Double-link Failures Research Articles

Zero-cost upgrade to a multi-fiber network with partial lane-change capabilities

Growing capacity requirements are leading to the deployment of multiple fibers in each optical network link. Even though deploying state-of-the-art multi-fiber network architectures with stacked and independent fiber layers simplifies network design and control, spectrum can be used more efficiently if the optical-network nodes allow fiber layers to be interconnected, i.e., if the so-called lane change is enabled. Unfortunately, lane change in high-degree optical nodes requires wavelength selective switches (WSSs) with a high number of ports, which is prohibitively costly or even unfeasible with current WSS technology. Instead, lane change in low-degree optical nodes can be enabled at no extra cost, using WSS ports that are otherwise left empty. In this study, we describe our proposal for a multi-fiber network with partial lane-change capabilities and perform a simulative study to identify the advantages of this architecture, as well as discuss the emerging resource allocation challenges associated with it. We demonstrate that, by enabling lane change in degree-2 nodes, we can increase network throughput by 3% and restore 5%–8% more traffic in the case of single- and double-link failures at no additional equipment cost.

Double-link-failure-tolerant shared protection for fully coupled/half-split switchable point-to-multipoint coherent optical systems

Beyond 5G, the next-generation wireless communication standard requires an optical communication network with a more reliable point-to-multipoint system. A highly reliable, futuristic point-to-multipoint coherent optical system must update wavelength-division-multiplexing-based passive optical networks to a more disaster-resistant architecture that can switch between bypass and backup links. We propose, to our knowledge, a novel link-pair shared protection that can respond locally to double-link failures that result from a significant disaster. We validate the high availability of several network configurations, assuming a double-link disconnection, can be obtained irrespective of the transmission distance of the feeder fiber. We experimentally demonstrate link-pair shared protection with bidirectional wavelength pre-assignment for two of the four feeder fiber failures and validate a penalty of less than 2 dB for double-link failures. Furthermore, we prove that reconnection can be performed with a penalty of at most 2 dB in an experiment with shared protection with a single-link broadcast-and-select function that can manage partial double-link failures using a simple configuration.

Double-Link Failure Protection Using a Single p-Cycle

This paper investigates the double-link protection in optical networks using pre-configured cycles (p-cycles) protection. The objectives of this work are to efficiently use redundant resources while providing double-link protection and reducing the computational complexity of the optimization model in an optical network. To accomplish these, we propose a SinGle p-Cycle (SG) method, which requires one p-cycle to protect a link from double-link failures. We formulated the Integer Linear Program for SG and DouBle cycle (DB) method. Simulation results obtained for SG are compared with DB, Improved DouBle cycle, and Link Pair Method (LPM) based on spare capacity and computation time. The computational complexity of SG is reduced by an order for the number of cycles compared to other p-cycles-based double-link protection methods. We demonstrate a significant reduction in computation time and spare capacity for the SG method for the same working capacity of an optical network. The SG method also computes spare capacity for big networks such as Net4, cost239, and USA Long haul.

WITHDRAWN: Resource efficient recovery scheme for double link failures in elastic optical networks

Abstract In order to avoid, double link failure in the optical network, we proposed a rapid connection recovery scheme for the survivable double link in elastic optical network (EON). The elastic optical network provides very high and flexible bandwidth as per the user’s requirement. Larger network have more number of failure probability. To control such failure, our proposed strategy provides a alternate backup light path by using minimum resources. Our proposed recovery scheme (PRS) provide better results in terms of recovery time, bandwidth blocking probability (BBP), and bandwidth provisioning ratio, when compared with the existing shared path protection (SPP) and dedicated path protection (DPP) schemes. ARPANET and COST239 topologies are considered for simulation.

TRACK: An algorithm for fault-tolerant, dynamic and scalable 2D mesh network-on-chip routing reconfiguration

Network-on-chip (NoC) is a reliable and scalable on-chip interconnect solution particularly used for MPSoCs and CMPs. Increasing susceptibility of NoC to failures is becoming a new research concern. Failures in components such as on-chip link or router may disrupt the underlying routing function. Reconfiguration of routing function is required to sustain network connectivity while maintaining deadlock-freedom in event of failure(s). Existing approaches either use routing tables or meta-data or involve all network nodes for participation in the reconfiguration process. This paper proposes TRACK, an algorithm for fast and scalable routing reconfiguration. It uses logic-based routing instead of tables and identifies affected nodes (i.e., rows/columns of mesh network) by single and double-link failures. In the proposed algorithm, reconfiguration is needed only for the affected nodes and the remaining network can continue to work. TRACK outperforms the existing one and reduces latency up to 42% and improves throughput up to 22% for single and double-link failures in 8 × 8 2D mesh network-on-chip. By employing logic-based routing, hardware cost is also reduced, i.e., 30% in area and 29.5% in power overhead for a 16 × 16 mesh router.

Maximizing double-link failure recovery of over-dimensioned optical mesh networks

Double-link failure models, in which any two links in the network fail in an arbitrary order, are becoming critical in survivable optical network designs. Optical networks that are over-dimensioned and purposely preplanned for full protection against any single-link failure may not survive well in an event of a double-link failure. It is therefore important to understand how much impact a subsequent second link failure may have upon traffic recovery of both failed links. This paper primarily aims to investigate traffic recoverability when a double-link failure occurs. We propose several methods for improving traffic recovery without using additional backup capacities other than the existing backup resources available for single-link failure recovery. In each proposed method, integer linear programming formulation is derived to optimize the backup resource allocation. Numerical results on various network configurations have shed some light on how network operators can choose one of five alternative methods to better handle a double-link failure. From numerical results, Method 1 offers some improvement on the traffic recoverability of the second failed link without disturbing the recovered traffic of the first failed link. Method 2 reveals that the traffic recoverability of the first failed link can be improved if the backup routes of the unrecovered traffic of the first failed link can be reassigned. Method 3 is useful for maximizing the traffic recoverability of the first failed link. Method 4 further increases the recoverability of the second failed link while maintaining the same recoverability of the first failed link as Method 3. Finally, Method 5 accomplishes the maximum overall traffic recoverability.

Abacus turn model-based routing for NoC interconnects with switch or link failures

With the aggressive scaling of the VLSI technology, Networks-on-Chip (NoCs) are becoming more susceptible to faults. Therefore, designing reliable and efficient routing methods is of significant importance. Most of the existing fault-tolerant techniques rely on rerouting solutions which may degrade the network performance drastically not only by taking unnecessary longer paths, but also by creating hotspots around the faults. Moreover, such off-line techniques cannot adapt to the dynamic traffic distribution in the network. In this paper, a reconfigurable and deadlock-free routing method is proposed based on the Abacus Turn Model (AbTM) to tolerate single and double switch or link failures. The required resources are kept to a minimum by avoiding to use virtual channels and routing tables. The proposed method is able to dynamically adjust the availability of the healthy paths according to the location of failures and congestion in the network to minimize rerouting. Moreover, it can grant a high degree of adaptiveness to the packets. This efficiency makes the proposed method a powerful asset for reliable routing in NoCs. The experimental results demonstrate that an 8 × 8 mesh network remains 100% reliable against single faults, and 99.8% and 99.94% reliable against double switch and link failures, respectively.

Comprehensive design methodology for control and data planes in wavelength-routed optical networks

We propose a comprehensive design methodology for control and data planes of wavelength-routed optical networks (WRONs) employing mixed-line-rate (MLR) transmission for cost-effective resource provisioning. The proposed approach attempts to minimize the maximum lightpath capacity demand in Gbps (representing the measure of lightpath congestion) in network for a given traffic matrix by using a mix of a heuristic scheme and linear programming (LP). In the first step of the proposed three-step design, some lightpaths are set up on a set of judiciously selected fiber links (with point-to-point lightpaths between neighboring nodes), on a specific wavelength throughout the network, and an appropriate fraction of the same set of lightpaths is utilized for carrying control information, forming therefore the control plane (CP) of the WRON. The remaining bandwidth of these lightpaths is utilized to carry the data traffic along with all other designed lightpaths of the WRON using appropriate algorithm, forming the overall data plane (DP) of the WRON. In the second step, traffic routing is carried out through LP to minimize lightpath congestion in the network. In the third step, we utilize the results of LP to assign rates to lightpaths, such that the cost (considering only the transceiver cost) of the network is minimized. This design leads to congestion-aware MLR network with due consideration to cost-effectiveness without compromising the network restoration response against link failures. We carry out simulation studies employing possible CPs using both symmetric (CP topology being same as the physical topology) as well as asymmetric (using fewer fiber links than the symmetric case) topology. The results of our simulations indicate that the proposed design of CP with symmetric/asymmetric topology and in-band transmission with sub-lightpath capacity can bring down network congestion and cost with respect to symmetric out-of-band transmission (using fully reserved lightpaths for CP), without any perceptible sacrifice in respect of the network restoration time. Failure can occur either in CP or DP, or in both the planes. We investigate the effect of design of CP with symmetric/asymmetric topology on network restoration time for single- and double-link failures. We further present DP design methodology with hybrid restoration scheme, i.e., combination of dedicated (1:1) path protection and path restoration. We analyze the effect of symmetric CP topology and degree of protection on the congestion of the network. Some lightpaths, that support more traffic, are protected against failures, while the others are left for path restoration in the event of failures. As more lightpaths are protected, the congestion and power consumption of network increase. We provide an analysis of the factors that come into play while altering the degree of protection and observe how the choice for the degree of protection in DP can be arrived at using an appropriate design methodology.

Resilient routing implementation in 2D mesh NoC

With the rapid shrinking of technology and growing integration capacity, the probability of failures in Networks-on-Chip (NoCs) increases and thus, fault tolerance is essential. Moreover, the unpredictable locations of these failures may influence the regularity of the underlying topology, and a regular 2D mesh is likely to become irregular. Thus, for these failure-prone networks, a viable routing framework should comprise a topology-agnostic routing algorithm along with a cost-effective, scalable routing mechanism able to handle failures, irrespective of any particular failure patterns. Existing routing techniques designed to route irregular topologies efficiently lack flexibility (logic-based), scalability (table-based) or relaxed switch design (uLBDR-based). Designing an efficient routing implementation technique to address irregular topologies remains a pressing research problem. To address this, we present a fault resilient routing mechanism for irregular 2D meshes resulting from failures. To handle irregularities, it avoids using routing tables and employs a few fixed configuration bits per switch resulting in a scalable approach. Experiments demonstrate that the proposed approach is guaranteed to tolerate all locations of single and double-link failures and most multiple failures. Also, unlike uLBDR it is not restricted to any particular switching technique and does not replicate any extra messages. Along with fault tolerance, the proposed mechanism can achieve better network performance in fault-free cases. The proposed technique achieves graceful performance degradation during failure. Compared to uLBDR, our method has 14% less area requirements and 16% less overall power consumption.

OPTIMIZATION OF DISJOINTS FOR MINIMIZATION OF FAILURE IN WDM OPTICAL NETWORK

In an optical network, the fiber optic cable is used for communication between the nodes in a network by passing lights. The main problem in optical network is finding the link disjoints as well as optimal solution for the disjoints. To tolerate a single link failure in the network, the enhanced active path first algorithm is used which computes the re-routed back-up path. The multiple link failure in a network called fibre span disjoint path problem is solved using integer linear programming algorithm. The loop back recovery is used to provide pre-planned recovery of link or node failures in a network which allows dynamic choice of routes over pre-planned directions. Considering reliability in a mesh networks, the reliability algorithm helps to achieve the maximum reliability in two-path protection. It addresses the multiple disjoint failures that arise in a network and discusses the best solution between paths shared nodes or links. The unified algorithm is used to generate the optimal results with minimum cost for multiple link failures. The heuristic algorithm namely maximum arbitrary double-link protection algorithm helps to pre-compute the back-up path for double-link failures. In all the above approaches the shortest optimized path must be improved. To find the best shortest path, link-disjoint lightpath algorithm is designed to compute the disjoint occurred in a network and it also satisfies the wavelength continuity constraint in wavelength division multiplexing. A polynomial time algorithm Wavelength Division Multiplexing – Passive Optical Networking is used to compute the disjoint happen in the network. The overall time efficiency is analyzed and performance is evaluated through simulations.

Co-spanning tree restoration mechanism for metro Ethernet switched networks

Ethernet, a popular technology in IT industry, with high transmission rate, simple maintenance, and compatibility with different types of links was invented for local and small-scale computer networks. However, current spanning tree-based Ethernet protocols do not meet the requirements for metro Ethernet networks in terms of network resilience. One of the most important weaknesses is slow re-convergence time in the event of a link failure when a new spanning tree must be reconstructed to ensure the survivability of networks. In this paper, we propose a co-spanning tree restoration (CSTR) mechanism for metro Ethernet switched networks to handle the link failures. Upon failure of a link on the network, a distributed failure restoration protocol will be activated to reconstruct the damaged spanning tree using a $$co\text {-}tree$$co-tree link. We explain the details of the protocol, including advertisement tables and fundamental reconfiguration processes. In addition, we propose a simple and effective solution for a double link failure and develop an optional feature to control unnecessary topology changes. The simulated results of CSTR on different network topologies show its features of efficiency and quick recovery.

Survivable green IP over WDM networks against double-link failures

In this paper, we study the energy efficient problem of survivable IP over WDM networks. A novel “virtual link” energy model is presented. The energy model is abstracted from the power consumption value of commercial network devices. Based on the new two-layer energy-aware auxiliary graph, we propose the Energy-Efficient and Survivable Routing (E2SR) algorithm for IP over WDM networks against double-link failures. In contrast to prior green networking algorithms, the novelty of our proposed routing algorithm is mainly twofold: first, the energy-efficient virtual topology iterative mapping method; second, the energy-efficient spare resource sharing method. From the numerical results for two typical carrier networks, our proposed E2SR algorithm achieves obvious energy consumption reduction for IP over WDM networks when guaranteeing traffic survivability against double-link failures.

Hybrid Survivability Schemes Achieving High Connection Availability With a Reduced Amount of Backup Resources [Invited

Maximizing connection availability in wavelength division multiplexing (WDM) networks is critical because even small disruptions can cause huge data losses. However, there is a trade-off between the level of network survivability and the cost related to the backup resources to be provided. One-hundred percent survivability can be achieved by dedicated path protection (DPP) with multiple prereserved protection paths for each provisioned connection, i.e., DPP (1:N). Unfortunately, the blocking probability performance of DPP (1:N) is negatively affected by the large number of prereserved backup wavelengths standing by unutilized. On the other hand, path restoration (PR)-based solutions ensure good blocking performance at the expense of lower connection availability. The work in this paper aims at finding hybrid network survivability strategies that combine the benefits of both techniques (i.e., high availability with low blocking rate). More specifically, the paper focuses on a double link failure scenario and proposes two strategies. The first one couples DPP (1:1) with path restoration (referred to as DPP + PR) to minimize the number of dropped connections. The second scheme adds the concept of backup reprovisioning (BR), referred to as DPP + BR + PR, in order to further increase the connection availability achieved by DPP + PR. Integer linear programming models for the implementation of the proposed schemes are formulated. Extensive performance evaluation conducted in a path-computation-element-based WDM network scenario shows that DPP + BR + PR and DPP + PR can significantly lower the blocking probability value compared to DPP (1:2) without compromising too much in terms of connection availability.

Capacity planning providing 100 % survivability against double-link failures for WDM Networks

Survivability is always a key concern in WDM optical transport networks as failures may result in large amount of traffic disruption and significant degradation of network performance. In this paper, we investigate the capacity planning problem against double-link failures considering wavelength--continuity constraint. Our objective is to minimize the resource consumption when guaranteeing connection request 100 % survivability. We propose two efficient approaches: (1) the New Static Preplanned Path Protection (NSPPP); (2) the New Dynamic Rerouting (NDR). In NSPPP, we present a new backup resource sharing rule to compress the spare capacity. In NDR, only the working path of connection request is necessary to be given, and the rerouting path can be dynamically found on the network after double-link failures. Compared to previous algorithms, our proposed two capacity planning approaches can efficiently solve double-link failures problem of WDM networks, also obtain higher resource utilization ratio and lower network resource.

Design of Resilient Ethernet Ring Protection (ERP) Mesh Networks With Improved Service Availability

Ethernet Ring Protection (ERP) has recently emerged to provide protection switching for Ethernet ring topologies with sub-50 ms failover capabilities. ERP's promise to provide protection in mesh packet transport networks positions Ethernet as a prominent competitor to conventional SONET/SDH and as the technology of choice for carrier networks. Higher service availability, however, in ERP has been challenged by the issue of network partitioning and contention for shared capacity caused by concurrent failures. In this paper, we show that in a network designed to withstand single-link failure, the service availability, in the presence of double link failures, depends on the designed ERP scheme, i.e., the RPL placement as well as the selection of ring hierarchy. Therefore, we present a study for characterizing service outages and propose a design method which strikes a balance between capacity requirement and service availability (i.e., the number of service outages resulting from concurrent failures). We observe that through effective design, remarkable reduction in service outages is obtained at a modest increase in capacity deployment.

On Exploiting Sharable Resources With Resource Contention Resolution for Surviving Double-Link Failures in Optical Mesh Networks

As the size and the complexity of optical mesh networks grow, double-link failures become more probable. To protect against double-link failures, we generally have to provision more backup resources with respect to single-link failures. To improve the resource efficiency, it is important to reduce backup resources used for surviving double-link failures. In this paper, we investigate some representative sharing schemes and propose an enhanced resource sharing scheme with resource contention resolution for double-link failures in survivable optical mesh networks. By fully taking into account the temporal and spatial factors, our scheme can accommodate reasonable contention for sharing resources and minimize backup resources for reservation with 100% protection guarantee. Simulation results show that this enhanced resource sharing scheme can achieve satisfactory performance in terms of resource utilization ratio and blocking probability.

Loop-Free IP Fast Rerouting Considering Double-Link Failures

Loop-Free IP Fast Rerouting Considering Double-Link Failures

Ellipse-underlay protection algorithm to deal with regional demolishments in mesh optical networks

For the abundant bandwidth, a malfunction in optical networks causes a great deal of loss to traffic, and hence the survivability of optical networks must be considered. Two technologies, protection and restoration, are used in general, and the former is investigated in this paper. The existing protection strategies mainly cope with a single link failure or a double-link failure in an optical network and not consider what causes these failures. In this paper, we study the reasons which lead to the network malfunctions, and pose a new concept named regional demolishment. A protection algorithm named Ellipse-underlay algorithm is also proposed. We compare the performance of the Ellipse-underlay algorithm to the Node-disjoint algorithm. Simulation results show that the Ellipse-underlay algorithm is more effective to the survivability of traffic than the Node-disjoint algorithm.

Performance Evaluation of Impairment-Aware Routing Under Single- and Double-Link Failures

This work evaluates the performance of an impairment-aware routing (IAR) scheme in the presence of single- and dual-link failures. Network resilience is provided through a shared backup path protection scheme, enhanced with a reinforced sharing mechanism. The results indicate that the IAR scheme provides significantly lower connection blocking compared with traditional minimum-hop routing because physical impairments have a significant contribution to the overall network blocking probability. Dual-link failures are also considered, and the performance of a network designed to be resilient to single-link failures is evaluated. Simulation results show low connection loss rates due to dual failures that can be further improved using a restoration mechanism activated on the occurrence of dual failures.

Assuring K-coverage in the presence of mobility and wear-out failures in wireless sensor networks

Along with energy conservation, it has been a critical issue to maintain a desired degree of coverage in Wireless Sensor Networks (WSNs). In this paper, we consider more realistic WSN environments where the sensor nodes are moving around, which can disappear due to wear-out failures. By enhancing a variant of random waypoint model (Li et al., 2005), we propose Mobility Resilient Coverage Control (MRCC) to assure K-coverage in the presence of mobility. Our basic goals are (1) to elaborate the probability of breaking K-coverage with moving-in and moving-out probabilities and (2) to issue wake-up calls to sleeping sensors to meet user requirement of K-coverage even in the presence of mobility. Furthermore, to show the impact of wear-out failures on the coverage achieved, we adopt a lognormal distribution to depict the conditional probability of failures and observe the influence of reduced number of active nodes on coverage. Our experiments with Network Survivability – Double Link Failure show that MRCC achieves better coverage by 1.4% with 22% fewer active sensors than that of the existing Coverage Configuration Protocol (CCP). By taking reliability of nodes into account, the performance drop with respect to coverage is 3.7% (for coverage >1) while the reduction in the number of sensor nodes is 18.19% when compared with pure MRCC. Comparing CCP and MRCC with reliability, we observe a 3.4% reduction in coverage for the average probabilistic case and 5.78% for the individual probabilistic case, while achieving a 12.82% and 28.2% reduction in number of nodes, respectively.