359 research outputs found

    Optimal Algorithms for Near-Hitless Network Restoration via Diversity Coding

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    Diversity coding is a network restoration technique which offers near-hitless restoration, while other state-of-the art techniques are significantly slower. Furthermore, the extra spare capacity requirement of diversity coding is competitive with the others. Previously, we developed heuristic algorithms to employ diversity coding structures in networks with arbitrary topology. This paper presents two algorithms to solve the network design problems using diversity coding in an optimal manner. The first technique pre-provisions static traffic whereas the second technique carries out the dynamic provisioning of the traffic on-demand. In both cases, diversity coding results in smaller restoration time, simpler synchronization, and much reduced signaling complexity than the existing techniques in the literature. A Mixed Integer Programming (MIP) formulation and an algorithm based on Integer Linear Programming (ILP) are developed for pre-provisioning and dynamic provisioning, respectively. Simulation results indicate that diversity coding has significantly higher restoration speed than Shared Path Protection (SPP) and p-cycle techniques. It requires more extra capacity than the p-cycle technique and SPP. However, the increase in the total capacity is negligible compared to the increase in the restoration speed.Comment: An old version of this paper is submitted to IEEE Globecom 2012 conferenc

    Survivable design in WDM mesh networks

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    This dissertation addresses several important survivable design issues in WDM mesh networks;Shared backup path protection has been shown to be efficient in terms of capacity utilization, due to the sharing of backup capacity. However, sharing of backup capacity also complicates the restoration process, and leads to slow recovery. The p-cycle scheme is the most efficient ring-type protection method in terms of capacity utilization. Recently, the concept of pre-cross-connected protection was proposed to increase the recovery speed of shared path protection. We overview these protection methods. The recovery time of these schemes are compared analytically. We formulate integer programming optimization problems for three protection methods in static traffic scenario, considering wavelength continuity constraint;We develop a p-cycle based scheme to deal with dynamic traffic in WDM networks. We use a two-step approach. In first step, we find a set of p-cycles to cover the network and reserve enough capacity in p-cycles. In second step, we route the requests as they randomly arrive one by one. We propose two routing algorithms. Compared to the shared path protection, the p-cycle based design has the advantage of fast recovery, less control signaling, less dynamic state information to be maintained. To evaluate the blocking performance of proposed method, we compare it with shared backup path protection by extensive simulations;We propose a path-based protection method for two-link failures in mesh optical networks. We identify the scenarios where the backup paths can share their wavelengths without violating 100% restoration guarantee (backup multiplexing). We use integer linear programming to optimize the total capacity requirement for both dedicated- and shared-path protection schemes;The recently proposed light trail architecture offers a promising candidate for carrying IP centric traffic over optical networks. The survivable design is a critical part of the integral process of network design and operation. We propose and compare two protection schemes. The survivable light trail design problem using connection based protection model is solved using a two-step approach. (Abstract shortened by UMI.

    Survivability issues in WDM optical networks

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    WDM optical networks make it possible for the bandwidth of transport networks to reach a level on which any failures would cause tremendous data loss and affect a lot of users. Thus, survivability issues of WDM optical networks have attracted a lot of research work. Within the scope of this dissertation, two categories of problems are studied, one is survivable mapping from IP topology to WDM topology, the other is p-cycle protection schemes in WDM networks.;Survivable mapping problem can be described as routing IP links on the WDM topology such that the IP topology stays connected under any single link failure in the WDM topology. This problem has been proved to be NP-complete [1]. At first, this dissertation provides a heuristic algorithm to compute approximated solutions for input IP/WDM topologies as an approach to ease the hardness of it. Then, it examines the problem with a different view, to augment the IP topology so that a survivable mapping can be easily computed. This new perspective leads to an extended survivable mapping problem that is originally proposed and analyzed in this dissertation. In addition, this dissertation also presents some interesting open problems for the survivable mapping problem as future work.;Various protection schemes in WDM networks have been explored. This dissertation focuses on methods based on the p-cycle technology. p-Cycle protection inherits the merit of fast restoration from the link-based protection technology while yielding higher efficiency on spare capacity usage [2]. In this dissertation, we first propose an efficient heuristic algorithm that generates a small subset of candidate cycles that guarantee 100% restorability and help to achieve an efficient design. Then, we adapt p-cycle design to accommodate the protection of the failure of a shared risk link group (SRLG). At last, we discuss the problem of establishing survivable connections for dynamic traffic demands using flow p-cycle

    Survivability through pre-configured protection in optical mesh networks

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    Network survivability is a very important issue, especially in optical networks that carry huge amount of traffic. Network failures which may be caused by human errors, malfunctional systems and natural disaster (eg. Earthquakes and lightening storms), have occurred quite frequently and sometimes with unpredictable consequences. Survivability is defined as the ability of the network to maintain the continuity of service against failures of network components. Pre-configuration and dynamic restoration are two schemes for network survivability. For each scheme, survivability algorithms can be applied at either Optical Channel sublayer (Och) known as link-based. Or, Optical Multiplex Section sublayer (OMS) known as path-based. The efficiency of survivability algorithms can be assessed through such criteria as capacity efficiency, restoration time and quality service. Dynamic restoration is more efficient than pre-configuration in terms of capacity resource utilization, but restoration time is longer and 100% service recovery cannot be guaranteed because sufficient spare capacity may not be available at the time of failures. Similarly, path-based survivability offers a high performance scheme for utilizing capacity resource, but restoration time is longer than link based survivability

    Dynamic p-cycles selection in optical WDM Mesh networks

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    P-cycles have been recognized as a useful protection scheme in WDM mesh networks. This is a type of shared link protection that not only retains the mesh-like capacity efficiency, but also achieves the ring-like protection switching speed. However, finding the optimal set of p-cycles for protecting traffic demands is not a simple task and is an NP-hard problem. A general approach is to determine a set of candidate p-cycles and then determine optimal or near-optimal solutions by using integer linear programming (ILP) models or heuristics. In a dense mesh network, however, the number of candidate cycles is huge, and increases exponentially if the node number is increased. Thus, searching for a suitable set of efficient candidate cycles is crucial and imperative to balancing the computational time and the optimality of solutions. In this paper, we propose a dynamic P-cycles selection (DPS) algorithm that improves the efficiency of enumerating candidate p-cycles. The dynamic approach for cycle selection is based on the network state. In the DPS algorithm, all cycles are found and stored, then an efficient and sufficient set of p-cycles is extracted to achieve 100% working protection, minimize the spare capacity, and reduce time complexity
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