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Survivability is a very important problem in telecom networks. Many previous works discuss availability-guaranteed and service-differentiated provisioning. Our work makes two new contributions. First, we consider link sharing between a primary path and backup path(s). In order to achieve better capacity utilization, a connection can share some highly reliable links in common among its primary and backup paths. Second, we consider 1+N (Nges2) protection schemes for those connections which have extremely high availability requirements or have always-on service quality demands. Multiple backup paths are provided to an availability-stringent connection, compared to the traditional 1+1 protection scheme which may have to block some high-availability connections. We develop a mathematical model to quantify a connection's availability with 1+N (Nges2) protection with k-link (kges1) sharing. Based on the model, we propose a provisioning algorithm for dynamic connections with differentiated availability requirements. A connection can be either unprotected, 1+1 protected, or 1+2 protected using our current model with the 1+N extension being an open problem. One-link sharing is allowed among primary and backup paths. The illustrative numerical results show that our approach achieves better performance in both blocking probability and resource utilization, compared to a traditional 1+1 provisioning strategy.