-based approach also made it difficult to scale up and down for different configurations and requirements, including future upgrades and optimiza- tions. To address these issues operators have been pushing to allow for NG-RAN functional splits that enable most of the RAN functionality (e.g. gNB-CU and O-DU, as defined in Chapter 4) to be run in a virtualized manner in data centers, using an open hardware. This allows an open and software-based model where the system can scale with the work- load leaving only the radios and a small amount of physical layer processing (e.g. O-DU, as defined in Chapter 4) to be implemented in hardware and deployed on site (see Section 4.5). Figure 6.2.1 shows the evolution of the RAN from dedicated hardware and fixed dimension- ing to a scalable, flexible, and software-based model running in the cloud where the telco applications are now applied to the innovations happening in the IT industry. 6.2.4 Containers and Microservices VMs and containers are two methods to realize virtualization on a compute platform. VMs, which were historically the first widely deployed virtualization method, allow an infras- tructure platform to be abstracted from the associated hardware (i.e. virtualized). This is typically implemented using a hypervisor running on the host operating system (or some- times on the real hardware, i.e. "bare metal"), which is a software component that manages Eliminate Map Mobile Constraints of Workloads to Physical Cloud Boundaries Resources Signaling Compute Context Storage Forwarding Network Figure 6.2.1 Network evolution toward virtualized RAN. 6.2 Virtualization VMs and presents them with a virtualized hardware, which is decoupled from the actual hardware. Thus, each application can run independently (i.e. in a separate operating sys- tem) from other applications on the server platform without impacting (or even the knowl- edge of) other applications running on the same hardware. In particular, this enables cloud providers to support many applications without constrai