Protection and restoration algorithms for WDM optical networks

Currently, Wavelength Division Multiplexing (WDM) optical networks play a major role in supporting the outbreak in demand for high bandwidth networks driven by the Internet. It can be a catastrophe to millions of users if a single optical fiber is somehow cut off from the network, and there is no protection in the design of the logical topology for a restorative mechanism. Many protection and restoration algorithms are needed to prevent, reroute, and/or reconfigure the network from damages in such a situation. In the past few years, many works dealing with these issues have been reported. Those algorithms can be implemented in many ways with several different objective functions such as a minimization of protection path lengths, a minimization of restoration times, a maximization of restored bandwidths, etc. This thesis investigates, analyzes and compares the algorithms that are mainly aimed to guarantee or maximize the amount of remaining bandwidth still working over a damaged network. The parameters considered in this thesis are the routing computation and implementation mechanism, routing characteristics, recovering computation timing, network capacity assignment, and implementing layer. Performance analysis in terms of the restoration efficiency, the hop length, the percentage of bandwidth guaranteed, the network capacity utilization, and the blocking probability is conducted and evaluated

Resilient network dimensioning for optical grid/clouds using relocation

In this paper we address the problem of dimensioning infrastructure, comprising both network and server resources, for large-scale decentralized distributed systems such as grids or clouds. We will provide an overview of our work in this area, and in particular focus on how to design the resulting grid/cloud to be resilient against network link and/or server site failures. To this end, we will exploit relocation: under failure conditions, a request may be sent to an alternate destination than the one under failure-free conditions. We will provide a comprehensive overview of related work in this area, and focus in some detail on our own most recent work. The latter comprises a case study where traffic has a known origin, but we assume a degree of freedom as to where its end up being processed, which is typically the case for e. g., grid applications of the bag-of-tasks (BoT) type or for providing cloud services. In particular, we will provide in this paper a new integer linear programming (ILP) formulation to solve the resilient grid/cloud dimensioning problem using failure-dependent backup routes. Our algorithm will simultaneously decide on server and network capacity. We find that in the anycast routing problem we address, the benefit of using failure-dependent (FD) rerouting is limited compared to failure-independent (FID) backup routing. We confirm our earlier findings in terms of network capacity savings achieved by relocation compared to not exploiting relocation (order of 6-10% in the current case studies)

Logical topology design for IP rerouting: ASONs versus static OTNs

IP-based backbone networks are gradually moving to a network model consisting of high-speed routers that are flexibly interconnected by a mesh of light paths set up by an optical transport network that consists of wavelength division multiplexing (WDM) links and optical cross-connects. In such a model, the generalized MPLS protocol suite could provide the IP centric control plane component that will be used to deliver rapid and dynamic circuit provisioning of end-to-end optical light paths between the routers. This is called an automatic switched optical (transport) network (ASON). An ASON enables reconfiguration of the logical IP topology by setting up and tearing down light paths. This allows to up- or downgrade link capacities during a router failure to the capacities needed by the new routing of the affected traffic. Such survivability against (single) IP router failures is cost-effective, as capacity to the IP layer can be provided flexibly when necessary. We present and investigate a logical topology optimization problem that minimizes the total amount or cost of the needed resources (interfaces, wavelengths, WDM line-systems, amplifiers, etc.) in both the IP and the optical layer. A novel optimization aspect in this problem is the possibility, as a result of the ASON, to reuse the physical resources (like interface cards and WDM line-systems) over the different network states (the failure-free and all the router failure scenarios). We devised a simple optimization strategy to investigate the cost of the ASON approach and compare it with other schemes that survive single router failures

Survivable design in WDM mesh networks

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.

Survivable mesh-network design & optimization to support multiple QoP service classes

Every second, vast amounts of data are transferred over communication systems around the world, and as a result, the demands on optical infrastructures are extending beyond the traditional, ring-based architecture. The range of content and services available from the Internet is increasing, and network operations are constantly under pressure to expand their optical networks in order to keep pace with the ever increasing demand for higher speed and more reliable links

Analysis and algorithms for partial protection in mesh networks

This paper develops a mesh network protection scheme that guarantees a quantifiable minimum grade of service upon a failure within a network. The scheme guarantees that a fraction q of each demand remains after any single link failure. A linear program is developed to find the minimum-cost capacity allocation to meet both demand and protection requirements. For q ≤ 1/2, an exact algorithmic solution for the optimal routing and allocation is developed using multiple shortest paths. For q >; 1/2, a heuristic algorithm based on disjoint path routing is developed that performs, on average, within 1.4% of optimal, and runs four orders of magnitude faster than the minimum-cost solution achieved via the linear program. Moreover, the partial protection strategies developed achieve reductions of up to 82% over traditional full protection schemes.National Science Foundation (U.S.) (NSF grant CNS-0626781)National Science Foundation (U.S.) (NSF grant CNS-0830961)United States. Defense Threat Reduction Agency (grant HDTRA1-07-1-0004)United States. Defense Threat Reduction Agency (grant HDTRA-09-1-005)United States. Air Force (Air Force contract #FA8721-05-C-0002

Priority based dynamic lightpath allocation in WDM networks.

Internet development generates new bandwidth requirement every day. Optical networks employing WDM (wavelength division multiplexing) technology can provide high capacity, low error rate and low delay. They are considered to be future backbone networks. Since WDM networks usually operate in a high speed, network failure (such as fiber cut), even for a short term, can cause huge data lost. So design robust WDM network to survive faults is a crucial issue in WDM networks. This thesis introduces a new and efficient MILP (Mixed Integer Linear Programming) formulation to solve dynamic lightpath allocation problem in survivable WDM networks, using both shared and dedicated path protection. The formulation defines multiple levels of service to further improve resource utilization. Dijkstra\u27s shortest path algorithm is used to pre-compute up to 3 alternative routes between any node pair, so as to limit the lightpath routing problem within up to 3 routes instead of whole network-wide. This way can shorten the solution time of MILP formulation; make it acceptable for practical size network. Extensive experiments carried out on a number of networks show this new MILP formulation can improve performance and is feasible for real-life network. Source: Masters Abstracts International, Volume: 43-01, page: 0249. Adviser: Arunita Jaekel. Thesis (M.Sc.)--University of Windsor (Canada), 2004

Survivable network design of all-optical network.

Kwok-Shing Ho.Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.Includes bibliographical references (leaves 69-71).Abstracts in English and Chinese.List of Figures --- p.viList of Tables --- p.viiChapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Overview --- p.1Chapter 1.2 --- Thesis Objectives --- p.6Chapter 1.3 --- Outline of Thesis --- p.8Chapter Chapter 2 --- The Spare Capacity Planning Problem --- p.9Chapter 2.1 --- Mathematical Model of the Spare Capacity Planning Problem --- p.12Chapter 2.1.1 --- Variable Definitions --- p.12Chapter 2.1.2 --- Objective Function and Constraints --- p.15Chapter 2.1.3 --- Complexity --- p.17Chapter 2.2 --- Greedy Algorithm - Spare Capacity Allocation and Planning Estimator (SCAPE) --- p.19Chapter 2.2.1 --- Working Principle of SCAPE --- p.20Chapter 2.2.2 --- Implementation of SCAPE --- p.22Chapter 2.2.3 --- Improved SCAPE --- p.23Chapter 2.3 --- Experimental Results and Discussion --- p.27Chapter 2.3.1 --- Experimental Platform --- p.27Chapter 2.3.2 --- Experiment about Accuracy of SCAPE --- p.27Chapter 2.3.3 --- Experiment about Minimization of Network Spare Capacity --- p.30Chapter 2.3.4 --- Experiment about Minimization of Network Spare Cost --- p.35Chapter 2.4 --- Conclusions --- p.38Chapter Chapter 3 --- Survivable All-Optical Network Design Problem --- p.39Chapter 3.1 --- Mathematical Model of the Survivable Network Design Problem --- p.42Chapter 3.2 --- Optimization Algorithms for Survivable Network Design Problem --- p.44Chapter 3.2.1 --- Modified Drop Algorithm (MDA) --- p.45Chapter 3.2.1.1 --- Drop Algorithm Introduction --- p.45Chapter 3.2.1.2 --- Network Design with MDA --- p.45Chapter 3.2.2 --- Genetic Algorithm --- p.47Chapter 3.2.2.1 --- Genetic Algorithm Introduction --- p.47Chapter 3.2.2.2 --- Network Design with GA --- p.48Chapter 3.2.3 --- Complexity of MDA and GA --- p.51Chapter 3.3 --- Experimental Results and Discussion --- p.52Chapter 3.3.1 --- Experimental Platform --- p.52Chapter 3.3.2 --- Experiment about Accuracy of MDA and GA --- p.52Chapter 3.3.3 --- Experiment about Principle of Survivable Network Design --- p.55Chapter 3.3.4 --- Experiment about Performance of MDA and GA --- p.58Chapter 3.4 --- Conclusions --- p.62Chapter Chapter 4 --- Conclusions and Future Work --- p.63Appendix A The Interference Heuristic for the path restoration scheme --- p.66Bibliography --- p.69Publications --- p.7

Design and operation of mesh-restorable WDM networks

The explosive growth of Web-related services over the Internet is bringing millions of new users online, thus creating a growing demand for bandwidth. Wavelength Division Multiplexed (WDM) networks, employing wavelength routing has emerged as the dominant technology to satisfy this growing demand for bandwidth. As the amount of traffic carried is larger, any single failure can be catastrophic. Survivability becomes indispensable in such networks. Therefore, it is imperative to design networks that can quickly and efficiently recover from failures.;In this dissertation, we explore the design and operation of survivable optical networks. We study several survivability paradigms for surviving single link failures. A restoration model is developed based on a combination of these paradigms. We propose an optimal design and upgrade scheme for WDM backbone networks. We formulate an integer programming-based design problem to minimize the total facility cost. This framework provides a cost effective way of upgrading the network by identifying how much resources to budget at each stage of network evolution. This results in significant cost reductions for the network service provider.;As part of network operation, we capture multiple operational phases in survivable network operation as a single integer programming formulation. This common framework incorporates service disruption and includes a service differentiation model based on lightpath protection. However, the complexity of the optimization problem makes the formulation applicable only for network provisioning and o2ine reconfiguration. The direct use of such methods for online reconfiguration remains limited to small networks with few tens of wavelengths. We develop a heuristic algorithm based on LP relaxation technique for fast, near optimal, online reconfiguration. Since the ILP variables are relaxed, we provide a way to derive a feasible solution from the relaxed problem. Most of the current approaches assume centralized information. They do not scale well as they rely on per-flow information. This motivates the need for developing dynamic algorithms based on partial information. The partial information we use can be easily obtained from traffic engineering extensions to routing protocols. Finally, the performance of partial information routing algorithms is compared through simulation studies