Double-link Failures Research Articles

An improved shared-path protection algorithm for double-link failures in meshed WDM optical networks

In this paper, we investigate survivability in wavelength division multiplexing (WDM) mesh networks and propose a new algorithm called improved shared-path protection (ISPP) to completely tolerate the double-link failures. Compared with previous algorithms for protecting double-link failures, i.e., shared-path protection (SPP) and shared-link protection (SLP), the advantage of ISPP is to allow primary paths and backup paths to share the mixed wavelength-links based on the proposed new rules in which some primary wavelength-links can be changed to mixed wavelength-links, which can be shared by primary paths and backup paths. In addition, some mixed wavelength-links also can be shared by different backup paths for saving resources. Simulation results show that ISPP algorithm performs better in resource utilization ratio and blocking probability than conventional SPP and SLP algorithms.

Achieving Resource-Efficient Survivable Provisioning in Service Differentiated WDM Mesh Networks

A resource-efficient provisioning framework (RPF) is proposed in this paper for optical networks providing dedicated path protection (DPP) and shared path protection (SPP) services. The framework reduces resource consumption by considering spare capacity reservation of DPP and SPP cooperatively while provides 100% survivability guarantee and maintains the recovery time for both protection types against the predominant single link failures. To tackle the service provisioning problem under the framework, an integer linear programming (ILP) formulation is presented to find the optimal routing solution for a given set of traffic demands. The objective is to minimize total capacities consumed by working and backup paths of all demands. Then, heuristics are developed for on-line routing under dynamic change of traffic. Numerical results show that compared with traditional provisioning framework (TPF), the RPF has the following advantages: (1) Over 10% capacity savings are achieved for static service provisioning; (2) blocking probability of both protection types is greatly reduced; (3) lower resource over build is achieved; and (4) average backup-path hop distance of shared-path-protected flows is reduced. Finally, network survivability in face of double link failures is discussed under the framework.

Reducing vulnerability of shared-path protection subject to double-link failures in WDM mesh networks

Shared-path protection (SPP) is a capacity- efficient mechanism to provide 100% single-link failure protection in WDM mesh networks. After the first link failure, however, if reconfiguration is unavailable, a second link failure may lead to tremendous service interruption. Vulnerability of a link is the percentage of links that are vulnerable to the arbitrary second link failure after the link failed and network vulnerability is defined as the average vulnerability of links in the network. In this article, we present three policies that can reduce network vulnerability by reducing backup sharing in shared-path protection. The first policy tries to restrict the times of sharing a wavelength-link by connections. The second policy tries to avoid backup sharing on highly vulnerable links. The third policy tries to avoid backup sharing on highly vulnerable wavelength-links. Algorithms to implement these policies based on a similar framework are presented. Numerical results suggest that there is a trade-off between capacity efficiency and network vulnerability in all the three policies. The third policy can deliver a better performance in terms of blocking probability and network vulnerability.

Surviving double-link failures for near optimal heuristic routing in protected optical networks

The survivability for double-link failures in WDM optical network has been studied in recent years. In previous algorithm, to survive the double-link failures each connection request will be assigned to one primary path and two link-disjoint backup paths. However, the previous algorithm is the so-called simple algorithm which may lead to low resources utilization and high blocking probability. In this paper, we propose a new heuristic algorithm called routing with optimal solution (ROS) to protect the double-link failures. Differing from the previous algorithm, ROS can obtain near optimal solution by recomputing the primary path and two backup paths based on the rerouting policy for each connection request. Simulation results show that ROS can significantly outperform the previous algorithm.

Heuristic of differentiated path-shared protection for dual failures in restorable optical networks

In wavelength-division-multiplexing optical networks, the fiber links may share some common physical resources (e.g., cables, conduits), and the consequence is that they have a correlated link failure probability (CLFP), which means that the probability that link l will fail depends on whether link f has failed. Based on CLFP, we propose a new heuristic survivable algorithm, called differentiated path-shared protection (DPSP), to protect against double-link failures in WDM optical networks. In DPSP, each connection request can be assigned one working path and additional backup paths according to the differentiated reliability requirements of users. Compared to previous work, DPSP can obtain better performances in resource utilization ratio and blocking probability.

Effective survivable routing algorithm with sharing of spare resources and fast failure recovery in wavelength division multiplexing mesh networks

This paper investigates the dynamic survivable routing problem and proposes an effective path-based protection algorithm, called the dynamic joint routing approach (DJRA), to completely protect against double-link failures in meshed wavelength division multiplexing optical networks. In DJRA, each connection is assigned a primary path and two link-disjoint backup paths to tolerate the simultaneous failures of two arbitrary fiber links. In order to improve the algorithm performance, we consider three key issues: (1) sharing spare backup resources, (2) failure recovery time, and (3) trap-path avoidance. Therefore, compared to previous algorithms, DJRA obtains better performance and is also able to yield flexible trade-off solutions.

On Finding Feasible Solutions With Shared Backup Resources for Surviving Double-Link Failures in Path-Protected WDM Mesh Networks

In this paper, we investigate the problem of dynamic survivable routing in wavelength-division-multiplexing optical networks and propose a new path-protection algorithm called Enhanced Shared Backup Paths Protection (ESBPP) to provide the complete survivability for double-link failures. In order to improve the resource-utilization ratio, we present the new rule of sharing backup resources that can yield better resource-utilization ratio than previous methods. In order to overcome the problem of trap paths, we develop a new routing method to find the feasible solution with three link-disjoint paths for each connection request. Compared to previous algorithms for double-link failures, ESBPP can obtain higher resource-utilization ratio and lower blocking probability

Hybrid survivable configuration for optical wavelength-division-multiplexing mesh networks

In this study we propose a new heuristic approach called the hybrid survivable configuration (HSC) to provide differentiated service for optical wavelength-division-multiplexing (WDM) networks subject to double-link failures. Compared with previous approaches, HSC not only can obtain higher survivability but also can save significant resources. The simulation results are shown to be promising.

A novel backup multiplexing scheme for surviving double-link failures in mesh optical networks without wavelength conversion capability

We consider the problem of recovery from any double-link failure by exploiting shared path protection in wavelength-division multiplexing (WDM) mesh networks. We for the first time discover the phenomenon of sharing contradiction, which results in the violation of 100% recovery guarantee. To completely eliminate the sharing contradiction, we introduce the so-called preference policy, which implies that one of two backup paths (BPs) for each connection is given priority over the other to recover the failed active path (AP). Based on this policy, we propose a backup-multiplexing scheme with 100% recovery guarantee. Further, we transform the problem of minimizing the total number of wavelength-links under the wavelength continuity constraint while recovering from any dual-link failure to integer linear programming (ILP) formulations. Additionally, we investigate three preference policies, i.e., the first backup path preference policy (FBPPP), the second backup path preference policy (SBPPP), and the optimal preference policy (OPP). The numerical results show that our proposed backup multiplexing scheme can reduce about 30% wavelength-link consumption, compared to dedicated protection. Also, the results show that the policy, which specifies that the shorter one of two backup paths is preferred, generally outperforms the policy, which specifies that the longer one of two backup paths is preferred. Furthermore, the results show that OPP has a better performance when two BPs for each connection are more comparable in their lengths.

Path-based protection in WDM mesh networks subject to double-link failures

This letter studies the protection problem in WDM mesh networks and proposes a new scheme called improved path-based shared protection (IPSP) to tolerate double-link failures. Differing from previous path-based shared protection (PSP), IPSP allows some primary and backup paths to share resources. Simulation results show that IPSP outperforms PSP.

Semi-Dynamic Protection Path Configuration for Hybrid Optical Cross-Connect Networks

In this paper, a semi-dynamic protection path configuration method is proposed for WDM optical networks. In the method, the protection path is established by connecting several sub-lightpaths from the source node to the destination node of the original working lightpath, as opposed to conventional path restoration method where a single protection lightpath between the source-destination pair performs restoration. The proposed method provides enhanced flexibility in protection path configuration and relieves the cost of spare capacity reservation. This paper also studies the effects of wavelength conversion capability of intermediate optical cross-connect nodes on protection path routing and spare capacity utilization. In terms of spare capacity utilization, the proposed method shows substantial reduction of spare capacity overhead compared with dedicated path restoration in all optical networks without wavelength conversion, and shows similar capacity efficiency compared with shared path restoration in opaque networks with full wavelength conversion capability. In terms of robustness, the proposed method shows nearly the same restoration ratio for double-link failure as that of dynamic restoration method.

Dynamic survivable algorithm for meshed WDM optical networks

In this paper, we propose a novel heuristic survivable algorithm called dynamic path-shared protection ( DPSP) to completely protect the double-link failures in meshed Wavelength-division-multiplexing ( WDM) optical networks. In order to improve the algorithm performance, we focus on considering two key issues that are load balancing and resource-sharing degree when computing the working and backup paths. We also investigate the trap situations and present a solution method, because the trap situations may lead to high blocking probability ( BP). Simulations results show that, DPSP can provide complete protection for the double-link failures; with respect to the previous work, DPSP not only can effectively avoid the trap situations but also is able to obtain higher resource utilization ratio and lower BP.

Improving signaling recovery in shared mesh optical networks

Current restoration signaling is a two-phase messaging procedure between the sender and the receiver and depends heavily on the message propagation delays during the recovery process and the cross-connect switching times. Offset time (OT) based restoration was proposed in [C. Assi, Y. Ye, S. Dixit, M. Ali. Control and management protocols for survivable optical mesh networks, IEEE Journal of Lightware Technology, November 2003.] to address the impact of these parameters and upper bound (OT-UB) expressions were derived. However, our closer investigation showed that as the network conditions change (e.g. increasing the number of wave-length channels per link) the benefits this restoration paradigm offer rapidly diminish, thereby rendering the argument of avoiding conventional restoration signaling inappropriate. In this paper, we propose a more accurate model to estimate the OT of each failed connection using a time-driven scheduling procedure. We also study the applicability of the proposed recovery protocol under double link failures assumption and we propose extensions to the protocol. We evaluate our proposal through simulation experiments and we show that substantial restoration gain can be achieved under varying network conditions.

Capacity Optimization for Surviving Double-Link Failures in Mesh-Restorable Optical Networks

Most research to date in survivable optical network design and operation, focused on the failure of a single component such as a link or a node. A double-link failure model in which any two links in the network may fail in an arbitrary order was proposed recently in literature [1]. Three loop-back methods of recovering from double-link failures were also presented. The basic idea behind these methods is to pre-compute two backup paths for each link on the primary paths and reserve resources on these paths. Compared to protection methods for single-link failure model, the protection methods for double-link failure model require much more spare capacity. Reserving dedicated resources on every backup path at the time of establishing primary path itself would consume excessive resources. Moreover, it may not be possible to allocate dedicated resources on each of two backup paths around each link, due to the wavelength continuous constraint. In M. Sridharan et al., [2,3] we captured the various operational phases in survivable WDM networks as a single integer programming based (ILP) optimization problem. In this work, we extend our optimization framework to include double-link failures. We use the double-link failure recovery methods available in literature, employ backup multiplexing schemes to optimize capacity utilization, and provide 100% protection guarantee for double-link failure recovery. We develop rules to identify scenarios when capacity sharing among interacting demand sets is possible. Our results indicate that for the double-link failure recovery methods, the shared-link protection scheme provides 10–15% savings in capacity utilization over the dedicated link protection scheme which reserves dedicated capacity on two backup paths for each link. We provide a way of adapting the heuristic based double-link failure recovery methods into a mathematical framework, and use techniques to improve wavelength utilization for optimal capacity usage.

Loopback Recovery From Double-Link Failures in Optical Mesh Networks

Network survivability is a crucial requirement in high-speed optical networks. Typical approaches of providing survivability have considered the failure of a single component such as a link or a node. We motivate the need for considering double-link failures and present three loopback methods for handling such failures. In the first two methods, two edge-disjoint backup paths are computed for each link for rerouting traffic when a pair of links fails. These methods require the identification of the failed links before recovery can be completed. The third method requires the precomputation of a single backup path and does not require link identification before recovery. An algorithm that precomputes backup paths for links in order to tolerate double-link failures is then presented. Numerical results comparing the performance of our algorithm with other approaches suggest that it is possible to achieve almost 100% recovery from double-link failures with a moderate increase in backup capacity. A remarkable feature of our approach is that it is possible to trade off capacity for restorability by choosing a subset of double-link failures and designing backup paths using our algorithm for only those failure scenarios.

An adaptive survivability admission control algorithm using backup path for high‐speed networks

AbstractIn this paper, we propose an adaptive survivability admission control algorithm using a backup path for high‐speed networks. For each call request, the proposed algorithm selects a combination of working path and backup path. Two BP selection methods, min‐cost and min‐expectation, are suggested. Computational experiments indicate that the proposed algorithm significantly reduces the consumption of backup capacity while still maintaining 100% survivability upon a single link failure and near 80% survivability upon double link failures. Copyright © 2003 John Wiley & Sons, Ltd.

Fast restoring gigabit wireless networks using a directional mesh architecture

Fourth Generation (4G) wireless networking may involve gigabit per second transmission based on a mesh network architecture. These networks may use Extremely High frequency or optical bands. The network is formed in an ad hoc manner. For this directional mesh network, we present a new restoration algorithm for broadband wireless optical networks. A special restoration strategy, called local recovery for local failure is applied in the proposed algorithm. Specifically, each node initializes the recovery process independently of other nodes in the network when the failed link is local to the node. This algorithm is a hybrid restoration scheme, consisting of a route pre-planning phase and a real-time rerouting phase. Transient link/node failure, lasting only a short duration is typical in wireless communications and specially handled in our algorithm. We explore the response times of the proposed restoration algorithm. Simulation results over typical network structures show that we could achieve a full recovery of single-link failure, nearly 100% recovery of single-node failure, as well as around 99.5% recovery of double-link failure.

Loopback recovery from neighboring double-link failures in WDM mesh networks

Traditional survivable network design assumes that at any time at most a single link or node fails. In optical networks, a single point of failure may lead to the failure of multiple links. In this paper, we consider the design of an optical network that can survive the failures of any two neighboring links. We present a loopback recovery method that requires the computation of backup paths for each link. An optimal algorithm for computing the backup paths is presented. Numerical results comparing the performance of our algorithm with other loopback approaches indicate that a slight increase in capacity can achieve 100% protection under this failure model.