165 research outputs found
Conflict Managers for Self-stabilization without Fairness Assumption
No full textInternational audienceIn this paper, we specify the conflict manager abstraction. Informally, a conflict manager guarantees that any two nodes that are in conflict cannot enter their critical section simultaneously (safety), and that at least one node is able to execute its critical section (progress). The conflict manager problem is strictly weaker than the classical local mutual exclusion problem, where any node that requests to enter its critical section eventually does so (fairness). We argue that conflict managers are a useful mechanism to transform a large class of self-stabilizing algorithms that operate in an essentially sequential model, into self-stabilizing algorithm that operate in a completely asynchronous distributed model. We provide two implementations (one deterministic and one probabilistic) of our abstraction, and provide a composition mechanism to obtain a generic transformer. Our transformers have low overhead: the deterministic transformer requires one memory bit, and guarantees time overhead in order of the network degree, the probabilistic transformer does not require extra memory. While the probabilistic algorithm performs in anonymous networks, it only provides probabilistic stabilization guarantees. In contrast, the deterministic transformer requires initial symmetry breaking but preserves the original algorithm guarantees
Self-stabilizing Vertex Coloring of Arbitrary Graphs
No full textInternational audienceA self-stabilizing algorithm, regardless of the initial system state, converges in finite time to a set of states that satisfy a legitimacy predicate without the need for explicit exception handler of backward recovery. The vertex coloration problem consists in ensuring that every node in the system has a color that is different from any of its neighbors. We provide three self-stabilizing solutions to the vertex coloration problem under unfair scheduling that are based on a greedy technique. We use at most different colors (in complete graphs), where is the graph degree, and ensure stabilization within processor atomic steps. Two of our algorithms deal with uniform networks where nodes do not have identifiers. Our solutions lead to directed acyclic orientation and maximal independent set construction at no additional cost
MODELISATION, VERIFICATION ET RAFFINEMENT DES ALGORITHMES AUTO-STABILISANTS
No full textORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF
Stabilization, Safety, and Security of Distributed Systems, 8th International Symposium, SSS 2006, Dallas, TX, USA, November 17-19, 2006, Proceedings
No full textInternational audienc
Content-based Publish/Subscribe using Distributed R-trees
No full textInternational audiencePublish/subscribe systems provide a useful paradigm for selective data dissemination and most of the complexity related to addressing and routing is encapsulated within the network infrastructure. The challenge of such systems is to organize the peers so as to best match the interests of the consumers, minimizing false positives and avoiding false negatives.In this paper, we propose and evaluate the use of R-trees for organizing the peers of a content-based routing network. We adapt three well-known variants of R-trees to the content dissemination problem striving to minimize the occurrence of false positives while avoiding false negatives. The effectiveness and accuracy of each structure is analyzed by extensive simulations
A Superstabilizing -Approximation Algorithm for Dynamic Steiner Trees
No full textInternational audienceIn this paper we design and prove correct a fully dynamic distributed algorithm for maintaining an approximate Steiner tree that connects via a minimum-weight spanning tree a subset of nodes of a network (referred as Steiner members or Steiner group) . Steiner trees are good candidates to efficiently implement communication primitives such as publish/subscribe or multicast, essential building blocks for the new emergent networks (e.g. P2P, sensor or adhoc networks). The cost of the solution returned by our algorithm is at most times the cost of an optimal solution, where is the group of members. Our algorithm improves over existing solutions in several ways. First, it tolerates the dynamism of both the group members and the network. Next, our algorithm is self-stabilizing, that is, it copes with nodes memory corruption. Last but not least, our algorithm is \emph{superstabilizing}. That is, while converging to a correct configuration (i.e., a Steiner tree) after a modification of the network, it keeps offering the Steiner tree service during the stabilization time to all members that have not been affected by this modification
Brief Announcement: Dynamic FTSS in Asynchronous Systems: The Case of Unison
No full textInternational audienceContext. The advent of ubiquitous large-scale distributed systems advocates that tolerance to various kinds of faults and hazards must be included from the very early design of such systems. Self-stabilization [1] is a versatile technique that permits forward recovery from any kind of transient fault, while Fault-tolerance [2] is traditionally used to mask the effect of a limited number of permanent faults. The seminal works of [3,4] define FTSS protocols as protocols that are both Fault Tolerant and Self-Stabilizing, i.e. able to tolerate a few crash faults as well as arbitrary initial memory corruption. In [3], some impossibility results in asynchronous systems are presented. In [4], a general transformer is presented for synchronous systems. The transformer of [4] was proved impossible to transpose to asynchronous systems in [5] due to the impossibility of tight synchronization in the FTSS context. It turns out that FTSS possibility results in fully asynchronous systems known to date are restricted to static tasks, i.e. tasks that require eventual convergence to some global fixed point (tasks such as naming or vertex coloring fall in this category)
A Framework for Secure and Private P2P Publish/Subscribe
No full textInternational audienceWe propose a novel and totally decentralized strategy for private and secure data exchange in peer-to-peer systems. Our scheme is particularly appealing for point-to-point exchanges and use zero-knowledge mechanisms to preserve privacy. Furthermore, we show how to plug our private and secure data exchange module in existing publish/subscribe architectures. Our proposal enriches the original system with security and privacy making it resilient to a broad class of attacks (e.g. brute-force, eavesdroppers, man-in-the middle or malicious insiders). Additionally, the original properties of the publish/subscribe system are preserved without any degradation. A nice feature of our proposal is the reduce message cost: only one extra message is sent for every message sent in the original system. Note that our contribution is more conceptual than experimental and can be easily exploited by new emergent areas such as P2P Internet Games or Social Networks where a major trend is to achieve a secure and private communication without relying on any fixed infrastructure or centralized authority
Self-stabilizing minimum-degree spanning tree within one from the optimal degree
No full textInternational audienceWe propose a self-stabilizing algorithm for constructing a Minimum-Degree Spanning Tree (MDST) in undirected networks. Starting from an arbitrary state, our algorithm is guaranteed to converge to a legitimate state describing a spanning tree whose maximum node degree is at most ∆∗ + 1, where ∆∗ is the minimum possible maximum degree of a spanning tree of the network. To the best of our knowledge our algorithm is the first self stabilizing solution for the construction of a minimum-degree spanning tree in undirected graphs. The algorithm uses only local communications (nodes interact only with the neighbors at one hop distance). Moreover, the algorithm is designed to work in any asynchronous message passing network with reliable FIFO channels. Additionally, we use a fine grained atomicity model (i.e. the send/receive atomicity). The time complexity of our solution is O(mn2 log n) where m is the number of edges and n is the number of nodes. The memory complexity is O(δ log n) in the send-receive atomicity model (δ is the maximal degree of the network)
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