Loop-Free Alternates with Loop Detection for Fast Reroute in Software-Defined Carrier and Data Center Networks

Loop-Free Alternates (LFAs) are a local fast-reroute mechanism defined for IP networks. They are simple but suffer from two drawbacks. Firstly, some flows cannot be protected due to missing LFAs, i.e., this concept does not provide full protection coverage, which depends on network topology. Secondly, some LFAs cause loops in case of node or multiple failures. Avoiding those LFAs decreases the protection coverage even further. In this work, we propose to apply LFAs to OpenFlow-based networks. We suggest a method for loop detection so that loops can be avoided without decreasing protection coverage. We propose an implementation with OpenFlow that requires only a single additional flow rule per switch. We further investigate the percentage of flows that can be protected, not protected, or even create loops in different types of failure scenarios. We consider realistic ring and mesh networks as well as typical topologies for data center networks. None of them can be fully protected with LFAs. Therefore, we suggest an augmented fat-tree topology which allows LFAs to protect against all single link and node failures and against most double failures.