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This paper addresses the problem of quality of service (QoS) differentiation of sub-wavelength level label switched path (LSP) requests considering both differentiated survivability services and transmission quality in terms of end-to-end delay requirements of requests. We define different classes of LSP requests and propose a novel QoS differentiation scheme for IP-over-WDM networks. The scheme adopts a multi-layer protection approach consists of dedicated lightpath protection, shared lightpath protection, and shared LSP protection methods. The inter-class backup resource sharing technique is used to improve the performance of different classes of traffic. The routing strategies consider efficient resource utilization and end-to-end delay requirements of different priority requests. In this work, LSPs belonging to different classes with different protection requirements are allowed to traverse the same lightpath to use resources effectively. This grooming approach is efficient in terms of resource usage and it poses several challenges: 1) lightpath protection can be used or modified to satisfy the protection requirement of a newly traversed LSP, and 2) when and how the protection resources are released or updated when an LSP is released while preserving the other LSPs' protection needs. An effective way of distributing signaling messages for failure recovery should also be considered as different protection methods are used. We address all these issues in the proposed scheme. Through simulation experiments, we investigate the impacts of the backup sharing strategies and the routing strategies on connections acceptance rate for different classes of traffic and end-to-end delay requirements of different priority requests. Based on simulation results we demonstrate how the selection of a suitable sharing strategy and a routing strategy can be done that gives the best performance for all the classes and show the effectiveness of the scheme in satisfying both users' QoS requirements and network services providers' requirements.