Design Of WDM Networks Research Articles

Leveraging the Survivable All-Optical WDM Network Design With Network Coding Assignment

This letter investigates a novel use of network coding (NC) in 1 + 1 protection for transparent wavelength-division multiplexing networks by utilizing a cost-effective all-optical XOR encoder/decoder. In applying this scheme, we introduce a new problem, called routing, wavelength, and NC assignment, and formulate it as the integer linear programming model, aiming at maximizing the network throughput under constrained bandwidth capacity. We evaluate our proposal on the realistic topology, COST239, with all-to-one traffic setting. The numerical results on studied case show that the our NC-based approach could support up to 30% traffic more than the conventional 1 + 1 protection.

Resource efficient multicast traffic grooming in WDM mesh networks

In this paper, we have considered an optimal design and provisioning of WDM networks for the grooming of sub-wavelengths traffic requests. As higher layer electronic ports, such as transceivers and optical splitters are dominant cost factors of an optical network, it is essential to reduce their numbers of use while grooming the multicast traffic requests into high bandwidth light-trees. This paper provides an optimal cost design of WDM networks with multicast traffic grooming under static traffic demand. We develop a unified framework for the optimal provisioning of different practical scenarios of multicast traffic grooming in a static traffic scenario. In this study, we design an Integer linear Programming (ILP) formulation for multicast traffic grooming to minimize the cost associated with the higher layer electronic ports such as transceivers, splitters and wavelengths, and simultaneously maximize the bandwidth utilization of the network. We propose a heuristic algorithm called Efficient Light-Tree based Multicast Traffic Grooming (ELT-MTG) algorithm to achieve scalability in large size optical networks. Simulations are conducted on several standard well-known WDM mesh networks to study the design cost (based on number of transceivers, optical splitters and wavelengths) used in the networks. The result, thus obtained by comparison, helped us to conclude that the proposed approach ELT-MTG gives better performance than well-known existing logical-first sequential routing with single-hop grooming (LFSEQSH) and logical-first sequential routing with multi-hop grooming (LFSEQMH) algorithms in a static traffic environment.

Two-level iterated local search for WDM network design problem with traffic grooming

Two important problems arise in WDM network planning: network design to minimize the operation cost and traffic grooming to maximize the usage of the high capacity channels. In practice, however, these two problems are usually simultaneously tackled, denoted as the network design problem with traffic grooming (NDG). In this paper, a mathematical formulation of the NDG problem is first presented. Then, this paper proposes a new metaheuristic algorithm based on two-level iterated local search (TL-ILS) to solve the NDG problem, where a novel tree search based neighborhood construction and a fast evaluation method are proposed, which not only enhance the algorithm's search efficiency but also provide a new perspective in designing neighborhoods for problems with graph structures. Our algorithm is tested on a set of benchmarks generated according to real application scenarios. We also propose a strengthening formulation of the original problem and a method to obtain the lower bound of the NDG problem. Computational results in comparison with the commercial software CPLEX and the lower bounds show the effectiveness of the proposed algorithm.

Discrete-Bandwidth Nonblocking Networks

In this paper, we describe a framework for designing a discrete-bandwidth nonblocking network. The theoretical foundation of the framework combines theories from both networking and switching. While the conventional Clos theory must assume a particular topology, the new theory allows us to design a nonblocking network with an arbitrary topology. Thus it can be considered as a generalization of the Clos theory. In addition to the design of WDM or SONET networks, applications such as grid computing and supercomputing can also benefit from the results developed in the paper.

Optical Power Aware Quality Analysis for the Selection of Optimal OVPN Connection over WDM Network

Traditional optical networks such as synchronous optical network/synchronous digital hierarchy (SONET/SDH) have been perceived as high transmission rate networks without providing any QoS to different connection request. Recently, some attention has been given to coarse-grain QoS using differentiated optical services. Some designs for static VPN have been proposed in literature. However, little research work has been considered to provide dynamic VPN on optical networks. By applying the virtual private network concept to WDM, which is called as Optical Virtual Private Network (OVPN), we explore how to compute a fine-grained QoS for dynamic OVPN connection request based on system components such as connectors, splices, etc. An important problem in WDM network design is to construct an algorithm to determine the optimal OVPN Connection from a set of possible connections in a network topology, which can maximize the quality of service to the OVPN clients. By keeping that in mind, we proposed a method of optimal OVPN selection mechanism based on the traditional power budget analysis.

Design of WDM Networks With Multicast Traffic Grooming

With the growing popularity of multicast applications and the recognition of the potential of achievable efficiency gain of traffic grooming, we face the challenge of optimizing the design of WDM networks with multicast traffic grooming. As higher layer electronic ports become the dominant factor of the WDM network cost, it is critical to reduce their number when grooming multicast traffic into high bandwidth light-trees. This paper provides an optimal cost design of WDM networks with multicast traffic grooming. In particular, a light-tree based Integer Linear Programming (ILP) formulation is proposed to minimize the network cost associated with the number of higher layer electronic ports and the number of wavelengths used. Since solving the ILP formulation is time consuming for large networks, we propose a heuristic algorithm, called sub-light-tree saturated grooming (SLTSG), to achieve scalability. This algorithm tries to construct sub-light-trees which can be fully utilized. Simulations are conducted on several networks to compare the design cost and the required number of electronic ports and wavelengths. The results demonstrate significant benefits of using a light-tree based design over a design that only uses lightpaths.

Translucent network design from a CapEx/OpEx perspective

Translucent wdm network design has been widely investigated during the last 10 years. Translucent networks stand halfway between opaque and transparent networks improving the signal budget while reducing the network cost. On one hand, opaque networks provide satisfying quality from source to destination by the use of electrical reg regeneration (Re-amplifying, Re-shaping, and Re-timing) at each network node. In addition to their high cost inherent to numerous 3R regenerations, opaque networks are also constrained by the bit-rate dependence of electrical components. Transparent networks, on the other hand, do not include any electrical regeneration; therefore, the signal quality is degraded due to the accumulation of linear and non-linear effects along the signal's route. Translucent networks include electrical regeneration at some network nodes. Among the different possible strategies for translucent network design, sparse regeneration inserts regenerators whenever needed to help establish connection requests. In this context the objective of translucent network design is to judiciously choose the regeneration sites in order to guarantee a certain quality of transmission while minimizing the network cost. In this paper, we propose to solve the translucent network design problem by introducing a heuristic for routing, wavelength assignment, and regenerator placement. This heuristic, called COR2P (Cross-Optimization for RWA and Regenerator Placement) aims not only to minimize the number of required regenerators, but also to minimize the number of regeneration sites. In this perspective, we introduce an original cost function that contributes to the optimization of CapEx/OpEx expenditures in translucent network design. In fact, the CapEx-to-OpEx ratio strongly depends on the pricing and management strategy of the carrier. In this respect, COR2P is designed in a way that its parameters can be adjusted according to carriers' strategies. In order to discuss its different features, we compare COR2P performance with two other algorithms proposed in the literature for translucent network design.

Erratum to “Design and Provisioning of WDM Networks With Many-to-Many Traffic Grooming”

Erratum to “Design and Provisioning of WDM Networks With Many-to-Many Traffic Grooming”

Design and Provisioning of WDM Networks With Many-to-Many Traffic Grooming

A large number of network applications today allow several users to interact together using the many-to-many service mode. In many-to-many communication, also referred to as group communication, a session consists of a group of users (we refer to them as members), where each member transmits its traffic to all other members in the same group. In this paper, we address the problem of designing and provisioning of WDM networks to support many-to-many traffic grooming. Our objective is to minimize the overall network cost, which is dominated by the cost of higher layer electronic ports (i.e., transceivers) and the number of wavelengths used. Based on different WDM node architectures, we propose four different WDM networks for many-to-many traffic grooming. For each network, we analyze the many-to-many traffic grooming problem and provide an optimal as well as a heuristic solution. A comprehensive comparison between the four networks reveals that each of the networks is the most cost-effective choice for a certain range of traffic granularities.

Introduction to the Focus Issue on Next-Generation WDM-PON-Based Optical Access Networks

The five selected papers in this focus issue are written by leading researchers in the field. The issue is an excellent reference for scientists who would like to understand the issues and challenges associated with the design and operation of WDM networks and get the latest update on state-of-the-art technologies.

Design of survivable WDM networks using pre-configured protection structures with unrestricted shapes

We propose a novel protection approach for the design of link-protection schemes in survivable Wavelength Division Multiplexing mesh networks by merging the well-known p-cycle- and p-tree-protection structures. So doing, we aim at gathering the advantages of p-cycles in terms of protection capabilities, and of p-trees in terms of protection flexibilities (local re-routing, scalability) in a single protection scheme. As opposed to existing protection schemes based on protection structures with a pre-defined shape, the building blocks of the new scheme are protection structures with unrestricted shapes. Thus, they allow more flexibility in provisioning spare capacity, and provide higher capacity efficiency when compared to the shaped-protection schemes that have been proposed so far. In order to cope with the size of the solution space which includes all the possible protection structures, we propose an efficient and scalable optimization technique in large-scale systems named column generation (CG). In our CG-based optimization approach, the shape of a candidate protection structure is dynamically decided during the optimization process according to a link spare capacity budget. Experimental results on different network instances show that the protection plan resulting from the merging of p-cycle and p-tree structures is, on average, ~15% less capacity redundant and ~15% more reliable than the pure p-cycle one. It also requires, on average, ~30% less protection structures. In addition, those structures provide backup paths ~30% smaller than those of the p-cycle-based scheme.

On DRC covering — a survey

This paper surveys the cycle covering problem of a graphs motivated by the design of survivable WDM networks, where the requests are routed on sub-networks which are protected independently from each other. The problem is stated as follows. Find a cycle partition or a cycle covering satisfying disjoint routing constraint of the edges of logical graph with an associated routing over physical graph such that the number of cycles is minimized. We give the value or lower bound of the number of cycles in a DRC-covering.

On DRC-covering of K(n) t λ by cycles

This paper considers the cycle covering of complete multipartite graphs motivated by the design of survivable WDM networks, where the requests are routed on sub-networks which are protected independently from each other. The problem can be stated as follows: for a given graph G, find a cycle covering of the edge set of K (n) t ? , where V( Kt (n))=V(G), such that each cycle in the covering satisfies the disjoint routing constraint (DRC). Here we consider the case where G=Ctn, a ring of size tn and we want to minimize the number of cycles ? (nt, ?) in the covering. For the problem, we give the lower bound of ? (nt, ?), and obtain the optimal solutions when n is even or n is odd and both ? and t are even.

Dynamic Versus Static Wavelength-Routed Optical Networks

It is widely believed that dynamic operation of wavelength-routed optical networks will help overcome the inefficiencies of static allocation in terms of wavelength utilization. In this paper, this hypothesis is reviewed. The wavelength requirements of dynamic wavelength-routed optical networks are quantified and compared to static routing. To do so, new analytical and algorithmic lower bounds for the wavelength requirements of dynamic networks are proposed. They are used to evaluate the optimality of the already proposed algorithms whose wavelength requirements are quantified - by means of simulation- with and without the wavelength continuity constraint, as well as for uniform and nonuniform traffic demand. Results show that, without wavelength conversion capability, the benefit of dynamic wavelength-routed optical networks is not significant: lower wavelengths requirements than static networks are achieved only at low traffic loads (< 0.3 - 0.4). In wavelength convertible networks instead, dynamic operation leads to lower wavelength requirements than static operation over a wide traffic load range (< 0.7 - 0.8), making dynamic operation attractive in this type of network. Under nonuniform traffic it was found that dynamic operation achieves slightly higher wavelength savings than in the uniform traffic case. But the savings were not high enough as to impact on results of the uniform traffic case. These results can aid network operators in the design and optimization of optical WDM networks.

Fuzzy Optimization Models for the Design of WDM Networks

The wavelength-division multiplexing network design problem is considered in this paper. The literature is replete with prescriptive integer programming models for various versions of wavelength-division multiplexing network design problems, but in no case they consider the real situation of solving them taking into account their inherent vagueness. In this paper, this vagueness is assumed and handled by means of fuzzy sets based methodologies. In particular, two fuzzy integer linear programming models are proposed to be used as auxiliary models for solving the former problem. As an original way to effectively solve these models obtaining cost-effective network designs, we use three metaheuristic procedures that are compared among them.

Some studies on path protection in WDM networks

Path protection in WDM networks is one of the popular ways to design resilient WDM networks. Although complete ILP formulations for optimal design of WDM networks have been proposed in literature, the computational cost of actually solving such formulations make this approach impractical, even for moderate sized networks. This high computational cost arises mainly due to the large number of integer variables in the formulations, which increases the complexity exponentially. As a result, most practical solutions use heuristics, which do not provide any guarantees on the performance. In this article, we propose two novel ILP formulations, which drastically reduce the number of integer variables compared to existing ILPs. This leads to much more efficient formulations. We also present a simple heuristic that may be used for larger networks for which ILP formulations become computationally intractable.

WDM Network Design by ILP Models Based on Flow Aggregation

Planning and optimization of WDM networks has raised much interest among the research community in the last years. Integer linear programming (ILP) is the most used exact method to perform this task and many studies have been published concerning this issue. Unfortunately, many works have shown that, even for small networks, the ILP formulations can easily overwhelm the capabilities of today state-of-the-art computing facilities. So in this paper we focus our attention on ILP model computational efficiency in order to provide a more effective tool in view of direct planning or other benchmarking applications. Our formulation exploits flow aggregation and consists in a new ILP formulation that allows us to reach optimal solutions with less computational effort compared to other ILP approaches. This formulation applies to multifiber mesh networks with or without wavelength conversion. After presenting the formulation we discuss the results obtained in the optimization of case-study networks.

Minimization of the number of ADMs in SONET rings with maximum throughput with implications to the traffic grooming problem

SONET ADMs are dominant cost factors in WDM/SONET rings. Whereas most previous papers on the topic concentrated on the number of wavelengths assigned to a given set of lightpaths, recent papers argue that the number of ADMs is a more realistic cost measure. The minimization of this cost factor has been investigated in recent years, where single-hop and multi-hop communication models, with arbitrary traffic and uniform traffic loads have been investigated. As a first attempt to understand the trade-off between the number of wavelengths and the number of ADMs, we concentrate on the all-to-all, uniform traffic instance with multi-hop, splittable communication. We look for a solution which makes full use of the bandwidth and uses the minimum possible number of ADMs. We develop an architecture based on successive nested polygons and present a necessary and sufficient condition for a solution in this architecture to be feasible. This architecture leads to a solution using O ( W log W + N ) ADMs where W is the number of wavelengths used, and N is the number of nodes in the ring. This is a substantial improvement compared to N W ADMs for the basic architecture in [O. Gerstel, P. Lin, G. Sasaki, Combined wdm and sonet network design, in: INFOCOM’99, Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies, vol. 2, 1999, pp. 734–743], and optimal for W = O ( N / log N ) . We further improve this result to O ( W log W ¯ + N ) ADMs, where W ¯ = o ( W ) . This architecture constitutes a solution for the traffic grooming problem, which is the subject of many recent works.

On routing in large WDM networks

An important problem in WDM network design is to construct a logical topology and determine an optimal routing over that topology. Mixed Integer Linear Program (MILP) formulations to generate optimal solutions for this problem have been presented. Such formulations are computationally intractable, even for moderate sized networks. A standard approach is to decouple the problem of logical topology design and the problem of routing the traffic on this logical topology. Heuristics for finding the logical topology exist and a straight-forward linear program (LP), based on the node-arc formulation can be used to solve the routing problem over a given logical topology. We have found that such LP formulations become computationally infeasible for large networks. In this paper, we present a new formulation, based on the arc-chain representation, for optimally routing the specified traffic over a given logical topology to minimize the congestion of the network. We have used the revised simplex method incorporating an implicit column generation technique, and exploited the special Generalized Upper Bounding structure as well as the possibility of eta-factorization for efficiently updating the dual variables and finding the solution. Experimental results on a number of networks demonstrate the suitability of this approach.

Minimum cost dimensioning of ring optical networks

We consider the problem of traffic grooming of low-rate traffic circuits in WDM rings where circuits are associated with a set of heterogeneous granularities. While networks are no longer limited by transmission bandwidth, the key issue in WDM network design has evolved towards the processing capabilities of electronic switches, routers and multiplexers. Therefore, we focus here on traffic grooming with minimum interconnecting equipment cost. We first formulate the problem as an integer linear programming (ILP) or a mixed integer linear programming (MILP) problem depending on the design specifications: UPSR vs BLSR, fixed vs variable wavelength capacities, non-bifurcated vs bifurcated flows, wavelength continuity vs possible signal regeneration on a different wavelength. Considering the case study of the second SONET ring generation with MSPP like interconnection equipment, we define the cost by a function of the number of transport blades, taking into account that the number of MSPP transport blades makes up a significant portion of the overall network design cost. Using the CPLEX linear programming package, we next compare the optimal solutions of the ILP or MILP programs for different design assumptions, including the classical ring network design scheme with a single hub where the lightpaths directly connect the hub to all other nodes.