transparent, therefore service relations can exist in any dimension in functional space. For a service relation to exist in functional space, the service network must first have been integrated in an abstract network (level 1), the abstract network in a protocol network and the protocol network in a logical network. Abstract networks integrate service networks. The units of abstract networks (abstract machines) provide an access domain for the units (service objects) of service networks, but communication between abstract machines is otherwise dis- tribution transparent, as for service networks. Thus, abstract networks also have no existence in functional space unless they are integrated in higher integration levels. Integration level 2 (protocol network) is defined by message protocols in the D- dimension and by (often temporary) connection or association endpoints in the C- dimension. Protocol networks represent the first step of implementing distribution transparent models (level 0 and 1) in functional space. By integrating abstract machines in protocol networks, abstract networks become distributable. However, abstract networks are distributed, i.e. the location in functional space of abstract protocols is fully defined first when protocol networks are integrated in logical net- works and logical networks in physical networks. In the following we will briefly present the five integration levels by discussing the four disintegration steps, starting from the bottom. A more thorough presenta- tion is left to later chapters. Disintegration step 1, physical networks -> logical networks: This step starts by separating each physical node into the network node function (NNF) and the node platform, as was discussed in Sect. 2.3.6. Assuming that the network interfaces are already specified, each network interface is analysed as to its discrimination functions, as we did in Sect. 2.3.4. Figure 2.47 shows the result of an initial analysis of the type of network interface that exists between the switching system MSC and o