Recent advances in photonic switching have paved the way for realizing all-optical time switched networks. The current technology of Wavelength Division Multiplexing (WDM) offers bandwidth granularity that match peak electronic transmission speed by dividing the fiber bandwidth into multiple wavelengths. However, the bandwidth of a single wavelength is too large for certain traffic. Time Division Multiplexing (TDM) allows multiple traffic streams to share the bandwidth of a wavelength efficiently. While introducing wavelength converters and time slot interchangers improve network blocking performance, it is often of interest to know the incremental benefits offered by every additional stage of switching. As all-optical networks in future are expected to employ heterogeneous switching architectures, it is necessary to have generalized network model that allows to study these networks under a unified framework. In this paper, a network model, called Trunk Switched Network (TSN), is proposed to facilitate modeling and analysis of such networks. An analytical model for evaluating the blocking performance of a class of TSN's has also been developed. Using the analytical model, it is shown that a significant performance improvement is obtained with a time-space switch with no wavelength conversion at each node in a multi-wavelength TDM switched network. Keywords---Optical networks, WDM/TDM switching, Performance modeling I.

It has been widely recognized that physical layer impairments, including power losses, must be taken into account when routing optical connections in transparent networks. In this paper we study the problem of constructing light-trees under optical layer power budget constraints, with a focus on algorithms which can guarantee a certain level of quality for the signals received by the destination nodes. We define a new constrained light-tree routing problem by introducing a set of constraints on the source-destination paths to account for the power losses at the optical layer. We investigate a number of variants of this problem, we characterize their complexity, and we develop a suite of corresponding routing algorithms

Abstract. This paper addresses multicast routing in multi-hop optical networks employing wavelength-division multiplexing (WDM). We consider a model in which multicast communication requests are made and released dynamically over time. A multicast connection is realized by constructing a multicast tree which distributes the message from the source node to all destination nodes such that the wavelengths used on each link and the receivers and transmitters used at each node are not used by existing circuits. We show that although the routing and wavelength assignment in this model is NP-complete, the wavelength assignment problem can be solved in linear time. 1

Given the ever increasing demand for network bandwidth, and the recent phenomenal advances in optical wavelength division multiplexing (WDM) networking technologies, a major component of the Next Generation Internet will be an Internat protocol (IP)-based optical WDM network. As IP over WDM networking technologies mature, a number of important architectural, management and control issues have surfaced. These issues need to be addressed before a true Next Generation Optical Internet can emerge. In this paper, we enumerate some of the key architectural, management and control issues and discuss corresponding approaches and advances made toward addressing these issues. We first review the different IP/WDM networking architectural models and their tradeoffs. We outline and discuss several management and control issues and corresponding approaches related to the configuration, fault, and performance management of IP over dynamic WDM networks. We present an analysis and supporting simulation results demonstrating the potential benefits of dynamic IP over WDM networks. We then discuss the issues related to IP/WDM traffic engineering in more detail, and present the approach taken in the NGI SuperNet Network Control and Management Project funded by DARPA. In particular, we motivate and present an innovative integrated traffic-engineering framework for reconfigurable IP/WDM networks. It builds on the strength of multiprotocol label switching for fine-grain IP load balancing, and on the strength of reconfigurable WDM networking for reducing the IP network’s weighted-hop-distance, and for expanding the bottleneck bandwidth.

Abstract—Recent advances in wavelength-division-multiplexing (WDM) technology are expected to facilitate bandwidth-intensive multicast applications. However, a single fiber (bundle) cut on such a network can disrupt the transmission of information to several destination nodes on a “light tree”-based multicast session. Thus, it is imperative to protect multicast sessions e.g., by reserving resources along backup trees. We show that, if a backup tree is directed-link-disjoint to its primary counterpart, then data loss can be prevented in the event of any single link failure. We provide mathematical formulations for efficient routing and wavelength assignment (RWA) of several multicast sessions (including their backup trees for dedicated protection) at a globally optimum cost. We present these formulations for networks equipped with two kinds of multicast-capable switch architectures: one using the opaque (O–E–O) approach and the other using transparent (all-optical) approach. We expand our formulations to accommodate sparse splitting constraints in a network, in which an optical splitter has limited splitting fanout and each node has a limited number of such splitters. We develop a profit-maximizing model that would enable a network operator to be judicious in selecting sessions and simultaneously routing the chosen ones optimally. We illustrate the solutions obtained from solving these optimization problem formulations for a representative-size network. Index Terms—Backup tree, directed-link disjointness, fiber cut, integer linear programming (ILP), light path, light tree, mesh network, multicasting, protection, wavelength-division multiplexing (WDM).

This article discusses the routing and wavelength assignment (RWA) problem in optical networks employing wavelenength division multiplexing (WDM) technology. Two variants of the problem are studied: static RWA, whereby the tra#c requirements are known in advance, and dynamic RWA in which connection requests arrive in some random fashion. Both point-topoint and multicast tra#c demands are considered.

This paper considers multicasting on wavelength-routing mesh optical networks. Although multicasting has been studied extensively in different network environments, multicasting in this environment is different, and more involved. The paper discusses the challenges of multicast support in optical wavelength routing networks, and reports on the advances made so far in this venue. The paper introduces a classification and a comparison of such techniques, and a study of their advantages and disadvantages.

Multicast communication in single-hop broadcast-and-select Wavelength Division Multiplexing (WDM) networks has received considerable attention from researchers. This paper presents a comprehensive survey of the multicast scheduling techniques in this environment. It considers different challenges that are faced in the design of multicasting techniques, and presents a classification of such schemes. A survey of the specific techniques is then presented, and a comparison is drawn between such techniques. Keywords: Multicast, Single-Hop, Broadcast-and-Select, WDM, Scheduled/Unscheduled transmission, MAC protocols. 1.

In this paper, we investigate approaches and algorithms for establishing a multicast session in a mesh network while protecting the session against any single link failure, e.g., a fiber cut in an optical network. First, we study these approaches and algorithms to protect a single multicast tree in a mesh network and then extend it to dynamically provision survivable multicast connections (where connections come and go) in an optical wavelength-division multipexing (WDM) network. We propose two new and efficient approaches for protecting a multicast session: 1) segment protection in which we protect each segment in the primary tree separately (rather than the entire tree) and allow these backup segments to share edges with the other existing primary and backup segments and 2) the path-pair protection in which we find a path-pair (disjoint primary and backup paths) to each destination and allow a new path pair

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