Loop-free constrained path computation for hop-by-hop QoS routing

We present the distributed multi-constrained routing (DMR) protocol for the computation of constrained paths for QoS routing in computer networks. DMR exploits distance vectors to construct a logical shortest multipath (LSM) for each destination with regard to a given optimization metric, from which a set of non-dominated paths are locally derived at each node. As such DMR is able to find feasible paths as well as optimize the utilization of routing resources.DMR operates in line with the hop-by-hop, connectionless routing model assumed in the IP Internet, and maintains instantaneous loop freedom. Nodes running DMR need not maintain a global view of network state (topology and resource information), and routing updates are sent only to neighboring nodes. This is in sharp contrast with all previous approaches that rely on complete or partial network state for constrained path computation, which incurs excessive communication overhead in large networks and is hard to achieve in practice.