a b s t r a c t Packet-switching WDM ring networks with a hotspot transporting unicast, multicast, and broadcast traffic are important components of high-speed metropolitan area networks. For an arbitrary multicast fanout traffic model with uniform, hotspot destination, and hotspot source packet traffic, we analyze the maximum achievable long-run average packet throughput, which we refer to as multicast capacity, of bi-directional shortest path routed WDM rings. We identify three segments that can experience the maximum utilization, and thus, limit the multicast capacity. We characterize the segment utilization probabilities through bounds and approximations, which we verify through simulations. We discover that shortest path routing can lead to utilization probabilities above one half for moderate to large portions of hotspot source multi- and broadcast traffic, and consequently multicast capacities of less than two simultaneous packet transmissions. We outline a one-copy routing strategy that guarantees a multicast capacity of at least two simultaneous packet transmissions for arbitrary hotspot source traffic.
There has been increasing research interest in recent years for the wide range of aspects of multicast in general mesh circuit-switched WDM networks, including lightpath design, see for instance @cite_29 , traffic grooming, see e.g., @cite_11 , routing and wavelength assignment, see e.g., @cite_45 @cite_58 @cite_56 , and connection carrying capacity @cite_32 . Similarly, multicasting in packet-switched single-hop star WDM networks has been intensely investigated, see for instance @cite_60 @cite_67 @cite_26 @cite_18 . In contrast to these studies, we focus on packet-switched WDM ring networks in this paper.
@cite_67 @cite_26 @cite_18 @cite_60 @cite_29 @cite_32 @cite_56 @cite_45 @cite_58 @cite_11
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As wavelength division multiplexing (WDM) technology matures and multicast applications become increasingly popular, supporting multicast at the WDM layer becomes an important and yet challenging topic. In this paper, we study constrained multicast routing in WDM networks with sparse light splitting, i.e., where some switches are incapable of splitting light (of copying data in the optical domain) due to evolutional and or economical reasons. Specifically, we propose four WDM multicast routing algorithms, namely, re-route-to-source, re-route-to-any, member-first, and member-only. Given the network topology, multicast membership information, and light splitting capability of the switches, these algorithms construct a source-based multicast "light-forest" (consisting one or more multicast trees) for each multicast session. While the first two algorithms can build on a multicast tree constructed by IP (which does not take into consideration the splitting capability of the WDM switches), the last two algorithms attempt to address the joint problem of optimal multicast routing and sparse splitting in WDM networks. The performance of these algorithms are compared in terms of the average number of wavelengths used per forest (or multicast session), average number of branches involved (bandwidth) per forest as well as average number of hops encountered (delay) from a multicast source to a multicast member. The results obtained from this research should present new and exciting opportunities for further theoretical as well as experimental work. This paper addresses the multicast wavelength assignment (MC-WA) problem in wavelength-routed WDM networks with full light splitting and wavelength conversion capabilities. Current approaches are based on the multicast switch model that supports only split-convert (S-C) switch scheme. This scheme leads to redundant wavelength conversions for a given multicast request. In this paper, we propose a new split-convert-split (S-C-S) switch scheme capable of eliminating the redundant wavelength conversions. In order to implement this new switch scheme, we develop a new multicast switch model based on the concept of sharing of light splitters and wavelength converters. Furthermore, existing multicast wavelength assignment algorithm allows only one wavelength to carry the light signal on a fiber link, the so-called single-wavelength assignment strategy. In this paper, we explore the advantages of a new multi-wavelength assignment strategy which allows multiple available wavelengths in a link to carry the multicast signal. This will reduce the number of wavelength conversions required for the multicast request. Consequently, based on the new S-C-S multicast switch model and the new multi-wavelength assignment strategy, we generalize the existing algorithms to produce a new Multicast 'Wavelength Assignment Algorithm (MWAA) to support both the new switch model and the new wavelength assignment strategy. Compared with the existing algorithm, our new algorithm is a more general one which makes the multicast wavelength assignment more flexible, covering different switch schemes and different assignment strategies. In addition, it delivers good performance in term of minimizing the number of wavelength conversions. The improvement percentage is sensitive to the maximum out-degree value of a node, D. For a 100-node multicast tree, the improvement percentage increases from 38 at D = 3 to about 73 at D = 16. This is highly significant Wavelength-division multiplexed (WDM) networks using wavelength-routing are considered to be potential candidates for the next generation wide-area backbone networks. This paper concerns with the problem of multicast routing in WDM networks. A node in the network may have both wavelength conversion and splitting capabilities which is called as virtual source. It is assumed that virtual sources are limited in number and are distributed evenly in the network. This paper proposes a new approach, which makes use of these special capable virtual sources to construct a multicast tree. 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.