Reducing the latency of OpenFlow rule changes in data centre networks

The number and size of data centres being constructed continues to grow, in response to increasing demand for cloud-based services. In a Data Centre Network (DCN), maximizing performance is essential, and network management tools that leverage the advantages of Software-Defined Networking (SDN) are key to achieving that goal. DCN switches are now expected to support the OpenFlow protocol — however, performance issues have been observed with hardware switch OpenFlow implementations in relation to path establishment for new flows, and path modification for existing flows. In particular, concerns have been raised regarding the delays in effecting changes to hardware flow tables. We report on recent research that seeks to address this issue. Specifically, we investigate the approach of temporarily tunnelling packets for new flows while more efficient non-tunnelled paths are being established, and to which the flows are later migrated. Our early results show the potential and limitations of this approach.