Flow aggregation for large-scale SDNs with scattered address space allocation

Abstract

Software-Defined Networking (SDN) has obtained a lot of attention in the last decade and has played a significant role in the development of next-generation networks (NGN). IP networks can also benefit from the SDN evolution to fulfill the data traffic booming. However, the transition of the traditional networking model to SDN architectures poses scalability issues due to the possible flow entry explosion in SDN switches. The limited size of flow-table of SDN switches is not sufficient to handle thousands upon thousands of flows in a large-scale IP network. On the other hand, the interleaved allocation of non-contiguous IP addresses also leads to inefficient routing aggregation and reduces the feasibility of the serious implementation of SDN severely. Therefore, we propose an aggressive flow aggregation scheme—Destination Address Translation and Source-Port Translation on Demand (DATSPToD), which is based on the modified address and port rewriting. DATSPToD enables the aggregation of flow entries in SDNs by translating the destination addresses of multiple same-destination flows with different-source into one flow entry, thus significantly reducing the volume of flow-table occupancy of core-layer SDN switches, even in freely scattered IP address space environments. Simulation results show that DATSPToD outperforms non-aggregation and both wildcard aggregation schemes for a significant reduction of the flow-table occupancy under varied traffic patterns and topologies, especially in large-scale SDNs such as the Internet during the SDN migration period. Compared to the competed schemes under varied traffic patterns and topologies, the simulation results of the DATSPToD could significantly reduce flow-table occupancies by at least1 13%, and by up to 52%. The table-miss rates could be reduced from 11% to 66%.