A segmentation method for shared protection in WDM networks

Shared link and shared path protections have been recognized as preferred schemes to protect traffic flows against network failures. In recent years, another method referred to as Shared Segment Protection has been studied as an alternative solution for protection. This method is more flexible and efficient in terms of capacity utilization and restoration time. However, to our best knowledge, this method has mostly been studied in dynamic provisioning scenarios in which searching for restoration paths is dynamically performed after a failure has occurred. In this paper, based on the path segmentation idea, we propose a method to generate good candidate routes for traffic demands in static provisioning. These candidates are used as input parameters of an Integer Linear Programming (ILP) model for shared backup protection. Numerical results show that the capacity efficiency resulting from these candidates is much better than the best known Shared Backup Path Protection (SBPP) schemes. In addition, although the restoration time of our scheme is a little bit longer than those implementing link protection, it is still faster than path protection schemes

Efficient Distributed Solution for MPLS Fast Reroute

As service providers move more applications to their IP/MPLS (Multiple Protocol Label Switching) networks, rapid restoration upon failure becomes more and more crucial. Recently MPLS fast reroute has attracted lots of attention as it was designed to meet the needs of real-time applications, such as voice over IP. MPLS fast reroute achieves rapid restoration by computing and signaling backup label switched paths (LSP) in advance and re-directing traffic as close to failure point as possible. To provide a guarantee of failure restoration, extra bandwidth has to be reserved on backup LSPs. To improve the bandwidth utilization, path-merging technique was proposed to allow bandwidth sharing on common links among a service LSP and its backup LSPs. However, the sharing is very limited. In this paper, we provide efficient distributed solution, which would allow much broader bandwidth sharing among any backup LSPs from different service LSPs. We also propose an efficient algorithm for backup path selection to further increase the bandwidth sharing. The associated signaling extension for additional information distribution and collection is provided. To evaluate our solution, we compare its performance with the MPLS fast reroute proposal in IETF via simulation. The key figure-of-merit for restoration capacity efficiency is restoration overbuild, i.e., the ratio of restoration capacity to service capacity. Our simulation results show that our distributed solution reduces restoration overbuild from 2.5 to 1, and our optimized backup path selection further reduces restoration overbuild to about 0.5

Designing Survivable Wavelength Division Multiplexing (WDM) Mesh Networks

This thesis focuses on the survivable routing problem in WDM mesh networks where the objective is to minimize the total number of wavelengths used for establishing working and protection paths in the WDM networks. The past studies for survivable routing suffers from the scalability problem when the number of nodes/links or connection requests grow in the network. In this thesis, a novel path based shared protection framework namely Inter-Group Shared protection (I-GSP) is proposed where the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy. Optimization is performed on these PGs such that sharing of protection wavelengths is considered not only inside a PG, but between the PGs. Simulation results show that I-GSP based integer linear programming model, namely, ILP-II solves the networks in a reasonable amount of time for which a regular integer linear programming formulation, namely, ILP-I becomes computationally intractable. For most of the cases the gap between the optimal solution and the ILP-II ranges between (2-16)%. The proposed ILP-II model yields a scalable solution for the capacity planning in the survivable optical networks based on the proposed I-GSP protection architecture

Availability-Aware Spare Capacity Allocation with Partially Protected Rings

This thesis work focuses on designing a survivable IP-core network with the minimal investment of spare capacity. A span-oriented spare capacity allocation (SCA) scheme is proposed to satisfy customers' availability requirements in the end-to-end (E2E) sense. The novelty of the proposed SCA scheme is that it meets the E2E availability requirements despite the lack of knowledge of E2E bandwidth by employing protection rings covering all links in the network. Different ring selection methods are presented and also compared from the aspect of network redundancy and LP feasibility which provide more flexibility to the design. The proposed SCA algorithm further minimizes total cost of spare capacity by incorporating partial protection within the proposed architecture. The simulation results show that it can significantly reduce the spare capacity consumption depending on the availability. The proposed SCA scheme also performs better in terms of redundancy than that of two other dominant methods available these days

Novel Approaches and Architecture for Survivable Optical Internet

Any unexpected disruption to WDM (Wavelength Division Multiplexing) based optical networks which carry data traffic at tera-bit per second may result in a huge loss to its end-users and the carrier itself. Thus survivability has been well-recognized as one of the most important objectives in the design of optical Internet. This thesis proposes a novel survivable routing architecture for the optical Internet. We focus on a number of key issues that are essential to achieve the desired service scenarios, including the tasks of (a) minimizing the total number of wavelengths used for establishing working and protection paths in WDM networks; (b) minimizing the number of affected working paths in case of a link failure; (c) handling large scale WDM mesh networks; and (d) supporting both Quality of Service (QoS) and best-effort based working lightpaths. To implement the above objectives, a novel path based shared protection framework namely Group Shared protection (GSP) is proposed where the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy, and optimization is performed on these PGs. To the best of our knowledge this is the first work done in the area of group based WDM survivable routing approaches where not only the resource sharing is conducted among the PGs to achieve the best possible capacity efficiency, but also an integrated survivable routing framework is provided by incorporating the above objectives. Simulation results show the effectiveness of the proposed schemes

Novel Approaches and Architecture for Survivable Optical Internet

Any unexpected disruption to WDM (Wavelength Division Multiplexing) based optical networks which carry data traffic at tera-bit per second may result in a huge loss to its end-users and the carrier itself. Thus survivability has been well-recognized as one of the most important objectives in the design of optical Internet. This thesis proposes a novel survivable routing architecture for the optical Internet. We focus on a number of key issues that are essential to achieve the desired service scenarios, including the tasks of (a) minimizing the total number of wavelengths used for establishing working and protection paths in WDM networks; (b) minimizing the number of affected working paths in case of a link failure; (c) handling large scale WDM mesh networks; and (d) supporting both Quality of Service (QoS) and best-effort based working lightpaths. To implement the above objectives, a novel path based shared protection framework namely Group Shared protection (GSP) is proposed where the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy, and optimization is performed on these PGs. To the best of our knowledge this is the first work done in the area of group based WDM survivable routing approaches where not only the resource sharing is conducted among the PGs to achieve the best possible capacity efficiency, but also an integrated survivable routing framework is provided by incorporating the above objectives. Simulation results show the effectiveness of the proposed schemes

Survivability stategies in all optical networks.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.Thesis (M.Sc.)-University of KwaZulu-Natal, 2006.Recent advances in fiber optics technology have enabled extremely high-speed transport of different forms of data, on multiple wavelengths of an optical fiber, using Dense Wavelength Division Multiplexing (DWDM). It has now become possible to deploy high-speed, multi-service networks using DWDM technology. As the amount of traffic carried has increased, 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. Most research to date in survivable optical network design and operation focuses on single link failures, however, the occurrence of multiple-link failures are not uncommon in networks today. Multi-link failure scenarios can arise out of two common situations. First, an arbitrary link may fail in the network, and before that link can be repaired, another link fails, thus creating a multi-link failure sequence. Secondly, it might happen in practice that two distinct physical links may be routed via the same common duct or physical channel. A failure at that shared physical location creates a logical multiple-link failure. In this dissertation, we conduct an intensive study of mechanisms for achieving survivability in optical networks. From the many mechanisms presented in the literature the focus of this work was on protection as a mechanism of survivability. In particular four protection schemes were simulated and their results analyzed to ascertain which protection scheme achieves the best survivability in terms of number of wavelengths recovered for a specific failure scenario. A model network was chosen and the protection schemes were evaluated for both single and multiple link and node failures. As an indicator of the performance of these protection schemes over a period of time average service availability and average loss in traffic for each protection scheme was also simulated. Further simulations were conducted to observe the percentage link and node utilization of each scheme hence allowing us to determine the strain each protection scheme places on network resources when traffic in the network increases. Finally based on these simulation results, recommendations of which protection scheme and under what failure conditions they should be used are made.Recent advances in fiber optics technology have enabled extremely high-speed transpor

Implications of Motion Planning: Optimality and k-survivability

We study motion planning problems, finding trajectories that connect two configurations of a system, from two different perspectives: optimality and survivability. For the problem of finding optimal trajectories, we provide a model in which the existence of optimal trajectories is guaranteed, and design an algorithm to find approximately optimal trajectories for a kinematic planar robot within this model. We also design an algorithm to build data structures to represent the configuration space, supporting optimal trajectory queries for any given pair of configurations in an obstructed environment. We are also interested in planning paths for expendable robots moving in a threat environment. Since robots are expendable, our goal is to ensure a certain number of robots reaching the goal. We consider a new motion planning problem, maximum k-survivability: given two points in a stochastic threat environment, find n paths connecting two given points while maximizing the probability that at least k paths reach the goal. Intuitively, a good solution should be diverse to avoid several paths being blocked simultaneously, and paths should be short so that robots can quickly pass through dangerous areas. Finding sets of paths with maximum k-survivability is NP-hard. We design two algorithms: an algorithm that is guaranteed to find an optimal list of paths, and a set of heuristic methods that finds paths with high k-survivability