Currently, many bandwidth-intensive applications require multicast services for efficiency purposes. In particular, as wavelength division multiplexing (WDM) technique emerges as a promising solution to meet the rapidly growing demands on bandwidth in present communication networks, supporting multicast at the WDM layer becomes an important yet challenging issue. In this paper, we introduce a systematic approach to analyzing the multicast connection capacity of WDM switching networks with limited wavelength conversion. We focus on the practical all-optical limited wavelength conversion with a small conversion degree d (e.g., d=2 or 3), where an incoming wavelength can be switched to one of the d outgoing wavelengths. We then compare the multicast performance of the network with limited wavelength conversion to that of no wavelength conversion and full wavelength conversion. Our results demonstrate that limited wavelength conversion with small conversion degrees provides a considerable fraction of the performance improvement obtained by full wavelength conversion over no wavelength conversion. We also present an economical multistage switching architecture for limited wavelength conversion. Our results indicate that the multistage switching architecture along with limited wavelength conversion of small degrees is a cost-effective design for WDM multicast switching networks.

We develop an analytical model to evaluate the network-wide blocking probability with sparse limited wavelength conversion in an arbitrary network topology, given the traffic loads and locations of limited wavelength converters with various degrees of conversion ability. The analytical model is applied to network examples such as the irregular NSFNET and the regular mesh-torus with uniform and nonuniform Poisson traffic. Our analytical and simulation results show that the analytical model is efficient and accurate. We also demonstrate how the analytical techniques can be used for studying wavelength converter placement in wavelength-routed optical networks.

Currently, many bandwidth-intensive applications require multicast services for efficiency purposes. In particular, as wavelength division multiplexing (WDM) technique emerges as a promising solution to meet the rapidly growing demands on bandwidth in present communication networks, supporting multicast at the WDM layer becomes an important yet challenging issue. In this paper, we present a new analytical model to compute blocking probabilities for multicast connections in WDM switching networks. Due to the non-uniform nature of multicast traffic, calculating blocking probability in a WDM multicast switching network becomes much more challenging than that under unicast traffic. Based on the link independence and wavelength independence assumptions, our model can calculate the blocking probability of any multicast connection from a single source to multiple destinations in WDM switching networks with various types of wavelength conversion capabilities, ranging from no wavelength conversion, to limited wavelength conversion, to full wavelength conversion. Our analytical results indicate that similar to unicast traffic, a significant improvement in the blocking performance of the network under multicast traffic can be achieved by limited wavelength conversion. We view that utilizing limited wavelength conversion with relatively small conversion degrees in WDM multicast switching networks is a more cost-effective choice. We also validate the analytical model through extensive simulations.

Multicast, or one-to-many, communication is one of the most important collective communication operations. Current trends in networking applications indicate that there will be an increasing demand in future networks for multicast. In particular, as wavelength division multiplexing (WDM) networks emerge, supporting multicast at the WDM layer becomes an important yet challenging topic. In this paper, we consider the issue of supporting WDM multicasting in the widely used three-stage Clos network. Our study demonstrates that the multistage construction with small degrees of limited wavelength conversion is a cost-effective design for WDM multicast switching networks.

We study the benefits of wavelength conversion in all-optical WDM switching networks. In particular, we focus on investigating network performance improvement by using the more realistic limited wavelength conversion. We present an analytical model for calculating the blocking probability of WDM switching networks with limited wavelength conversion and validate the model through simulations. The analytical and simulation results reveal that a significant improvement in the blocking performance of the network can be achieved by limited wavelength conversion with small conversion degrees (e.g., d=2,3,4). We take the view that utilizing limited wavelength conversion with small conversion degrees in a WDM switching network is a more cost-effective choice.

In previous years, with the rapid exhaustion of the capacity in wide area networks led by Internet and multimedia applications, demand for high bandwidth has been growing at a very fast pace. Wavelength-division multiplexing (WDM) is a promising technique for utilizing the huge available bandwidth in optical fibers. We consider efficient designs of nonblocking WDM permutation switching networks. Such designs require nontrivial extensions from the existing designs of electronic switching networks. We first propose several permutation models in WDM switching networks ranging from no wavelength conversion, to limited wavelength conversion, to full wavelength conversion, and analyze the network performance in terms of the permutation capacity and network cost, such as the number of optical cross-connect elements and the number of wavelength converters required for each model. We then give two methods for constructing nonblocking multistage WDM switching networks to reduce the network cost.

In recent years, with the rapid exhaustion of the capacity in wide area networks (WAN) led by Internet and multimedia applications, demand for high bandwidth has been growing at a very fast pace. Wavelength division multiplexing (WDM) is a promising technique to utilize the huge available bandwidth in optical fibers. We consider efficient designs of nonblocking WDM permutation switching networks. Such designs require nontrivial extensions from the existing designs of electronic switching networks. We first propose several permutation models in WDM switching networks ranging from no wavelength conversion, limited wavelength conversion, to full wavelength conversion, and analyze the network performance in terms of the permutation capacity and network cost such as the number of optical crossconnect elements and the number of wavelength converters required for each model. We then give two methods for constructing nonblocking multistage WDM switching networks to reduce the network cost.