Service level agreement framework for differentiated survivability in GMPLS-based IP-over-optical networks

In the next generation optical internet, GMPLS based IP-over-optical networks, ISPs will be required to support a wide variety of applications each having their own requirements. These requirements are contracted by means of the SLA. This paper describes a recovery framework that may be included in the SLA contract between ISP and customers in order to provide the required level of survivability. A key concern with such a recovery framework is how to present the different survivability alternatives including recovery techniques, failure scenario and layered integration into a transparent manner for customers. In this paper, two issues are investigated. First, the performance of the recovery framework when applying a proposed mapping procedure as an admission control mechanism in the edge router considering a smart-edge simple-core GMPLS-based IP/WDM network is considered. The second issue pertains to the performance of a pre-allocated restoration and its ability to provide protected connections under different failure scenarios

Overlay Protection Against Link Failures Using Network Coding

This paper introduces a network coding-based protection scheme against single and multiple link failures. The proposed strategy ensures that in a connection, each node receives two copies of the same data unit: one copy on the working circuit, and a second copy that can be extracted from linear combinations of data units transmitted on a shared protection path. This guarantees instantaneous recovery of data units upon the failure of a working circuit. The strategy can be implemented at an overlay layer, which makes its deployment simple and scalable. While the proposed strategy is similar in spirit to the work of Kamal '07 & '10, there are significant differences. In particular, it provides protection against multiple link failures. The new scheme is simpler, less expensive, and does not require the synchronization required by the original scheme. The sharing of the protection circuit by a number of connections is the key to the reduction of the cost of protection. The paper also conducts a comparison of the cost of the proposed scheme to the 1+1 and shared backup path protection (SBPP) strategies, and establishes the benefits of our strategy.Comment: 14 pages, 10 figures, accepted by IEEE/ACM Transactions on Networkin

Network protection with guaranteed recovery times using recovery domains

We consider the problem of providing network protection that guarantees the maximum amount of time that flow can be interrupted after a failure. This is in contrast to schemes that offer no recovery time guarantees, such as IP rerouting, or the prevalent local recovery scheme of Fast ReRoute, which often over-provisions resources to meet recovery time constraints. To meet these recovery time guarantees, we provide a novel and flexible solution by partitioning the network into failure-independent “recovery domains”, where within each domain, the maximum amount of time to recover from a failure is guaranteed. We show the recovery domain problem to be NP-Hard, and develop an optimal solution in the form of an MILP for both the case when backup capacity can and cannot be shared. This provides protection with guaranteed recovery times using up to 45% less protection resources than local recovery. We demonstrate that the network-wide optimal recovery domain solution can be decomposed into a set of easier to solve subproblems. This allows for the development of flexible and efficient solutions, including an optimal algorithm using Lagrangian relaxation, which simulations show to converge rapidly to an optimal solution. Additionally, an algorithm is developed for when backup sharing is allowed. For dynamic arrivals, this algorithm performs better than the solution that tries to greedily optimize for each incoming demand.National Science Foundation (U.S.) (NSF grant CNS-1017800)National Science Foundation (U.S.) (grant CNS-0830961)United States. Defense Threat Reduction Agency (grant HDTRA-09-1-005)United States. Defense Threat Reduction Agency (grant HDTRA1-07-1-0004)United States. Air Force (Air Force contract # FA8721-05-C-0002

Network protection with multiple availability guarantees

We develop a novel network protection scheme that provides guarantees on both the fraction of time a flow has full connectivity, as well as a quantifiable minimum grade of service during downtimes. In particular, a flow can be below the full demand for at most a maximum fraction of time; then, it must still support at least a fraction q of the full demand. This is in contrast to current protection schemes that offer either availability-guarantees with no bandwidth guarantees during the downtime, or full protection schemes that offer 100% availability after a single link failure. We develop algorithms that provide multiple availability guarantees and show that significant capacity savings can be achieved as compared to full protection. If a connection is allowed to drop to 50% of its bandwidth for 1 out of every 20 failures, then a 24% reduction in spare capacity can be achieved over traditional full protection schemes. In addition, for the case of q = 0, corresponding to the standard availability constraint, an optimal pseudo-polynomial time algorithm is presented.National Science Foundation (U.S.) (NSF grants CNS-1116209)National Science Foundation (U.S.) (NSF grants CNS-0830961)United States. Defense Threat Reduction Agency (grant HDTRA-09-1-005)United States. Defense Threat Reduction Agency (grant HDTRA1-07-1-0004)United States. Air Force (Air Force contract # FA8721-05-C-0002

p-Cycle Based Protection in WDM Mesh Networks

Abstract p-Cycle Based Protection in WDM Mesh Networks Honghui Li, Ph.D. Concordia University, 2012 WDM techniques enable single fiber to carry huge amount of data. However, optical WDM networks are prone to failures, and therefore survivability is a very important requirement in the design of optical networks. In the context of network survivability, p-cycle based schemes attracted extensive research interests as they well balance the recovery speed and the capacity efficiency. Towards the design of p-cycle based survivableWDM mesh networks, some issues still need to be addressed. The conventional p-cycle design models and solution methods suffers from scalability issues. Besides, most studies on the design of p-cycle based schemes only cope with single link failures without any concern about single node failures. Moreover, loop backs may exist in the recovery paths along p-cycles, which lead to unnecessary stretching of the recovery path lengths. This thesis investigates the scalable and efficient design of segment p-cycles against single link failures. The optimization models and their solutions rely on large-scale optimization techniques, namely, Column Generation (CG) modeling and solution, where segment pcycle candidates are dynamically generated during the optimization process. To ensure full node protection in the context of link p-cycles, we propose an efficient protection scheme, called node p-cycles, and develop a scalable optimization design model. It is shown that, depending on the network topology, node p-cycles sometimes outperform path p-cycles in iii terms of capacity efficiency. Also, an enhanced segment p-cycle scheme is proposed, entitled segment Np-cycles, for full link and node protection. Again, the CG-based optimization models are developed for the design of segment Np-cycles. Two objectives are considered, minimizing the spare capacity usage and minimizing the CAPEX cost. It is shown that segment Np-cycles can ensure full node protection with marginal extra cost in comparison with segment p-cycles for link protection. Segment Np-cycles provide faster recovery speed than path p-cycles although they are slightly more costly than path p-cycles. Furthermore, we propose the shortcut p-cycle scheme, i.e., p-cycles free of loop backs for full node and link protection, in addition to shortcuts in the protection paths. A CG-based optimization model for the design of shortcut p-cycles is formulated as well. It is shown that, for full node protection, shortcut p-cycles have advantages over path p-cycles with respect to capacity efficiency and recovery speed. We have studied a whole sequence of protection schemes from link p-cycles to path p-cycles, and concluded that the best compromise is the segment Np-cycle scheme for full node protection with respect to capacity efficiency and recovery time. Therefore, this thesis offers to network operators several interesting alternatives to path p-cycles in the design of survivable WDM mesh networks against any single link/node failures

Dynamic routing of reliability-differentiated connections in WDM optical networks

Master'sMASTER OF ENGINEERIN

Differentiated quality-of-recovery and quality-of-protection in survivable WDM mesh networks

In the modern telecommunication business, there is a need to provide different Quality-of-Recovery (QoR) and Quality-of-Protection (QoP) classes in order to accommodate as many customers as possible, and to optimize the protection capacity cost. Prevalent protection methods to provide specific QoS related to protection are based on pre-defined shape protection structures (topologies), e.g., p -cycles and p -trees. Although some of these protection patterns are known to provide a good trade-off among the different protection parameters, their shapes can limit their deployment in some specific network conditions, e.g., a constrained link spare capacity budget and traffic distribution. In this thesis, we propose to re-think the design process of protection schemes in survivable WDM networks by adopting a hew design approach where the shapes of the protection structures are decided based on the targeted QoR and QoP guarantees, and not the reverse. We focus on the degree of pre-configuration of the protection topologies, and use fully and partially pre-cross connected p -structures, and dynamically cross connected p -structures. In QoR differentiation, we develop different approaches for pre-configuring the protection capacity in order to strike different balances between the protection cost and the availability requirements in the network; while in the QoP differentiation, we focus on the shaping of the protection structures to provide different grades of protection including single and dual-link failure protection. The new research directions proposed and developed in this thesis are intended to help network operators to effectively support different Quality-of-Recovery and Quality-of-Protection classes. All new ideas have been translated into mathematical models for which we propose practical and efficient design methods in order to optimize the inherent cost to the different designs of protection schemes. Furthermore, we establish a quantitative relation between the degree of pre-configuration of the protection structures and their costs in terms of protection capacity. Our most significant contributions are the design and development of Pre-Configured Protection Structure (p-structure) and Pre-Configured Protection Extended-Tree (p -etree) based schemes. Thanks to the column generation modeling and solution approaches, we propose a new design approach of protection schemes where we deploy just enough protection to provide different quality of recovery and protection classe

A robust optimization approach to backup network design with random failures

This paper presents a scheme in which a dedicated backup network is designed to provide protection from random link failures. Upon a link failure in the primary network, traffic is rerouted through a preplanned path in the backup network. We introduce a novel approach for dealing with random link failures, in which probabilistic survivability guarantees are provided to limit capacity over-provisioning. We show that the optimal backup routing strategy in this respect depends on the reliability of the primary network. Specifically, as primary links become less likely to fail, the optimal backup networks employ more resource sharing amongst backup paths. We apply results from the field of robust optimization to formulate an ILP for the design and capacity provisioning of these backup networks. We then propose a simulated annealing heuristic to solve this problem for largescale networks, and present simulation results that verify our analysis and approach.National Science Foundation (U.S.) (grant CNS-0626781)National Science Foundation (U.S.) (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