This document discusses software defined networks (SDN). SDN separates the network control plane from the data plane, allowing a control plane to control multiple devices. The SDN architecture has three layers - the infrastructure layer consists of switches and routers that collect network status and process packets, the control layer bridges the application and infrastructure layers using a high-level language and network status information, and the application layer offers services through the control layer like load balancing and security. OpenFlow is a protocol that exchanges messages between controllers and switches to implement SDN functionality. SDN provides benefits like improved performance, flexibility, and reduced costs compared to traditional networks.