 are derived nodes, including all kinds of layers. For example, hosts will contain layer elements of all of IP, UDP, TCP, DNS (the resolver part), and application layers. Routers will contain IP, UDP, and TCP only while DNS servers will contain IP, UDP, TCP, and DNS. If we introduce the logi- cal-network structure of Fig. 1.30, the N dimension resolves into a logical network dimension (NW) and a separate logical node dimension (NO) for each logical net- work (see Fig. 1.42). 1.4 Modeling Network Systems in AMLn (DNS) nw1,nw2 hosts (application) nw1,nw2 (application) (IP,UDP,TCP) Fig. 1.42 Logical network structures implies that the N dimension expands into an NW-NO plane Nodes of logical network nw1, for example, are now no longer hosts, routers, etc., but logical nodes of the IP/TCP/UDP switching logical network. Nodes of nw2 are nodes of the DNS logical network only, and SO on. Each of these logical networks are considerably simpler to deal with than with a single logical network for the whole network system. In summary: The logical dimensions that are defined by AMLn have evolved from the dimen- sions originally defined by the OSI RM, which are the layer dimension (L) and the node dimension (N). By introducing the separation between management and managed system, we have defined the management dimension (M). By introducing the logical network concept we have expanded the N dimension to a plane defined by the logical network dimension (NW) and the logical node dimension (NO). By introducing the actor-agent separation, we have separated the L dimension into a layer dimension for control structures (Lac) and a layer dimension for connectivity structures (Lco). Figure 1.43 summarizes these refinements. 1 Introduction to Network System Modeling Legend: Traffic Defined by the OSI RM plane Layer dimension Node dimension Defined by AML Management Management dimension plane Lac Control structure dimension Lco Connectivity structure dimension Lac Lco NW Logical network dimension NO Logical node dimension Interfaces of t