Survivable telecommunications network design under different types of failures

Telecommunications networks are expected to provide near-instantaneous restoration in the event that some network elements fail. Models for designing survivable networks are very complex and difficult to solve optimally. In this paper, we provide simple heuristics that augment existing network resources to ensure restoration under several scenarios of a single failure. The goal is to demonstrate that effective, though not necessarily optimal, survivable designs can be achieved by augmenting capacities along prudently selected variants of spanning tree and ring structures, without resorting to complex mathematical programming methods. The first model considers line restoration (reroutes around the failed link) under a partial link failure. We propose a heuristic that augments capacities of selected network links by forming a "virtual" spanning tree of restoration capacity. The second model provides line restoration under a complete link failure. We propose a heuristic that ensures survivability by repeatedly constructing spanning trees to various subnetworks. The third model provides path restoration (end-to-end reroutes) under a node failure. We propose a heuristic that repeatedly constructs restoration rings that cover a subset of source-destination nodes that carry traffic through intermediate nodes.