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.

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

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

Link failure protection and restoration in WDM optical networks

In a wavelength-division-multiplexing (WDM) optical network, the failure of fiber links may cause the failure of multiple optical channels, thereby leading to large data loss. Therefore the survivable WDM optical networks where the affected traffic under link failure can be restored, have been a matter of much concern. On the other hand, network operators want options that are more than just survivable, but more flexible and more efficient in the use of capacity. In this thesis, we propose our cost-effective approaches to survive link failures in WDM optical networks. Dynamic establishment of restorable connections in WDM networks is an important problem that has received much study. Existing algorithms use either path-based method or link-based method to protect a dynamic connection; the former suffers slow restoration speed while the latter requires complicated online backup path computation. We propose a new dynamic restorable connection establishment algorithm using p-cycle protection. For a given connection request, our algorithm first computes a working path and then computes a set of p-cycles to protect the links on the working path so that the connection can survive any single link failure. The key advantage of the proposed algorithm over the link-based method is that it enables faster failure restoration while requires much simpler online computation for connection establishment. Tree-based schemes offer several advantages such as scalability, failure impact restriction and distributed processing. We present a new tree-based link protection scheme to improve the hierarchical protection tree (p-tree) scheme [31] for single link failure in mesh networks, which achieves 100% restorability in an arbitrary 2-connected network. To minimize the total spare capacity for single link failure protection, an integer linear programming (ILP) formulation is provided. We also develop a fast double-link failure restoration scheme by message signaling to take advantage of the scalable and distributed processing capability of tree structure

Survivability through pre-configured protection in optical mesh networks

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

Spare capacity allocation using shared backup path protection for dual link failures

This paper extends the spare capacity allocation (SCA) problem from single link failure [1] to dual link failures on mesh-like IP or WDM networks. The SCA problem pre-plans traffic flows with mutually disjoint one working and two backup paths using the shared backup path protection (SBPP) scheme. The aggregated spare provision matrix (SPM) is used to capture the spare capacity sharing for dual link failures. Comparing to a previous work by He and Somani [2], this method has better scalability and flexibility. The SCA problem is formulated in a non-linear integer programming model and partitioned into two sequential linear sub-models: one finds all primary backup paths first, and the other finds all secondary backup paths next. The results on five networks show that the network redundancy using dedicated 1+1+1 is in the range of 313-400%. It drops to 96-181% in 1:1:1 without loss of dual-link resiliency, but with the trade-off of using the complicated share capacity sharing among backup paths. The hybrid 1+1:1 provides intermediate redundancy ratio at 187-310% with a moderate complexity. We also compare the passive/active approaches which consider spare capacity sharing after/during the backup path routing process. The active sharing approaches always achieve lower redundancy values than the passive ones. These reduction percentages are about 12% for 1+1:1 and 25% for 1:1:1 respectively

Risk based resilient network design

This paper presents a risk-based approach to resilient network design. The basic design problem considered is that given a working network and a fixed budget, how best to allocate the budget for deploying a survivability technique in different parts of the network based on managing the risk. The term risk measures two related quantities: the likelihood of failure or attack, and the amount of damage caused by the failure or attack. Various designs with different risk-based design objectives are considered, for example, minimizing the expected damage, minimizing the maximum damage, and minimizing a measure of the variability of damage that could occur in the network. A design methodology for the proposed risk-based survivable network design approach is presented within an optimization model framework. Numerical results and analysis illustrating the different risk based designs and the tradeoffs among the schemes are presented. © 2011 Springer Science+Business Media, LLC

Optimal Algorithms for Near-Hitless Network Restoration via Diversity Coding

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

Design of survivable WDM network based on pre-configured protection cycle

Wavelength Division Multiplexing (WDM) is an important technique which allows the trans- port of large quantities of data over optical networks. All optical WDM-based networks have been used to improve overall communication capacity and provide an excellent choice for the design of backbone networks. However, due to the high traffic load that each link can carry in a WDM network, survivability against failures becomes very important. Survivability in this context is the ability of the network to maintain continuity of service against failures, since a failure can lead to huge data losses. In recent years, many survivability mechanisms have been studied and their performance assessed through capacity efficiency, restoration time and restorability. Survivability mechanisms for ring and mesh topologies have received particular attention