Efficient Data Plane Protection for SDN

Abstract

Software-defined networks (SDN) usually require intervention of a controller to restore connectivity in case of link or node failures. To avoid this dependence, a fast failover function enables switches to locally detect a failure and deviate affected traffic. In this paper, we develop fast reroute (FRR) methods leveraging that feature and the principle of loop-free alternates (LFAs) from IP networks for network-wide configuration. We explain how LFAs, remote LFAs, and novel explicit-path LFAs may be implemented with OpenFlow so that SDN with general destination-based routing can be protected. An advanced loop detection and termination function is suggested to prevent loops that may be caused by FRR in case of severe failures. We evaluate the FRR methods on a large set of representative network topologies and compare them with existing FRR methods. Classic rLFAs from IP networks generate many loops in case of node failures so that they are not appropriate for SDN. One developed protection method is particularly suitable for SDN as it can protect all flows in a network against any single link and node failure. The solution is efficient because it secures most traffic also in case of dual failures, leads to short backup paths, and requires in most networks only a few additional forwarding entries per node. The latter is important as OpenFlow switches can accommodate only a moderate number of forwarding entries in their flow tables.