As the Internet expands in reach and capacity, the energy consumption of network equipment increases. To date, the cost of transmission and switching equipment has been considered to be the major barrier to growth of the Internet. But energy consumption rather than cost of the component equipment may eventually become a barrier to continued growth. Research efforts on ldquogreening the Internetrdquo have been initiated in recent years, aiming to develop energy-efficient network architectures and operational strategies so as to reduce the energy consumption of the Internet. The direct benefits of such efforts are to reduce the operational costs in the network and cut the greenhouse footprint of the network. Second, from an engineering point of view, energy efficiency will assist in reducing the thermal issues associated with heat dissipation in large data centers and switching nodes. In the present research, we concentrate on minimizing the energy consumption of an IP over WDM network. We develop efficient approaches ranging from mixed integer linear programming (MILP) models to heuristics. These approaches are based on traditional virtual-topology and traffic grooming designs. The novelty of the framework involves the definition of an energy-oriented model for the IP over WDM network, the incorporation of the physical layer issues such as energy consumption of each component and the layout of optical amplifiers in the design, etc. Extensive optimization and simulation studies indicate that the proposed energy-minimized design can significantly reduce energy consumption of the IP over WDM network, ranging from 25% to 45%. Moreover, the proposed designs can also help equalize the power consumption at each network node. This is useful for real network deployment, in which each node location may be constrained by a limited electricity power supply. Finally, it is also interesting and useful to find that an energy-efficient network design is also a cost-efficient design because of the fact that IP router ports play a dominating role in both energy consumption and network cost in the IP over WDM network.

Energy-Minimized Design for IP Over WDM Networks

Survivability, the ability of a network to withstand and recover from failures, is one of the most important requirements of networks. Its importance is magnified in fiber optic networks with throughputs on the order of gigabits and terabits per second. This article takes a look at the techniques used to achieve survivability in traditional optical networks, and how those techniques are evolving to make next-generation WDM networks survivable.

Survivability in optical networks

Wavelength conversion has been proposed for use in wavelength-division multiplexed networks to improve efficiency. This study highlights systems challenges and performance issues which need to be addressed in order to incorporate wavelength conversion effectively. A review/survey of the enabling technologies, design methods, and analytical models used in wavelength-convertible networks is provided.

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Wavelength conversion in WDM networking

On a router-port basis, our previous study [1] found that lightpath bypass strategy can significantly save power consumption over the lightpath non-bypass strategy. However, in real network systems, router ports are organized by network line cards or modules; on each line card there are multiple router ports. In this paper, we evaluate the energy consumption of an IP over WDM network in the context of modularized router ports. We develop mixed integer linear programming (MILP) model for power consumption minimization under the lightpath bypass strategy. We also compare the cases of lightpath bypass and nonbypass. It is found that for modularized route ports, the strategy of optical bypass can significantly outperform the strategy of non-bypass. Also, under different types of modular router line cards, a mixed deployment of different types of router line cards consumes the least energy compared to the deployment of a single type of line card.

Energy-minimized design for IP over WDM networks under modular router line cards

This paper investigates the problem of dynamic survivable lightpath provisioning in optical mesh networks employing wavelength-division multiplexing (WDM). In particular, we focus on shared-path protection because it is resource efficient due to the fact that backup paths can share wavelength links when their corresponding working paths are mutually diverse. Our main contributions are as follows. 1) First, we prove that the problem of finding an eligible pair of working and backup paths for a new lightpath request requiring shared-path protection under the current network state is NP-complete. 2) Then, we develop a heuristic, called CAFES, to compute a feasible solution with high probability. 3) Finally, we design another heuristic, called OPT, to optimize resource consumption for a given solution. The merits of our approaches are that they capture the essence of shared-path protection and approach to optimal solutions without enumerating paths. We evaluate the effectiveness of our heuristics and the results are found to be promising.

New and improved approaches for shared-path protection in WDM mesh networks

In this paper routing, planning of working capacity, rerouting, and planning of spare capacity in wavelength division multiplexing (WDM) networks are investigated. Integer linear programming (ILP) and simulated annealing (SA) are used as solution techniques. A complex cost model is presented. The spare capacity assignment is optimized with respect to three restoration strategies. The benefit of wavelength conversion, the choice of the fiber line system, and the influence of cost parameter values are discussed, with respect to the different restoration strategies and solution techniques. Wavelength conversion is found to be of limited importance, whereas tunability at the end points of the connections has substantial benefits.

Dimensioning of survivable WDM networks

Wavelength translation is still a controversial subject in the optical network research world. From simulation results of different groups we may, however, conclude that the increased management complexity, if no wavelength translators are used, may be a stronger point to justify wavelength translation than the performance increase, which is relatively small. Most of the performance comparisons between wavelength translated networks [with virtual wavelength paths (VWP)] and wavelength routed networks [with wavelength paths (WP)] done so far assume a fixed traffic matrix.

Reduction of wavelength blocking through partitioning with wavelength convertors

Summary form only given. Wavelength-division multiplexed (WDM) networks are considered to offer the bandwidth required to accommodate future data traffic and new services. Various concepts are under study and being reported. Recently a number of papers have been published reporting on the performance ofthese networks under dynamic traffic condition^.This work aims on a simple, and thus practical and applicable approach to route the traffic under dynamic conditions trying to minimize the blocking, occurring when traffic requests can't be accommodated. The networks considered are WDM networks carrying virtual wavelength paths, i.e., along the paths the wavelength can be changed in the intermediate optical cross-connect through the use of wavelength converters.

Reduction of Blocking in Arbitrary Meshed Wdm Networks through a Biased Routing Approach

Summary form only given. A lot of work has been reported on the use of wavelength converters (WCs) in wavelength-division multiplexed (WDM) networks. Recent research indicates that for a wide variety of applications the use of WCs in WDM networks results only in modest improvements in throughput, compared to networks without WCs. It has been observed that a limited set of nodes equipped with WCs can give almost equal performance as a virtual wavelength path network, where all nodes are fully equipped with WCs. Furthermore, it has been shown that already a limited form of wavelength conversion can enhance the performance of WDM ring networks. Former work indicates that a limited number of converters should be sufficient to provide decent performance. This paper reports the impact of two different architectures for the optical cross-connect (OXC), containing a limited number of WCs, on the performance of meshed WDM networks. The two OXC architectures considered are: (1) an OXC containing a pool of WCs, where a free WC can be used by any incoming channel, and (2) an OXC where the WCs are dedicated to a particular channel, conversion occurs before the signal is multiplexed on the outgoing fiber.

Meshed wavelength-division multiplexed networks partially equipped with wavelength converters

WDM transport networks are moving fast from the laboratory and field trial environment to deployment in operational networks One of the key issues is the management of these transparent networks and the impact on the required component functionalities This paper will address these issues in more detail

B. Van Caenegem

Papers

Dimensioning of survivable WDM networks

Reduction of wavelength blocking through partitioning with wavelength convertors

Reduction of Blocking in Arbitrary Meshed Wdm Networks through a Biased Routing Approach

Meshed wavelength-division multiplexed networks partially equipped with wavelength converters

Impact of WDM network management on optical component functionalities