clusion The overview presented in this chapter is just the foundation for the chapters that follow. The difference between OSS and BSS was discussed in the context of sup- port systems. The ambiguity associated with OSS as a complete support system including network management, against a support system for service management alone was also handled in this chapter. The shift from the popular TMN to eTOM was also handled. Support systems are a vast subject and once the reader gets the fundamentals from this book there are many support processes where the reader can specialize as a professional. Additional Reading 1. Kornel Terplan. OSS Essentials: Support System Solutions for Service Providers. New York: John Wiley & Sons, 2001. 2. Hu Hanrahan. Network Convergence: Services, Applications, Transport, and Operations Support. New York: John Wiley & Sons, 2007. 3. Kornel Terplan. Telecom Operations Management Solutions with NetExpert. Boca Raton, FL: CRC Press, 1998. Chapter 20 OSS/BSS Functions This chapter is intended to give the reader an understanding of the fulfillment, assurance, and billing support systems. The building blocks in each of these sup- port systems and the activities performed by the building blocks are explained in this chapter. There is fulfillment, assurance, and billing associated with both busi- ness 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 ma