A customized and cost-efficient backup scheme in software-defined networks

Among the schemes proposed for failure recovery in software-defined networks, installing backup paths in advance is considered to be an effective approach to reduce the recovery latency. However, the pre-installation poses undue storage overheads on flow tables. In this paper, we propose a customized and cost-efficient backup scheme, which achieves fast recovery from any single-link failure. We introduce an improved breadth first search algorithm to construct the customized backup paths of flows to accommodate their diverse routing demands. By analyzing the path characteristics carefully, we observe that non-conflicted backup paths can be aggregated with each other to reduce the number of backup rules. We formulate this backup path aggregation as an optimization problem. The challenge is how to aggregate the backup paths without causing routing ambiguity. To this end, we design a two-stage aggregation (2SA) algorithm. At its core, 2SA leverages conflict matrixes to guarantee the correctness of aggregation. We evaluate our scheme comprehensively with both the real-world topologies and generated topologies. Simulation results show that our scheme can pre-install the customized backup paths with much fewer, typically one order of magnitude, backup rules compared to the traditional flow-based protection without aggregation.