In the past, each implementor normally developed and offered its own manage- ment system to network operators. As operator networks became more open, com- prising equipment from many vendors and a multitude of services, network operators had to handle several management systems. This increased the already high costs for operation and maintenance. That became obvious for the ITU-T nearly 20 years ago. A lot of effort has been spent since then on developing a man- agement system concept for open systems. This system was originally called the OSI Management concept and was later developed into the Telecommunication Management Network (TMN) concept, published in the early 1990s (see ITU-T recommendations in the M.3000 series). A TMN is a sysnet of its own (the correspondence to a sysnet model of TMN is described in ITU-T M.3010). It has a logical network structure of its own, and it has a (generic) physical network model of its own. The processing system para- digm applies to TMN: TMN is a process control system. The TMN resource sys- tem is, from the management systems point of view, a traffic system (comprising the Teleservice System and the Connectivity Systems of the model in Fig. 3.91, with all their logical and physical components and relations). The purpose of TMN was to create a system that could be used for management of any type of traffic system. Since, however, every network concept has its own type of components, the most important issues were to define a common language for describing resources in a traffic system (comparable to the resource modelling language in AML, see Sect. 7.3), and to develop a standardized protocol for manip- ulating resources that were described by that language. The common language, GDMO, see ITU-T X. .722, was based on defining each resource that had to be managed as a managed object (MO), and storing all descriptions of MOs in a data- base, called managed information base (MIB) in the management system. The protocol is called common management information protocol (CMIP), whi