Fundamental schemes to determine disjoint paths for multiple failure scenarios

Disjoint path routing approaches can be used to cope with multiple failure cenarios. This can be achieved using a set of k (k>2) link- (or node-) disjoint path pairs (in single-cost and multi-cost networks). Alternatively, if Shared Risk Link Groups (SRLGs) information is available, the calculation of an SRLG-disjoint path pair (or of a set of such paths) can protect a connection against the joint failure of the set of links in any single SRLG. Paths traversing disaster-prone regions should be disjoint, but in safe regions it may be acceptable for the paths to share links or even nodes for a quicker recovery. Auxiliary algorithms for obtaining the shortest path from a source to a destination are also presented in detail, followed by the illustrated description of Bhandari’s and Suurballe’s algorithms for obtaining a pair of paths of minimal total additive cost. These algorithms are instrumental for some of the presented schemes to determine disjoint paths for multiple failure scenarios.info:eu-repo/semantics/publishedVersio

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

Technology-related disasters:a survey towards disaster-resilient software defined networks

Resilience against disaster scenarios is essential to network operators, not only because of the potential economic impact of a disaster but also because communication networks form the basis of crisis management. COST RECODIS aims at studying measures, rules, techniques and prediction mechanisms for different disaster scenarios. This paper gives an overview of different solutions in the context of technology-related disasters. After a general overview, the paper focuses on resilient Software Defined Networks

The minimum cost D-geodiverse anycast routing with optimal selection of anycast nodes

Consider a geographical network with associated link costs. In anycast routing, network nodes are partitioned into two sets - the source nodes and the anycast (destination) nodes - and the traffic of each source node is routed towards the anycast node providing the minimum routing cost path. By considering a given geographical distance parameter D, we define an anycast routing solution as D-geodiverse when for each source node there are two routing paths, each one towards a different anycast node, such that the geographical distance between the two paths is at least D. Such a solution has the property that any disaster with a coverage diameter below D affecting one routing path (but without involving neither the source node nor its entire set of outgoing links) cannot affect the other path, enhancing in this way the network robustness to natural disasters. The selection of the anycast nodes has an impact both on the feasibility and cost of a D- geodiverse anycast routing solution. Therefore, for a desired number of anycast nodes R, we define the minimum cost D- geodiverse anycast problem (MCD-GAP) aiming to identify a set of R anycast nodes that obtain a minimum cost routing solution. The problem is defined based on integer linear programming and is extended to consider the existence of vulnerability regions in the network, i.e., by imposing the geographical distance D only between network elements belonging to the same region. We present computational results showing the tradeoff between D and R in the optimal solutions obtained with and without vulnerability regions.This paper is based upon work from COST Action CA15127 ("Resilient communication services protecting end user applications from disaster-based failures ‒ RECODIS") supported by COST Association. The work was financially supported by FCT, Portugal, under the projects CENTRO- 01-0145-FEDER-029312 and UID/EEA/50008/2013 and through the postdoc grant SFRH/BPD/ 111503/2015.publishe

A Logically Centralized Approach for Control and Management of Large Computer Networks

Management of large enterprise and Internet Service Provider networks is a complex, error-prone, and costly challenge. It is widely accepted that the key contributors to this complexity are the bundling of control and data forwarding in traditional routers and the use of fully distributed protocols for network control. To address these limitations, the networking research community has been pursuing the vision of simplifying the functional role of a router to its primary task of packet forwarding. This enables centralizing network control at a decision plane where network-wide state can be maintained, and network control can be centrally and consistently enforced. However, scalability and fault-tolerance concerns with physical centralization motivate the need for a more flexible and customizable approach. This dissertation is an attempt at bridging the gap between the extremes of distribution and centralization of network control. We present a logically centralized approach for the design of network decision plane that can be realized by using a set of physically distributed controllers in a network. This approach is aimed at giving network designers the ability to customize the level of control and management centralization according to the scalability, fault-tolerance, and responsiveness requirements of their networks. Our thesis is that logical centralization provides a robust, reliable, and efficient paradigm for management of large networks and we present several contributions to prove this thesis. For network planning, we describe techniques for optimizing the placement of network controllers and provide guidance on the physical design of logically centralized networks. For network operation, algorithms for maintaining dynamic associations between the decision plane and network devices are presented, along with a protocol that allows a set of network controllers to coordinate their decisions, and present a unified interface to the managed network devices. Furthermore, we study the trade-offs in decision plane application design and provide guidance on application state and logic distribution. Finally, we present results of extensive numerical and simulative analysis of the feasibility and performance of our approach. The results show that logical centralization can provide better scalability and fault-tolerance while maintaining performance similarity with traditional distributed approach

Management of Temporally and Spatially Correlated Failures in Federated Message Oriented Middleware for Resilient and QoS-Aware Messaging Services.

PhDMessage Oriented Middleware (MOM) is widely recognized as a promising solution for the communications between heterogeneous distributed systems. Because the resilience and quality-of-service of the messaging substrate plays a critical role in the overall system performance, the evolution of these distributed systems has introduced new requirements for MOM, such as inter domain federation, resilience and QoS support. This thesis focuses on a management frame work that enhances the Resilience and QoS-awareness of MOM, called RQMOM, for federated enterprise systems. A common hierarchical MOM architecture for the federated messaging service is assumed. Each bottom level local domain comprises a cluster of neighbouring brokers that carry a local messaging service, and inter domain messaging are routed through the gateway brokers of the different local domains over the top level federated overlay. Some challenges and solutions for the intra and inter domain messaging are researched. In local domain messaging the common cause of performance degradation is often the fluctuation of workloads which might result in surge of total workload on a broker and overload its processing capacity, since a local domain is often within a well connected network. Against performance degradation, a combination of novel proactive risk-aware workload allocation, which exploits the co-variation between workloads, in addition to existing reactive load balancing is designed and evaluated. In federated inter domain messaging an overlay network of federated gateway brokers distributed in separated geographical locations, on top of the heterogeneous physical network is considered. Geographical correlated failures are threats to cause major interruptions and damages to such systems. To mitigate this rarely addressed challenge, a novel geographical location aware route selection algorithm to support uninterrupted messaging is introduced. It is used with existing overlay routing mechanisms, to maintain routes and hence provide more resilient messaging against geographical correlated failures

Survivable Cloud Networking Services

Cloud computing paradigms are seeing very strong traction today and are being propelled by advances in multi-core processor, storage, and high-bandwidth networking technologies. Now as this growth unfolds, there is a growing need to distribute cloud services over multiple data-center sites in order to improve speed, responsiveness, as well as reliability. Overall, this trend is pushing the need for virtual network (VN) embedding support at the underlying network layer. Moreover, as more and more mission-critical end-user applications move to the cloud, associated VN survivability concerns are also becoming a key requirement in order to guarantee user service level agreements. Overall, several different types of survivable VN embedding schemes have been developed in recent years. Broadly, these schemes offer resiliency guarantees by pre-provisioning backup resources at service setup time. However, most of these solutions are only geared towards handling isolated single link or single node failures. As such, these designs are largely ineffective against larger regional stressors that can result in multiple system failures. In particular, many cloud service providers are very concerned about catastrophic disaster events such as earthquakes, floods, hurricanes, cascading power outages, and even malicious weapons of mass destruction attacks. Hence there is a pressing need to develop more robust cloud recovery schemes for disaster recovery that leverage underlying distributed networking capabilities. In light of the above, this dissertation proposes a range of solutions to address cloud networking services recovery under multi-failure stressors. First, a novel failure region-disjoint VN protection scheme is proposed to achieve improved efficiency for pre-provisioned protection. Next, enhanced VN mapping schemes are studied with probabilistic considerations to minimize risk for VN requests under stochastic failure scenarios. Finally, novel post-fault VN restoration schemes are also developed to provide viable last-gap recovery mechanisms using partial and full VN remapping strategies. The performance of these various solutions is evaluated using discrete event simulation and is also compared to existing strategies

Minimization of the network availability upgrade cost with geodiverse routing for disaster resilience

Telecommunication networks are a critical infrastructure of our society. Wide area backbone communication networks are based on optical networks, where each fiber has a very large capacity. These networks must offer high end-to-end availability and a high resilience to large-scale disasters. Routing with geodiversity can mitigate the impact of disasters but will result in longer paths, making it difficult to achieve the availability levels required by critical services. In this paper, we consider a given core optical network such that the current availability and the cost of upgrading it to a higher value are known for each network link (or edge). Then, the problem of selecting a set of edges to be upgraded at a minimum cost, while guaranteeing desired values of end-to-end availability and geodiversity, is considered and formulated as an arc based integer non-linear programming model. The non-linear constraints of the model are approximated and linearized, resulting in a new ILP based heuristic. A filtering procedure is proposed for decreasing (if possible) the cost and the number of upgraded edges of the solutions obtained by previously proposed greedy heuristics and also by the ILP based heuristic. The relative performance of the heuristics is evaluated using different geodiverse distances and end-to-end availability values in two reference core optical networks.publishe