sible 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 building and implementation activities, both for decision making and design. Billing mediation or accounting management take care of the collection, buffering and delivering of information from the network elements or call control servers, either for billing or accounting purposes. Accounting management could be illustrated by means of an international call. If a Swedish subscriber calls a friend in the UK, the Swedish operator sends the bill and gets the full income. However, the call has also passed the network of the British operator, and it may even have been transited through networks belonging to other operators. The call income must then be shared among the operators involved. This is called accounting. How the money is shared is strictly defined by interconnection agreements. The accounting management takes cares of data collection in order to produce the call accounting and assist the income distribution among the different operators, either through accounting determination or checks. Configuration management and corrective measures are downstream functions, based on command execution. The previous functions were based on event collection. Configuration management plays a major role when trying to set the network behaviour. Examples are configuration of installed equipment, capacity extension on a path and network