Spare bandwidth is required for recovering the network service from network faults. However, it degrades the efficiency of network utilization. Spare bandwidth demand can be reduced significantly by letting spare bandwidth be shared among several network services. Spare bandwidth reserved on a network element can be shared by a set of network services for a network fault if they are not simultaneously affected by the network fault. A new, and more practical spare bandwidth sharing scheme, which is based on the network reliability, is proposed in this paper. In the proposed scheme, multiple link failures are allowed with a given link failure rate, and a reasonable restoration level of near 100%; while in the conventional scheme, only a single link failure, and 100% restoration level are considered. To develop the spare bandwidth sharing scheme, we first investigate the framework for evaluating the reliability of path-based network services, and then we explain the proposed spare bandwidth sharing scheme with decision parameters such as lifetime of the path, restoration level, and the maximum number of working paths which can be protected by a backup link. Simulation results show that the proposed spare bandwidth sharing scheme requires a smaller amount of spare bandwidth than the conventional scheme.