## 6 Architecture for Cross-Domain End-to-End Network and Service Management  
The cloud-native future network with network-cloud/edge convergence makes the cross-domain network and service management particularly important and challenging. A key attribute of the network virtualization is the heterogeneous technology domains in the shared infrastructure; for example, the NFV virtualized infrastructure layer comprises the compute, storage, and network domains. Diverse management capabilities are required in the different technology domains for data transport, process, and storage. In addition to technology domains, end-to-end service provisioning in future networks often traverses different administration domains, e.g., domains managed by mobile network providers, edge service providers, transport network operators, cloud service providers, etc. Heterogeneous management mechanisms and polices are employed in different administration domains. Therefore, future networks call for unified resource management across heterogeneous technology domains and federated service management spanning over multiple administration domains. Although the 3 GPP NWDAF, ETSI ENI, and ITU-T ML architectures have defined capabilities that are able to handle the management diversity in technology domains, these standards all focus on the management scenarios within a single administration domain. An overarching framework is required to face the challenge of end-to-end cross-domain management. Toward this direction, ETSI is developing the ZSM architecture with the goal to define a holistic management framework that enables the integration of the management capabilities specified in various standards for supporting end-to-end management across technology and administration domains [39; 40]. The ZSM architecture follows the service-oriented architectural principle in order to build a service-based framework for inter-domain network and service management. The set of specific principles for ZSM design include modularity, extensibility, scalability, simplicity, service composability, management concern separation, and functional abstraction. The ZSM architecture defines management domains as an abstraction of technology/administration domains to support the separation of management concerns. Each management domain exposes a set of management services that can be accessed via standard interfaces (service end-points). The self-contained management services are the basic ZSM system modules that can be deployed and scaled independently to accommodate the management load. Loose-coupling between management services allows new services and service capabilities to be added easily, thus making the system highly extensible. Through a consistent set of composition patterns and interfaces defined in the ZSM architecture, management services may be used collectively to construct more complex management functions [41]. As depicted in Figure 5, the ZSM reference architecture is composed of multiple Management Domains (MDs); each is responsible for managing a domain infrastructure and one End-to-End Service Management Domain (E2 EMD) that orchestrates the management services provided by individual MDs for cross-domain end-to-end management. Each management domain, including the E2 EMD, exposes a set of management services provided by the management functions in the domain [42]. The management services realized by each MD can be categorized into the following groups. Domain data collection services monitor the managed infrastructure and collect data as requested by other management functions in the MD. Domain analytics services perform various data analytics on the collected data and/or data stored in the domain to provide domain-specific insights and generate domain-specific predictions. Domain intelligence services are responsible for driving intelligent closed-loop automation to enable autonomous management for the domain infrastructure.