Traffic-Oblivious Routing for Guaranteed Bandwidth Performance

A virtual private network provides network connectivity among the different sites of an enterprise. The bandwidth requirement of a VPN is typically specified by peak ingress-egress traffic volumes for each site. The actual distribution of traffic from each site to other sites in the VPN is not known a priori and could vary over time (e.g., at an intra-day or daily level or due to special activities). This is captured by the hose traffic model. It is the responsibility of the Internet service provider to provision the VPN so that variable traffic subject to aggregate ingress-egress constraints can be transported with bandwidth guarantees. We describe a capacity-efficient, robust, and traffic-oblivious routing strategy, called two-phase routing, that allows preconfiguration of the VPN such that all traffic patterns permissible within the network's natural ingress-egress capacity constraints can be routed with bandwidth guarantees. The scheme routes traffic in two phases: traffic entering the VPN is sent from the source to a set of intermediate nodes in predetermined split ratios that depend on the intermediate nodes, and then from the intermediate nodes to the final destination. (The traffic split ratios can also be generalized to depend on the source and/or destination of traffic.) A significant benefit of the described schemes is that the network can be configured for completely static operation while providing service-level guarantees to widely varying VPN traffic. This is unlike previous approaches based on direct source-destination routing, which need dynamic adaptation to changing traffic conditions in order to provide service-level guarantees