Abstract. This paper investigates the problern of dynamic survivable lightpath provisioning against single node/link failures in optical mesh networks employing wavelength-division multiplexing (WDM). We present a new approach to provisioning lightpath requests according to their differentiated quality-of-protection (QoP) requirements. We focus on one of the most important QoP parameters, namely protection-switching time, since lightpath requests may have differentiated protection-switching-time requirements. For example, lightpaths carrying voice traffic may require 50-ms protection while lightpaths carrying data traffic may have a wide range of requirements. Numerical results show that, compared to shared-path protection, our approach achieves significant performance gain which Ieads to remarkable reduction in blocking probability. While our focus is on optical WDM network, the basic ideas of our approaches can be applied to multiprotocol labe! switching (MPLS) networks with appropriate variations, e.g., differentiated bandwidth granularities.