Virtual private networks (VPNs) provide customers with a secure and manageable communication environment. A VPN resource provisioning model, called hose model, provides customers with the flexibility to specify the bandwidth requirement of a VPN. For the network service provider (NSP), traffic engineering is an essential requirement for better utilization of the network backbone, while meeting the requirements specified by customers. In this paper, two vital traffic engineering problems for hose-model VPNs are investigated: (1) how to maximize the number of VPNs successfully established on the network backbone, and (2) how to find a set of resource-efficient backup paths for a VPN under a single link failure model. To address these problems, we propose two novel algorithms for hose-model VPN provisioning. We use rejection ratio for the first problem and protected bandwidth allocation for the second as the main performance metrics to evaluate different algorithms, respectively. Simulation results show that our algorithms outperform previous proposed approaches.

A weighted double-loop network can be modeled by a directed graph G(n; h/sub 1/, h/sub 2/; w/sub 1/, w/sub 2/) with vertex set Z/sub n/={0, 1, ..., n-1} and edge set E=E/sub 1//spl cup/E/sub 2/, where E/sub 1/={(u, u+h/sub 1/)|u/spl isin/Z/sub n/}, E/sub 2/={(u, u+h/sub 2/)|u/spl isin/Z/sub n/}. Assume that the weight of each edge in E/sub 1/ is w/sub 1/ and the weight of each edge in E/sub 2/ is w/sub 2/. In this paper, we present an optimal routing algorithm on double-loop networks under the case where there is at most one faulty element. Our algorithm is based on the fact that the shortest path from a vertex to any other vertex in a double-loop network is in the L-shape region.