## 4 Evolution of the Smart Grid Infrastructure: SDN-Enabled Smart Grid
### Potential Benefits of the SDN-Enabled Smart Grid  
* Simplified system management: The main purpose of SDN is to realize simplified network management that allows an extension of the scale and flexibility of a network. To reduce the management complexity of the network system, SDN isolates the control and data forwarding planes [15]. The control plane of the network is implemented using an SDN controller that constructs the network topology, and the data forwarding plane of the network is implemented using feedback information from the SDN devices on the network. The feedback information between the SDN controller and the device is exchanged using a secure control channel that is established using network tunneling [29]. Service providers can deploy application and network functionalities, such as the routing strategy, topology and QoS policy, using a secure control channel. In the SDN-enabled smart grid HAN, resource-constrained AMI devices do not need to decide their own routing path, QoS or transmission strategies. Instead, the centralized SDN controller architecture determines the optimal configuration of the network, reducing the resource usage of the AMI devices in terms of power consumption and the number of control messages required [30]. The management software for the SDN controller can be categorized into two types, namely open-source-based and commercial systems. Nox [39] and Floodlight [12] are the most famous SDN control software frameworks that can handle the request and response messages that are sent between the application layer and network layer [39]. The SDN controller determines the network policy using an SDN application, and it maintains the flow information, route, forwarding strategy, topology and  
Figure 4: Abstraction of the SDN-enabled smart grid: business model process, categorized SDN application and system architecture. OVS, Open vSwitch; PLC, powerline communication. (**a**) Simplified business model. (**b**) The example of SDN applications. (**c**) SDN enabled Smart Grid System architecture. network status. Figure 4c shows an example of the SDN-enabled smart grid architecture. In this figure, SDN applications, such as network configuration, IEC 61850 configuration and system monitoring, are connected to the SDN controller using Southbound and REST APIs. Southbound is a connection application program interface (API) between the application and communication interface. When the AMI device receives a new flow, such as AMI metering data, it requests the forwarding policy from the SDN controller using the secure control channel. The forwarding policy of the requested flow is generated using the SDN application and is transmitted to the AMI meter. This process, which is carried out by the SDN-enabled smart grid, provides not only simplified network management, but also reduces the computational overhead of the AMI meter. Further, service providers simply add, remove or update network policies without the need for any hardware replacement or upgrade. * Interoperability: SDN provides data and control message exchange between different types of communication infrastructure by using tunneling and Open vSwitch (OVS) and OpenFlow standards [29]. Figure 4c shows an example of the SDN system architecture. In this figure, the IEC 61850 utility protocol of the application and OVS is connected through the REST APIs of the OpenFlow interfaces. OpenFlow is the de facto SDN standard software that provides an interface between the control and forwarding layers of the SDN. OpenFlow allows direct access to and manipulation of the forwarding plane of network devices, such as switches, routers, whether they are physical or virtual (hypervisor based) [28]. OVS is an alternative to the bridge module that has been part of the kernel since the 2.4 series. OVS enables communication interface virtualization and port mapping for SDN router construction.