2.2.3 Application layer
The application layer consists of management and business-oriented software. It can also be understood as a user interface for the control layer. From the management point of view, the programs running in the application layer may provide the network engineers with statistics about their networks. Currently using application layer metrics in the form of a common measurement solution received minor attention. Such as application of a measurement can be a generic usage-based charging as a service. In another word, a more flexible measurement which is software defined and written by providers of service customized for their own specific use, transparent from their interior applications and end-users [24].

2.3 OpenFlow protocol …show more content…
The OpenFlow idea is currently the most commonly deployed SDN technology. The software-of controller is in charge of for managing the forwarding information of one or multi-switches; the hardware only handles the forwarding of traffic depending on the rules set by the controller. OpenFlow protocol provides a specialization to migrate the control logic from a switch into the controller. OpenFlow is modern technology proposed to standardize the way that a controller communicates with devices in SDN architecture. It was proposed to enable researchers to test new minds in a production environment. OF also defines a protocol for the connection between the switches and controller [25]. OpenFlow uses the fact that the most of Ethernet switches contain tables flow (Flow-Tables) though each of these is specific manufacturers own identified several common features which are used by the OpenFlow to program these flow tables