he present book. 6 Enabling Technologies OSS / BSS / E-Services / Big Data Global Orchestrator NFVO, MEAO Workloads Global Edge apps, analytics, network functions Virtualization Software Containers, VMs, virtual storage, overlay networking, dataplane acceleration VNFM, MEPM-V SDN Controller Commodity Hardware Kubernetes/ servers, storage, switches OpenStack Figure 6.2.5 ONAP framework (Source: Reproduced by permission of © ONAP). VNFs and analytics applications. As of now, ONAP is primarily used in the core network; however, it may be extended to include at least parts of NG-RAN (e.g. virtualized gNB-CU). 6.2.5 NFV Evolution Many operators have already deployed virtualized core networks for 4G and are now in different stages of their NFV evolution toward a cloud native virtualization platform for RAN. This process is expected to accelerate with 5G deployments. Generally, the following stages in deployment evolution toward virtualization can be envisioned: 1. Bare-metal (no virtualization). In this stage, an application is run on bare-metal servers. The signaling and data plane are not decoupled. The system is often operated manually. 2. Virtualization. In this stage, an application runs in a virtualized environment where software and hardware are decoupled. However, scaling capabilities are still manual and require reconfiguration when new network and computational resources are added. 3. Orchestration. In this stage, orchestration is deployed to bring up the virtualized environments, with limited scaling, diagnosis, and healing. 4. Containers. In this stage, the system is running on containers, where an application runs as a microservice where possible. 5. Automation. In this stage, the system moves to a "Web-Scale IT"4 platform, providing a fully auto- mated system with the highest service assurance, analytics, and scaling. 4 Web-scale IT is an industry term referring to a modern networking architecture which is open, scalable, and implements intelligence in software. 6.2 Virtualization Currently, most operator