Abstract: In order to solve the problems of high routing algorithm complexity, low QoS flow satisfaction and single link failure in current software-defined network (SDN) architecture, a multi- constraint QoS dual-path routing optimization algorithm based on software-defined network (SDN_ MCQDP) is proposed. The controller is used to obtain the global network state information, and generate a directed acyclic graph based on the destination node. In the multi-constraint QoS routing stage, the multi-constraint problem is transformed into a linear programming problem by the Lagrangian relaxation dual algorithm. The reverse link is used to delete redundant dual-path links that meet multi-constraint QoS and ensure data transmission after link failure. The algorithm is simulated and analyzed from the aspects of routing calculation time, link utilization, and QoS flow satisfaction. The results show that, compared with MODLARAC, QT, RMCDP_RD, and H_MCOP algorithms, SDN_MCQDP can effectively reduce the transmission delay and route calculation time, improve the link utilization, and still meet the QoS requirements after link failure.

Key words: software defined network (SDN), multi-constrained QoS, directed acyclic graph, Lagrangian relaxation dual algorithm, dual-path redundant link