solated at different levels. Guaranteed performance: Network slicing seamlessly integrates different domains to satisfy industry-defined 5G performance specifications and to accommodate vertical industry requirements. Scalability: Owing to virtualization, which is one of the key enabling technologies for network slicing, resources occupied by an NSI can dynamically change. 44 Chapter 1 Operation and management capability exposure: Tenants may use dedicated, shared, or partially shared NSIs. Furthermore, different tenants may have independent operation and management demands. The NSM system provides access to a number of operation and management functions of NSIs for the tenants, which for instance allows them to configure NSI-related parameters such as policy. Support for multi-vendor and multi-operator scenarios: Network slicing allows a single operator to manage multiple technical domains, which may be composed of network elements supplied by different vendors. In addition, the architecture needs to support a scenario, where the services from the tenants may cover different administrative domains owned by different operators. As we mentioned earlier, an NSI is a managed entity in the operator's network with a life cycle independent of the life cycle of the service instance(s). In particular, service instances are not necessarily active through the entire duration of the run-time phase of the supporting NSI. The NSI life cycle typically includes an instantiation, configuration and activation phase, a run-time phase, and a decommissioning phase. During the NSI life cycle the opera- tor manages the NSI. As shown in Fig. 1.19, the network slice life cycle is described by a number of phases as follows [7]: Preparation: In this phase, the NSI does not exist. The preparation phase includes the creation and verification of NST(s), on-boarding, preparing the necessary network envi- ronment which is used to support the life cycle of NSIs, and any other preparations that are needed in the network. Instantiation, configura