Advance Bandwidth Scheduling in Software-Defined Networks

In software-defined networks (SDNs) with multiple logically centralized controllers, it is challenging to maintain accurate link-state information, perceived as a global network view (GNV), at every controller in a consistent manner. Since online bandwidth scheduling, where every successful reservation triggers a GNV update at the controller, is expensive in terms of overhead, most networks adopt periodic scheduling with infrequent link-state information update, which, however, is the main cause of such inaccuracy/inconsistency. Even if up-to-date information is available, a controller does not always make frequent updates as it may cause network convergence issues. Consequently, bandwidth scheduling in such environments may lead to blocking or rejection of reservation requests, which deteriorates as the level of inaccuracy/inconsistency increases. To minimize such service disruptions, we formulate bandwidth scheduling in SDNs as an optimization problem and propose a randomization-based routing scheme to schedule bandwidth reservation requests such that the total number of blocked requests due to the inaccurate/inconsistent GNV is minimized. Simulation results show that the proposed solution exhibits a superior performance over existing methods.