Traffic grooming and delay constrained multicast routing in IP over WDM networks

In this paper, we investigate delay constrained multicast routing for supporting QoS guaranteed point to multi-point communications in IP over WDM networks. To achieve high bandwidth utilization, packets coming from different multicast connections are groomed and carried together over a single wavelength. Lightpath scheme is adopted in this paper that unicast lightpath is provisioned to support the multicast traffic in the IP network. Hop count constraint is introduced to deal with and queueing delay from traffic grooming. The challenge of the problem comes not only from considering delay constrained multicast routing but also WDM lightpath routing and wavelength assignment (RWA). We formulated the problem as an integer optimization problem in which the revenue from admitting multicast groups is to be maximized. The problem constraints include hop count constraint for end-to-end QoS requirements, tree constraint for multicast routing, IP link capacity and WDM fiber link capacity constraints, and wavelength continuity constraint. We apply Lagrangean relaxation technique to perform constraint relaxation and propose optimization-based heuristics (LGR) to tackle this problem. We draw performance comparisons between the LGR and the Minimum Hop (MH) heuristics. Numerical results demonstrate that LGR outperforms MH algorithm under all experimental cases.