2 research outputs found
Light-Hierarchy: The Optimal Structure for Multicast Routing in WDM Mesh Networks
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
Is light-tree structure optimal for multicast routing in sparse light splitting WDM networks
To minimize the number of wavelengths required by a multicast session in sparse light splitting Wavelength Division Multiplexing (WDM) networks, a light-hierarchy structure, which occupies the same wavelength on all links, is proposed to span as many destinations as possible. Different from a lighttree, a light-hierarchy accepts cycles, which are used to traverse crosswise a 4-degree (or above) multicast incapable (MI) node twice (or above) and switch two light signals on the same wavelengths to two destinations in the same multicast session. In this paper, firstly, a Graph Renewal and Distance Priority Light-tree algorithm (GRDP-LT) is introduced to improve the quality of light-trees built for a multicast request. Then, it is extended to compute light-hierarchies. Obtained numerical results demonstrate the GRDP-LT light-trees can achieve a much lower links stress, better wavelength channel cost, and smaller average end-to-end delay as well as diameter than the currently most efficient algorithm. Furthermore, compared to light-trees, the performance in terms of link stress and network throughput is greatly improved again by employing the light-hierarchy, while consuming the same amount of wavelength channel cost