Ensure Fault Tolerance Research Articles

SEAL: SDN based secure and agile framework for protecting smart city applications from DDoS attacks

Evolution of smart cities induces critical challenges related to cyber and network security. The increased reliance of a smart city on Information and Communication Technologies (ICT) infrastructure improves automation, efficiency, and sustainability of city services. However, it also poses enormous challenges for ensuring continued operations and services at all times and especially under cyber-attacks. Any lapse in cyber security can lead to critical disaster across the city. Distributed Denial of Service (DDoS) attacks are considered to be the most predominant and prevalent cyber-attacks. We believe that smart city could consist of numerous applications with varying level of network and security requirements. Therefore, providing an adaptive mechanism against DDoS attacks for all applications in a smart city is a key challenge. Further, considering the wide-scale requirements of a smart city, developing an adaptive and flexible solution is a key requirement. Considering these requirements, this paper presents SEAL (SEcure and AgiLe) – a novel Software Defined Networking (SDN) based adaptive framework for protecting smart city applications against DDoS attacks. The SEAL framework leverages key characteristics of SDN such as the global visibility, centralized control, and programmability to enhance the security and resilience. SEAL is capable of effectively detecting and mitigating DDoS attacks not only on application servers but also on network resources. SEAL is also unique in this regard that it provides application specific DDoS attack security solution instead of static threshold mechanism. Moreover, inherently distributed architecture of the SEAL framework ensures fault tolerance, scalability and reliability of the smart city. The SEAL framework comprises three modules, namely D-Defense, A-Defense and C-Defense. These modules collectively provide a mechanism to detect and mitigate DDoS attack on smart city applications and the network infrastructure. Adaptability in SEAL is achieved through implementing customized version of estimated-weighted moving average (EWMA) filters. Three types of filters, Proactive Filter, Active Filter, and Passive Filter are proposed and implemented to compute the dynamic threshold in real time for various types of applications. Experimental evaluation of the SEAL framework has been conducted to establish the efficacy of the framework and its components in detecting and mitigating DDoS attacks. The results prove that SEAL is able to detect and mitigate DDoS attacks effectively. The focus of the SEAL framework is to protect smart city applications, however, the SEAL framework can potentially be utilized in a wide range of systems.

Adjustment of genetic algorithm parameters for solving the problem of topology optimization of the sensory network

The paper is devoted to the optimal placement of devices within a wireless sensor network. Modern requirements to ensure public safety in buildings with a complex structure imply the existence of systems that can detect and position emergency situation, inform rescue and tenants about the status and help them to either evacuate or eliminate the danger. Nowadays the main approach to create indoor emergency system is based on wireless sensor network. The network is built with a big number of usually battery-operating devices, each consists of a sensors set for hazard detection, and radio frequency module for communication. To evaluate the state of indoor environment different sensors can be used, such as temperature, humidity, light, flame, smoke, gas, etc. The problem of optimizing the network topology as a covering problem is formulated. A set of points in the area that is not covered by circles, a set of points belonging to the region and the intersection of two or more circles of coverage, set of points that do not belong to the area need to be minimized. To ensure fault tolerance of the wireless sensor network, it is necessary to allow the connection of each sensor with at least two routers, in case one of the routers is accidentally switched off, and also it is necessary to ensure connection of the router with at least one router. To take into account these additional conditions, the method of penalty functions is used. The genetic algorithm for solving the problem is used. The main genetic operators are adapted to the problem of designing the topology of wireless sensor networks. A computa-tional experiment was carried out, during which the optimal population size was estab-lished; the procedure of homogeneous crossing, procedure of tournament selection is chosen; procedure of homogeneous mutation. As a criterion for stopping the genetic algorithm, the stagnation of the results on the iterations of the algorithm is chosen.

Hardware-Oriented Authentication for Advanced Metering Infrastructure

This paper introduces a novel authentication scheme for advanced metering infrastructure of smart grid using ring oscillator physically unclonable functions (ROPUFs). The scope of the design covers the communication between the utility company and the smart meter network. The scheme is based on hardware-oriented security and can be implemented on existing smart meters. Authentication keys of 64 bits are used for security level 1 communication. The size of keys can increase up to 1024 bits for security level 5. The cryptographic keys used in this scheme are extremely difficult to model by adversaries as each key is used only once. These authentication keys are generated from ROPUF response bits using the Hamming code. The design of the scheme ensures fault tolerance as ring oscillator comparison pairs with high frequency differences are selected to prevent bit flips and only 10% discrepancy is tolerated in parity bits. The proposed scheme is highly secure and efficient in terms of latency and data storage. As a proof of concept, two different machine learning algorithms, support vector machine and multigene genetic programming, are used to show that the scheme cannot be modeled by adversaries.

Resiliency in Distributed Sensor Networks for Prognostics and Health Management of the Monitoring Targets

In condition-based maintenance, real-time observations are crucial for on-line health assessment. When the monitoring system is a wireless sensor network (WSN), data loss becomes highly probable and this affects the quality of the remaining useful life prediction. In this paper, we present a fully distributed algorithm that ensures fault tolerance and recovers data loss in WSNs. We first theoretically analyze the algorithm and give correctness proofs, then provide simulation results and show that the algorithm is (i) able to ensure data recovery with a low failure rate and (ii) preserves the overall energy for dense networks.

Sensorless efficient fault-tolerant control of wind turbines with geared generator

This paper proposes a sensorless (i.e. not requiring feedback information about rotor speed and position, and about wind velocity) control technique solving the tracking problem of the maximum delivered power characteristic for a wind energy conversion system equipped with a permanent magnet synchronous generator. A previously published sensorless control scheme ensuring the achievement of maximum power efficiency of the wind turbine is here extended to consider the drive-train dynamics. A novel observer of the electrical speed, based on the electrical variables only, is proposed, and asymptotic vanishing of the observation error is proved, as well as boundedness of the observer variables. Moreover, it is proved that the derived control algorithm can be easily modified also to ensure fault tolerance with respect to a class of system faults, sensor faults occurring in mechanical sensors being absent because of the sensorless approach here pursued. The proposed control solution has been validated on a 5−MW three-blade wind turbine using the National Renewable Energy Laboratory (NREL) wind turbine simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code.

Integrating fault tolerant scheme with feedback Control scheduling algorithm at software level for real time embedded systems

In order to provide Quality of Service (QoS) in open and unpredictable environment, Feedback based Control Scheduling Algorithm (FCSA) is designed to keep the processor utilization at the scheduling utilization bound. FCSA controls CPU utilization by assigning task periods that optimize overall control performance, meeting deadlines even if the task execution time is unpredictable and through performance control feedback loop. Current FCSA doesn’t ensure Fault Tolerance (FT) while providing QoS in terms of CPU utilization and resource management. In order to assure that tasks should meet their deadlines even in the presence of faults, a FT scheme has to be integrated at control scheduling co-design level. This paper presents a novel approach on integrating FT scheme with FCSA for real time embedded systems. This procedure is especially important for control scheduling co-design of embedded systems.

Architecture and design of high-throughput, low-latency, and fault-tolerant routing algorithm for 3D-network-on-chip (3D-NoC)

Despite the higher scalability and parallelism integration offered by Network-on-Chip (NoC) over the traditional shared-bus based systems, it is still not an ideal solution for future large-scale Systems-on-Chip (SoCs), due to limitations such as high power consumption, high-cost communication, and low throughput. Recently, extending 2D-NoC to the third dimension (3D-NoC) has been proposed to deal with these problems; however, 3D-NoC systems are exposed to a variety of manufacturing and design factors making them vulnerable to different faults that cause corrupted message transfer or even catastrophic system failures. Therefore, a 3D-NoC system should be fault tolerant to transient malfunctions or permanent physical damages. In this paper, we propose a low-latency, high-throughput, and fault-tolerant routing algorithm named Look-Ahead-Fault-Tolerant (LAFT). LAFT reduces the communication latency and enhances the system performance while maintaining a reasonable hardware complexity and ensuring fault tolerance. We implemented the proposed algorithm on a real 3D-NoC architecture (3D-OASIS-NoC) and prototyped it on FPGA, then we evaluated its performance over various applications. Evaluation results show that the proposed algorithm efficiently reduces the communication latency that can reach an average of 38 % and 16 %, when compared to conventional XYZ and our early designed Look-Ahead-XYZ routing algorithms, respectively, and enhances the throughput with up to 46 % and 29 %.

Power optimization in ad hoc wireless network topology control with biconnectivity requirements

We consider the problem of assigning transmission powers to the nodes of an ad hoc wireless network, so that the total power consumed is minimized and the resulting network is biconnected, i.e., there are at least two node-disjoint paths between any pair of nodes. Biconnected communication graphs are important to ensure fault tolerance, since ad hoc networks are used in critical application domains where failures are likely to occur. A mixed integer programming formulation of the problem can be exactly solved to optimality by a commercial solver only for moderately sized problems. We recall a mixed integer programming formulation that can be exactly solved to optimality by a commercial solver only for very moderately sized problems. We propose a quick greedy algorithm and a GRASP with path-relinking heuristic for solving real-life sized problems. Computational experiments involving practical issues such as energy consumption and interference have been performed and reported for problems with up to 800 nodes, illustrating the effectiveness and the efficiency of the new algorithms. Both the greedy algorithm and the GRASP heuristic outperformed the best heuristic in the literature for very large problem sizes.

A Failure Detection System for Large Scale Distributed Systems

Failure detection is a fundamental building block for ensuring fault tolerance in large scale distributed systems. It is also a difficult problem. Resources under heavy loads can be mistaken as being failed. The failure of a network link can be detected by the lack of a response, but this also occurs when a computational resource fails. Although progress has been made, no existing approach provides a system that covers all essential aspects related to a distributed environment. This paper presents a failure detection system based on adaptive, decentralized failure detectors. The system is developed as an independent substrate, working asynchronously and independent of the application flow. It uses a hierarchical protocol, creating a clustering mechanism that ensures a dynamic configuration and traffic optimization. It also uses a gossip strategy for failure detection at local levels to minimize detection time and remove wrong suspicions. Results show that the system scales with the number of monitored resources, while still considering the QoS requirements of both applications and resources.

Effectiveness of Optimal Maintenance Strategy in Fault-Tolerant Multi-Robot Systems

This paper focuses on the effectiveness of maintenance in fault-tolerant multi-robot systems. The multi-robot system intended in this paper is completely parallel. That is to say, the system is enabled to work as long as one robot works. For this system, it is required to ensure fault tolerance and keep high performance taking robot failure and maintenance, such as prevention and correction of robots, into account. Therefore, we propose an optimal maintenance strategy on the basis of reliability engineering. This strategy enables robots to undergo preventive maintenance at an optimal interval and corrective maintenance each time they fail. Consequently, the number of robots undergoing maintenance or its effect on the system performance is minimized. Through simulation experiments, the effectiveness of the optimal maintenance strategy for the higher system performance is shown. In addition, the influence of robots undergoing maintenance on the system performance is mathematically and experimentally discussed on the basis of the number of robots used and maintenance strategies.

A dependability layer for large-scale distributed systems

Ensuring dependability in large-scale distributed systems represents an important research subject today. Despite the fact that many projects obtained valuable results in this domain, no acceptable solution was yet found that could integrate all the requirements for designing a dependable system and that could exploit all the capabilities of modern systems. We present a unitary and aggregate approach to ensuring reliability, availability, safety and security of distributed systems. Starting from the proposed architecture, we present implementation details for two solutions designed to ensure fault tolerance, using virtualisation and container-based replication of services. We also present an approach to enhance security using combined modern security models in large-scale distributed systems. The results and implementation details can serve as a methodology to assist distributed infrastructures in adopting such a middleware layer designed to enforce dependability in large-scale distributed systems.

3304 耐故障システムのためのロボット群制御と最適保全(OS8 無人化・遠隔監視,次世代物流システム・建設機械,オーガナイズド・セッション(OS))

Ensuring fault tolerance of robotic systems is a challenge for factory automation. For this challenge, we propose behavior coordination strategies and optimal maintenance policy for multiple mobile robots. The coordination strategies enable a system to continue operating even if a working robot undergoes preventive maintenance or fails and undergoes corrective maintenance. In addition, working robots are allowed to undergo preventive maintenance at an optimal interval and corrective maintenance each time they fail. Finally, through simulation experiments, we demonstrate that the behavior coordination strategies and optimal maintenance policy are both effective for the fault-tolerant systems.

Restrictions on Transversal Encoded Quantum Gate Sets

Transversal gates play an important role in the theory of fault-tolerant quantum computation due to their simplicity and robustness to noise. By definition, transversal operators do not couple physical subsystems within the same code block. Consequently, such operators do not spread errors within code blocks and are, therefore, fault tolerant. Nonetheless, other methods of ensuring fault tolerance are required, as it is invariably the case that some encoded gates cannot be implemented transversally. This observation has led to a long-standing conjecture that transversal encoded gate sets cannot be universal. Here we show that the ability of a quantum code to detect an arbitrary error on any single physical subsystem is incompatible with the existence of a universal, transversal encoded gate set for the code.

Fault-tolerant Internal Model Control with Application to a Diesel Engine

The paper proposes a new structure for fault-tolerant control of nonlinear systems subject to persistent faults. The principle of Internal Model Control (IMC) is extended to ensure fault tolerance with respect to faults that do not affect the plant stability. The method is based on a representation of sensor, actuator and plant faults as parameter changes of the plant model, which is part of the IMC control law. It is proved that the IMC control loop, which is extended by a diagnostic unit, tolerates substantial faults and ensures the nominal loop performance unless the fault changes the structure of the nonlinear plant. These results are illustrated for the air path of a Diesel engine.

Short length Menger's theorem and reliable optical routing

In the minimum path coloring problem, we are given a graph and a set of pairs of vertices of the graph and we are asked to connect the pairs by colored paths in such a way that paths of the same color are edge disjoint. In this paper we deal with a generalization of this problem where we are asked to connect each pair by k edge disjoint paths of the same color. The objective is to minimize the number of colors. The reason for multiple paths between the same pair of vertices is to ensure fault tolerance of the connections. We propose an O ( k 2 F ) = O ( k 2 Δ α - 1 log n ) approximation algorithm for this problem where F is the flow number of the graph, Δ is the maximum degree and α is the expansion. This is an improvement even for the special case k = 1 where, to our knowledge, the best previously known bound is weaker by a factor of log n . The underlying problem is that of finding several disjoint paths between a given pair of vertices. Menger's theorem provides a necessary and sufficient condition for the existence of k such paths. However, it does not say anything about the length of the paths although in communication problems the number of links used is an issue. We show that any two k -connected vertices are connected by k edge disjoint paths of average length O ( kF ) which improves an earlier result of Galil and Yu (Proceedings of the 27th Annual ACM Symposium on Theory of Computing, 1995) for several classes of graphs. In fact, this is only a corollary of a stronger result for multicommodity flow on networks with unit edge capacities: any multicommodity flow with k units for each commodity can be rerouted such that the flow for each commodity is shipped through k -tuples of edge disjoint paths of average length O ( kF ) without exceeding the edge capacities significantly.

Nonblocking Conditions for Multiring Commutators and Generalized Hypercubes for Arbitrary Commutations. II. Generalized Hypercubes. Intranode Commutation

Necessary and sufficient conditions for implementing arbitrary commutations without blocking in generalized hypercubes are formulated. These conditions are shown to ensure fault tolerance to individual faults of nodes. Maximal speed and minimal complexity of generalized hypercubes are studied. Methods for resolving intranode conflicts and a functional scheme of nodes for a multiring commutator and a generalized hypercube are investigated.

The role of distributed, real-time Ada & C++ on the Airborne Surveillance Testbed (AST) program

The Airborne Surveillance Testbed (AST) program, managed by SMDC for BMDO, is a technology demonstration program that supports development, test, and evaluation of defensive systems to counter intercontinental and theater ballistic missiles (ICBMs and TBMs) and their warheads. The heart of the AST program is a Boeing 767 aircraft equipped with a Raytheon-built, large-aperture, multiband, high data rate infrared sensor and a wide variety of processing equipment designed to detect, track, and discriminate ballistic missiles at long ranges. A Raytheon interceptor seeker (part of a Navy risk reduction effort) has recently been integrated onto the aircraft; a staring medium wave infrared (MWIR) camera is currently being added as well. Onboard processing capabilities include a Concurrent TurboHawk (multi-CPU PowerPC flight computer) along with a variety of custom and off-the-shelf signal processing equipment, SGI workstations, DEC Alphas, and PCs, largely programmed in Ada and C++. These systems are linked via SCRAMNet, Ethernet, 1553B, RS422 and RS232, and communicate externally via various radio systems. Since the start of the program in 1984, AST has been making use of Ada83, Ada95, and C++ for both simulations and embedded flight software. During that time, we have gathered a lot of experience in the use of Ada for real-time distributed systems, especially concerning:• The pitfalls of task scheduling algorithms and priorities• The benefits of the (careful) use of generics• The importance of some changes between Ada83 and Ada95• Interfacing Ada software to hardware (and standardized interrupt handling)• The importance of proper use of exception handling to ensure fault tolerance

Replica management for fault-tolerant systems

Replication has traditionally been used to assure fault tolerance. Active parallel replication is a new technique that, in addition to ensuring fault tolerance, dramatically reduces computation time and cost.