RWA Algorithm Research Articles

Attack-aware resource planning and sparse monitor placement in optical networks

This work presents joint optimization algorithms for lightpath establishment as well as sparse placement of optical performance monitoring (OPM) equipment in optical networks. OPMs are necessary to efficiently monitor the impact of physical layer attacks and are usually placed at locations that are more probable to be impacted by jamming attacks. A jamming attack is defined as a harmful signal interference with other signals, leading to service degradation, that is possible through intra-channel or inter-channel crosstalk effects. An Integer Linear Program (ILP) formulation is proposed to solve the problem of attack-aware routing and wavelength assignment (Aa-RWA), jointly with the placement of OPM equipment, in order to minimize the impact of physical layer jamming attacks in optical networks. Moreover, a Genetic Algorithm (GA) is proposed to solve the same optimization problem. The proposed GA algorithm is compared to the ILP formulation as well as to an attack-unaware RWA algorithm that has as an objective the minimization of the number of wavelengths required to accommodate all traffic demands, not accounting for the crosstalk interactions. Simulation results indicate that the proposed GA algorithm provides a solution that is close to the optimal in terms of crosstalk interactions, while also providing a very good solution in resource usage, measured in terms of the required number of wavelengths.

A hybrid load-balancing and energy-aware RWA algorithm for telecommunication networks

In the last years, the power consumption of telecommunication networks has attracted the attention of both researchers and field experts in order to contain the associated energy bills and reduce their ecological impact. Many of the proposed solutions have been focused exclusively on the reduction of the power consumption, without adequately considering more traditional network engineering objectives such as balancing resource utilization, routing policy, or resilience schemes. As a consequence, network control plane strategies passed from one extreme to the other, from being totally energy-unaware to exclusively energy-efficient at the expenses of load-balancing, with obvious impacts on the power consumption in the former case and on the blocking rate in the latter one.In this paper, we present a hybrid routing and wavelength assignment algorithm that, when the network is lightly loaded, operates in an energy-efficient way, by routing the connections on the paths requiring the lowest amount of energy, while, when the network load increases, it dynamically switches to a pure load-balancing scheme in order to best allocate the available communication resources. The switching decision among load-balancing and energy-awareness is taken dynamically, driven by a threshold on the number of new connections requests reaching the network during a prefixed time window.Simulation results show the effectiveness of the hybrid algorithm, which achieves lower energy consumption than a pure load-balancing algorithm while keeping the network load fairly distributed on the available resources.

A Better ACA for Routing and Wavelength Assignment in ASON with Supporting Different SLA of Services and 10Pbps Network Capacity

Dynamic RWA algorithm which supports differentiating business service quality levels becomes a hot research in optical networks. This paper proposes a better ant colony algorithm for routing and wavelength assignment in ASON with supporting differentiating SLA of services and 10P bps network capacity. Firstly, the algorithm adds the concept of business interval period M to dynamically adjust the wavelength grouped in different periods So as to better meet the sercice requests of different levels; Secondly the algorithm adds a link selection control factor in the transition probability function ACA in order to achieve a better link load balancing. Simulation results show that after joining the cyclical and link selection control factor, blocking rate becomes lower and the load of network becomes more evenly.

Limited Range Wavelength Converter Based PLI-Signal Quality RWA (PLI-SQRWA) Algorithm for Translucent Optical Wavelength Division Multiplexed (WDM) Networks

Limited Range Wavelength Converter Based PLI-Signal Quality RWA (PLI-SQRWA) Algorithm for Translucent Optical Wavelength Division Multiplexed (WDM) Networks

An Improved Ant Colony Optimization RWA Algorithm and its Application in Optical Network Wavelength Converter Allocation Strategy

An improved Ant Colony Optimization based RWA algorithm and its application in optical network wavelength converter allocation strategy is given. The link idle rate is introduced as new constraint along with the random perturbation to prevent searching converged into unexpected local optimum. Theoretical and simulation shows the improved algorithm has better blocking probability and resources utilization performance.

A Novel Offline PLI-RWA and Hybrid Node Architecture for Zero Blocking and Time Delay Reduction in Translucent Optical WDM Networks

In this paper, we contrive a model that underpins the offline Physical Layer Impairment-Routing and Wavelength Assignment (PLI-RWA) issue in translucent networks. We introduce an innovative PLI-Signal Quality Aware RWA (PLI-SQARWA) algorithm that (a) guarantees zero blocking due to signal degradation and wavelength contention and (b) aims at minimizing the total required number of network components i.e. regenerators and all-optical wavelength converters (AOWCs). Further, in view of reducing the time delay due to optical-electrical-optical (OEO) conversions, we propose a novel electro-optical hybrid translucent node architecture. We show that PLI-SQARWA outperforms a recent heuristic for RWA and regenerator placement (RP) in terms of capital expenditure (CapEx) and time delay; while demonstrating superior blocking performance at all traffic loads. In addition, at high traffic loads, PLI-SQARWA also starts to provision savings on operational expenditure (OpEx). We proceed to the performance comparison of network equipped with the proposed hybrid node and existing translucent and transparent node architectures. The results clearly show that use of the hybrid node incurs less time delay at a similar blocking performance shown by nodes which use OEO conversion for both, regeneration and/or wavelength conversion. The results presented also highlight the significance of equipping the PLI-RWA routing phase with signal quality awareness in order to reduce the network component count and the use of AOWCs to minimize time delay due to OEO conversions.

A dynamic and quasi-centralized RWA method for optical fast circuit switching networks employing route pre-prioritization

We propose a new dynamic RWA algorithm for optical fast circuit switching networks, agile optical networks that can accommodate changing broadband demands. The algorithm utilizes pre-computed prioritized route candidates that reflect statistical information such as traffic distribution characteristics to attain better load balancing. The route priority is periodically distributed over a network and RWA for each path connection demand is processed in a distributed manner. Numerical experiments demonstrate that the algorithm matches the performance of a centralized RWA algorithm that uses all the necessary information on a network.

A methodology to design the link cost functions for impairment aware routing algorithms in optical networks

We propose a methodology to design the link cost function and, consequently, a systematic form to design a RWA algorithm. We call this methodology link cost function design (LCFD) and it consists of four steps: The choice of the link cost function input variables, the expansion of the cost function in terms of a series, the selection of an overall network performance indicator as the optimization target, and finally, the execution of an optimization process to find the series coefficients that optimize the network performance indicator based on off-line network simulations. The optimization process is performed by a computational intelligence technique, the particle swarm optimization. The proposed methodology (LCFD) is used to design an adaptive IA-RWA algorithm, which we call Power Series Routing (PSR). The effectiveness of both methodology and IA-RWA algorithm is investigated. The PSR is compared with other algorithms found in the literature by means of computational simulations and our proposal presented lower blocking probabilities with shorter computation time. Furthermore, we investigate the sensitivity and the ability of the proposed PSR to adapt itself to topological changes in the network due to both link/node addition/failure. We also investigate the behavior of the PSR in a scenario where the traffic load distribution is randomly chosen (non-uniform traffic), and we compared it to other three routing algorithms.

A Novel Impairment Aware RWA Algorithm With Consideration of QoT Estimation Inaccuracy

In all-optical networks the physical layer impairments accumulate along a light-path and also vary dynamically, and a number of impairment aware routing and wavelength assignment (IA-RWA) techniques have been proposed in order to mitigate the physical layer impairments and find lightpaths that meet a required quality of transmission (QoT) constraint predefined by the network operator. However, in order to compute lightpaths, IA-RWAs typically rely on analytical models, which cannot be guaranteed to be fully accurate, and hence acceptance of lightpaths with poor QoT or rejection of lightpaths with acceptable QoT may ensue. We present a novel IA-RWA algorithm that not only considers the impact of physical impairments on RWA decisions, but also, for the first time, accounts for inaccuracy of the QoT estimators. The performance of our algorithm is compared with algorithms selected from the recent literature. All algorithms are evaluated through simulations in a realistic scenario. Our proposed novel algorithm outperforms the selected algorithms in terms of blocking rate and also the amount of required resources for achieving a very low (i.e., 5 x 10-6 ) blocking rate under similar assumptions. In addition we show that accounting for QoT estimation inaccuracy changes the performance of the proposed IA-RWA substantially, and hence that the QoT estimator inaccuracy is an important design parameter in transparent optical networking.

A New Kind of Dynamic RWA Algorithm with QoS and Link Protection Under the Constraint of Wavelength Continuity

A new kind of dynamic RWA algorithm with QoS and link protection mechanism under the constraint of wavelength continuity is presented. Using a peculiar link protection method, a protection routing is established with unique links and working routing for every service request. Additionally, the wavelength information is taken into account to make the entire network load balanced with respect to routing choice. It is known that when the network is trouble-free, load balance is needed, and when there are some links destroyed in the network, a protection mechanism is needed. This new algorithm includes these two mechanisms while also adopting a kind of QoS guaranteed mechanism. This allows for a better network performance even under the situation that some links were destroyed and includes a higher quality of service guarantee and a lower rate of service blocking. The simulation results show that this algorithm can significantly improve the rate of service blocking and guarantee the quality of service to meet expectations.

A Novel Offline Physical Layer Impairments Aware RWA Algorithm With Dedicated Path Protection Consideration

Physical layer impairments accumulate as light propagates through a lightpath in the transparent optical networks. Therefore, it is possible to provision a lightpath, while its quality of transmission (QoT) does not meet the required threshold. Considering the physical layer impairments in the network planning phase gives rise to a set of offline Impairments Aware Routing and Wavelength Assignment (IA-RWA) algorithms. There are very few offline IA-RWA algorithms that consider dedicated path protection demands. In this work we propose a novel offline IA-RWA algorithm, called Rahyab and perform a comparative performance evaluation study, which considers two enhanced algorithms from the literature. Simulation results indicates that demand pre-processing, diverse routing, and adaptive wavelength assignment are the main reasons of lower blocking rate of Rahyab algorithm compared to the selected algorithms.

Experimental Translucent-Oriented Routing for Dynamic Lightpath Provisioning in GMPLS-Enabled Wavelength Switched Optical Networks

In the evolution from opaque networks, using 3R regenerators and OEO conversions for every wavelength channel, towards transparent networks, relying on end-to-end all-optical connections, translucent networks is considered as an intermediate step. A translucent network is a cost-efficient infrastructure between opaque and transparent networks, that aims at attaining an adequate trade-off between network construction cost (i.e., due to the high cost of 3R regenerators) and the service provisioning performance (i.e., end-to-end optical signal quality). This article addresses the dynamic provisioning of connections within a GMPLS-enabled translucent wavelength switched optical network with sparse 3R regenerators. To this end, translucent-oriented GMPLS protocol extensions are proposed to, on the one hand, disseminate required per node regenerator availability and OSNR-related link and node attributes and, on the other hand, allocate regenerator resources when setting up connections. An on-line OSNR-based impairment-aware RWA algorithm is devised to compute routes aiming at satisfying two constraints: the wavelength continuity constraint and the end-to-end optical signal quality. If either constraint cannot be satisfied, available regenerators along the route are used. To the best of our knowledge, the novelty and progress of this work is that, for the first time, both the proposed translucent GMPLS protocol enhancements and the performance of the RWA algorithm are combined within an experimental control plane network scenario (CTTC's ADRENALINE testbed). This allows validating and evaluating the feasibility of the described translucent GMPLS routing strategy when being potentially deployed into real WSON networks. Several configurations with numbers of 3R regenerators and wavelength channels per link, are experimentally evaluated and compared mainly in terms of the connection blocking probability. Although concrete details about the measured average setup delay are also discussed.

Constrained minimum lightpath affinity routing in multi-layer optical transport networks

In this paper, a new traffic engineering-capable routing and wavelength assignment scheme is proposed to efficiently handle LSP and lightpath setup requests with different QoS requirements on modern multi-layer (fully optical core and time-division multiplexed edge) transport networks. The objectives of the proposed algorithm are to minimize the rejection probability by maximizing the network load balancing and efficiently handling the grooming of several LSPs on the same lightpath while respecting the constraints of the optical node architecture and considering both traffic engineering and QoS requirements. The proposed solution consists of a two-stage RWA algorithm: each time a new request arrives, an on-line dynamic grooming scheme finds a set of feasible lightpaths which fulfill the QoS and traffic engineering requirements; then, the best feasible lightpath is selected, aiming to keep the network unbalancing and blocking probability as low as possible in the medium and long term, according to a novel global path affinity minimization concept. Extensive simulation experiments have been performed in which our on-line dynamic RWA algorithm demonstrated significant performances. Thanks to its optimal network resource usage and to its reasonable computational space and time complexity, the algorithm can be very attractive for the next-generation optical wavelength-switched networks.

A Minimum Cut Interference-based Integrated RWA Algorithm for Multi-constrained Optical Transport Networks

Advances in optical technologies have enabled the deployment of wavelength division-multiplexed (WDM) transmission systems capable of providing huge amounts of bandwidth across long distances. In this scenario, dynamic routing for direct provisioning of optical paths at the WDM layer becomes a challenging problem. Any distributed algorithm for routing dynamic traffic demands on optical transport infrastructures should be simple, flexible, efficient and scalable. The contribution of this paper is a novel integrated routing and grooming scheme for setting-up bandwidth guaranteed paths on hybrid wavelength and label switched networks. Our proposal exploits and refines the minimum interference routing idea according to an improved and re-optimized resource and traffic-aware approach, where critical links are detected and weighted according to a low complexity all-pairs minimum cut strategy that substantially reduce the overall number of calculations and hence the computational cost. The valuable results achieved in the comparison against other well-known reference techniques clearly demonstrate that our algorithm is very time-efficient while performing better in terms of blocking probability.

A dynamic hop count shifting RWA algorithm for wavelength routed optical networks

In this article, we find that the limiting hop count in a lightpath impacts on the performance of optical networks. Based on this observation, we propose a dynamic hop count shifting (DYHOS) algorithm that limits the hop count of lightpaths dynamically, depending on the traffic load. The proposed algorithm searches an available route, while minimizing the waste of network resources and limiting excessive traffic on the network. Hence, the proposed algorithm increases the network throughput and reduces the blocking probability. Comparing with shortest path routing and adaptive path routing algorithms, we show the performance of the proposed algorithm has the lowest blocking probability influenced by the hop count of lightpaths for a given routing algorithm.

A novel dynamic RWA algorithm with intelligent granularity regulation in multi-granular all-optical networks

With the great advances of DWDM technology, optical cross-connects have to deal with much more wavelengths. Accordingly, the size of optical cross-connects become larger and larger; also the management cost is much higher. To simplify the architecture of cross-connects for low-complexity maintenance, waveband switching (WBS) in conjunction with several optical cross-connect architectures have been proposed and attracted much attention recently. The main concept of WBS is to group multiple wavelengths into a single waveband and what it concerns includes cross-connect cost and port count reduction. In this paper, we investigate the dynamic RWA problem (MG_DRWA) in WBS networks comprising of all-optical switches based on a cost-effective multi-granular optical cross-connect (MG-OXC) architecture. With this reconfigurable architecture, an optical cross-connect can switch at either fiber level, waveband level, or wavelength level according to its configuration. In order to effectively accommodate dynamic traffic demand, we propose a new MG_DRWA algorithm. Numerical results reveal that the proposed algorithm can achieve significantly better blocking performance as compared to a previously proposed algorithm named MILB under various traffic loads.

Dynamic Fuzzy Controlled RWA Algorithm for IP/GMPLS over WDM Networks

This paper proposes a dynamic RWA scheme using fuzzy logic control on IP/GMPLS over WDM networks to achieve the best quality of network transmission. The proposed algorithm dynamically allocates network resources and reserves partial bandwidth based on the current network status, which includes the request bandwidth, average utilization for each wavelength and its coefficient of variance (C.V.) of data traffic, to determine whether the connection can be set up. Five fuzzy sets for request bandwidth, average rate and C.V. of data traffic are used to divide the variable space: very large (LP), large (SP), normal (ZE), small (SN), and very small (LN). Setting the fuzzy limit is a key part in the proposed algorithm. The simulation of scenarios in this paper has two steps. In the first step, the adaptive fuzzy limits are evaluated based on average transmission cost pertaining to ten network statuses. The second step is to compare the proposed algorithm with periodic measurement of traffic (PMT) in ATM networks in six network situations to show that the proposed FC-RWA algorithm can provide better network transmission.

Dynamic routing and wavelength assignment with optical bypass using ring embeddings

We consider routing and wavelength assignment in ring, torus, and tree topologies with the twin objectives of minimizing wavelength usage and maximizing optical bypass. The P -port dynamic traffic assumption is used, which allows each node to send and receive at most P calls. For rings we show that ⌈ P N / 4 ⌉ wavelengths are necessary and sufficient, and provide a four-hub ring architecture that requires only half of these wavelengths to be locally processed. We extend this approach to develop RWA and bypass algorithms for both tori and trees by embedding virtual rings within these topologies and applying the ring algorithms. For an R × C torus, we embed R + C rings onto the torus and provide an approach to RWA and banding based on solving disjoint RWA/banding problems for each ring. Our RWA algorithm is more wavelength efficient than any currently known algorithm and uses the minimum number of wavelengths for R ≥ 2 C . Our subsequent banding algorithm allows half of these wavelengths to bypass all but 4 R hub nodes. Finally, we give a RWA for trees that embeds a single virtual ring and uses the ring to obtain a RWA that requires no more than ⌈ P N / 2 ⌉ total wavelengths; this figure is shown to be optimal for balanced binary trees. A banding algorithm follows that allows half these wavelengths to bypass all non-hub nodes.

Connection Management Protocols for Dynamic Lightpath Provisioning in Future WDM Networks

This paper investigates and compares the performance of two GMPLS-based distributed control and management protocols for dynamic lightpath provisioning in future IP networks. The first protocol is a global information-based link state approach that consists of both an integrated RWA algorithm and a signaling algorithm. Two triggering mechanisms for the LSAs update procedures are considered; one is periodic-based and the other is threshold-based. The second protocol is a local-information based fixed alternate link routing approach where the signaling protocol is closely integrated with the RWA protocols.

Investigation of dynamic resource allocation based on transmission performance analysis and service classification in wavelength-division-multiplexing optical networks

In wavelength-routed optical networks, the transmission performance of the optical lightpaths available may not always satisfy the service requirements due to the quality degradation of signals induced by crosstalk, polarized mode dispersion (PMD), nonlinear effects, etc. Based on the integrated consideration of signal transmission impairments and service classification, a novel model on dynamic resource allocation in optical networks is presented in this paper. The model classifies the service requirements with different priorities and provides differentiated QoS in the optical domain. By adopting a multi-path RWA algorithm, called DMC-OVWP, the lightpath candidates are found out for each connection request of the services. Afterwards, by analyzing the transmission qualities of the lightpath candidates, an appropriate lightpath matched the request priority are picked out and set up.