Self-stabilization Research Articles

Self-stabilizing multivalued consensus in asynchronous crash-prone systems

The multivalued consensus problem is a fundamental issue in fault-tolerant distributed computing. It encompasses a wide range of agreement problems where processes must unanimously decide on a specific value v∈V, with |V|≥2. Existing solutions that handle process crash failures simplify the multivalued consensus problem by reducing it to the binary consensus problem. Examples of such solutions include Mostéfaoui-Raynal-Tronel [IPL 2000] and Zhang-Chen [IPL 2009].In this work, we aim to design an even more reliable solution by leveraging the concept of self-stabilization, which provides a strong form of fault tolerance. Self-stabilizing algorithms can recover from transient faults, which represent any deviation from the system's intended behavior (as long as the algorithm code remains intact) in addition to process and communication failures.To the best of our knowledge, this work presents the first self-stabilizing algorithm for multivalued consensus in asynchronous message-passing systems susceptible to process failures and transient faults. Our solution uses, at most, n concurrent invocations of binary consensus. This is another way we advance state-of-the-art solutions compared to previous non-self-stabilizing ones. For example, Mostéfaoui-Raynal-Tronel's solution requires an unbounded number of sequential invocations of binary consensus.

Selection by differential survival among marine animals in the Phanerozoic

The Gaia hypothesis posits that the Earth and its biosphere function as a single self-stabilizing system, but a key challenge is explaining how this could have arisen through Darwinian evolution. One theory is that of “selection by differential survival,” in which a clade’s extinction probability decreases with age as it accumulates adaptations resisting environmental disturbances. While this is hard to assess during early Earth history, we can assess whether this process operated among marine animal genera throughout the Phanerozoic. To that end, we analyzed time ranges of 36,117 extinct animal genera using fossil occurrence data from the Paleobiology Database in order to calculate marine metazoan extinction age selectivity, extinction rates, and speciation rates over the Phanerozoic. We identify four signatures of selection by differential survival: lower extinction rates among older lineages, heritability and taxonomically nested propagation of extinction resistance, reduced age selectivity during rare environmental perturbations, and differential extinction rather than speciation as the primary driver of the phenomenon. Evidence for this process at lower taxonomic levels also implies its possibility for life as a whole – indeed, the possibility of Gaia.

Self-Stabilizing Algorithms for Computing Maximal Distance-2 Independent Sets and Minimal Dominating Sets in Networks

Self-Stabilizing Algorithms for Computing Maximal Distance-2 Independent Sets and Minimal Dominating Sets in Networks

Self-stabilizing synchronous unison in directed networks

Self-stabilization is a general paradigm that characterizes the ability of a distributed system to recover from transient faults. Since its introduction by Dijkstra in 1974, self-stabilization has been successfully applied to efficiently solve many networking tasks. However, most of the literature focuses on bidirectional networks. Now, in today's networks such as WSNs, some communication channels may be one-way only. Considering such network topologies, a.k.a. directed graphs, makes self-stabilization more complicated, and sometimes even impossible. In this paper, we investigate the gap in terms of requirements and efficiency when considering a directed graph instead of an undirected one as network topology for a self-stabilizing algorithm. Our case study is a variant of a synchronous unison algorithm proposed by Arora et al.; the synchronous unison being a clock synchronization problem.

Japan’s Border Measures during Covid-19: How the Crisis Shaped ‘Others’ to Protect the ‘Stability of Self’

The Covid-19 pandemic has prompted countries to implement a wide range of specific cross-border security measures. The fear and anxiety induced by this crisis have rapidly expanded and contracted countries’ understanding of ‘self’ and ‘other’. This study examines Japan’s shift from liberal pre- Covid-19 border policies to the most stringent border closure measures among the G7 countries during the pandemic. In this study, we argue that the pandemic-induced fear increased anxiety in Japan’s public health safety identity, rapidly reshaping the conceptualization of the ‘self’ and ‘other’ in crisis scenarios. This shift aligns with Japan’s historical narrative of combating unprecedented threats to public health.

Self-stabilizing indulgent zero-degrading binary consensus

Guerraoui proposed an indulgent solution for the binary consensus problem. Namely, he showed that an arbitrary behavior of the failure detector never violates safety requirements even if it compromises liveness. Consensus implementations are often used in a repeated manner. Dutta and Guerraoui proposed a zero-degrading solution, i.e., during system runs in which the failure detector behaves perfectly, a node failure during one consensus instance has no impact on the performance of future instances.Our study, which focuses on indulgent zero-degrading binary consensus, aims at the design of an even more robust communication abstraction. We do so through the lenses of self-stabilization—a very strong notion of fault-tolerance. In addition to node and communication failures, self-stabilizing algorithms can recover after the occurrence of arbitrary transient faults; these faults represent any violation of the assumptions according to which the system was designed to operate (as long as the algorithm code stays intact).This work proposes the first, to the best of our knowledge, self-stabilizing algorithm for indulgent zero-degrading binary consensus for time-free message-passing systems prone to detectable process failures. The proposed algorithm recovers within a finite time after the occurrence of the last arbitrary transient fault. Since the proposed solution uses an Ω failure detector, we also present the first, to the best of our knowledge, self-stabilizing asynchronous Ω failure detector, which is a variation on the one by Mostéfaoui, Mourgaya, and Raynal.

Eventually lattice-linear algorithms

Lattice-linear systems allow nodes to execute asynchronously. We introduce eventually lattice-linear algorithms, where lattices are induced only among the states in a subset of the state space. The algorithm guarantees that the system transitions to a state in one of the lattices. Then, the algorithm behaves lattice linearly while traversing to an optimal state through that lattice.We present a lattice-linear self-stabilizing algorithm for service demand based minimal dominating set (SDMDS) problem. Using this as an example, we elaborate the working of, and define, eventually lattice-linear algorithms. Then, we present eventually lattice-linear self-stabilizing algorithms for minimal vertex cover (MVC), maximal independent set (MIS), graph colouring (GC) and 2-dominating set problems (2DS).Algorithms for SDMDS, MVC and MIS converge in 1 round plus n moves (within 2n moves), GC in n+4m moves, and 2DS in 1 round plus 2n moves (within 3n moves). These results are an improvement over the existing literature. We also present experimental results to show performance gain demonstrating the benefit of lattice-linearity.

Ultra-lightweight anthropomorphic dual-arm rolling robot for dexterous manipulation tasks on linear infrastructures: A self-stabilizing system

Ultra-lightweight anthropomorphic dual-arm rolling robot for dexterous manipulation tasks on linear infrastructures: A self-stabilizing system

A Wide Frequency Response Fabry–Pérot Acoustic Sensor Based on the Self-Stabilization System

A self-stabilization system based on the operating point is built for measuring the membrane-free optical acoustic sensor constructed of a rigid Fabry-Pérot (F-P) cavity. The system can directly lock and track the quadrature point of the sensor’s spectrum to realize broadband acoustic detection with high sensitivity. Compared with the demodulation system based on phase modulation spectrum technology, the system is simple in construction and has the advantage of fast real-time demodulation rate and wide detection bandwidth. The experimental results show the acoustic sensor achieves a wide frequency response of 700 Hz-411 kHz with a flatness of ±1.78 dB, and a sensitivity of 31.83 mV/Pa, while the maximum detectable sound pressure reaches 136.9 dB. The sensor performs well in broadening the frequency response range, which includes a medium and high frequency range from 700 Hz to 20 kHz for noise monitoring, as well as an ultrasound range from 20 to 411 kHz for aeroacoustics and photoacoustic imaging. The improvement of the frequency band characteristics of the sensor in this research will further contribute to the development of application fields.

Self-stabilizing Byzantine fault-tolerant repeated reliable broadcast

We study a well-known communication abstraction called Byzantine Reliable Broadcast (BRB). This abstraction is central in the design and implementation of fault-tolerant distributed systems, as many fault-tolerant distributed applications require communication with provable guarantees on message deliveries. Our study focuses on fault-tolerant implementations for message-passing systems that are prone to process-failures, such as crashes and malicious behavior.At PODC 1983, Bracha and Toueg, in short, BT, solved the BRB problem. BT has optimal resilience since it can deal with t<n/3 Byzantine processes, where n is the number of processes. The present work aims to design an even more robust solution than BT by expanding its fault-model with self-stabilization, a vigorous notion of fault-tolerance. In addition to tolerating Byzantine and communication failures, self-stabilizing systems can recover after the occurrence of arbitrary transient-faults. These transient faults allow the model to represent temporary deviations from the assumptions on which the system was originally designed to operate (provided that the algorithm code remains intact).We propose, to the best of our knowledge, the first self-stabilizing Byzantine fault-tolerant (BFT) solution for repeated BRB in signature-free message-passing systems (that follows BT's problem specifications). Our contribution includes a self-stabilizing variation on BT that solves a single-instance BRB for asynchronous systems. We also consider the problem of recycling instances of single-instance BRB. Our self-stabilizing BFT recycling for time-free systems facilitates the concurrent handling of a predefined number of BRB invocations and, in this way, can serve as the basis for self-stabilizing BFT consensus.

Self−Mode−Locked 2−μm GaSb−Based Optically Pumped Semiconductor Disk Laser

We present a mode−locked GaSb−based optically pumped semiconductor disk laser operating at 2 µm based on the self−mode−locked mechanism. Using the delay differential equation model, we discuss the influence of cavity length on the stability of self−mode−locking and design a Z−shaped long cavity for self−mode−locking. Employing an aperture and an F−P etalon in the cavity length of ~365 mm, we obtain stable self−mode−locking at a center wavelength of 2034.5 nm, with a pulse duration of 255.48 ps and average output power of 173 mW at a repetition rate of 404 MHz.

The stability of non-uniform self gravitating system in the presence of non-uniform CRs pressure

The stability of non-uniform self gravitating system in the presence of non-uniform CRs pressure

Self-stabilizing systems in spite of high dynamics

We initiate research on self-stabilization in highly dynamic identified message-passing systems where dynamics is modeled using time-varying graphs (TVGs). More precisely, we address the self-stabilizing leader election problem in three wide classes of TVGs: the class TCB(Δ) of TVGs with temporal diameter bounded by Δ, the class TCQ(Δ) of TVGs with temporal diameter quasi-bounded by Δ, and the class TCR of TVGs with recurrent connectivity only, where TCB(Δ)⊆TCQ(Δ)⊆TCR. We first study conditions under which our problem can be solved. We introduce the notion of size-ambiguity to show that the assumption on the knowledge of the number n of processes is central. Our results reveal that, despite the existence of unique process identifiers, any deterministic self-stabilizing leader election algorithm working on the class TCQ(Δ) or TCR cannot be size-ambiguous, justifying why our solutions for those classes assume the exact knowledge of n. We then present three self-stabilizing leader election algorithms for Classes TCB(Δ), TCQ(Δ), and TCR, respectively. Our algorithm for TCB(Δ) stabilizes in at most 3Δ rounds. However, we show that stabilization time cannot be bounded for the leader election problem in TCQ(Δ) and TCR. Nevertheless, we circumvent this issue by showing that our solutions are speculative in the sense that their stabilization time in TCB(Δ) (⊆TCQ(Δ)⊆TCR) is O(Δ) rounds.

Optimal Space Lower Bound for Deterministic Self-Stabilizing Leader Election Algorithms

Given a boolean predicate $\Pi$ on labeled networks (e.g., proper coloring, leader election, etc.), a self-stabilizing algorithm for $\Pi$ is a distributed algorithm that can start from any initial configuration of the network (i.e., every node has an arbitrary value assigned to each of its variables), and eventually converge to a configuration satisfying $\Pi$. It is known that leader election does not have a deterministic self-stabilizing algorithm using a constant-size register at each node, i.e., for some networks, some of their nodes must have registers whose sizes grow with the size $n$ of the networks. On the other hand, it is also known that leader election can be solved by a deterministic self-stabilizing algorithm using registers of $O(\log \log n)$ bits per node in any $n$-node bounded-degree network. We show that this latter space complexity is optimal. Specifically, we prove that every deterministic self-stabilizing algorithm solving leader election must use $\Omega(\log \log n)$-bit per node registers in some $n$-node networks. In addition, we show that our lower bounds go beyond leader election, and apply to all problems that cannot be solved by anonymous algorithms.

Location functions for self-stabilizing byzantine tolerant swarms

This paper proposes a novel framework to realize self-stabilizing Byzantine tolerant swarms. In this framework, non-Byzantine robots execute tasks while satisfying location functions. That is, the robots use a policy for their location choice, which restricts their location to satisfy the functions. We give a general Byzantine-resilient self-stabilizing algorithm based on the location function. Then we provide an efficient implementation of the self-stabilizing algorithms for special classes of tasks, called polynomial-based tasks and shape-based tasks. We also demonstrate the usefulness of the proposed framework by implementing typical tasks of robots.

Stability and Resilience of Distributed Information Spreading in Aggregate Computing

Spreading informationthrough a network of devices is a core activity for most distributed systems. Self-stabilizing algorithms for information spreading are one of the key building blocks enabling aggregate computing to provide resilient coordination in open complex distributed systems. This article improves a general spreading block in the aggregate computing literature by making it resilient to network perturbations, establishes its global uniform asymptotic stability, and proves that it is ultimately bounded under persistent disturbances. The ultimate bounds depend only on the magnitude of the largest perturbation and the network diameter, and three design parameters trading off competing aspects of performance. For example, as in many dynamical systems, values leading to greater resilience to network perturbations slow convergence and vice versa.

A greedy randomized adaptive search procedure (GRASP) for minimum weakly connected dominating set problem

The minimum weakly connected dominating set problem (MWCDSP), a variant of the classical minimum dominating set problem, aims to find a minimum weakly connected dominating set on a given connected and undirected graph. To address this problem, a 0–1 integer linear programming (ILP) model and a framework of greedy randomized adaptive search procedure (GRASP) for MWCDSP are proposed. Specially, two novel local search procedures are introduced to improve the initial candidate solution in GRASP based on two greedy functions and tabu strategy. First, two greedy functions Dscore and Nscore are proposed to define the dominating score and neighbor score of each vertex respectively. Second, a tabu strategy is introduced to avoid the cycling problems. Third, a new local search procedure for searching a (k-1)-size solution after obtaining a k-size solution based on the Dscore function and tabu strategy is proposed, which is further improved by integrating Nscore into the selection process of moving vertices in an improved local search algorithm. Experimental results on four kinds of graph instances show that our GRASPs outperforms the famous CPLEX, the self-stabilizing algorithm MWCDS and the memetic algorithm MA. Specially, the GRASP with improved local search procedure outperforms all of the competitors.

Self-Stabilizing and Private Distributed Shared Atomic Memory in Seldomly Fair Message Passing Networks

We study the problem of privately emulating shared memory in message-passing networks. The system includes clients that store and retrieve replicated information on N servers, out of which e are data-corrupting malicious. When a client accesses a data-corrupting malicious server, the data field of that server response might be different from the value it originally stored. However, all other control variables in the server reply and protocol actions are according to the server algorithm. For the coded atomic storage algorithms by Cadambe et al., we present an enhancement that ensures no information leakage and data-corrupting malicious fault-tolerance. We also consider recovery after the occurrence of transient faults that violate the assumptions according to which the system was designed to operate. After their last occurrence, transient faults leave the system in an arbitrary state (while the program code stays intact). We present a self-stabilizing algorithm, which recovers after the occurrence of transient faults. This addition to Cadambe et al. considers asynchronous settings as long as no transient faults occur. The recovery from transient faults that bring the system counters (close) to their maximal values may include the use of a global reset procedure, which requires the system run to be controlled by a fair scheduler. After the recovery period, the safety properties are provided for asynchronous system runs that are not necessarily controlled by fair schedulers. Since the recovery period is bounded and the occurrence of transient faults is extremely rare, we call this design criteria self-stabilization in the presence of seldom fairness. Our self-stabilizing algorithm uses a bounded amount of storage during asynchronous executions (that are not necessarily controlled by fair schedulers). To the best of our knowledge, we are the first to address privacy, data-corrupting malicious behavior, and self-stabilization in the context of emulating atomic shared memory in message-passing systems.

ONTOLOGICAL (IN) SECURITY IN THE EU: THE CASE OF CYPRUS

Ontological (in)security concept has been recently introduced to the security studies and qained popularity. Individuals and states instinctively pursue their physical security, but they never feel completely safe in an environment which stability and security of self’s existence cannot be guaranteed. They’re in a search for attaining ontological security through narratives, habits, and routines to generate a sense of trust in an uncertainty environment. In this regard, this article tries to answer a key question: how ongoing Cyprus conflict be explained through ontological (in)security considering the EU’s failure to unravel security dilemmas between Turkish and Greek communities on the island? The findings of the article will contribute to the existing literature and open up new debates concerning the role of ontological (in)security in ongoing conflicts

Augmented network stability and lifetime of self–organization based clustering in manet using group mobility

Augmented network stability and lifetime of self–organization based clustering in manet using group mobility