dentifies the route between n11 and the nw1 node that hosts the node that is referred to by the GT. Note that the output of the T-GT table is an input to the T-RE table. 3 3.2 Logical Networks Layer Layer element element REi=n32 REdef=n32 REdef AddrPar Functions that {ap1,.. manage nw1 nw01AddrPar(n12) resources nw02AddrPar(n13) nw02AddrPar(n14) nw02AddrPar(n15) Legend: nw01AddrPar(n12) Switched route Link route nw01 layer nw02 layer Global route element element Fig. 3.13 Tables in a hosting node that supports address transparency The model also shows a scenario where node n31 sends something to n32: n31 addresses this node by the global title n32. By using the T-AP table, the common element creates a message that includes the APi value for n32 (which in this case is equivalent to the APi for n31). The common element must then find the nw1 route that shall be used, which is given by the T-GT table (as n12). The common element then consults the T-RE table to find out which hosting net- work to used (here nw01) and how n12 is addressed over nw01. The data is then sent over nw01. Through the realization of these tables in common layer elements, a high degree of addressing transparency is achieved. We regard this as the most important prop- erty to be shown in graphical models of logical networks. Route symbols are there- fore defined primarily for different addressing methods (see Sect. 3.3). 3.2.2 Simulation and Realization of Logical-Network Structures Layer interfaces are the entities in logical-network structures that create the func- tional structure of a network. However, the model in Fig. 3.13 identifies (deliber- ately) layer interfaces only indirectly by referring to identifiers (NWi) of hosted and The T-GT table translates a GT to an REi in this case, since n11 has direct routes to all other nw1 nodes. If nw1 had been a switching network, the T-GT would have translated a GT to an nw1 net- work address (NA) instead, to be used as an input to a routing table, T-ROs. 3 Node Structures hosting logical networks