Balancing flow table occupancy and link utilization in software-defined networks

Software-Defined Networking (SDN) employs a centralized control with a global network view and provides great opportunities to improve network performance. However, due to the limitation of flow table space at the switches and unbalanced traffic allocation on links, an SDN may suffer from flow table overflow and inefficient bandwidth allocation among flows, increasing the controller's burden and degrading network performance. In this paper, we present a dynamic routing scheme named DIFF that differentiates flows based on their impact on network resource and adaptively selects routing paths for them to mitigate the problems of flow-table overflow and inefficient bandwidth allocation. DIFF pre-generates a set of paths for each pair of source-destination edge switches and intelligently selects the paths from the pre-generated path-sets for new flows with an objective to balance flow-table utilizations. It adaptively reroutes some elephant flows to achieve maximum throughput under the rule of max-min fair bandwidth allocation. Simulation results show that DIFF simultaneously balances the flow table and link utilizations, reduces the controller's workload and packet delay, while increasing network throughput, compared with baseline schemes. (C) 2018 Elsevier B.V. All rights reserved.