  Software-defined networking (SDN) as a new paradigm for networking provides
efficient resource reallocation platform in emerging cloud data center
networks. The dynamic nature of cloud data center network's traffic, as well as
the existence of big flows make it necessary to periodically reprogram the
network through the SDN controller. Therefore, it is critical for network
researchers to minimize the side-effects of network reconfiguration. In this
way, the most challenging issue is the number of rerouted flows that affect the
network stability and QoS parameters. As a result, dynamic reconfiguration of
the network with minimum overhead (i.e. minimum flow rerouting) is an
interesting problem in SDN-based resource reallocation. In this paper, we
mathematically formulated the resource reallocation problem as an optimization
problem with minimum network reconfiguration overhead subject to QoS
requirements of the applications flows. In order to reduce the time complexity
of solving the optimization problem, a forwarding table compression technique
is devised making the proposed scheme an efficient resource reallocation method
which can be used as an application on top of the SDN controller. Our
Experimental results show that the proposed scheme decreases the network
reconfiguration overhead dramatically while meeting the QoS constraints. Since
the reconfiguration overhead of the proposed scheme is low, the controller can
reallocate the resources more frequently based on the network condition. We
also studied the impact of the proposed network reconfiguration scheme on
packet loss and delay in the network. The results show that the proposed
approach outperform the conventional methods.
