A Distributed Algorithm for Delay-Constrained Unicast Routing

In this paper, we study the NP-hard delay-constrained least-cost path problem, and propose a simple, distributed heuristic solution: the delay-constrained unicast routing (DCUR) algorithm. DCUR requires limited network state information to be kept at each node: a cost vector and a delay vector. We prove DCUR’s correctness by showing that it is always capable of constructing a loop-free delayconstrained path within finite time, if such a path exists. The worst case message complexity of DCUR is O(jV j 3) messages, where jV j is the number of nodes. However, simulation results show that,on the average, DCUR requires much fewer messages. Therefore, DCUR scales well to large networks. We also use simulation to compare DCUR to the optimal algorithm, and to the least-delay path algorithm. Our results show that DCUR’s path costs are within 10% from those of the optimal solution.