and nw4. The DNS network uses socket routes as well. 1.4 Modeling Network Systems in AMLn This logical-network structure contains all information that is needed for config- uration, provided that its relation to layer elements in the L dimension are known. Such relations are stored as allo(-cates) relations in the model, as exemplified in Fig. 1.31. hosts CP,UDP/IP n44 T'nw1 Fig. 1.31 A part of an IP-based network in both L and N dimensions. L..., DNS, TCP, UDP, IP =layers or strata that are implemented in the logical networks A logical-network structure separates configuration activities in tasks that con- cern only single logical networks and tasks that concern hosts relations between networks. Relations of type allocates show which layer functions are included in different networks and nodes, and thereby if and how functional modifications con- cern a particular logical network. These are all properties of the modelling tech- nique that makes it possible to maintain correct models over time. Note that the logical-network structure in the previous figures is developed within a single network level. When layer interfaces between logical networks are realized as network interfaces, some logical nodes will have an existence in more than one hosting logical network, defined on different network levels. This requires that an additional relation, the term(-inates) relation, has to be maintained. This relation relates the allocation of a layer element in a node on a higher network level to one or several nodes on a lower. Read more about this in Chap 4. 1 Introduction to Network System Modeling 1.4.4 The Boundary Between Traffic and Management Systems All functions that are not executed on-demand by requests from network users are, by definition in AMLn, management functions. As discussed in Sect. 1.4.1.2, man- agement functions belong to a management plane defined in an L-N plane, similar to but separate from the plane where we model functions of the traffic system. Interfaces between these two planes belong to the m