Connectivity Preserving Graph Sequences for Routing Arborescence Construction

Fast reroute (FRR) is among the fastest survivable routing approaches in packet-switched networks, because the routers are equipped with a resilient routing table in advance such that the packets can be rerouted instantly upon failures solely relying on local information, i.e., without notification messages. However, designing the routing algorithm for FRR is challenging as the number of possible sets of failed network links can be extremely high, while the algorithm should keep track of which routers are aware of the failure. Therefore, FRR methods often rely on spanning arborescences, which provide multiple disjoint failover paths up to the global connectivity of the network. In this paper, we propose a generic algorithmic framework that theoretically increases the number of failover paths to the local connectivity between each node and the root by extending an efficient connectivity preserving operation from graph theory – called edge splitting-off – to decompose the network topology node-by-node, and use Integer Linear Programs (ILPs) on these partial subproblems to build routing arborescences in the reverse direction for the original topology. Although our practical implementation cannot reach the local connectivity in all instances, we demonstrate through simulations that it still outperforms the state-of-the-art FRR mechanisms and provides better resilience with shorter paths in the arborescences.