action between services, interaction with service providers, interfacing with customers and maintaining statistical data. Business Management Layer (BML) has responsibility for the total enterprise. The key functions of BML are: Supporting the decision-making process for the optimal investment and use of new telecommunications resources. Next Generation Mobile Communications Ecosystem Supporting the management of OA&M related budget. Supporting the supply and demand of OA&M related manpower. Maintaining aggregate data about the total enterprise. An example of TMN setup is an ISP (customer) that uses a third party service provider to connect to its routers to provide Internet services. As shown in Figure 8.18(b) there are three a-reference points from the IP service provider to the SDH/DWDM service provider, one each from EML, NML and SML. All these reference points as shown in Figure 8.18(b) will be connected to SML, first it is not as such required to connect to other layers and secondly the service provider will not allow the customer (ISP) to monitor or modify its network. 8.3.3.3 TMN Management Services A TMN is intended to support a wide variety of management areas which cover the OAM&P of telecom- munications networks and services. ITU-T has categorized management into five broad management functional areas namely [3,25]: Performance Management is concerned with data collection measurement and storage. It is also associated with quality assurance, performance control and analysis. Performance management control supports the transfer of information to control the operation of the network in the area of performance management. Fault Management is a set of functions which enables the detection, isolation and correc- tion of irregular operation of the telecommunication network. It deals with alarm collection and storing, alarm filtering, and alarm acknowledgment. It is also responsible for fault localization and fault correction. Configuration Management provides functions to exercise control over, identify, co