vice delivery, assurance, and billing. Even after much maturity of the IMS technology, there was a lag in adoption because of the absence of a well-defined OSS/BSS stack that could manage the IMS and proper billing system to get business value to service providers when moving to IMS. Operations support systems (OSS) as a whole includes the systems used to sup- port the daily operations of the service provider. These include business support Fundamentals of EMS, NMS and OSS/BSS systems (BSS) like billing and customer management, service operations like service provisioning and management, element management, and network management applications. In the layered management approach, BSS corresponds to business management and OSS corresponds to service management, while the other man- agement layers include network management and element management. Let us start the discussion with the complete picture where OSS corresponds to support systems that will reduce service provider operating expenses while increas- ing system performance, productivity and availability. The OSS is both the hard- ware and software that service providers use to manage their network infrastructure and services. There are multiple activities in the service provider space associated with offer- ing a service that requires an underlying OSS to manage. For a service starting up, the service needs to be provisioned first, the underlying network including con- nectivity and the elements needs to be provisioned, then the service and network needs to be configured, the billing system and SLA management system needs to be configured, the customer records need to be updated and when the service is acti- vated the billing system also needs to start working on records. This is just a basic line up of activities and there are many supporting operations associated with just getting a service ready for the customer. The OSS brings in automation and reduces the complexity in managing the services. After activation of service there needs to be a service assuran