A QoS-aware routing in SDN hybrid networks

Changing the whole network into a software defined network (SDN) is impractical due to high replacement cost. Therefore, there exist SDN hybrid networks, where SDN switches and legacy switches coexist at the same time. In this paper, we propose an SDN hybrid network architecture which can discover existence of legacy switches by using the Spanning Tree Protocol and thus have a global view of the SDN hybrid network. We also enable OpenFlow switches to cooperate with legacy switches by using the Learning Bridge Protocol without requiring any modification on legacy switches. By utilizing the characteristics of SDN, SDN applications can dynamically find routing paths according to pre-defined QoS requirements and current network status. We also propose a simulated annealing based QoS-aware routing (SAQR) algorithm which can adaptively adjust weights of delay, loss rate and bandwidth requirements in a cost function to find the best fit path according to QoS requirements. We evaluate the proposed SAQR in a simulated SDN hybrid network which runs applications with different QoS requirements. Simulation results show that the SAQR performs better than related work MINA in terms of the fitness ratios of delay, loss rate and bandwidth, with 88%, 90.8% and 86.5% of flows meeting their respective QoS requirements, in contrast to MINA, with only 63%, 82.4% and 87.5% of flows meeting their respective QoS requirements.