Routing And Wavelength Assignment Scheme 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.

A routing and wavelength assignment scheme considering full optical carrier replication in multi-carrier-distributed optical mesh networks with wavelength reuse

This paper proposes a routing and wavelength assignment (RWA) scheme that considers full optical carrier replication to minimize the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. Unlike the conventional wavelength division multiplexing networks where each node contains multiple laser diodes, the WRMD networks use a light source, called the multi-carrier light source, to ease the difficulty of controlling many light source devices. The optical carrier replication at any node of optical carrier or any end node of lightpath, called full optical carrier replication, improves the performance of the conventional schemes, which do not consider full optical carrier replication. This paper first formulates the RWA problem considering full optical carrier replication as an integer linear programming problem that minimizes the number of required wavelengths to satisfy the given lightpath setup requests. A heuristic RWA scheme is then proposed to solve the RWA problem in practical times. Simulation results show that our proposed heuristic RWA scheme for the WRMD network achieves a near-optimum number of wavelengths. In addition, it is able to reduce the number of required wavelengths for lightpath establishment, compared to the conventional scheme.

Manycast, Anycast, and Replica Placement in Optical Inter-Datacenter Networks

The expanding adoption of cloud-based services in recent years puts stringent requirements on datacenters (DCs) and their interconnection networks. Optical inter-datacenter networks represent the only viable option for satisfying the huge bandwidth required to replicate and update content for cloud-based services across geographically dispersed datacenters. In addition to content replication and synchronization, optical inter-datacenter networks must also support communication between datacenters and end-users. The resulting new traffic patterns and the enormous traffic volumes call for new capacityefficient approaches for inter-datacenter network designs that incorporate both transport and datacenter resource planning. This paper introduces an integrated approach to optimally place content replicas across DCs by concurrently solving the routing and wavelength assignment (RWA) problem for both inter-DC content replication and synchronization traffic following the manycast routing paradigm, and end-user-driven user-to-DC communication following the anycast routing paradigm, with the objective to reduce the overall network capacity usage. To attain this goal, the manycast, anycast, and replica placement (MARP) problem is formulated as an integer linear program to find optimal solutions for smaller problem instances. Due to the problem complexity, a scalable and efficient heuristic algorithm is developed to solve larger network scenarios. Simulation results demonstrate that the proposed integrated MARP strategy can significantly reduce the network capacity usage when compared to the benchmarking replica placement and RWA schemes aimed at minimizing the resources consumed by either of the two types of traffic independently.

Design and Analysis of Stimulated Raman Scattering-Aware Algorithm in RWA

Abstract A stimulated Raman scattering (SRS)-aware routing and wavelength assignment (RWA) scheme, called assign minimum interference and shortest algorithm, is proposed to minimize the effect of SRS in network. The design parameter, the number of interference of routes in the proposed algorithm is investigated to analyze its capabilities of influence the network performance. The various setting of the parameter is tested in 15-nodes Mesh and 14-nodes National Science Foundation networks for analysis in order to provide useful guidelines for designing effective SRS-aware RWA scheme. The ultimate objective is to define the necessary and sufficient rules that must be followed in the proposed algorithm by identifying the necessary RWA parameters in order to minimize the effect of SRS in optical networks. The result shows that the smaller the number of interference of routes, the lower the blocking probability in the mentioned topologies.

A routing and wavelength assignment scheme supporting multiple light-source nodes in multi-carrier-distributed optical mesh networks with wavelength reuse

This paper proposes a routing and wavelength assignment (RWA) scheme that supports multiple light-source nodes to minimize the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. These networks use a light source, called the multi-carrier light source (MCLS), to ease the difficulty of controlling many light source devices. Moreover, they are able to reuse optical carriers for improving the effectiveness of wavelength usage. Since the WRMD network suffers constraints different from those of the conventional wavelength division multiplexing (WDM) network, an RWA scheme for the WRMD network with a single light source was recently developed. To use the resources of large-scale networks efficiently, there may be a need to have more than one MCLS node. In this paper, we first formulate the RWA problem as the integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths to satisfy the given lightpath setup requests. A heuristic RWA scheme is then introduced to solve the RWA problem in practical times. Simulation results show that the proposed heuristic RWA scheme for the WRMD network achieves a near-optimum number of wavelengths. In addition, optimizing MCLS node location is shown to reduce the number of required wavelengths for lightpath establishment.

TRANSMISSION WINDOW PARTITION MECHANISM IN A FOUR-WAVE MIXING BASED WDM/DWDM NETWORK

This research work proposes an efficient four-wave mixing (FWM) based routing and wavelength assignment (RWA) scheme for the improvement of connection blocking probability in WDM/DWDM networks. However, the traditional RWA schemes are less efficient for the better quality of transmission, and the proposed RWA scheme partitions the entire fiber transmission window into N number of bands and assigns wavelength randomly from one of the band based on connection length. Finally, the analytical result proves that the mechanism reduces the FWM effect significantly in terms of connection blocking probability with higher partition, lower FWM effect and better performance.

Performance of a routing and wavelength assignment scheme for an optical‐carrier‐reusable ring network

This study investigates a heuristic routing and wavelength assignment (RWA) scheme for an optical-carrier-reusable ring network. This network has two unique features. First, only one light source, called the multi-carrier light source, is required which eases the difficulty of controlling many light source devices. Second, optical carriers are reused in order to improve the efficiency of wavelength usage. Given the target of wavelength-resource-efficient channel establishment, performance of the heuristic RWA scheme is evaluated. To realise efficient wavelength usage, the authors formulate the RWA problem as an integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths for given requests. With the ILP approach, the calculation process is not tractable in practical time. The heuristic RWA scheme introduced in this study solves the RWA problem. This scheme consists of two algorithms. Channel routes are obtained by the routing algorithm, and the wavelength assignment algorithm is then performed to assign a wavelength to each route. Moreover, two candidates, considering the shortest path and considering the avoidance of wavelength conversion, for the routing algorithm are examined. Numerical results show that the first candidate is more suitable in terms of reducing the number of required wavelengths than the second candidate.

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.

A routing and wavelength assignment scheme in multi-carrier-distributed optical mesh networks with wavelength reuse

This paper proposes a routing and wavelength assignment (RWA) scheme that minimizes the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. These networks have two unique features. First, only one light source, called the multi-carrier light source (MCLS), is required, which eases the difficulty of controlling many light source devices. Second, optical carriers are reused to improve the efficiency of wavelength usage. Since there are differences between the WRMD network and the conventional network, an efficient RWA scheme for the WRMD network is needed for wavelength-resource-efficient lightpath establishment. To realize efficient wavelength usage, we first formulate the RWA problem as an integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths to satisfy the given requests. For large-scale networks, the ILP approach is not practical solution times. A heuristic RWA scheme is introduced in this paper to solve the RWA problem. Simulation results show that the proposed heuristic scheme with two carrier regenerations for the WRMD network approaches the near-optimum number of wavelengths. In addition, the optimum placement of the MCLS node is shown to reduce the number of required wavelengths for lightpath establishment, and achieve the optimum number of wavelengths.

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.

A proof of wavelength conversion not improving Lagrangian bounds of the sliding scheduled RWA problem

Extensive previous studies confirmed that wavelength conversion may only marginally improve the solutions to the static Routing and Wavelength Assignment (RWA) problem. This means that, for the static RWA problem, certain RWA schemes that do not use wavelength conversion can achieve a performance almost as good as the one from the best RWA scheme. Previous research work on sliding scheduled RWA problems, where a given set of lightpath demands are allowed to slide within their time windows, has also indicated in limited simulation results that the benefit of using wavelength conversion is marginal. However, the observation cannot be conclusive without the solid mathematical proof. We are thus motivated to investigate whether schedule sliding really requires wavelength conversion to achieve a better performance. In this paper, we prove that wavelength conversion does not improve the Lagrangian bound of the sliding scheduled RWA problem. In most test cases, this bound is very close to the best achieved objective function value. Our proof implies that, for those cases, the improvements achieved by making use of wavelength conversion are very marginal.

Review and Performance Analysis on Routing and Wavelength Assignment Approaches for Optical Networks

For the past several years, traffic especially, Internet traffic has been increased tremendously and this growth demands for a high-speed communication network such as optical network. Routing and Wavelength Assignment (RWA) is one of the key tasks for the optical network, due to its information transparency and wavelength reuse characteristics. In this paper, we discuss different conventional RWA approaches in the wavelength-routed optical networks and compare them with our proposed Priority-based RWA (PRWA) scheme under wavelength continuity constraint. The performance analysis of different conventional RWA approaches including our PRWA scheme is conducted in terms of blocking probability. Finally, we address a number of research issues that appear to us to be both important and challenging.

A Holistic Solution to the Bi-Link-Failure-Free RWA Problem for 2-D-Torus-Based WDM LANs

We provide a holistic routing and wavelength assignment (RWA) solution to a 2-D-torus-based fault-tolerance problem in which an arbitrary bidirectional link (bilink) failure is tolerated. First, we introduce an optimal working lightpath RWA (WRWA) scheme for an N <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\,\times\,$</tex> </formula> N torus. Then, by observing a uniform pattern by which WRWA arranges working lightpaths through a bilink, we propose a spare lightpath RWA (SRWA) scheme that provisions spare resources to accommodate all traffic originally carried on the bilink subject to failure. The proposed SRWA scheme is at a spare wavelength cost within 1/N of that for the working lightpaths. We show a factor-2 performance guarantee for the proposed SRWA scheme. Finally, we derive a polynomial-time resolvable connection reliability expression for the proposed bilink-failure-free scheme and numerical results show a clear evidence of fault-tolerance capacity improvement.

Dynamic Routing and Wavelength Assignment in Multifiber WDM Networks with Wavelength Conversion Capability

This paper proposes a dynamic routing and wavelength assignment (RWA) scheme in multifiber WDM networks with wavelength conversion capability. In multifiber WDM networks, each link consists of multiple fibers. Thus, multiple lightpaths with the same wavelength can be established in the same link as long as they use different fibers. In WDM networks with wavelength conversion, the network nodes have wavelength conversion capability which can convert one wavelength to another. In order to efficiently utilize multifiber and wavelength conversion capability, an appropriate RWA scheme is necessary. The proposed scheme provides RWA for multifiber WDM networks with sparse and full wavelength conversion capability. In the proposed scheme, a route and wavelengths are selected for each lightpath based on wavelength availability and location of nodes with wavelength conversion capability. Through simulation experiments, we show that the proposed scheme reduces the blocking probability of lightpath establishment efficiently.

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.

A new model for allocating resources to scheduled lightpath demands

Recent research has clearly established that holding-time-aware routing-and-wavelength-assignment (RWA) schemes lead to significant improvements in resource utilization for scheduled traffic. Two different models have been proposed for scheduled traffic in the literature – (i) the fixed window model, where the setup and the teardown times of the scheduled demands are known in advance and (ii) the sliding window model, where a demand can be allocated anytime within a larger time-window. In this paper, we introduce a new model, the segmented sliding window model, where a demand may be decomposed into two or more components and each component can be sent separately. We present an integer linear program (ILP) formulation for resource allocation under the proposed segmented sliding window model and show that both the fixed and the traditional sliding window models can be treated as a special case of our generalized segmented sliding window model. We consider networks both with and without wavelength converters, and include the option of path protection for each lightpath. For larger networks, we also present a heuristic algorithm for allocating resources. Finally, we show through simulations that our approach leads to significantly higher throughput, even compared to the recent holding-time-aware RWA schemes, which have already been shown to outperform holding-time-unaware models.

Routing and Wavelength Assignment Problem in PCE-Based Wavelength-Switched Optical Networks

As a key problem in wavelength-switched optical networks (WSONs), in which wavelengths are the most important resources, the routing and wavelength assignment (RWA) problem has been researched extensively. Due to the advantages of path computation in multilayer and multidomain networks, especially in multiconstraint scenarios, the path computation element (PCE) has been introduced into WSONs, which provides a better approach to the solution of the RWA problem in WSONs. This paper focuses on the RWA problem in PCE-based WSONs. A PCE-based routing framework and two PCE-based routing models are first designed, and then two distributed resource reservation schemes based on forward reservation protocol (FRP) and backward reservation protocol (BRP) are proposed and simulated in a PCE-based WSON. Finally, eight PCE-based RWA schemes are proposed in WSONs, the performances of which have been investigated and validated using the discrete event simulation tool OMNeT++. Numeric results show that the RWA (first-fit) scheme has the best performance in terms of blocking probability and average delay time.

On the use of adaptive weight functions in wavelength-continuous WDM multi-fiber networks under dynamic traffic

In this paper, we address the problem of efficient routing and wavelength assignment (RWA) in multi-fiber wavelength division multiplexing (WDM) networks without wavelength translation, under dynamic traffic. We couple Dijkstra's shortest path algorithm with a suitable weight function which chooses optical paths based both on wavelength availability and multi-fiber segments. We compare our approach with other RWA schemes both for regular and irregular WDM multi-fiber network topologies in terms of blocking probability and overall link utilization.

A Lagrangean Relaxation and Subgradient Framework for the Routing and Wavelength Assignment Problem in WDM Networks

Unlike traditional heuristics, we provide in this paper an optimization framework for the routing and wavelength assignment (RWA) problems with the objective of minimizing the rejection penalty of the connection demands in an all-optical wavelength-division-multiplexing (WDM) network. Our new link-based formulation takes the fairness issue and the limited wavelength conversion into consideration. The framework employs a decomposition approach to decide on the rejection/selection of the route and wavelength assignment for a semilightpath, by appropriately relaxing some of the constraints in the Lagrangean relaxation (LR) method. At the higher level, we update Lagrange multipliers iteratively with the subgradient method. At the lower level, we propose the modified minimum cost semilightpath (MMCSLP) algorithm to solve all the subproblems. A heuristic algorithm is also proposed to generate a feasible RWA scheme based on the solution to the dual problem. When compared with some latest methodology in the literature, we demonstrate that our framework can achieve better performance in terms of the computation time and the number of connection demands rejected. The much shorter computation time is due to the polynomial time complexity of our framework. In addition to achieving a very good (near-optimal) solution, the influence from the change of the number of converters is studied. Finally, we demonstrate that our framework produces fairer routing decisions by adjusting some design parameters in our framework.

Routing and Wavelength Assignment in All-Optical Networks with Multihop Connections

Summary In this paper, we study the blocking probability in all-optical wavelength-routed networks. The main problem in wavelength-routed networks is the routing and wavelength assignment (RWA) problem. Currently, many researchers are working on this problem and many algorithms have been proposed. However, most of the current studies consider single-optical-hop connections only. Because of the wavelength continuity constraint, using multi-optical-hop connections may reduce the blocking probability. In addition, because the access nodes are electronic devices, the number of connections that can be processed in each node simultaneously is not negligible in all-optical networks, which will strongly affect the network performance, especially when multihop approach is used. We consider these two issues in this paper and analytical models are proposed for both fixed routing and adaptive routing schemes. Numerical results show that our analytical model is accurate for both the two RWA schemes in most cases.