Dynamic routing of restorable QoS connections in MPLS networks

In this paper we consider dynamic routing of restorable Quality of Service (QoS) connections in multi-protocol label switched (MPLS) networks under a single link failure model. To route a restorable QoS connection, two link disjoint label switched paths from the ingress to the egress node need to be computed such that both paths comply with the QoS constraints. When looking at QoS constraints like bandwidth guarantee and end-to-end delay bound, the current approach described in the literature converts the end-to-end delay bound into an effective bandwidth in a pre-processing step before computing two link disjoint bandwidth guaranteed paths. We argue that the current approach results in poor network performance and suggest a new approach that exploits the dependency between the end-to-end delay, chosen path and provisioned bandwidth. Thus, the two link disjoint paths are computed dynamically with their respective bandwidths so that they meet both the bandwidth guarantee and the end-to-end delay bound. In this paper, we present a new generic algorithm and two new linear programming formulations that implement the new approach. The two linear programming formulations are not intended to be used in a production environment due to their extensive running times, up to 2.5 minutes on average per request, but rather to benchmark approximation algorithms that in turn can be used in production. Furthermore our experiments show that the network performance improvement when exploiting the dependency between end-to-end delay, chosen path and provisioned bandwidth is substantial.