Rudra Dutta

Traffic grooming in WDM networks: past and future

Traffic grooming refers to techniques used to combine low-speed traffic streams onto high-speed wavelengths in order to minimize the networkwide cost in terms of line terminating equipment and/or electronic switching. Such techniques become increasingly important for emerging network technologies, including SONET/WDM rings and MPLS/MP/spl lambda/S backbones, for which traffic grooming is essential. In this article we formally define the traffic grooming problem, and we provide a general formulation that captures the features of a wide range of problem variants. We then present a comprehensive comparative survey of the literature that unveils the significant amount of research on this subject (the traffic grooming past). We also offer a broad set of ambitious research directions (the traffic grooming future) that are motivated by the exciting new challenges arising with the advent of MP/spl lambda/S technology.

The SILO Architecture for Services Integration, controL, and Optimization for the Future Internet

We propose a new internetworking architecture that represents a departure from current philosophy and practice, as a contribution to the ongoing debate regarding the future Internet. Building upon our experience with the design and prototyping of the just-in-time protocol suite, we outline a framework consisting of (1) building blocks of fine-grain functionality, (2) explicit support for combining elemental blocks to accomplish highly configurable complex communication tasks, and (3) control elements to facilitate (what is currently referred to as) cross-layer interactions. In this position paper, we take a holistic view of network design, allowing applications to work synergistically with the network architecture and physical layers to select the most appropriate functional blocks and tune their behavior so as to meet the applications needs within resource availability constraints. The proposed architecture is flexible and extensible so as to foster innovation and accommodate change, it supports a unified Internet, it allows for the integration of security and management features at any point in (what is now referred to as) the networking stack, and it is positioned to take advantage of hardware-based performance-enhancing techniques.

Network Virtualization: Technologies, Perspectives, and Frontiers

Network virtualization refers to a broad set of technologies. Commercial solutions have been offered by the industry for years, while more recently the academic community has emphasized virtualization as an enabler for network architecture research, deployment, and experimentation. We review the entire spectrum of relevant approaches with the goal of identifying the underlying commonalities. We offer a unifying definition of the term “network virtualization” and examine existing approaches to bring out this unifying perspective. We also discuss a set of challenges and research directions that we expect to come to the forefront as network virtualization technologies proliferate.

Traffic Grooming: A Changing Role in Green Optical Networks

The traffic grooming problem in optical networks has been extensively studied. It tackles the problem of aggregating sub-wavelength traffic onto optical lightpaths so that the network cost can be reduced. As of yet, the network cost considered is in terms of the number of wavelengths, SONET ADMs, and the amount of OEO processing. However, in recent years, the steadily rising cost of energy consumption of the network has raised a lot concerns. In this paper, we revisit the traffic grooming problem and provide formulations for green optical network design, and show a simple algorithm working at one of the layers identified by the model.

On hierarchical traffic grooming in WDM networks

The traffic grooming problem is of high practical importance in emerging wide-area wavelength division multiplexing (WDM) optical networks, yet it is intractable for any but trivial network topologies. In this work, we present an effective and efficient hierarchical traffic grooming framework for WDM networks of general topology, with the objective of minimizing the total number of electronic ports. At the first level of hierarchy, we decompose the network into clusters and designate one node in each cluster as the hub for grooming traffic. At the second level, the hubs form another cluster for grooming intercluster traffic. We view each (first- or second-level) cluster as a virtual star, and we present an efficient near-optimal algorithm for determining the logical topology of lightpaths to carry the traffic within each cluster. Routing and wavelength assignment is then performed directly on the underlying physical topology. We demonstrate the effectiveness of our approach by applying it to two networks of realistic size, a 32-node, 53-link topology and a 47-node, 96-link network. Comparisons to lower bounds indicate that hierarchical grooming is efficient in its use of the network resources of interest, namely, electronic ports and wavelengths. In addition to scaling to large network sizes, our hierarchical approach also facilitates the control and management of multigranular networks.

Choice as a principle in network architecture

There has been a great interest in defining a new network architecture that can meet the needs of a future Internet. One of the main challenges in this context is how to realize the many different technical solutions that have developed in recent years in a single coherent architecture. In addition, it is necessary to consider how to ensure economic viability of architecture solutions. In this work, we discuss how to design a network architecture where choices at different layers of the protocol stack are explicitly exposed to users. This approach ensures that innovative technical solutions can be used and rewarded, which is essential to encourage wide deployment of this architecture.

Dynamic traffic grooming: the changing role of traffic grooming

Traffic grooming refers to the techniques used to aggregate subwavelength traffic onto high speed lightpaths, while at the same time minimizing some measure of network cost, usually optoelectronic equipment cost. In the last few years, traffic grooming has come to be recognized as an important research area, and has produced extensive literature. Recently, the dynamic traffic grooming problem, where traffic carried in the network varies with the time, has gained in interest. This is because of the growing applicability of QoS concerns and associated network design methodologies in networks closer to the indivdual users than backbone networks, where the traffic cannot be well modeled as essentially static. A number of studies in this area have recently appeared in the literature, but there is as yet no good resource that introduces a reader to the problem in all its forms, and provides a review of the literature. In this paper, we fill this void by presenting a comprehensive survey of the literature in this emerging topic, and indicating some essential further directions of research in dynamic traffic grooming.

Clustering Methods for Hierarchical Traffic Grooming in Large-Scale Mesh WDM Networks

We consider a hierarchical approach for traffic grooming in large multiwavelength networks of a general topology. Inspired by similar concepts in the airline industry, we decompose the network into clusters, and select a hub node in each cluster to groom traffic originating and terminating locally. At the second level of the hierarchy, the hub nodes form a virtual cluster for the purpose of grooming intra-cluster traffic. Clustering and hierarchical grooming enables us to cope with large network sizes and facilitates the control and management of traffic and network resources. Yet, determining the size and composition of clusters so as to yield good grooming solutions is a challenging task. We identify the grooming-specific factors affecting the selection of clusters, and we develop a parameterized clustering algorithm that can achieve a desired trade-off among various goals. We also obtain lower bounds on two important objectives in traffic grooming: the number of lightpaths and wavelengths needed to carry the subwavelength traffic. We demonstrate the effectiveness of clustering and hierarchical grooming by presenting the results of experiments on two network topologies that are substantially larger than those considered in previous traffic grooming studies.

On optimal traffic grooming in WDM rings

We consider the problem of designing a virtual topology to minimize electronic routing, that is, grooming traffic, in wavelength routed optical rings. We present a new framework consisting of a sequence of bounds, both upper and lower, in which each successive bound is at least as strong as the previous one. The successive bounds take larger amounts of computation to evaluate, and the number of bounds to be evaluated for a given problem instance is only limited by the computational power available. The bounds are based on decomposing the ring into sets of nodes arranged in a path, and adopting the locally optimal topology within each set. Our approach can be applied to many virtual topology problems on rings. The upper bounds we obtain also provide a useful series of heuristic solutions.

Traffic Grooming for Optical Networks

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