f openness and disaggregation align with those of O-RAN. Disaggregation and software cen- tricity allow for scalability where the core network (both CP and UP) components can either be software elements that reside as a function in an enterprise network or a dedicated hard- ware function that resides in the operator network. 48 Open Radio Access Network (O-RAN) Systems Architecture and Design Wired networking analogy The concept of CP/data plane (DP) separation has been around since a long time in wired network- ing-notably the early 2000s with the advent of network processors. Software-defined networking (SDN), for example, defined by the Open Networking Foundation (ONF), is about separation of CP and DP operations. Separation of these components from a software/API perspective allows them to (potentially) run in different hardware, physically colocated or explicitly not, and in fact nonvirtua- lized or virtualized. As such, also the concept of standardization of the CP/DP API, through initia- tives such as the Network Processor Forum has been standardized in the wired networking world for long time (http://www.oiforum.com/public/NPF_IA.html). A fair question at this point is: "why should people adopt SDN explicitly?" One piece of the answer is: SDN allows the replacement of control that is standard, application-dependent, often distributed with control that is generalized across standards, applications, as well as more centralized. This means that SDN matters to entities who can benefit from centralized control and who are able to develop application-specific control SW. Motivations often involve simplicity of network management, but even the management becomes network-specific: SDN provides for a standardized interface between CP and data plane, as such "exposing the network" to networking applications developers. OpenFlow, an SDN standardization vehicle driven by the Open Networking Foundation (ONF), is a concept that is closely associated with SDN. OpenFlow defines an API level inter- face between (today) La