the potential of next generation networks and make it increasingly difficult to implement new products and services in a reliable and cost-effective manner. They need a new generation of support systems that can keep pace with the network. These systems must leverage the features and functions of the NGN infrastructure, allow providers to deploy new services more effectively, provide better customer service, help reduce operations cost and support easier customization and integration among OSS components. The OSS systems categorized as "next-generation" will have some common characteristics that will set them apart from their legacy ancestors. 3.1 Multi-Domain Management A key concept in managing next-generation networks is that of "domains." The NGN infrastructure will be made of a variety of technologies on the access front, such as DSL, broadband cable, wireless, and gigabit ethernet, and in the core network such as DWDM, optical, IP-MPLS and ATM. Furthermore we have application/service networks that need to be managed - media gateways, signaling gateways, media and feature servers, AAA servers and DHCP servers. We generically refer to each of these technologies/areas as domains. In addition to the domains of the next- generation, we have legacy domains such as POTS and its associated circuit- switched components, ISDN, frame relay, and SONET. These legacy and next-generation domains have to be managed in an integrated manner, because a customer service can span across the two. Figure 39 shows a framework for a next-generation OSS/NMS based on multi-domain management architecture. Chapter 8 - Next-Generation OSS Trouble Customer Management Billing Workflow Inter-Domain Manager Inter-Domain Manager Domain Manager Domain Manager Domain Manager DSL Access Core IP and Optical Transport ATM Switching Figure 39. Framework for Multi-Domain Management The multi-domain management framework covers the EML, NML and SML layers of the TMN structure. The EML layer usually consists of network equipment vendor provided Elemen