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.
Studies of non-uniform traffic in optical networks have generally focused on issues arising in circuit-switched optical networks, see for instance @cite_21 @cite_2 @cite_42 @cite_25 @cite_13 @cite_22 @cite_69 . A comparison of circuit-switching to optical burst switching network technologies, including a brief comparison for non-uniform traffic, was conducted in @cite_55 . The throughput characteristics of a mesh network interconnecting routers on an optical ring through fiber shortcuts for non-uniform unicast traffic were examined in @cite_70 . The study @cite_34 considered the throughput characteristics of a ring network with uniform unicast traffic, where the nodes may adjust their send probabilities in a non-uniform manner. The multicast capacity of a single-wavelength packet-switched ring with non-uniform traffic was examined in @cite_54 . In contrast to these works, we consider non-uniform traffic with an arbitrary fanout, which accommodates a wide range of unicast, multicast, and broadcast traffic mixes, in a WDM ring network.
@cite_69 @cite_22 @cite_70 @cite_55 @cite_21 @cite_42 @cite_54 @cite_2 @cite_34 @cite_13 @cite_25
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We study the SMARTNet (scalable multichannel adaptable ring terabit network), an optical wavelength-division packet-switching meshed-ring network employing wavelength routers. We investigate the ways to configure these wavelength routers in adapting to the underlying traffic matrix. One heuristic algorithm for this purpose is developed. We show that for any traffic matrix, the throughput performance of the SMARTNet employing wavelength cross-connect routing devices is upper bounded by that of a corresponding meshed-ring network employing store-and-forward switching devices. The difference diminishes as the number of employed wavelengths increases. Furthermore, for a specific meshed-ring: topology, we show that the above upper bound throughput level is achievable under uniform traffic loading at even a small number of wavelengths. Under nonuniform traffic loading, we show that a throughput level equal to 80 to 90 of the upper bound value can be achieved with a small number (five to seven) of wavelengths. As the operation of our fiber-optic backbone networks migrates from interconnected SONET rings to arbitrary mesh topology, traffic grooming on wavelength-division multiplexing (WDM) mesh networks becomes an extremely important research problem. To address this problem, we propose a new generic graph model for traffic grooming in heterogeneous WDM mesh networks. The novelty of our model is that, by only manipulating the edges of the auxiliary graph created by our model and the weights of these edges, our model can achieve various objectives using different grooming policies, while taking into account various constraints such as transceivers, wavelengths, wavelength-conversion capabilities, and grooming capabilities. Based on the auxiliary graph, we develop an integrated traffic-grooming algorithm (IGABAG) and an integrated grooming procedure (INGPROC) which jointly solve several traffic-grooming subproblems by simply applying the shortest-path computation method. Different grooming policies can be represented by different weight-assignment functions, and the performance of these grooming policies are compared under both nonblocking scenario and blocking scenario. The IGABAG can be applied to both static and dynamic traffic grooming. In static grooming, the traffic-selection scheme is key to achieving good network performance. We propose several traffic-selection schemes based on this model and we evaluate their performance for different network topologies. With the advent of next-generation, bandwidth-intensive multimedia applications such as HDTV, interactive distance learning, and movie broadcasts from studios, it is becoming imperative to exploit the enormous bandwidth promised by the rapidly growing wavelength-division-multiplexing (WDM) technology. These applications require multicasting of information from a source to several destination nodes which should be performed judiciously to conserve expensive network resources. In this study, we investigate two switch architectures to support multicasting in a WDM network: one using an opaque (optical-electronic-optical approach and the other using a transparent (all-optical) approach. For both these switch architectures, we present mathematical formulations for routing and wavelength assignment of several light-tree-based multicast sessions on a given network topology at a globally optimal cost. We expand our work to also accommodate: 1) fractional-capacity sessions (where a session's capacity is a fraction of a wavelength channel's bandwidth, thereby leading to "traffic-groomed" multicast sessions) and 2) sparse splitting constraints, i.e., limited fanout of optical splitters and limited number of such splitters at each node. We illustrate the solutions obtained on different networks by solving these optimization problems, which turn out to be mixed integer linear programs (MILPs). Because the MILP is computationally intensive and does not scale well for large problem sizes, we also propose fast heuristics for establishing a set of multicast sessions in a network with or without wavelength converters and with fractional-capacity sessions. We find that, for all scenarios, the heuristics which arrange the sessions in ascending order with respect to destination set size and or cost perform better in terms of network resource usage than the heuristics which arrange the sessions in descending order. Hotspot traffic is common in metro ring networks connecting access networks with backbone networks, and these metro rings are also expected to support a mix of unicast, multicast, and broadcast traffic. Shortest path (SP) routing, as employed in the IEEE 802.17 Resilient Packet Ring (RPR), is widely considered for metro rings as it maximizes spatial reuse and, thus, the achievable packet throughput (capacity) for uniform traffic. In this paper, we analyze the capacity of bidirectional optical ring networks, such as RPR, employing SP routing for multicast (nonuniform) hotspot traffic (whereby unicast and broadcast are considered as special cases of multicast). We find that, when the traffic originating at the hotspot exceeds a critical threshold, then SP routing leads to substantial reductions in capacity to a value close to one simultaneous packet transmission. To overcome this limitation of SP routing, we propose a simple combined SP one-copy routing Hotspot traffic is common in metro ring networks connecting access networks with backbone networks, and these metro rings are also expected to support a mix of unicast, multicast, and broadcast traffic. Shortest path (SP) routing, as employed in the IEEE 802.17 resilient packet ring (RPR), is widely considered for metro rings as it maximizes spatial reuse and, thus, the achievable packet throughput (capacity) for uniform traffic. In this paper, we analyze the capacity of bidirectional optical ring networks, such as RPR, employing SP routing for multicast (nonuniform) hotspot traffic (whereby unicast and broadcast are considered as special cases of multicast). We find that, when the traffic originating at the hotspot exceeds a critical threshold, then SP routing leads to substantial reductions in capacity to a value close to one simultaneous packet transmission. To overcome this limitation of SP routing, we propose a simple combined SP one-copy routing strategy that provides a capacity of at least two simultaneous packet transmissions.strategy that provides a capacity of at least two simultaneous packet transmissions.