Dynamic Routing And Wavelength Assignment Research Articles

Dynamic routing and wavelength assignment for efficient traffic grooming

Abstract The routing and wavelength assignment (RWA) schemes play an important role in all computer networks. The performance of a computer network and resource utilization largely depend on the RWA. The demand for higher bandwidth is increasing with each passing day, so more efficient RWA schemes need to be devolved to cater the increasing requirements. RWA becomes more challenging for dynamic traffic as the nature and flow of data are not known in advance. In this paper, a dynamic RWA scheme has been proposed for establishing a path in optical networks. The proposed scheme is based upon dynamic conversion sensing algorithm. It can be applied on a number of different network topologies. The proposed scheme is dynamic in nature, which is significantly useful for dynamic traffic grooming. The proposed scheme has been applied on 14 nodes National Science Foundation Network (NFSNet). Simulation results have shown that the blocking probability of this scheme is very low as compared to the existing schemes. So, the proposed dynamic RWA scheme enhances the network efficiency. It is useful for congestion hit networks. The reduced blocking probability in wavelength division multiplexing optical networks leads to better resource utilization and enhanced performance.

Efficient Spectrum Utilization in Large Scale RWA Problems

While the routing and wavelength assignment (RWA) has been widely studied, a very few studies attempt to solve realistic size instances, namely, with 100 wavelengths per fiber and a few hundred nodes. Indeed, state of the art is closer to around 20 nodes and 30 wavelengths, regardless of what the authors consider, heuristics or exact methods with a very few exceptions. In this paper, we are interested in reducing the gap between realistic data sets and test bed instances that are often used, using exact methods. Even if exact methods may fail to solve in reasonable time very large instances, they can, however, output $\varepsilon $ -solutions with a very good and proven accuracy. The novelty of this paper is to exploit the observations that optimal solutions contain a very large number of light paths associated with shortest paths or $k$ -shortest paths with a small $k$ . We propose different RWA algorithms that lead to solve exactly or near exactly much larger instances than in the literature, i.e., with up to 150 wavelengths and 90 nodes. Extensive numerical experiments are conducted on both the static and dynamic incremental planning RWA problem.

Security-Aware Dynamic RWA for Reducing In-band and Out-of-band Jamming Attacks in WDM Optical Networks

The high data transfer capacities of current wavelength division multiplexing optical networks put large amounts of data at risk of getting corrupted in the presence of faults and attacks. A wide range of techniques for handling component failures in transparent optical networks are already available in the literature. In recent years, there is growing recognition of the need to develop suitable mechanisms for reducing the adverse effects of malicious attacks such as high-power jamming and tapping attacks. A number of recent papers have proposed static lightpath allocation approaches that take such security issues into consideration. However, most of these approaches consider the routing problem separately from the wavelength assignment problem. In this paper we propose a new security-aware scheme for the complete dynamic routing and wavelength assignment (RWA) problem. Unlike previous approaches, we consider both in-band and out-of-band attacks under dynamic traffic scenario and present an integer linear program (ILP) formulation with two possible objectives for solving the security-aware dynamic RWA problem. For larger networks we present an efficient heuristic algorithm SA-DRWA (Security-Aware Dynamic Routing and Wavelength Assignment) that aims to minimize both in-band and out-of-band attacks. To the best of our knowledge, this is the first such formulation to jointly consider in-band and out-of-band attacks, for dynamic traffic

Request differentiation in dynamic light-path establishment for WDM routed all optical networks of data centers

Existing routing and wavelength assignment (RWA) solutions try to minimize the blocking rate as the main quality of service (QoS) metric. However, in ultra high-speed all optical interconnection networks of data centers, more important metrics such as network throughput and channel utilization are of interest for network designers. This paper proposes dynamic request buffering routing and wavelength assignment (DRB-RWA) that aims at maximizing the network throughput and total amount of transmitted data in addition to minimizing the blocking rate by proposing a dynamic RWA scheme based on request differentiation. The proposed scheme tries to exploit buffering approach in order to be able to achieve a pseudo static traffic out of a dynamic traffic; and hence, it would be able to differentiate requests in terms of desired metrics. However, conventional dynamic RWA solutions solely aim at minimizing the blocking rate. We evaluate the performance of the proposed algorithm via analytical approach as well as comprehensive simulations to confirm the fact that the network throughput, and therefore, total amount of transmitted data are maximized when the proposed scheme is applied.

Comparative Analysis of Routing and Wavelength Assignment Algorithms used in WDM Optical Networks

This study aims at highlighting the Routing and Wavelength Assignment (RWA) problems in WDM Optical networks and describes the Routing Algorithms and their performance comparison. Since routing decisions play an important role in evaluating the blocking performance of a network it is critical to choose a wavelength assignment scheme that should take into account its compatibility with the chosen routing protocol in addition to its blocking performance. This study presents problems in Wavelength Assignment, describes various Routing schemes and different approaches to solve both the static and the dynamic RWA problems. RWA algorithms’ role is to assign a light-path (a route and a wavelength) to incoming calls in a network. RWA algorithms block calls if a continuous wavelength from source to destination cannot be found (wavelength blocking), thus degrading the performance of All Optical Networks, by call blocking. The failure of RWA algorithm to find an available wavelength on all links from source to destination causes congestion resulting in packet loss. This study examines the RWA algorithms and their problems in WDM Optical networks. The various measures taken to improve the blocking performance of WDM optical networks are also studied. We compared the performance of two wavelength assignment schemes, the Random wavelength assignment and the First-Fit wavelength assignment scheme via simulation. It was observed that the Random wavelength assignment algorithm performs well under low load, while for high load First Fit algorithm performs better.

Establishment of Dynamic Lightpaths in Filterless Optical Networks

In this paper, we study the performance of dynamic routing and wavelength assignment (RWA) in filterless optical networks. These types of broadcast and select networks benefit from breakthroughs in advanced transmission technologies for replacing optical filters and active photonic switching devices, such as wavelength selective switches, with passive optical interconnections between nodes, creating passive optical light trees. We introduce an RWA scheme for establishing passive optical lightpaths in a filterless context and managing unfiltered channels at intermediate egress nodes, which, by propagating downstream of the terminating nodes, participate in wavelength usage and increase the risk of wavelength exhaustion. Simulation results are presented for six network topologies, along with the performance evaluation of active photonic and filterless optical network solutions with static and dynamic RWA schemes. We show that the performance of the proposed scheme depends on the average degree of node connectivity.

QoT aware evolutionary programming algorithm for transparent optical networks

This paper presents an evolutionary programming algorithm to solve the quality of transmission (QoT) aware dynamic routing and wavelength assignment (DRWA) problem in transparent optical networks using wavelength division multiplexing (WDM). In this algorithm, the initial population is assumed to consist of a single individual and the algorithm uses only the mutation operator to explore the search space, both the features contributing to a reduction in algorithm execution time. A novel fitness function has been designed that takes into account the number of hops, the path cost, and the variance contributions due to the amplified spontaneous emission (ASE) noise and dynamic crosstalk at the nodes of each lightpath while evaluating a lightpath. This paper also proposes a new wavelength ordering assignment technique to reduce both the switch crosstalk and adjacent channel rejection crosstalk and hence, attempts to improve the mean blocking probability of the incoming call requests. This paper also, analyses the time complexity of the proposed algorithm.

A metaheuristic approach for optical network optimization problems

Two of the most complex optimization problems encountered in the design of third generation optical networks are the dynamic routing and wavelength assignment (DRWA) problem under the assumptions of ideal and non-ideal physical layers. Both these problems are NP-complete in nature. These are challenging due to the presence of multiple local optima in the search space. Even heuristics-based algorithms fail to solve these problems efficiently as the search space is non-convex. This paper reports the performance of a metaheuristic, that is, an evolutionary programming algorithm in solving different optical network optimization problems. The primary motivation behind adopting this approach is to reduce the algorithm execution time. It is demonstrated that the same basic approach can be used to solve different optimization problems by designing problem-specific fitness functions. Also, it is shown how the algorithm performance can be improved by integrating suitable soft constraints with the original constraints. Exhaustive simulation studies are carried out assuming the presence of different levels of linear impairments such as switch and demultiplexer crosstalk and non-linear impairments like four wave mixing to illustrate the superiority of the proposed algorithms.

An evolutionary programming algorithm for survivable routing and wavelength assignment in transparent optical networks

The dynamic routing and wavelength assignment (DRWA) problem is a challenging optimisation problem in optical wavelength division multiplexed (WDM) networks. This paper proposes a novel evolutionary programming algorithm, namely, ERWA, to reduce the set-up time of lightpaths in a WDM network. It is shown that the proposed algorithm with simple extensions, referred to in this paper as ESRWA, is able to provide dedicated protection at the optical layer of the network, thereby addressing the survivable DRWA problem. In contrast to other bio-inspired algorithms available in the literature for the DRWA problem, ERWA facilitates the online discovery of a requested lightpath. The novelty of ERWA lies in the fact that it uses an initial population consisting of only one individual or chromosome and integrates a soft constraint with a set of hard constraints to accomplish proper load balancing. These features result in a lower mean blocking probability and a lower mean execution time compared to those exhibited by the existing bio-inspired algorithms for both the DRWA and the survivable DRWA problems.

Dynamic Routing and Wavelength Assignment with Backward Reservation in Wavelength-routed Multifiber WDM Networks

In wavelength-routed WDM networks, blocking probability of lightpath establishments is generally high due to coarse granularity and wavelength continuity constraint. Therefore, blocking of lightpath establishments is one of crucial issues which must be resolved. Multifiber environments reduce blocking probability of lightpath establishments because each link consists of multiple fibers and multifiber links can be viewed as limited-range wavelength conversion. Blocking probability can be further reduced by an appropriate routing and wavelength assignment (RWA) scheme. This paper proposes a dynamic RWA scheme using signaling of backward reservation for wavelength-routed multifiber WDM networks. In the proposed scheme, information on link state is collected by signaling of backward reservation along multiple routes between a sender node and a receiver node whenever a new lightpath-setup request arrives. Then the proposed scheme selects a combination of a route and a wavelength at the receiver node based on the collected information in such a way that it avoids the generation of bottleneck links and the depletion of a specific wavelength. Through simulation experiments, we show that the proposed scheme efficiently reduces blocking probability of lightpath establishments in multifiber WDM networks.

Review of Dynamic Impairment-Aware Routing and Wavelength Assignment Techniques in All-Optical Wavelength-Routed Networks

Since light-paths are the basic connections in wavelength routed networks, their effective establishment is very important. Routing and Wavelength Assignment (RWA) techniques can be divided into two categories. The first category (pure RWA) concentrates on setting up light-paths under the assumption of an ideal physical layer. However, this assumption could be suitable for opaque networks, where a signal is regenerated at each optical switch along its path. On the other hand, as an optical signal propagates along a light-path to its destination in a transparent (all-optical) network, the signal's quality degrades because there is no signal regeneration, thus increasing Bit-Error-Rate (BER) of the signal. However, users would not accept a light-path with a high BER. Even it is not acceptable if the establishment of a light-path causes the BER of other existing light-paths to become unacceptably high. Therefore, considering physical layer impairments, the quality of a light-path must be checked during the light-path setup in the second category. In this article, the operations of dynamic RWA techniques proposed in transparent networks for the second category are reviewed in detail. These techniques are called Quality of Transmission Aware (QoT-aware) RWA and are grouped in two groups: integrated QoT and RWA, and QoT after Pure RWA. Each group can be further divided into direct modelling and indirect modelling sub-groups. A comprehensive discussion is also provided to compare dynamic QoT-aware RWA techniques based on different network and physical layer parameters.

Optimal regenerator assignment and resource allocation strategies for translucent optical networks

Physical layer impairments in wavelength-routed networks limit the maximum distance, a signal can travel in the optical domain, without significant distortion. Therefore, signal regeneration is required at some intermediate nodes for long-haul lightpaths. In translucent WDM networks, sparsely located regenerators at certain nodes can be used to offset the impact of physical layer impairments. The routing and wavelength assignment (RWA) techniques in such translucent networks need to take into consideration the availability of regenerators and the maximum optical reach of the transparent lightpaths (without any regeneration). Although there has been significant research interest in RWA algorithms for translucent networks, much of the research has focused on dynamic RWA techniques. Only a handful of recent papers have considered the static (offline) case, and they typically propose heuristic algorithms to solve this complex design problem for practical networks. In this paper, we propose a generalized integer linear program (ILP) based formulation for static regenerator assignment and RWA in translucent WDM optical networks, with sparse regenerator placement. To the best of our knowledge, such a formulation that optimally allocates resources for a set of lightpaths for translucent networks, given the physical network, the locations of the regenerators, and the maximum optical reach has not been considered before. The proposed formulation is important for two reasons. First, it can serve as a benchmark for evaluating different heuristic approaches that may be developedin the future. Second, we show that using a novel node representation technique, it is possible to drastically reduce the number of integer variables. This means that unlike existing ILP formulations, our approach can actually be used to generate optimal solutions for practical networks, with hundreds of lightpath demands.

Dynamic Impairment-Aware RWA in Multifiber Wavelength-Routed All-Optical Networks Supporting Class-Based Traffic

A quality-of-transmission- (QoT-) aware routing and wavelength assignment (RWA) technique suitable for multifiber wavelength-routed all-optical networks supporting class-based lightpaths (LPs) is proposed, where QoT is evaluated not only for any candidate LP being set up but also for already-set-up LPs. In this paper, QoT refers to the quality of transmission at the physical layer and quality of service (QoS) refers to the network-level quality issues. Four performance improvement techniques are proposed: (1) preempting an existing low-quality (LQ) LP by a high-quality (HQ) connection considering bandwidth utilization to provide better QoS for HQ traffic; (2) class-based buffering of connection requests in edge switches to provide the chance of setup for the LPs that are going to be blocked, and therefore, improving the performance of the LP setup; (3) differentiated routing in which LQ LPs are routed through large dispersion paths and HQ LPs through small dispersion paths; and (4) wavelength ordering to reduce crosstalk in switches and interchannel crosstalk on fibers. Our performance evaluations show the effectiveness of the proposed improvements in reducing blocking probability.

Research on dynamic RWA algorithm supporting service-differentiated provision

In the multi-service requirement of the next generation of optical networks, differentiated services should be provided, and the transmission quality of signal and the path reliability are two important parameters of service class differentiation. A new dynamic routing and wavelength assignment (RWA) algorithm supporting service-differentiated provision, which takes account of both requirements of the signal transmission quality and the path reliability, is proposed. The numerical results from simulation show that the algorithm can not only overcome the impact of impairment on signal transmission quality and guarantee lightpath reliability, but also offer the service-differentiated lightpath according to its class.

A Novel Solution to the Dynamic Routing and Wavelength Assignment Problem in Transparent Optical Networks

We present an evolutionary programming algorithm for solving the dynamic routing and wavelength assignment (DRWA) problem in optical wavelength-division multiplexing (WDM) networks under wavelength continuity constraint. We assume an ideal physical channel and therefore neglect the blocking of connection requests due to the physical impairments. The problem formulation includes suitable constraints that enable the algorithm to balance the load among the individuals and thus results in a lower blocking probability and lower mean execution time than the existing bio-inspired algorithms available in the literature for the DRWA problems. Three types of wavelength assignment techniques, such as First fit, Random, and Round Robin wavelength assignment techniques have been investigated here. The ability to guarantee both low blocking probability without any wavelength converters and small delay makes the improved algorithm very attractive for current optical switching networks.

Dynamic RWA with FWM-induced crosstalk awareness and modulation format conversion in wavelength-routed optical networks

The constraint of signal transmission quality and network resources utilization in transparent optical networks are herein addressed through a representative cost function based upon an impairment-constraint-base routing (ICBR) approach, taking into account link capacity utilization and the nonlinear physical effect, in the primary instance due to Four-Wave Mixing (FWM)-induced crosstalk. The FWM effect is considered one of the most severe physical impairments for the future photonic networks since the accumulation of FWM crosstalk may cause a fatal degradation in the teletraffic network performance. This paper presents an added functionality to the network model design based on all-optical modulation format conversion from conventional on-off keying (OOK) to quadrature phase-shift keying (QPSK) sending more data within the same bandwidth while minimizing the blocking probability. The joint effect of physical impairment (i.e., FWM-induced crosstalk) awareness and two different modulation formats is considered through numerical simulations. The proposed scheme is expected to realize an all-optical transparent interconnection between networks that employ diverse modulation formats. Results show that the proposed FWM-aware Routing and Wavelength Assignment (RWA) algorithm leads to a more realistic system performance while giving a significant improvement on the network performance.

Reducing the lightpath establishing time of FWM-aware dynamic RWA for wavelength-routed optical networks

A dynamic routing and wavelength allocation technique with an interplay between physical and network layer parameters encompassing Four-wave mixing (FWM) awareness and teletraffic performance of wavelength-routed optical networks has previously been proposed for a distributed approach. In this article, we present a fast computational algorithm for our routing and wavelength assignment (RWA) encompassing FWM-induced crosstalk. The objective is to minimize the time of establishing a dynamic lightpath. For this purpose, a precomputed matrix of FWM crosstalk products is used in an adapted version of the FWM-aware dynamic RWA algorithm. The approach is validated through simulations showing improvement up to 30–50% on the provisioning time of lightpaths for different network topologies compared to an online full computational scheme.

FWM-Aware Dynamic Routing and Wavelength Assignment for Wavelength-Routed Optical Networks

A dynamic routing and wavelength assignment (RWA) algorithm encompassing physical impairment due to Four-Wave Mixing (FWM) is proposed, assuming conventional On-Off-Keying (OOK) modulation format. The FWM effect is one of the most severe physical impairments to be considered for the future photonic networks since the accumulation of FWM crosstalk causes a fatal degradation in the wavelength-routed optical network performance. A novel cost function is introduced based upon an impairment-constraint-based routing (ICBR) approach, taking into account the network utilization resources and the physical impairment due to FWM crosstalk. Simulations results show that the proposed algorithm leads to a more realistic system performance compared to those of related approaches of dynamic RWA that fail to consider physical impairments into the routing scheme.

SPARK: A smart parametric online RWA algorithm

The large potential bandwidth available in wavelength-division multiplexed optical networks makes this technology of crucial importance for satisfying the ever increasing capacity requirements of the next-generation Internet. In this scenario, the routing and wavelength assignment (RWA) problem that concerns deter- mining the optical paths and wavelengths to be used for connection establishment in a wavelength-routed network, is still one of the most important open issues. In this paper we propose a new on- line dynamic grooming-capable RWA heuristic scheme working on wavelength division multiplexing (WDM) networks as a multistage selection process. The proposed algorithm is transparent with respect to the presence of wavelength converters, achieves very low connection rejection ratios with minimal computational complexity and is appropriate for the modern multilayer optical circuit and wavelength switched networks with sparse wavelength conversion capability.

Simultaneous effect of connection admission control in distance and bandwidth capacity on WDM network performance

This article presents an algorithm for dynamic-routing and wavelength assignment (D-RWA) in an optical WDM network. The approach is based on a genetic algorithm (GA) and it includes a connection admission control (CAC), to provide a network with simultaneous fairness in distance and bandwidth capacity. The algorithm is evaluated by means of computer simulations using a mesh network with two types of node architectures capable of performing traffic grooming. Combining the two types of nodes, the performance of four network configurations is compared. Assuming that one of the two node types is more costly, two sparse node allocations are suggested to maintain the network cost-effective. The algorithm assigns wavelengths to the ligthpaths, routes the traffic streams, manages the grooming of sub-wavelength tributaries onto full wavelength channels, provides fairness, and minimizes the overall blocking probability of connection requests. Numerical results attest the usefulness of the proposed approach considering several scenarios of distance and bandwidth capacity classes of requests. Simultaneous and isolated simulations of the two fairness schemes are also compared, emphasizing the versatility of the algorithm.