ossibility to learn from previous network faults experiences and from network expert indications, to improve alarm correlation. Suppression of secondary alarms is a recognized method. Fault management has advanced alarm correlation tools, which allow the operator better understanding of the real alarm situation, and leads to shorter times for service recovery and fault repair. Performance management portraits the network performance through diagrams and reports, either standardized or specially selected by the network administrator. The net- work status in each moment is usually compared with the performance corresponding to some level of network activity defined as a reference. This reference consists of the network status when working without network element's faults and with normal traffic conditions. The reference is often mentioned as the 'net- work baseline' or the 'network normal condition'. Also comparison of the network status with the baseline raises alarms when the measured traffic or workload goes over certain threshold values, defined by the network administrator. Understanding Changing Telecommunications - Building a Successful Telecom Business In this case, alarms are emitted to alert the network operator about abnormal traffic conditions. This information permits the operator to act in advance to any possible prob- lem. The operator can then utilize the network management tools to solve or mitigate the congestion and its associated effects, or eventually plan new network expansions before the situation becomes critical. Performance management is a key function to verify end-to-end QoS and network availability to the end user. It is extensively used to verify SLA compliance and to detect and measure possible SLA deviations. It also provides information about network per- formance and congestion levels, allowing fault detection. Finally it facilitates network re-engineering, monitoring on network element life cycles and network capacity supervi- sion. All this gives the necessary input to future bui