Comparative Performance Analysis of SDN Controllers Across Fat -Tree and Mesh Data Center Topologies

Software Defined Networking (SDN) plays a major role in today’s modern cloud and 5G systems. It separates control from forwarding and allows operators to manage the network through programmable controllers. The actual performance of an SDN deployment is dependent on the selected controller and underlying topology. This work examines eight widely used controllers POX, RYU, Floodlight, Faucet, Beacon, ONOS, OpenDaylight (ODL), and default OpenFlow controller under topologies like Fat-Tree and Mesh. Using Mininet, we evaluated each controller on various network instances and recorded round-trip time, latency, throughput, and bandwidth usage. Across all experiments, ONOS and ODL achieved lower delay and higher throughput than the other controllers. Controllers such as RYU and floodlight performed steadily under moderate load, whereas POX and reference controller show higher delay and low throughput as network size increases. The distributed processing and efficient handling of ONOS and ODL provide significant advantages in large Fat-Tree and Mesh environments.