Survivable 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.

Hybrid scheme for fault tolerant survivable WDM optical networks: An analytical approach with wavelength conversion

Dynamic lightpath protection in survivable WDM networks requires finding a pair of diverse routes (i.e., a primary route and a backup route that are link-disjoint) that form a cycle upon the arrival of a new connection request. This paper presents a hybrid adaptive survivability algorithm that combines the positive effects of restoration and protection. The overall goal of the proposed approach is to improve the restoration efficiency by providing tradeoffs between proactive protection and dynamic restoration. Experimental results simulated by ns-2 network simulator and analytical results for wavelength conversion case using MATLAB 7.3 are compared. In both the case hybrid scheme achieves significantly lower blocking probability, higher throughput, higher utilization and lower restoration than the conventional dynamic survivable techniques. The results obtained by approximate analytical model are almost identical with that of ns-2 simulated results.

Delay tolerance aware queueing and scheduling for differentiated services in dynamic survivable WDM networks

Set-up delay tolerance is an important metric that can be used in user-controlled and bandwidth intensive applications such as IPTV, backup storage, and grid computing. It is defined by customer and stated in service level agreement (SLA). Therefore, service differentiation based on the delay tolerance and holding time provides great opportunity for service providers to maximize their profit. The service classes with high delay tolerance could have been serviced with some delay. However, they are traditionally provisioned without tolerating any delay. In this study, we use the set-up delay tolerance more efficiently. We intentionally insert these service classes into a queue to save optical resources for future requests. Moreover, in order to increase the acceptance rate of the waiting connections, we develop a strategy rescheduling the queue after each departure event and chooses the best group of the waiting connections to provision. Different algorithms, Dif-SC-2-3 and Dif-SC-3-G, are presented in this paper based on these approaches. For a typical wavelength convertible US nationwide and Pan-European network (USNET and EON), our approach results in significant decrease in overall blocking probability (BP), while reducing the BP of the service classes with stringent delay tolerance as well. For example, around 100 Erlangs, Dif-SC-3-G algorithm provides a BP reduction of up to 72% and 75% in USNET and EON, respectively. In addition, the proposed algorithms improve the fairness. Around 100 Erlangs, Jain׳s fairness indexes for Dif-SC-2-3 are the best values which are 97% and 96% in USNET and EON, respectively.

On DRC-covering of λ-fold complete graphs

In this article, we will study the DRC-cycle covering problems of λ-fold complete graphs which was motivated by the design in survivable WDM networks. As a consequence, we give optimal solutions for cycles or directed cycles.

Light Path Optimization Implementation for Survivable Routing and Wavelength Assignment in Optical Networks

In this paper, establishing a light path setup in WDM network done by implementing an ant-based mechanism Ant Colony Optimization (ACO) algorithm used for providing survivable routing in WDM network. The major problem in survivable routing WDM network is routing wavelength and assignment (RWA) problem, It sets up light path by routing and assigning a wavelength to each connection such that no light path use the same wavelength on same link .Our study aims to develop an routing and optimize the light path setup for survivable routing based upon the bit transmission to which supports data transfer supports to run continuously thus it can provide dynamic path. By adopting a new routing table structure and keeping a number of mobile agents in the network to cooperatively explore the network states and continuously update the routing tables, our new ant algorithm can efficiently support the ants' foraging tasks of route selection and wavelength assignment in WDM networks. Each path in the network is assigned by feasibility value. This feasibility value is calculated by considering the metrics such as bandwidth availability, path length and number of free wavelengths. When an ant is launched in the network by its node, it moves towards random destination to gather information such as bandwidth availability, path length and free wavelengths in that path. The value of path load is dynamically updated by the mobile agents in the load table. Using NS-2 simulation we show that the proposed ant based routing achieves better channel utilization and throughput with reduced delay, when compared with the normal routing. Optimization of light path performance is measured by varying the CBR traffic sending rate and flows.

Fast and Efficient Network Protection Method Using Path Pre-Cross-Connected Trails

This paper investigates design methods of protection schemes in survivable WDM networks using the path protection p-trail in order to provide better capacity efficiency by eliminating the rigidness of the protection structure of the well-accepted protection scheme, the failure independent path protection (FIPP) pre-configured protection cycle (p-cycle). The flexibility in the protection structure yields lower cost in terms of spare capacity allocation while maintaining the high speed of protection switching. We develop two design approaches, the fully pre-cross-connected path protection trail (fpp-trail) and the partially pre-cross-connected path protection trail (ppp-trail), based on the degree of pre-cross-connectivity of the protection structure. In order to obtain optimally designed trails, we develop an optimization model based on a large-scale optimization technique, namely, column generation. Numerical results show that fpp-trails significantly improve the spare capacity efficiency compared to the FIPP p-cycle, and ppp-trails strike a balance between capacity redundancy and recovery delay. We observe that ppp-trails can achieve as low capacity redundancy as shared backup path protection (SBPP), while the recovery delay is kept lower than in SBPP and slightly higher than FIPP p-cycles by using selective signaling through a control plane that is aware of the location of the cross-connects that are not pre-configured in advance.

Stability of FIPP $p$-Cycles Under Dynamic Traffic in WDM Networks

Application opportunities associated with video, voice, and data triple-play result in a dramatic demand increase in metro transport networks, with traffic patterns becoming increasingly dynamic and difficult to predict. This is driving the need of core networks with a high degree of flexibility and multigranularities to carry traffic. We propose to investigate the question of what this means in terms of dynamic protection provisioning. In other words, we want to study how stable are the protection structures under dynamic traffic, i.e., how much and how often they need to be updated in a dynamic survivable WDM network. While most studies on the stability of protection structures have been conducted on p-cycles and link shared protection, we propose to investigate here the stability of failure-independent path-protecting (FIPP) p-cycles under dynamic traffic. For doing so, we design and develop an original scalable mathematical model that we solve using large-scale optimization tools. Numerical results show that FIPP p-cycles are remarkably stable under the evaluation of the number of required optical bypass reconfigurations under dynamic traffic.

Migrating from static to dynamic survivable WDM networks: the capacity-availability trade-off

The benefit of migrating from fault-tolerant static WDM networks to survivable dynamic WDM networks is evaluated in terms of the trade-off between the additional network capacity (number of wavelengths) required to provide fault tolerance capability and the availability obtained by doing so.For the static WDM network case, wavelength requirements were obtained using a near-to-optimal dimensioning heuristic procedure, considering shared protection. For the dynamic WDM network case, wavelength requirements to guarantee a blocking probability threshold were evaluated using simulation-based techniques, for shared protection and restoration survivability mechanisms.Results show that, for every additional wavelength in the network, the availability gain of restored dynamic WDM networks is higher than that obtained using static or dynamic protected networks. We expect these results will help network operators in the decision making of migration processes.

Differentiated Quality-of-Recovery in Survivable Optical Mesh Networks Using $p$-Structures

This paper investigates design methods of protection schemes in survivable WDM networks that use preconfigured protection structures ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$p$</tex></formula> -structures) in order to provide different quality-of-recovery (QoR) classes within 100% resilient single-link protection schemes. QoR differentiation is a practical and effective approach in order to strike different balances among protection cost, recovery delay, and management complexity. Based on the degree of pre-cross connectivity of the protection structures, we develop three design approaches of shared protection capacity schemes based on the following: 1) fully pre-cross-connected <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$p$</tex></formula> -structures ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$fp$</tex></formula> -structures); 2) partially pre-cross-connected <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$p$</tex></formula> -structures ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$pp$</tex></formula> -structures); and 3) dynamically reconfigured <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$p$</tex> </formula> -structures ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$dp$</tex> </formula> -structures). In order to identify the optimal combinations of protection structures to meet the requirements of the three QoR classes, we use a column generation (CG) model that we solve using large-scale optimization techniques. Our CG decomposition approach is based on the separation processes of the design and selection of the protection structures. In the design process of the protection structures, the shape and protection capability of each <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$p$</tex></formula> -structure is decided dynamically during the selection process depending on the network topology and the targeted QoR parameters. Extensive experiments are carried out on several data instances with different design constraints in order to measure the protection capacity cost and the recovery delay for the three QoR classes.

An efficient resources allocation strategy for survivable WDM network under static lightpath demand

We present an optimized heuristic strategy for enhancing the utilization of network resources in survivable WDM networks under static lightpath demand (SLD). The primary as well as backup connection establishment is efficiently managed in the proposed strategy. For the establishment of primary connections, the requests are arranged in ascending order of the path lengths. If, for a connection request more than one shortest path/route is available in the network, then the route with the minimum wavelength index is selected. This results in uniform distribution of load among the links and avoids congestion. To enhance the backup lightpath establishment and increase restorability, a single wavelength of each link over the entire network is reserved in advance for setting up the path disjoint backup lightpaths. The effectiveness of the proposed strategy has been evaluated by undertaking extensive simulation experiments and the performance compared with respect to existing strategies of shared path protection (SPP) and hybrid connection approach (HCA). The network topologies of MESH, NATIONAL, and ARPANET have been used for the simulation. The results demonstrate that among all the strategies, the proposed strategy establishes maximum number of connections, avoids congestion, and uses the minimum network capacity (wavelength links).

The backup reprovisioning problem of NEPCs on survivable WDM networks

Protection techniques for optical networks mainly rely on pre-allocated backup bandwidth, which may not be able to provide full protection guarantee when multiple failures occur in a network. After recovering from the previous failure, if failure occurs again, unprotected or vulnerable lightpaths cannot be recovered. In this paper, the minimal backup reprovisioning (MBR) problem is studied, in which, the node-encircling protecting cycles (NEPCs) scheme is considered for single node-failure on WDM networks. The NEPC Recovery Algorithm is proposed to recover the protecting capabilities of the NEPC. Simulation results show that the performance of the proposed method is better than that of the traditional one.

Guaranteed Protection in Survivable WDM Mesh Networks – New ILP Formulations for Link Protection and Path Protection

In this paper we propose new simple integer linear programs (ILPs) formulations for minimizing capacity (in wavelength link) utilization in survivable WDM network. The study examines the performance of shared based protection schemes, such as path protection scheme and link protection scheme under single fiber failure. The numerical results obtained show a reduction in capacity utilization using random traffic compared to the reported ILP formulation. We also present the results using Poisson’s traffic to identify the frequently used links for the widely used NSF network. The proposed work not only reduces the wavelength consumption in different traffic scenarios but also efficient in terms of simulation time. In this paper we propose new simple integer linear programs (ILPs) formulations for minimizing capacity (in wavelength link) utilization in survivable WDM network. The study examines the performance of shared based protection schemes, such as path protection scheme and link protection scheme under single fiber failure. The numerical results obtained show a reduction in capacity utilization using random traffic compared to the reported ILP formulation. We also present the results using Poisson’s traffic to identify the frequently used links for the widely used NSF network. The proposed work not only reduces the wavelength consumption in different traffic scenarios but also efficient in terms of simulation time.

The backup reprovisioning problem of FIPP p-cycles for node failure on survivable WDM networks

Protection techniques for optical networks mainly rely on pre-allocated backup bandwidth, which may not be able to provide full protection guarantee when multiple failures occur in a network. After recovering from the previous failure, if failure occurs again, unprotected or vulnerable lightpaths cannot be recovered. In this paper, the minimal backup reprovisioning (MBR) problem is studied, in which the failure-independent path protecting p-cycles (FIPP p-cycles) scheme is considered for single-node failure on WDM networks. After recovering the affected lightpaths from a node failure, the goal of the MBR is to re-arrange the protecting and available resources such that working paths can be protected against next node failure if possible. An algorithm is designed to recover the protecting capabilities of the FIPP p-cycles, unless there is no sufficient network resource. The simulation results of the proposed method are also given.

Near optimal routing and capacity management for PWCE-based survivable WDM networks

Protected Working Capacity Envelope (PWCE) has been proposed to simplify resource management and traffic control for survivable WDM networks. In a PWCE-based network, part of the link capacity is reserved for accommodating working routes, and the remaining capacity is reserved for backup routes. The shortest path routing is applied in PWCE-based networks. An arrival call is accepted only when each link along the shortest path has a free working channel. Such a working path routing scheme greatly simplifies the call admission control process for dynamic traffic, and it is especially suitable for implementation in a distributed manner among network nodes. In this article, we investigate two protection strategies: Bundle Protection (BP) and Individual Protection (IDP). In BP, only one backup path can be used to protect a failure component, whereas multiple backup paths can be used in IDP. We formulate four mixed integer non-linear programming (MINLP) problems using BP and IDP strategies for single link and single node failure protection. Each model is designed to determine link metrics for shortest working path routing, working and backup channel assignments, and backup path planning. Our objective is to minimize call-blocking probability on the bottleneck link. Since these models are highly non-linear and non-convex, it is difficult to obtain exact global optimal solutions. We propose a Simulated Annealing-based Heuristic (SAH) algorithm to obtain near optimal solutions. This SAH adopts the concepts of simulated annealing as well as the bi-section technique to minimize call-blocking probabilities. To evaluate the performance, we made simulation comparisons between SAH and the unity link weight assignment scheme. The results indicate that SAH can greatly reduce call-blocking probabilities on benchmark and the randomly generated networks.

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.

A new approach for designing fault-tolerant WDM networks

In recent years, path protection has emerged as a widely accepted technique for designing survivable WDM networks. This approach is attractive, since it is able to provide bandwidth guarantees in the presence of link failures. However, it requires allocating resources for backup lightpaths, which remain idle under normal fault-free conditions. In this paper, we introduce a new approach for designing fault-tolerant WDM networks, based on the concept of survivable routing. Survivable routing of a logical topology ensures that the lightpaths are routed in such a way that a single link failure does not disconnect the network. When a topology is generated using our approach, it is guaranteed to have a survivable routing. We further ensure that the logical topology is able to handle the entire traffic demand after any single link failure. We first present an ILP that optimally designs a survivable logical topology, and then propose a heuristic for larger networks. Experimental results demonstrate that this new approach is able to provide guaranteed bandwidth, and is much more efficient in terms of resource utilization, compared to both dedicated and shared path protection.

New results for path-based shared protection and link-based Hamiltonian cycle protection in survivable WDM networks

In this paper, we study the path-based shared protection (PBSP) and the link-based Hamiltonian cycle protection (LBHCP) schemes for tolerating single-link failures in survivable wavelength-division-multiplexing networks. Although previous work indicated that PBSP can perform better than link-based shared protection including the case of LBHCP, from theoretical analysis and simulation results in this paper, we can clearly see that this indication of previous work is not suitable for LBHCP since it can have a better resource utilization ratio and a faster recovery time than PBSP. Therefore, the new result of this paper is a modification for the previous inaccurate idea and it also can well guide future work of researchers.

Resource provisioning for survivable WDM networks under a sliding scheduled traffic model

Resource allocation in WDM networks, under both the static and dynamic traffic models have been widely investigated. However, in recent years there has been a growing number of applications with periodic bandwidth demands. Resources for such applications can be scheduled in advance, leading to a more efficient utilization of available network capacity. The setup and teardown times of the scheduled demands may be fixed, or may be allowed to slide within a larger window. A number of optimal integer linear program (ILP) solutions for the first problem (fixed setup/teardown times) have been presented in the literature. In this paper we present two new ILP formulations for the more general sliding scheduled traffic model, where the setup and teardown times may vary within a specified range. We first consider wavelength convertible networks and then extend our model to networks without wavelength conversion. Our ILP formulations jointly optimize the problem of scheduling the demands (in time) and allocating resources for the scheduled lightpaths. The fixed window model can be treated as a special case of our formulations. Our formulations are able to generate optimal solutions for practical sized networks. For larger networks, we have proposed a fast two-step optimization process. The first step schedules the demands optimally in time, so that the amount of overlap is minimized. The second step uses a connection holding time aware heuristic to perform routing and wavelength assignment for the scheduled demands.