectivity layers. Control structures and connectivity structures can be maintained separately SAGs and SACs are specified. A model may define more than one control structure if it is stratified A single control structure may rely on several independent connectivity struc- tures. 1.4 Modeling Network Systems in AMLn ISDN services (user ISDN services data) requesters users DSS1 L3 Call-handling agent layer (DSS1) actor layer agent layer (ISUP/TCAP) T