Energy Aware Scheduling and Routing of Periodic Lightpath Demands in Optical Grid Networks

AbstractOptical grid networks provide an ideal infrastructure to support large-scale data intensive applications and interconnection of data centers. The power consumption of communications equipment for such networks has been increasing steadily over the past decade and energy efficient routing schemes and traffic models can be utilized to reduce the energy consumption. In many applications it is possible to select the destination node from a set of possible destinations, which have the required computing/storage resources. This is known as anycasting. We propose a novel formulation that exploits knowledge of demand holding times and the flexibility of anycast routing to optimally schedule demands (in time) and route them in order to minimize overall network energy consumption. Our simulation results demonstrate that the proposed approach can lead to significant reductions in energy consumption, compared to traditional routing schemes

Virtual Topology Reconfiguration Issues in Evolution of WDM Optical Networks

We consider the reconfiguration problem in multi-fiber WDM optical networks. In a real-time network as the traffic evolves with time: the virtual topology may not remain optimal for the evolving traffic, leading to a degradation of network performance. However, adapting the virtual topology to the changing traffic may lead to service disruption. This optimization problem hence captures the trade-off between network performance and number of reconfigurations applied to the virtual topology. The above problem is solved through a Mixed Integer Linear Programming formulation with a multivariate objective function, that captures both these parameters. However the problem is NP-hard and such an approach is unable to solve large problem instances in a reasonable time. In this paper, we also propose a simulated annealing based heuristic algorithm for solving problems of higher complexity. We compare the performance and the computation time of the MILP model and the heuristic algorithm considering different tests instances. Our results indicate that simulated annealing obtains results within 5% of the optimal solution, thus making it a viable approach in large scale networks

Dynamic Routing with Partial Information in Mesh-Restorable Optical Networks

Changing trends in backbone transport networks towards dynamic path provisioning and evolving optical technologies have motivated the study of dynamic routing algorithms in the context of Multi Protocol Label Switching (MPLS) based networks. Several methods have been proposed for joint optimization of working and spare capacity in survivable optical networks. These techniques are centralized and do not scale well as they rely on per-flow information. This motivates the need for developing a) distributed algorithms with complete infor­mation, b) source based algorithms with partial information which can be easily obtained from traffic engineering extensions to routing protocols. In this paper, we develop dynamic algorithms for source based routing with partial information. The algorithms are classified based on the path selection ap­proach used for the primary path. We compare the performance of various routing algorithms through simulation studies, based on metrics such as the call blocking probability, average path length of an accepted connections, capacity redundancy, and effective network utilization. Our studies show that dynamic routing algo­rithms perform better than static routing algorithms using pre-computed paths even when the path selection in static algorithms is based on optimizing a global network metric. The other interesting observation we make is that the perfor­mance improvement of dynamic routing algorithms using K pre-computed paths is significant even for small values of K

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. 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. In Ref. 2 and 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

Capacity optimization for surviving double-link failures in mesh-restorable optical networks

Network survivability is a crucial requirement in high-speed optical networks. Most research to date has been focused on the failure of a single component such as a link or a node. A double-link failures model in which any two links in the network may fail in an arbitrary order was proposed recently in literature. 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 reserve excessive resources. In this thesis, we capture the surviving double link failures in WDM optical networks as a single Integer Linear Programming (ILP) based optimization problem. We use the double-link failures recovery method available in literature, develop rules to identify the scenarios where the backup capacity among intersecting demand sets can be shared. We employ the backup multiplexing technique and use ILP to optimize the capacity requirement while providing 100% protection for double-link failures. The numerical results indicate that, for the given example network and randomly picked demand matrix, the shared-link protection scheme that uses backup multiplexing provides 10-15% saving in capacity utilization over the dedicated-link protection scheme that reserves dedicated capacity on two backup paths for each link. The main contribution of this thesis is that we provide a way of adapting the heuristic based double-link failure recovery method into a mathematical framework, and use technique to improve wavelength utilization for optimal capacity usage

Resource Allocation in Survivable WDM Networks Under a Sliding Scheduled Traffic Model

In recent years there has been an increasing number of applications that require periodic use of lightpaths at predefined time intervals, such as database backup and on-line classes. A new traffic model, referred to as the scheduled traffic model, has been proposed to handle such scheduled lightpath demands. In this thesis we present two new integer linear program ( ILP) formulations for the more general sliding scheduled traffic model, where the setup and teardown times may vary within a specified range. We consider both wavelength convertible networks and networks without wavelength conversion capability. Our ILP formulations jointly optimize the problem of scheduling the demands ( in time) and allocating resources for the scheduled lightpaths. Simulation results show that our formulations are able to generate optimal solutions for practical sized networks. For larger networks, we have proposed a fast two-step heuristic to solve the demand scheduling problem and the RWA problem separately

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

Survivability algorithms in MPLS and WDM optical networks

In modern ultra-wide bandwidth, high speed and high reliable communication networks, the failure of network components including equipment (such as routers) and transmission media (such as fibers) may cause a huge volume of data loss. Therefore network survivability mechanisms, by which the disrupted traffic upon failures can be restored, are crucial in network design and deserve thorough investigation. In this thesis, we propose some survivability approaches to survive failures in MPLS and WDM optical networks. MPLS is a promising technology that enables much faster failure recovery than conventional IP rerouting in IP networks. While the traditional MPLS path-based protection scheme is capacity efficient, it is relatively slow in restoration; on the other hand, while traditional MPLS link-based scheme has fast restoration speed, its capacity efficiency is low. In this thesis, we propose a new restoration scheme called UNIFR, which can provide fast restoration as link-based scheme while achieving better capacity efficiency than link-based scheme. We present a MPLS resilience framework that supports UNIFR and give two ILP formulations to solve the spare capacity optimization problem for UNIFR-based restoration model. Simulation study shows that the capacity efficiency of UNIFR-based model is much better than that of link-based model and close to that of path-based model. In WDM optical networks, although lots of pervious works have been done in both protection and restoration survivability techniques, to our best knowledge, little study focuses on improving the dynamic restoration success ratio. To address this problem, we first identify two restoration blocking types called primary holding and mutual competition. To address primary holding, we propose a dynamic routing and wavelength assignment algorithm for connection establishment that takes the future possible failures into consideration and choose route and wavelength for the working lightpath that could lead to higher chance of successful restoration for the potential failures. To address mutual competition, we present some heuristics ideas to increase restoration success ratio. Simulation shows that our algorithms can clearly reduce the restoration blocking probability while not affecting primary blocking probability and restoration speed much

WDM optical network: Efficient techniques for fault-tolerant logic topology design

The rapid increase of bandwidth intensive applications has created an unprecedented demand for bandwidth on the Internet. With recent advances in optical technologies, especially the development of wavelength division multiplexing (WDM) techniques, the amount of raw bandwidth available on the fibre links has increased by several orders of magnitude. Due to the large volume of traffic these optical networks carry, there is one very important issue---design of robust networks that can survive faults. Two common mechanisms to protect against the network failure: one is protection and another is restoration. My research focuses on studying the efficient techniques for fault-tolerant logical topology design for the WDM optical network. In my research, the goal is to determine a topology that accommodates the entire traffic flow and provides protection against any single fiber failure. I solve the problem by formulating the logical topology design problem as a MILP optimization problem, which generates the optimum logical topology and the optimum traffic routing scheme. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .S54. Source: Masters Abstracts International, Volume: 43-01, page: 0244. Adviser: Arunita Jaekel. Thesis (M.Sc.)--University of Windsor (Canada), 2004