ke order management, network manage- ment, and mediation system that interoperate to fulfill a customer order, assure service continuity, and bill the customer for the ordered service. The order management systems allow operators to perform the process of con- figuring the network to deliver the services ordered by a customer. Activating ser- vices on the allocated resource infrastructure is performed by the operator using provisioning systems. The allocation of resource and tracking the assets itself is performed by the operator using an inventory management system. After activa- tion, the task of monitoring the network to detect and isolate network failures and quickly restore services is performed using a network management system. A ser- vice management module works above the network manager to correlate network performance with service quality requirements, and appropriately communicate and compensate customers for any disruption. Finally, mediation systems allow operators to determine service usage. This information is taken utilized by a rating system that allows operators to determine how much to bill based on the service usage for a particular customer. Fundamentals of EMS, NMS and OSS/BSS Interaction between support system modules can be made simpler when service oriented architecture (SOA) is used, where the modules are developed as services with defined interfaces for interaction. Integration activity can be made easier by deploying an enterprise application integration (EAI) layer. The EAI allow opera- tors to quickly integrate diverse support systems and network elements. Electronic integration of support systems is required for an automated back-office in large-scale operations. This integration layer creates an open data exchange platform optimized for heterogeneous interprocess communication. The EAI is not limited to OSS and can be used to support communication between software systems in other domains also. Some of the key players in EAI development are Tibco, BEA Systems (acquired by Oracle), 