o extensibility is a must. Many OSS vendors believe that a stronger case can be made for their products' value- add if they can ensure that their software is "future-proof" to some degree. This is where application programming interfaces (APIs) enter the picture. Many OSS sys- tems implement APIs and examples will be described in this book. Network Management OSS Overview 2.1 Introduction Operations and maintenance (O&M) preceded modern operational support systems (OSS) software and its associated network management model. O&M referred to control and supervision of telecom networks. O&M has now developed to the extent that it is included under the head of network management, which is broader than merely control and supervision. It also includes fault management, traffic manage- ment, service provisioning and service management. The network management OSS software industry is growing because carriers are realising that O&M, under the broader meaning, is critical to their capability to offer diverse services and to extract maximum return on investment (ROI) from their infrastructure. The capital investment required for advanced network management systems is a fraction of that required for network infrastructure. At the same time, a network management system must dovetail with operational processes. Introducing a new network management OSS often causes an operator to see that their opera- tional processes also need an overhaul. Changing processes requires serious man- agement commitment because it involves the way in which people do their work on a daily basis. Business process re-engineering (BPR) can be expensive, especially in terms of the time required of upper management. The re-engineering gurus are the first to admit that re-engineering is very hard. However, by streamlining processes and eliminating unnecessary costs, the eventual cost saving from re-engineering can be huge. Further, a successful BPR project in a telecom operator will provide a solid base from which a wide variety of advanced telematic servi