ternative to XML. 5G Network Architecture Application layer Business applications Control layer Network services OpenFlow Infrastructure layer Network Network devices devices Network Network devices devices Figure 1.8 Illustration of the SDN concept [49]. applications include network management, analytics, or business applications that are used to run large data centers. For example, an analytics application might be built to recognize suspicious network activity for security purposes. SDN controller: The SDN controller is a logical entity that receives instructions or requirements from the SDN application layer and relays them to the networking components. The controller also extracts information about the network from the hardware devices and communicates back to the SDN applications with an abstract view of the network, including statistics and events. The control plane consists of one or a set of SDN controllers (e.g., Open Network Operating System19 OpenDayLight²0 which logically maintain a global and dynamic network view, and provide control tasks to manage the network devices in the user plane via south-bound Open Network Operating System is an open-source software-defined network operating system (https://wiki.- onosproject.org/). OpenDaylight is an open-source software-defined networking project hosted by Linux Foundation, which was created in order to advance software-defined networking adoption and to create a strong basis for net- work function virtualization. It was created as a community-led and industry-supported open-source frame- work. The goal of the OpenDaylight project is to offer a functional software-defined networking platform that can provide the users with directly deployable software-defined networking platform without the need for other components. In addition to this, contributors and vendors can deliver add-ons and other pieces that will offer more value to OpenDaylight (https://www.opendaylight.org/). 28 Chapter 1 interfaces (e.g., OpenFlow or ForCES²1) based on requests from the app