Minimum Interference Routing with Applications to MPLS Traffic Engineering

This paper presents a new algorithm for dynamic routing of bandwidth guaranteed tunnels where tunnel routing requests arrive one-by-one and there is no a priori knowledge regarding future requests. This problem is motivated by service provider needs for fast deployment of bandwidth guaranteed services and the consequent need in backbone networks for fast provisioning of bandwidth guaranteed paths. Offline routing algorithms cannot be used since they require a priori knowledge of all tunnel requests that are to be routed. Instead, on-line algorithms that handle requests arriving one-by-one and that satisfy as many potential future demands as possible are needed. The newly developed algorithm is an on-line algorithm and is based on the idea that a newly routed tunnel must follow a route that does not “interfere too much” with a route that may be critical to satisfy a future demand. We show that this problem is NP-hard. We then develop a path selection heuristic that is based on the idea of deferred loading of certain “critical” links. These critical links are identified by the algorithm as links that, if heavily loaded, would make it impossible to satisfy future demands between certain ingress-egress pairs. Like min-hop routing, the presented algorithm uses link-state information and some auxilliary capacity information for path selection. Unlike previous algorithms, the proposed algorithm exploits any available knowledge of the network ingress-egress points of potential future demands even though the demands themselves are unknown. If all nodes are ingressegress nodes the algorithm can still be used, particularly to reduce the rejection rate of requests between a specified subset of important ingressegress pairs. The algorithm performs well in comparison to minimum hop and widest-shortest path routing on several metrics like the number of rejected demands and successful re-routing of demands upon link failure.