Trade-offs in resource management for virtual private networks

Virtual private networks (VPNs) feature notable characteristics in structure and traffic patterns that can be exploited by the service provider to achieve significant capacity savings. Efficient provisioning of point-to-point connections using statistical admission control is well understood. However, provisioning a VPN involves provisioning a set of point-to-multipoint connections and features an additional dimension in the form of a traffic matrix. Consequently we have multiple network mechanisms that are important for efficient operation: a) admission control, b) signaling-based per-link reservations, c) traffic matrix estimation. In this paper we examine the relative importance of mechanisms that positively affect the operational efficiency in the context of VPN provisioning. Using insights from our extensive measurement based study on the structural properties usually observed in VPNs, we build a simulation framework to quantify the trade-offs in opting for one mechanism over the other. We arrive at our conclusions with the help of simulations featuring a variety of VPN structures and network topologies. We find that the structural characteristics of VPNs cause traffic matrix estimation to be a dominant factor in determining the utilization gains. Consequently, we find that deploying statistical techniques might not be worth the effort if the traffic matrix is not incorporated. While signaling-based reservation mechanisms lead to higher utilization, edge-based techniques prove to be lot more scalable and simpler to realize. We explore the means to reduce the performance penalty associated with such simpler techniques.