Carrier Grade Ethernet Versus SDH in Optical Networks: Planning Methods and CAPEX Comparisons

The new Carrier Ethernet services offered by providers require not only a huge amount of bandwidth, but also a more flexible access to bandwidth that the traditional transport networks, based on circuit-switching, can hardly provide. Carriers have nowadays the option of migrating to new layer-2 frame-switched technologies developed ad hoc to support Carrier Ethernet. An important question is whether this migration is really cost effective. This paper deals with the problem of designing a transport network able to support Carrier Ethernet. We compare two network models, one based on layer-2 switching and Ethernet interfaces, the other based on legacy circuit switching and SDH interfaces. Minimization of investments for network interfaces is carried out for the two models, given the same static-traffic matrix to be supported. Both an ILP formulation and a heuristic method are proposed to solve the design problem. The results presented for comparison are obtained by applying the optimization procedures to a case-study network.