Providing Software Support for Reconfigurable Networks

Workload patterns in Data Center Networks (DCNs) vary by time. As such, deployment of reconfigurable topologies to handle these varying workloads is a promising approach. Network efficiency can be improved by tailoring the network topology to the workload, which can reduce the average path length thus supporting more flows simultaneously. However, without proper software support, physically altering a network is very disruptive to active flows and results in significant periods of poor network utilization. We propose a software support framework for reconfigurable networks that reduces the amount of disruption to existing flows during topology reconfiguration. This framework deconstructs the planned topology changes (link additions and removals) into a series of smaller steps where each step only affects a small fraction of existing flows. It also proactively reroutes flows before and after each step to avoid packet losses due to topology reconfiguration and allow existing flows to take advantage of newly added links. We evaluate our prototype using iperf and find that without software support, there is a window during which new links may be under-utilized or not used at all due to congestive collapse. In contrast, our prototype system is able to ensure those links remain usable, and quickly increase overall network efficiency after the reconfiguration.