Design Of Fault-tolerant Networks Research Articles

Restorable Shortest Path Tiebreaking for Edge-Faulty Graphs

The restoration lemma by Afek et al. [ 3 ] proves that, in an undirected unweighted graph, any replacement shortest path avoiding a failing edge can be expressed as the concatenation of two original shortest paths. However, the lemma is tiebreaking-sensitive : if one selects a particular canonical shortest path for each node pair, it is no longer guaranteed that one can build replacement paths by concatenating two selected shortest paths. They left as an open problem whether a method of shortest path tiebreaking with this desirable property is generally possible. We settle this question affirmatively with the first general construction of restorable tiebreaking schemes . We then show applications to various problems in fault-tolerant network design. These include a faster algorithm for subset replacement paths, more efficient fault-tolerant (exact) distance labeling schemes, fault-tolerant subset distance preservers and + 4 additive spanners with improved sparsity, and fast distributed algorithms that construct these objects. For example, an almost immediate corollary of our restorable tiebreaking scheme is the first nontrivial distributed construction of sparse fault-tolerant distance preservers resilient to three faults.

Raptor: a network tool for mitigating the impact of spatially correlated failures in infrastructure networks

Current practices of fault-tolerant network design ignore the fact that most network infrastructure faults are localized or spatially correlated (i.e., confined to geographic regions). Network operators require new tools to mitigate the impact of such region-based faults on their infrastructures. Utilizing the support from the U.S. Department of Defense, and by consolidating a wide range of theories and solutions developed in the last few years, the authors of this paper have developed Raptor, an advanced Network Planning and Management Tool that facilitates the design and provisioning of robust and resilient networks. The tool provides multi-faceted network design, evaluation, and simulation capabilities for network planners. Future extensions of the tool currently being worked upon not only expand the tool’s capabilities, but also extend these capabilities to heterogeneous interdependent networks such as communication, power, water, and satellite networks.

Reliable and energy efficient wireless sensor network design via conditional multi-copying for multiple central nodes

Design of reliable wireless sensor networks considering energy efficiency is of utmost importance given their specific application domains and technical properties. As a contribution to the vast literature on resilient and fault tolerant network design, this paper offers a novel energy efficient conditional multi-copy and multi-path routing strategy. The motivation is to use limited energy of sensors as efficiently as possible and to improve network reliability and security via restricted redundant data generation. Namely, rather than all only the data passing through some central nodes are duplicated as a precaution against their malfunctioning. A limited number of nodes with higher data transmission allowance are determined as central at the design stage considering lifetime maximization objective. Consequently, 0–1 mixed integer programming models of two variants of the proposed strategy are presented in order to determine optimal routing. Moreover, several valid inequalities so as to improve solution times with commercial solvers and an efficient heuristic method for finding good solutions for large instances in reasonable times are proposed. Extensive test results show that simple restricted multi-copy strategies where every sensor duplicates its data are improved since the proposed strategies provide comparable levels of network reliability and yet extend network lifetime significantly.

Fault tolerant network design inspired by Physarum polycephalum

Physarum polycephalum, a true slime mould, is a primitive, unicellular organism that creates networks to transport nutrients while foraging. The design of these natural networks proved to be advanced, e.g. the slime mould was able to find the shortest path through a maze. The underlying principles of this design have been mathematically modelled in literature. As in real life the slime mould can design fault tolerant networks, its principles can be applied to the design of man-made networks. In this paper, an existing model and algorithm are adapted and extended with stimulation and migration mechanisms which encourage formation of alternative paths, optimize edge positioning and allow for automated design. The extended model can then be used to better design fault tolerant networks. The extended algorithm is applied to several national and international network configurations. Results show that the extensions allow the model to capture the fault tolerance requirements more accurately. The resulting extended algorithm overcomes weaknesses in geometric graph design and can be used to design fault tolerant networks such as telecommunication networks with varying fault tolerance requirements.

An Efficient Constructive Approximation Approach to Design A K-Connected Network Topology

The purpose of designing an optimal and fault tolerant communication network is to achieve a precise performance without any disruption at a minimal cost. A network is said to be k- link fault tolerant (nodes are assumed reliable) if it is able to maintain connectivity in the presence of failures in any set of arbitrarily k links simultaneously. Communication network topology design cost depends on the number of the links used to design a desired fault tolerant communication network and is equal to the sum of the cost of all required links. The main objective of a fault tolerant network design approach is therefore to select the minimum number of low cost links while satisfying the pre-specified fault tolerance/connectivity. It has also been proved that designing a minimum cost communication network topology under the connectivity constraint is a NP hard problem. Several constructive approximation algorithms have be enproposed to design a fault tolerant network topology. But the existing algorithms are not so much effective for selecting minimum number of low cost links to design a computer network topology. In this paper, we have proposed an efficient constructive approximation approach for designing a k – connected network which is survivable in the presence of k-1 links failures in the network. The design cost and number of links required to design such network using proposed approach is less than the existing approaches. Effectiveness of proposed approach is also checked using various examples.

Design of fault‐tolerant networks for satellites (TWTA redundancy)

AbstractThis article deals with the design of networks to be placed on satellites. These networks should connect inputs (corresponding to signals arriving at the satellite) to outputs (corresponding to amplifiers, also called Traveling Wave Tube Amplifiers (TWTA)), even in case of failures of amplifiers. The networks are made of links and expensive switches; hence, we want to minimize the number of switches subject to the following conditions: Each input and each output is connected to exactly one switch; each switch is adjacent to exactly four links; there are n inputs and n + k outputs; among the n + k outputs, k can fail permanently; and, finally, all the input signals should be sent to valid amplifiers, that is, outputs, via disjoint paths. So, the aim is to design networks having as few switches as possible and satisfying the following property: There exist n edge‐disjoint paths from the n inputs to any set of n outputs chosen from the n + k total number of outputs. We call such networks valid k‐fault tolerant networks. Let 𝒩(n, k) denote the minimum number of switches of a valid network with n inputs, n + k outputs, and k output failures. In this article, we give some details on the problem and some preliminary results such as the fact that 𝒩(n, k) ≥ n. We also propose a general construction which yields (under some conditions) 𝒩(n + n′, k) ≤ 𝒩(n, k) + 𝒩(n′, k). © 2002 Wiley Periodicals, Inc.

Fault-tolerant meshes with small degree

In this paper, we study the design of fault-tolerant networks for arrays and meshes by adding redundant nodes and edges. For a target graph G (linear array or mesh in this paper), a graph G' is called a k-fault-tolerant graph of G if when we remove any k nodes from G', it still contains a subgraph isomorphic to G. The major quality measures for a fault-tolerant graph are the number of spare nodes it uses and the maximum degree it has. The degree is particularly important in practice as it poses constraints on the scalability of the system. In this paper, we aim at designing fault-tolerant graphs with both a small degree and a small number of spare nodes. The fault-tolerant graphs we obtain have degree O(1) for arrays and O(log/sup 3/ k) for meshes. The number of spare nodes used are O(k log/sup 2/ k) and O(k/sup 2//log k), respectively. Compared to the previous results, the number of spare nodes used in our construction has one fewer linear factor in k.

Reconfigurable fault tolerant networks for fast packet switching

The authors consider the design and analysis of reconfigurable networks for fast packet switching. The design constraints resulting from the use of fast packet switching that affect fault-tolerant network design are carefully studied. A reconfigurable network with high link redundancy is then proposed. An abstract replacement model that characterizes the proposed reconfigurable network is presented. Network fault tolerance problems are transformed into well known assignment problems. Two practical designs based on feasible technology are presented. An appreciable reliability improvements is achieved and full bandwidth is maintained up to a tolerable level of failures, with relatively few spare switches. >