Restoration of virtual private networks with QoS guarantees in the pipe model

Abstract

We propose heuristic algorithms to compute efficient restorable tunnel paths for IP Virtual Private Networks (IPVPNs). We first propose a Customer Premises Equipment (CPE) based solution to the problem and then optimize it by activating selectively few core ISP routers. We consider link cost as a function of bandwidth and loss over the link. The VPN tunnel paths are computed taking into account two parameters, the link cost and the cost of core routers that serve as end points of the tunnel. These paths we then call as Active Paths. Reliability of a VPN depends on the reliability of links in the Active path. To guarantee service quality and VPN availability to the Corporate users, seamless recovery from failures is mandatory. For the sake of survivability we propose heuristics for computing optimal backup path. We assume that the residual capacity available over the links for the VPN is sufficient to satisfy the Service Level Agreement (SLA). The problem of finding optimal paths for both Active and Backup is similar to constructing a directed steiner tree routed at source and spanning all the destinations which is NP-hard. Our heuristic algorithms provide an efficient solution to this problem with polynomial computation time. © Springer-Verlag Berlin Heidelberg 2004.