 IP Address: 137.52.76.29 Quality of Service in SDN Technology Figure 1. SDN architecture APPLICATION LAYER Business Applications CONTROL LAYER Network Services Network Services OpenFlow INFRASTRUCTURE LAYER Figure 2. SDN operation overview Global Network View High-Performance Machine Northbound API Controller Formating Southbound API Forwaring Forwaring flows flows Forwarding Forwarding Forwarding Devices flows flows Forwarding Forwarding constructed previously when the controller downloaded appropriate flow rules to the device. If the SDN device finds a match, it takes the appropriate configured action, which usually entails forwarding the packet. If it does not find a match, the switch can either drop the packet or pass it to the controller, depending on the version of Downloaded 4/15/2022 9:44:49 AM Nova Southeastern University IP Address: 137.52.76.29 Quality of Service in SDN Technology OpenFlo and the configuration of the switch (Egilmez H. E., Dane, Gorkemli, Tekalp 2012). The SDN controller is responsible for abstracting the network of SDN devices it controls and presenting an abstraction of these network resources to the SDN applications running above. The controller allows the SDN application to define flows on devices and to help the application respond to packets that are forwarded to the controller by the SDN devices. Southbound API: The interaction between the controller and the deployed device is commonly referred to as southbound application programing interface (API). A common, open standard SDN protocol, and one of the most popular options for southbound APIs is OpenFlow. Northbound API: The opposite of the southbound API is the northbound API, which is labeled in Figure 2 as just API; it involves the communications from a business application to the controller. This is the point where the real meat and potatoes exists for SDN. However, the northbound API can be very complex, like providing a Quality of Service provisioned path from one end of a network to another dynamically, then tearing it b