Proceedings of the 22nd International Conference on Distributed Computing and Networking最新文献

{"title":"Phase Transitions of the k-Majority Dynamics in a Biased Communication Model","authors":"Emilio Cruciani, Hlafo Alfie Mimun, Matteo Quattropani, Sara Rizzo","doi":"10.1145/3427796.3427811","DOIUrl":"https://doi.org/10.1145/3427796.3427811","url":null,"abstract":"Consider a graph where each of the n nodes is in one of two possible states, say or . Herein, we analyze the synchronous k-majoritydynamics, where nodes sample k neighbors uniformly at random with replacement and adopt the majority binary state among the nodes in the sample (potential ties are broken uniformly at random). This class of dynamics generalizes other well-known dynamics, e.g., voter and 3-majority, which have been studied in the literature as distributed algorithms for consensus. We consider a biased communication model: whenever nodes sample a neighbor they see, w.l.o.g., state with some probability p, regardless of the state of the sampled node, and its true state with probability 1 − p. Such a communication model allows to reason about the robustness of a consensus protocol when communication channels between nodes are noisy. Differently from previous works where specific graph topologies—typically characterized by good expansion properties—are considered, our analysis only requires the graphs to be sufficiently dense, i.e., to have minimum degree ω(log n), without any further topological assumption. In this setting we prove two phase transition phenomena, both occurring asymptotically almost surely, depending on the bias p and on the initial unbalance toward state . More in detail, we prove that for every k ≥ 3 there exists a such that if the process reaches in rounds a -almost-consensus, i.e., a configuration where a fraction 1 − γ of the volume is in state , for any arbitrarily-small positive constant γ. On the other hand, if , we look at random initial configurations in which every node is in state with probability 1 − q independently of the others. We prove that there exists a constant such that if then a -almost-consensus is still reached in rounds, while, if , the process spends nω(1) rounds in a metastable phase where the fraction of volume in state is around a constant value depending only on p and k. Finally we also investigate, in such a biased setting, the differences and similarities between k-majority and other closely-related dynamics, namely voter and deterministic majority.","PeriodicalId":335477,"journal":{"name":"Proceedings of the 22nd International Conference on Distributed Computing and Networking","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123775589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gathering with a strong team in weakly Byzantine environments","authors":"Jion Hirose, Junya Nakamura, Fukuhito Ooshita, M. Inoue","doi":"10.1145/3427796.3427799","DOIUrl":"https://doi.org/10.1145/3427796.3427799","url":null,"abstract":"We study the gathering problem requiring a team of mobile agents to gather at a single node in arbitrary networks. The team consists of k agents with unique identifiers (IDs), and f of them are weakly Byzantine agents, which behave arbitrarily except falsifying their identifiers. The agents move in synchronous rounds and cannot leave any information on nodes. If the number of nodes n is given to agents, the existing fastest algorithm tolerates any number of weakly Byzantine agents and achieves gathering with simultaneous termination in O(n4 · |Λgood| · X(n)) rounds, where |Λgood| is the length of the maximum ID of non-Byzantine agents and X(n) is the number of rounds required to explore any network composed of n nodes. In this paper, we ask the question of whether we can reduce the time complexity if we have a strong team, i.e., a team with a few Byzantine agents, because not so many agents are subject to faults in practice. We give a positive answer to this question by proposing two algorithms in the case where at least 4f2 + 9f + 4 agents exist. Both the algorithms take the upper bound N of n as input. The first algorithm achieves gathering with non-simultaneous termination in O((f + |Λgood|) · X(N)) rounds. The second algorithm achieves gathering with simultaneous termination in O((f + |Λall|) · X(N)) rounds, where |Λall| is the length of the maximum ID of all agents. The second algorithm significantly reduces the time complexity compared to the existing one if n is given to agents and |Λall| = O(|Λgood|) holds.","PeriodicalId":335477,"journal":{"name":"Proceedings of the 22nd International Conference on Distributed Computing and Networking","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129291571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance analysis of a distributed algorithm for admission control in wireless networks under the 2-hop interference model","authors":"Ashwin Ganesan","doi":"10.1145/3427796.3427806","DOIUrl":"https://doi.org/10.1145/3427796.3427806","url":null,"abstract":"A general open problem in networking is: what are the fundamental limits to the performance that is achievable with some given amount of resources? More specifically, if each node in the network has information about only its 1-hop neighborhood, then what are the limits to performance? This problem is considered for wireless networks where each communication link has a minimum bandwidth quality-of-service (QoS) requirement. Links in the same vicinity contend for the shared wireless medium. The conflict graph captures which pairs of links interfere with each other and depends on the MAC protocol. In IEEE 802.11 MAC protocol-based networks, when communication between nodes i and j takes place, the neighbors of both i and j remain silent. This model of interference is called the 2-hop interference model because the distance in the network graph between any two links that can be simultaneously active is at least 2. In the admission control problem studied in the present paper, the objective is to determine, using only localized information, whether a given set of flow rates is feasible. In the present work, a distributed algorithm is proposed for this problem, where each node has information only about its 1-hop neighborhood. The worst-case performance of the distributed algorithm, i.e. the largest factor by which the performance of this distributed algorithm is away from that of an optimal, centralized algorithm, is analyzed. Lower and upper bounds on the suboptimality of the distributed algorithm are obtained, and both bounds are shown to be tight. The exact worst-case performance is obtained for some ring topologies. While distance-d distributed algorithms have been analyzed for the 1-hop interference model, an open problem in the literature is to extend these results to the K-hop interference model, and the present work initiates the generalization to the K-hop interference model.","PeriodicalId":335477,"journal":{"name":"Proceedings of the 22nd International Conference on Distributed Computing and Networking","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128316023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bio-Inspired Energy Distribution for Programmable Matter","authors":"Joshua J. Daymude, A. Richa, Jamison Weber","doi":"10.1145/3427796.3427835","DOIUrl":"https://doi.org/10.1145/3427796.3427835","url":null,"abstract":"In systems of active programmable matter, individual modules require a constant supply of energy to participate in the system’s collective behavior. These systems are often powered by an external energy source accessible by at least one module and rely on module-to-module power transfer to distribute energy throughout the system. While much effort has gone into addressing challenging aspects of power management in programmable matter hardware, algorithmic theory for programmable matter has largely ignored the impact of energy usage and distribution on algorithm feasibility and efficiency. In this work, we present an algorithm for energy distribution in the amoebot model that is loosely inspired by the growth behavior of Bacillus subtilis bacterial biofilms. These bacteria use chemical signaling to communicate their metabolic states and regulate nutrient consumption throughout the biofilm, ensuring that all bacteria receive the nutrients they need. Our algorithm similarly uses communication to inhibit energy usage when there are starving modules, enabling all modules to receive sufficient energy to meet their demands. As a supporting but independent result, we extend the amoebot model’s well-established spanning forest primitive so that it self-stabilizes in the presence of crash failures. We conclude by showing how this self-stabilizing primitive can be leveraged to compose our energy distribution algorithm with existing amoebot model algorithms, effectively generalizing previous work to also consider energy constraints.","PeriodicalId":335477,"journal":{"name":"Proceedings of the 22nd International Conference on Distributed Computing and Networking","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129424482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Self-stabilizing Systems in Spite of High Dynamics","authors":"K. Altisen, Stéphane Devismes, Anaïs Durand, C. Johnen, F. Petit","doi":"10.1145/3427796.3427838","DOIUrl":"https://doi.org/10.1145/3427796.3427838","url":null,"abstract":"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 of TVGs with temporal diameter bounded by Δ, the class of TVGs with temporal diameter quasi-bounded by Δ, and the class of TVGs with recurrent connectivity only, where . 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 in the class or 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 , , and , respectively. Our algorithm for stabilizes in at most 3Δ rounds. In and , stabilization time cannot be bounded, except for trivial specifications. However, we show that our solutions are speculative in the sense that their stabilization time in is O(Δ) rounds.","PeriodicalId":335477,"journal":{"name":"Proceedings of the 22nd International Conference on Distributed Computing and Networking","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121368046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Asymmetric Distributed Trust","authors":"C. Cachin, Björn Tackmann","doi":"10.1145/3427796.3433933","DOIUrl":"https://doi.org/10.1145/3427796.3433933","url":null,"abstract":"Quorum systems are a key abstraction in distributed fault-tolerant computing for capturing trust assumptions. They can be found at the core of many algorithms for implementing reliable broadcasts, shared memory, consensus and other problems. This talk introduces asymmetric Byzantine quorum systems that model subjective trust. Every process is free to choose which combinations of other processes it trusts and which ones it considers faulty. Asymmetric quorum systems strictly generalize standard Byzantine quorum systems, which have only one global trust assumption for all processes. The talk presents also several protocols that tolerate Byzantine faults with asymmetric trust, such as shared-register implementations and reliable Byzantine broadcasts. Consensus is arguably one of the most important notions in distributed computing and also relevant for practical systems. We also show how to realize consensus protocols with asymmetric trust, illustrating our approach for protocols in partially synchronous systems and for asynchronous protocols that use randomization with asymmetric trust. Asymmetric quorum systems offer a way to understand some ideas behind the Ripple and Stellar blockchain protocols, which aim at relaxing symmetric trust assumptions and permit flexible trust. The presentation is based on joint work with Björn Tackmann and Luca Zanolini [1, 2].","PeriodicalId":335477,"journal":{"name":"Proceedings of the 22nd International Conference on Distributed Computing and Networking","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127913562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}