This article first presents a broad overview of the fault management mechanisms involved in deploying a survivable optical mesh network, employing optical crossconnects. We review various protection and restoration schemes, primary and backup route computation methods, sharability optimization, and dynamic restoration. Then we describe different parameters that can measure the quality of service provided by a WDM mesh network to upper protocol layers (e.g., IP network backbones, ATM network

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... bones, leased lines, virtual private networks), such as service availability, service reliability, restoration time, and service restorability. We review these concepts, the factors that affect them, and how to improve them. In particular, we present a framework for cost-effective availability-aware connection provisioning to provide differentiated services in WDM mesh networks. Through the framework, the more realistic scenario of multiple near-simultaneous failures can be handled. In addition, the emerging problem of protecting low-speed connections of different bandwidth granularities is also reviewed.