d in Chapter 3: the modern centralized 'spider' structure of the management From the telecom side the need to concentrate and standardize many different types of management systems into an integral network management became apparent. The business side put forward a requirement to cope with the increasing operational costs derived from network expansion. On the data side the explosion of Internet networking caused a tremendous expansion on the networks that brought many of them close to collapse. The network administrators needed solutions to smoothly adapt the networks to the pace of expansion. Telecom: ITU-T developed the TMN concept (telecommunication network manage- ment). TMN is based on an OSS (operation support system) platform. It has a hierarchical structure based on two nodes levels, the OMC (operation and maintenance centre) and the NMC (network maintenance centre). The OMC takes care of the direct management of the network nodes, called network elements (NEs), while network configuration, performance data, alarm and traffic statistics are managed by the NMC. Several OMCs may exist in large networks to regionally distribute the NE management. There is usually one single NMC. Additional centres have lately been introduced for service management and enterprise management. The ITU-T defined the Q3 interface based on the SMI model (structure of management information) and a group of ISO standards like CMIP (common management information protocol) for manager-agent communication, and FTAM (file transfer access and man- agement). The NE agents and the central manager communicate by means of a network called DCN (data communication network). For DCN the fairly secure X.25 technology was proposed. TMN is a detailed model that has not become fully implemented. This is partly due to the strong advance of IP technology and the progressive obsolescence of X.25 networks, Telecom Management - Operations making IP a better solution (but less secure) for the DCN communication. The telecom- munication management communi