Near-optimal delay constrained routing in virtual circuit networks

An essential issue in designing, operating and managing a modern network is to assure end-to-end quality-of-service (QoS) from users´ perspective, and in the meantime to optimize a certain “average” performance objective from the system´s perspective. We consider the problem of minimizing the average cross-network packet delay in virtual circuit networks subject to an end-to-end delay constraint for each origin-destination user pair. The problem is formulated as a multicommodity network flow problem with integer routing decision variables, where additional end-to-end delay constraints are considered. The difficulties of this problem result from the integrality nature and particularly the nonconvexity associated with the end-to-end delay constraints. The basic approach to the algorithm development is Lagrangean relaxation in conjunction with number of optimization-based heuristics. In the computational experiments, it is shown that the proposed algorithm calculates solutions which are within 1% and 3% of optimal solutions under lightly and heavily loaded conditions, respectively, in minutes of CPU time for networks with up to 26 nodes