 virtual private networks based on IP (like the intranets). The enterprises have natural reasons to take care of the business critical areas them- selves, such as competition between the end users (in this case the enterprises). What Telecom Management - Operations areas are considered business-critical depends on the enterprise, but they might include streamlining the connections, managing a call centre and monitoring things like the QoS or the call-completion rate. Therefore, large enterprises may need to control these resources in the same way as the operator. See also customer network management in Figure 16.1. Summing up, the ability to create effective, highly automated processes for operation and service delivery, together with a pragmatic approach to technology choices is crucial. 16.4 THE TMN FUNCTIONAL AREAS The TMN functional area segments follow the well-known network management model from ISO. The management functions are frequently known by the acronym FCAPS, which refers to: Fault management Configuration management Accounting Performance management Security management Fault management covers all the necessary functions to show the network fault status in real time. It is known that a fault originating in one network element may lead to an avalanche of alarm indications. This is due to the incidence the original fault has on other network elements. In spite of working properly, they are not able to carry traffic due to the original fault, and therefore they are detected as faulty. For instance a transmission repeater fault may lead to fault indications at different levels on the transmission system, a rather high number of declared faults on associated routes, and also fault indications switching devices utilizing those routes. The process through which the original fault is obtained from a rather high number of alarm indications is called alarm (or fault) correlation. Alarm correlation becomes more complex with network heterogeneity and increased number of network elements. Some systems have the p