Light-Hierarchy: The Optimal Structure for Multicast Routing in WDM Mesh Networks

TL;DR

This paper introduces the light-hierarchy structure for multicast routing in WDM networks, leveraging cross pair switching at MI nodes to reduce costs compared to traditional light-trees.

Contribution

It proposes the novel light-hierarchy structure that allows cycles via CPS, proving it to be more cost-effective than light-trees for multicast routing.

Findings

Light-hierarchy reduces multicast routing costs.

CPS enables MI nodes to be traversed multiple times.

Numerical results confirm the efficiency of light-hierarchy.

Abstract

Based on the false assumption that multicast incapable (MI) nodes could not be traversed twice on the same wavelength, the light-tree structure was always thought to be optimal for multicast routing in sparse splitting Wavelength Division Multiplexing (WDM) networks. In fact, for establishing a multicast session, an MI node could be crosswise visited more than once to switch a light signal towards several destinations with only one wavelength through different input and output pairs. This is called Cross Pair Switching (CPS). Thus, a new multicast routing structure light-hierarchy is proposed for all-optical multicast routing, which permits the cycles introduced by the CPS capability of MI nodes. We proved that the optimal structure for minimizing the cost of multicast routing is a set of light-hierarchies rather than the light-trees in sparse splitting WDM networks. Integer linear programming (ILP) formulations are developed to search the optimal light-hierarchies. Numerical results verified that the light-hierarchy structure could save more cost than the light-tree structure.