and operation support systems. The reader will get a chance to understand where the different OSS/BSS solutions available in the market fit in with the holis- tic support system perspective. 20.1 Introduction Usually operation and business support systems deal with fulfillment, assurance, and billing (FAB) for a service associated with a customer requirement. The back- end planning to do the real-time support is more a process rather than the actual support system. The business map as in eTOM brings in an E2E perspective for all processes in service provider space having FAB as a major module. This chapter details the basic building blocks for fulfillment, assurance, and billing that make up the major portion of all support systems. For ease of understanding, the expla- nations are given using activities in each process without reference to any standard models like eTOM. 20.2 Fulfillment Process The fulfillment process involves the set of operations used to fulfill a customer order (see Figure 20.1). These operations use a set of solutions like order management Fundamentals of EMS, NMS and OSS/BSS Sales Order Customer management handling Service Service Service planning and Inventory development provisioning management Network Network Network planning and development provisioning Figure 20.1 Fulfillment process. module, inventory management module, provisioning module, service configura- tion module, and SO on to complete the fulfillment process. Fulfillment spans busi- ness support systems with modules such as sales and order management and it spans the operation support systems with modules like provisioning and inventory management. It is first the operations of sales to work with the customer to ensure that an order can be placed. The order management system (OMS) then captures all relevant information from the customer to offer the requested service. The OMS also has the capability to support changes in the order based on customer requests. Though the OMS is mainly for the service provider, the customer also