On surviving dual-link failures in path protected optical WDM mesh networks

Abstract

In this paper, we investigate the problem of enhancing dual-failure restorability in path protected mesh-restorable optical Wavelength Division Multiplexed (WDM) networks. Recent studies have demonstrated the need to survive simultaneous dual-link failures and have also provided solutions for handling such failures. A key finding of these early efforts is that designs providing complete (i.e. 100%) protection from all dual-failures need almost triple the spare capacity compared to a system that protects against all single-link failures. However, it has also been shown that systems designed for 100% single-link failure protection can provide reasonable protection from dual-link failures [M. Clouqueur, W. Grover, Mesh-restorable networks with 74 enhanced dual-failure restorability properties, in: Proc. SPIE OPTICOMM, Boston, MA, 2002, pp. 1–12]. Thus, the motivation for this work is to develop a hybrid mechanism that provides maximum (close to 100%) dual-failure restorability with minimum additional spare capacity. The system architecture considered is circuit-switched with dynamic arrival of sessions requests. We propose an adaptive mechanism, which we term active protection, that builds upon a proactive path protection model (that provides complete single-failure restorability), and adds dynamic segment-based restoration to combat dual-link failures. The objective is to optimize network survivability to dual-link failures while minimizing additional spare capacity needs. We also propose a heuristic constraint-based routing algorithm, which we term best-fit, that aids backup multiplexing among additional spare paths towards this goal. Our findings indicate that the proposed active protection scheme achieves close to complete (100%) dual-failure restorability with only a maximum of 3% wavelength-links needing two backups, even at high loads. Moreover, at moderate to high loads, our scheme attains close to 16% improvement over the base model that provides complete single-failure restorability. Also, the best-fit routing algorithm is found to significantly assist backup multiplexing, with around 15%–20% improvement over first-fit at all loads. The segment-based restoration algorithm reiterates the importance of utilizing wavelength converters in protection and is seen to provide around 15%–20% improvement over link restoration especially at moderate to high loads.