QoS-based Virtual Private Network Design for an MPLS network

 In this paper, a VPN design model is proposed for the Next Generation Internet (NGI). With the use of MultiProtocol Label Switching (MPLS) in a backbone network, it is possible to create multiple logical sink-trees (directed multipoint-to-point trees ending at one exit node) carrying traffic of multiple VPNs. This makes the VPN design problem with MPLS different from those of circuit-switched networks and connection-oriented packet networks such as ATM. A big question is how to construct a tree and how to incorporate it in the network design model. Here, the VPN design is modeled as a mixed integer programming (InP) optimization problem to minimize the cost of laying out a VPN supporting different traffic types and service classes on a given topology while meeting QoS requirements. Realizing a sink-tree routing path, the proposed model aims to find an optimal VPN layout supporting multi-service classes during different time periods (multi-hour periods) considering that the traffic demand may vary during the course of the day. Our numerical results show that use of sink-tree approach in VPN design can greatly reduce the amount of bandwidth and the number of label switched paths required.