Load-Optimal Local Fast Rerouting for Resilient Networks

Abstract

Abstract-Reliable and highly available computer networks must implement resilient fast rerouting mechanisms: upon a link or node failure, an alternative route is determined quickly, without involving the network control plane. Designing such fast failover mechanisms capable of dealing with multiple concurrent failures however is challenging, as failover rules need to be installed proactively, i.e., ahead of time, without knowledge of the actual failures happening at runtime. Indeed, only little is known today about the design of resilient routing algorithms. This paper presents a deterministic local failover mechanism which we prove to result in a minimum network load for a wide range of communication patterns, solving an open problem. Our mechanism relies on the key insight that resilient routing essentially constitutes a distributed algorithm without coordination. Accordingly, we build upon the theory of combinatorial designs and develop a novel deterministic failover mechanism based on symmetric block design theory which tolerates a maximal number of Ω(n) link failures in an n-node network and in the worstcase, while always ensuring routing connectivity. In particular, we show that at least Ω(φ 2 ) link failures are needed to generate a maximum link load of at least φ, which matches an existing bound on the number of link failures needed for an optimal failover scheme. We complement our formal analysis with simulations, showing that our approach outperforms prior schemes not only in the worst-case.

Local Fast Rerouting with Low Congestion: A Randomized Approach

“…The authors of [18] showed that deterministic failover algorithms are bound to result in a high load even in case of an initially completely connected network which is still highly connected after the failures [18]. The proof has been generalized further by Pignolet et al in [19]. More specifically, the authors showed that: (1) when only relying on destinationbased failover rules, an adversary can always induce a maximum edge load of Ω(ϕ) by cleverly failing ϕ edges; (2) when failover rules can also depend on the source address, an edge load of Ω( √ ϕ) can be achieved, when failing ϕ many edges.…”

PURR: a primitive for reconfigurable fast reroute

“…Detecting port failures falls beyond the scope of this paper as it depends on specific hardware support. FRR mechanisms can generally be categorized along different dimensions, e.g., whether they tolerate only a single link/node failure [52,67,70] or multiple ones [22,62], or whether routing tables are static (e.g., [13,17,45,61,62]) or dynamic (e.g., [25,44]), whether packet header rewriting is required (e.g., [22,42,44,46]) or packet duplication (e.g., [31]), whether provide low stretch [17,23]or load [54,63,68].…”

Network Coding for Critical Infrastructure Networks

“…Rather, in the packet store-and-forward paradigm, the resiliency is provided by carefully routing the packets around a failed link or network device [3] [4] [5] [6]. However, such an approach requires solving complex combinatorial problems.…”