or wanted, but it is the only MO the system will open as a result of the operators original request. Thus, network MOs can easily be defined and used by operators of a manage- ment system, provided that the traffic system is described as an AMLn model (or by any equivalent modelling language). If network MOs are to exist, Compilation of the model into data structures must be supported, which implies that a formally defined language (such as AMLn) must be used for modeling. Furthermore, a management function must be added to allow managers to create network MOs according to operators' access rights. Work stations must know the language's graphical notations SO that model frag- ments can be displayed. Summary We can summarize the discussion about traffic versus management systems by drawing generic layer structure models. In Fig. 5.21 we show the two planes, assuming a simple traffic system that consist of four layers. This model is an applied version of Fig. 5.1, extended with what we know about service and control points and other concepts used to model management functions. 5 Management and Traffic Systems Traffic system users AMFs and management T protocol layer Operators AMF protocol mpCP protocols msCP protocols Connectivity services used within manage- ment plane only: - OSI L4 - IIOP - TCP/UDP Fig. 5.21 The combined layer structures of the traffic and management planes We define as management plane all functions that deal with management in some form, whether they exist in the management system or the traffic system, and whether they are just management agents (AFs, parts of the management layer) or autonomous management functions (AMF). Two types of relations exists between the planes: mrCPs and connectivity serv- ice points for AMFs (CSPM). The layer structures of the traffic plane and the management plane are com- pletely separate and independent of each other, since all relations that the traffic plane has to the management plane terminate either in the single management layer or in AMFs. Connectivity s