e fixed to fixed, mobile to fixed, and mobile to mobile. When the user keeps on switching networks for a single usage record itself, the type is Roaming. SMS and call forward are grouped under value added service type. A part of the usage data collection the mediation system performs is a set of key activities: Polling for data: The mediation system continuously looks for data on usage records from network infrastructure. While polling is a pull based mechanism where the mediation system checks for new record availabil- ity and collects data, a push based mechanism can also be implemented, where the billing agents in the network infrastructure actively sends data to the mediation system when a new record is generated with details on the usage. To make the billing agents independent of the media- tion system implementation, it is a usual practice to implement a polling mechanism for data collection where responsibility to collect and per- form mediation to map to a format lies with the mediation system. b. Consolidation of data: Once data is collected by a "push or pull" mecha- nism, next the data across network elements needs to be consolidated. The Fundamentals of EMS, NMS and OSS/BSS information sent from the mediation system to the upper business layer modules needs to be formatted data that can be directly interpreted. So the aggregation, correlation, and filtering between billing records takes place in the mediation system to send consolidation information to other business modules. Standard interface for interaction: Multiple business modules make use of the information from the mediation system. Hence it is important that the mediation system is not designed for communication for a specific module. The interfaces for data request and response need to be stan- dardized. These standard interfaces are published for business modules to easily interoperate with the mediation system. The function here is a seamless flow of information between the mediation system and business support systems. d. Drop nonbillable