Capacity dimensioning of VPN access links for elastic traffic

In this paper, we are studying the capacity dimensioning of virtual private networks (VPN) access-links for elastic traffic, such as the Web or ftp. Under the assumption that the core-VPN network is provisioned with sufficient large capacity, the capacity management of the VPN access link is a matter of bandwidth-sharing for elastic traffic of the two bottleneck links, the ingress and egress access links, the processor -sharing model gives a simple formulae of mean transfer time, but in our case, the value may be less than the actual transfer time. In contrast, max-min fair sharing provides an accurate sharing model which is similar to the TCP, but it is difficult to obtain a closed form of performance statistics. We propose a closed form approximation for a max-min fair sharing model, in a specific but realistic topology, by investigating the difference between the max-min and the processor sharing model. Using the approximation, we are performing the capacity dimensioning of VPN access links.