ions for Network Management, Security Policy Enforcement, Traffic Engineering and QoS Policy Enforcement. Service Management Application: These set of applications include applications for Automated (multi-layer, multi-vendor) Network Provisioning, Virtual Private Cloud Provisioning and SLA Monitoring. Revenue Generating application: These set of applications include applications for Software-Defined Data Center (SDDC), Big Data Applications (based on L4-L7 data) and End-to-End QoS Management. SDN Controller: As mentioned earlier, the controller is the brain of the network. It can be either distributed, centralized or hybrid. In centralized type, a controller manages all the forwarding elements in the system, and retains a global view of the entire network. Controllers such as ODL, ONOS etc. are centralized controllers. Whereas in distributed type, more than one controllers are used and are distributed over the entire network. Hybrid type controllers are those that have both the centralized as well as the distributed concepts. Most widely used SDN controllers are Floodlight, OpenDaylight, OpenContrail, Ryu, flowVisor, BEACON, NOX and POX. SDN Switches: SDN switches or devices are non-intelligent forwarding devices that follow the rules installed on them by their controllers. Most common SDN switches are the OpenFlow switches that work on the OpenFlo protocol, defined by ONF. An OpenFlow switch has a flow table that gives provision for lookup and then packet forwarding based on the rules on the table. The switches are connected to the controller by a secured channel. Each switch has a unique DPID, also known as the data path identifier. When a packet arrives at the switch and the switch finds no matching rules for the particular data packet i.e., a packet miss is encountered, then about 200 bytes of the data is sent to the controller, which then decides what appropriate actions need to be taken as given by the network administrator or operators. The controller then install Downloaded: 4/15/2022 9:44:49 AM Nova Sou