Uniform dynamic self-stabilizing leader election

A distributed system is self-stabilizing if it can be started in any possible global state. Once started the system regains its consistency by itself, without any kind of outside intervention. The self-stabilization property makes the system tolerant to faults in which processors exhibit a faulty behavior for a while and then recover spontaneously in an arbitrary state. When the intermediate period in between one recovery and the next faulty period is long enough, the system stabilizes. A distributed system is uniform if all processors with the same number of neighbors are identical. A distributed system is dynamic if it can tolerate addition or deletion of processors and links without reinitialization. In this work, we study uniform dynamic self-stabilizing protocols for leader election under readwrite atomicity. Our protocols use randomization to break symmetry. The leader election protocol stabilizes in O(ΔD log n) time when the number of the processors is unknown and O(ΔD), otherwise. Here Δ denotes the maximal degree of a node, D denotes the diameter of the graph and n denotes the number of processors in the graph. We introduce self-stabilizing protocols for synchronization that are used as building blocks by the leader-election algorithm. We conclude this work by presenting a simple, uniform, self-stabilizing ranking protocol     

Design and analysis of dynamic leader election protocols in broadcast networks

Summary.  The well-known problem of leader election in distributed systems is considered in a dynamic context where processes may participate and crash spontaneously. Processes communicate by means of buffered broadcasting as opposed to usual point-to-point communication. In this paper we design a leader election protocol in such a dynamic context. As the problem at hand is considerably complex we develop the protocol in three steps. In the initial design processes are considered to be perfect and a leader is assumed to be present initially. In the second protocol, the assumption of an initial leader is dropped. This leads to a symmetric protocol which uses an (abstract) timeout mechanism to detect the absence of a leader. Finally, in the last step of the design processes may crash without giving any notification of other processes. The worst case message complexity of all protocols is addressed. A formal approach to the specification and verification of the leader election protocols is adopted. The requirements are specified in a property-oriented way and the protocols are denoted by means of extended finite state machines. It is proven using linear-time temporal logic that the fault-tolerant protocol satisfies its requirements. Received: September 1993 / Revised: September 1995     

New protocols for the election of a leader in a ring

In this paper we investigate the impact of time for the election of a leader in a distributed environment. We propose a new protocol schema that can be specialized to obtain several protocols with different communication-time characteristics when the network is ring-shaped and the communications between processors are synchronous.     

Broadcast-efficient protocols for mobile radio networks

The main contribution of this work is to present elegant broadcast-efficient protocols for permutation routing, ranking, and sorting on single-hop Mobile Radio Networks with p stations and k radio channels, denoted by MRN(p,k). Clearly, any protocol performing these tasks on n items must perform ⁿ/_k broadcast rounds because each item must be broadcast at least once. We begin by presenting an optimal off-line permutation routing protocol using ⁿ /_k broadcast rounds for arbitrary k, p, and n. Further, we show that optimal on-line routing can be performed in ⁿ/ _k broadcast rounds, provided that either k=1 or p=n. We then go on to develop an online routing protocol that takes 2ⁿ/ _k+k-1 broadcast rounds on the MRN(p,k), whenever k⩽√^p/₂. Using these routing protocols as basic building blocks, we develop a ranking protocol that takes 2ⁿ /_k+o(ⁿ/_k) broadcast rounds as well as a sorting protocol that takes 3ⁿ/_k+o(ⁿ/_k) broadcast rounds, provided that k ϵ o(√n) and p=n. Finally, we develop a ranking protocol that takes 3ⁿ/_k+o(ⁿ/ _k) broadcast rounds, as well as a sorting protocol that takes 4ⁿ/_k+o(ⁿ/_k) broadcast rounds on the MRN(p,k), provided that k⩽√^p/₂ and p ϵ o(n). Featuring very low proportionality constants, our protocols offer a vast improvement over the state of the art     

A leader election algorithm for dynamic networks with causal clocks

An algorithm for electing a leader in an asynchronous network with dynamically changing communication topology is presented. The algorithm ensures that, no matter what pattern of topology changes occurs, if topology changes cease, then eventually every connected component contains a unique leader. The algorithm combines ideas from the Temporally Ordered Routing Algorithm for mobile ad hoc networks (Park and Corson in Proceedings of the 16th IEEE Conference on Computer Communications (INFOCOM), pp. 1405–1413 (1997) with a wave algorithm (Tel in Introduction to distributed algorithms, 2nd edn. Cambridge University Press, Cambridge, MA, 2000), all within the framework of a height-based mechanism for reversing the logical direction of communication topology links (Gafni and Bertsekas in IEEE Trans Commun C–29(1), 11–18 1981). Moreover, a generic representation of time is used, which can be implemented using totally-ordered values that preserve the causality of events, such as logical clocks and perfect clocks. A correctness proof for the algorithm is provided, and it is ensured that in certain well-behaved situations, a new leader is not elected unnecessarily, that is, the algorithm satisfies a stability condition.     

New model and algorithms for leader election in synchronousfiber-optic networks

We improve on I. Cidon, I. Gopal and S. Kutten's leader election algorithm (Proc. 7th ACM Symp. Principles Distrib. Computing, Toronto, Ont., Canada. Aug. 1988) by presenting an algorithm that uses only O(√n log D + f) time units to run on synchronous networks of degree f and diameter D, where f⩾3. When f is 2, the algorithm uses only O(log D) time units     

Fast protocols for leader election and spanning tree construction in a distributed network

We consider leader election and spanning tree construction problems in a synchronous network. Protocols are designed under the assumption that nodes in the network have identifiers but the size of an identifier is unlimited. We present fast protocols with runtime O(D log L+L), where L is the size of the minimal identifier and D is the network diameter.     

Randomized leader election

We present an efficient randomized algorithm for leader election in large-scale distributed systems. The proposed algorithm is optimal in message complexity (O(n) for a set of n total processes), has round complexity logarithmic in the number of processes in the system, and provides high probabilistic guarantees on the election of a unique leader. The algorithm relies on a balls and bins abstraction and works in two phases. The main novelty of the work is in the first phase where the number of contending processes is reduced in a controlled manner. Probabilistic quorums are used to determine a winner in the second phase. We discuss, in detail, the synchronous version of the algorithm, provide extensions to an asynchronous version and examine the impact of failures.     

Quantum leader election

A group of n individuals \(A_{1},\ldots A_{n}\) who do not trust each other and are located far away from each other, want to select a leader. This is the leader election problem, a natural extension of the coin flipping problem to n players. We want a protocol which will guarantee that an honest player will have at least \(\frac{1}{n}-\epsilon \) chance of winning (\(\forall \epsilon >0\)), regardless of what the other players do (whether they are honest, cheating alone or in groups). It is known to be impossible classically. This work gives a simple algorithm that does it, based on the weak coin flipping protocol with arbitrarily small bias derived by Mochon (Quantum weak coin flipping with arbitrarily small bias, arXiv:0711.4114, 2000) in 2007, and recently published and simplified in Aharonov et al. (SIAM J Comput, 2016). A protocol with linear number of coin flipping rounds is quite simple to achieve; we further provide an improvement to logarithmic number of coin flipping rounds. This is a much improved journal version of a preprint posted in 2009; the first protocol with linear number of rounds was achieved independently also by Aharon and Silman (New J Phys 12:033027, 2010) around the same time.     

Optimal asynchronous agreement and leader election algorithm for complete networks with Byzantine faulty links

Summary.  We consider agreement and leader election on asynchronous complete networks when the processors are reliable, but some of the channels are subject to failure. Fischer, Lynch, and Paterson have already shown that no deterministic algorithm can solve the agreement problem on asynchronous networks if any processor fails during the execution of the algorithm. Therefore, we consider only channel failures. The type of channel failure we consider in this paper is Byzantine failure, that is, channels fail by altering messages, sending false information, forging messages, losing messages at will, and so on. There are no restrictions on the behavior of a faulty channel. Therefore, a faulty channel may act as an adversary who forges messages on purpose to prevent the successful completion of the algorithm. Because we assume an asynchronous network, the channel delays are arbitrary. Thus, the faulty channels may not be detectable unless, for example, the faulty channels cause garbage to be sent. We present the first known agreement and leader election algorithm for asynchronous complete networks in which the processors are reliable but some channels may be Byzantine faulty. The algorithm can tolerate up to [n−22] faulty channels, where n is the number of processors in the network. We show that the bound on the number of faulty channels is optimal. When the processors terminate their corresponding algorithms, all the processors in the network will have the same correct vector, where the vector contains the private values of all the processors. Received: May 1994/Accepted: July 1995     

An analysis on decentralized adaptive MAC protocols for cognitive radio networks

The scarcity of bandwidth in the radio spectrum has become more vital since the demand for more and more wireless applications has increased. Most of the spectrum bands have been allocated although many studies have shown that these bands are significantly underutilized most of the time. The problem of unavailability of spectrum and inefficiency in its utilization has been smartly addressed by the cognitive radio (CR) technology which is an opportunistic network that senses the environment, observes the network changes, and then uses knowledge gained from the prior interaction with the network to make intelligent decisions by dynamically adapting their transmission characteristics. In this paper, some of the decentralized adaptive medium access control (MAC) protocols for CR networks have been critically analyzed, and a novel adaptive MAC protocol for CR networks, decentralized non-global MAC (DNG-MAC), has been proposed. The results show the DNG-MAC outperforms other CR-MAC protocols in terms of time and energy efficiency.     

How much memory is needed for leader election

We study the minimum memory size with which nodes of a network have to be equipped, in order to solve deterministically the leader election problem. Nodes are unlabeled, but ports at each node have arbitrary fixed labelings which, together with the topology of the network, can create asymmetries to be exploited in leader election. We consider two versions of the leader election problem: strong LE in which exactly one leader has to be elected, if this is possible, while all nodes must terminate in a state “infeasible” when the election of a unique leader fails, and weak LE, which differs from strong LE in that no requirement on the behavior of nodes is imposed, if leader election is impossible. Nodes are modeled as identical automata and we ask what is the minimum amount of memory of such an automaton to enable leader election. We show that logarithmic memory is optimal for both strong and weak leader election in the class of arbitrary connected graphs. By contrast we show that strong LE can be accomplished in the class of trees of maximum degree Δ using only O(log log Δ) bits of memory, thus proving an exponential gap in memory requirements for leader election between the class of trees and the class of arbitrary graphs.     

Efficient leader election using sense of direction

Summary.  This paper presents a protocol for leader election in complete networks with a sense of direction. Sense of direction provides nodes the capability of distinguishing between their incident links according to a global scheme. We propose a protocol for leader election which requires O(N) messages and O(log N) time. The protocol is message optimal and the time complexity is a significant improvement over currently known protocols for this problem. Received August 1995 / Accepted December 1996     

A highly available local leader election service

We define the highly available local leader election problem (G. LeLann, 1977), a generalization of the leader election problem for partitionable systems. We propose a protocol that solves the problem efficiently and give some performance measurements of our implementation. The local leader election service has been proven useful in the design and implementation of several fail-aware services for partitionable systems     

Erratum to: An analysis on decentralized adaptive MAC protocols for cognitive radio networks

正Erratum to:International Journal of Automation and Computing DOI:10.1007/s11633-013-0695-z The original version of this article unfortunately contained a mistake.The received date and revised date were incorrect.The corrected received date and revised date are given below.     

机会网络路由协议

在机会网络中由于网络稀疏、节点移动和通信范围等因素的影响,有可能出现网络分裂或节点脱网,源节点和目的节点之间不一定存在完整的端到端路径,这为路由协议的设计带来巨大挑战,此问题近年来引起了研究人员越来越多的关注。首先介绍了机会网络的基本概念、体系结构和特点等;然后阐述了机会网络路由协议研究的进展,概括了机会网络路由协议中的新机制,对现有路由协议进行分类并详述它们的基本原理;通过比较对各种协议的特点进行分析阐述,最后给出未来研究的方向。