Asynchronous Deterministic Rendezvous in Graphs

Marco, Gianluca De; Gargano, Luisa; Kranakis, Evangelos; Kriz̧anc, Danny; Pełc, Andrzej; Vaccaro, Ugo

doi:10.1007/11549345_24

Cited by 42 publications

(55 citation statements)

References 27 publications

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“…For asynchronous networks, many works consider the gathering problem with additional assumptions. De Marco et al [7] proposed an algorithm to achieve a gathering of two agents in asynchronous networks without considering Byzantine agents. They considered infinite lines and rings under the assumption that agents have unique IDs and can meet inside an edge.…”

Section: Related Workmentioning

confidence: 99%

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Gathering of Mobile Agents in Asynchronous Byzantine Environments with Authenticated Whiteboards

2019

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We propose two algorithms for the gathering problem of k mobile agents in asynchronous Byzantine environments. For both algorithms, we assume that graph topology is arbitrary, each node is equipped with an authenticated whiteboard, agents have unique IDs, and at most f weakly Byzantine agents exist. Under these assumptions, the first algorithm achieves gathering without termination in O(m + f n) moves per agent (m is the number of edges and n is the number of nodes). The second algorithm achieves gathering with termination in O(m + f n) moves per agent by additionally assuming that agents on the same node are synchronized, f < ⌈ 1 3 k⌉ holds, and agents know k. To the best of our knowledge, this is the first work to address the gathering problem of mobile agents for arbitrary topology networks in asynchronous Byzantine environments. 1 This algorithm is originally proposed for a rendezvous problem (i.e., gathering of two agents). However, it can be easily extended to the gathering problem by a technique in [12] and its time complexity is not changed. 2 Agents on a single node are synchronized.

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Section: Related Workmentioning

confidence: 99%

“…In rings, they proposed an algorithm to achieve a gathering in O(nλ) moves. Dieudonné et al [10] considered a gathering problem for arbitrary graphs under the same assumptions as [7]. They realized a gathering in polynomial moves of the number of nodes and the length of the minimum ID of agents.…”

Section: Related Workmentioning

confidence: 99%

Gathering of Mobile Agents in Asynchronous Byzantine Environments with Authenticated Whiteboards

2019

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“…For instance, deterministic rendezvous with agents equipped with tokens used to mark nodes was considered, e.g., in [27]. Deterministic rendezvous of agents with unique labels was discussed in [15,16,25,32]. (In the latter scenario, symmetry is broken by the use of the different labels of agents, and thus rendezvous is sometimes possible even for symmetric initial positions of the agents).…”

Section: Related Workmentioning

confidence: 99%

“…Apart from the synchronous model used in this paper, several authors have investigated asynchronous rendezvous in the plane [12,19] and in network environments [9,14,15]. In the latter scenario the agent chooses the edge which it decides to traverse but the adversary controls the speed of the agent.…”

Section: Related Workmentioning

confidence: 99%

Time versus space trade-offs for rendezvous in trees

2013

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International audienceTwo identical (anonymous) mobile agents start from arbitrary nodes of an unknown tree and have to meet at some node. Agents move in synchronous rounds: in each round an agent can either stay at the current node or move to one of its neighbors. We consider deterministic algorithms for this rendezvous task. The main result of this paper is a tight trade-off between the optimal time of completing rendezvous and the size of memory of the agents. For agents with $k$ memory bits, we show that optimal rendezvous time is $\Theta(n+n^2/k)$ in $n$-node trees. More precisely, if $k \geq c\log n$, for some constant $c$, we design agents accomplishing rendezvous in arbitrary trees of size $n$ {(unknown to the agents)} in time $O(n+n^2/k)$, starting with arbitrary delay. We also show that no pair of agents can accomplish rendezvous in time $o(n+n^2/k)$, even in the class of lines of known length and even with simultaneous start. Finally, we prove that at least logarithmic memory is necessary for rendezvous, even for agents starting simultaneously in a $n$-node line

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“…Marco et al [8] studied the asynchronous version of rendezvous problem. Note that in the asynchronous setting, meeting at a node (which is normally required in rendezvous) is in general impossible.…”

Section: Asynchronous Deterministic Rendezvous In Graphsmentioning

confidence: 99%

Cooperating Mobile Agents

Ghosh

Dasgupta

2012

Mobile Agents in Networking and Distributed Computing

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This article discusses four different applications where mobile agents cooperate with one another to accomplish a task in a network of processes. These applications range from topology discovery and distributed data structure implementation to fault diagnosis and system stabilization. IntroductionA mobile agent is a piece of code that migrates from one machine to another. The code (often called the script), which is an executable program, executes at the host machine where it lands. In addition to the code, agents carry data values or procedure arguments or results that need to be transported across machines. Compared to messages that are passive, agents are active, and can be viewed as messengers.Mobile agents are convenient tools in distributed systems, both at the applications layer and as well as at the middleware level. The promise of mobile agents in bandwidth conservation or disconnected modes of operation is now well accepted. Deploying multiple mobile agents cooperating with one another can add a new dimension to distributed applications. While parallelism is the obvious advantage, the issues of load balancing, agent rendezvous, and fault tolerance play major roles. Among numerous possible applications, we highlight the following four problems, each with a different flavor of cooperation.Mapping of an unknown network. Network mapping is also known as the topology discovery problem. Making such a discovery using a single mobile agent is equivalent to developing an efficient algorithm for graph traversal. With multiple agents, the challenge is to develop an efficient cooperation mechanism so that the discovery is complete in the fewest number of hops and redundant traversals are avoided.Concurrent reading and writing. A distributed data structure has different components mapped to host machines at different geographic locations. As multiple agents concurrently access such a distributed data structure, the reading agent the writing agent need to be properly synchronize their operations so that the semantics of data sharing are preserved. Black hole search.A black hole is a node that can potentially capture a visiting agent and thus, disrupt an application. Although it implies a malicious intent on the part of the host, a black hole can be as simple as a crashed node. If black holes can be located, then traversal paths can be rerouted without incurring further loss of mobile agents.Stabilization. Transient failures occasionally corrupt the global state of a distributed system, and stabilization is an important technique for restoring normal operation. To stabilize a network, a mobile agent patrols the network, and plays the role of traveling repairperson. Multiple agents can expedite the process of stabilization, but in doing so, some synchronization issues need to be resolved. We will address how multiple agents can be deployed for maximum speedup of a stabilizing application.This article has seven sections. Section 2 describes the model and the notations. Sections 3 through 6 address the four problems high...

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Asynchronous Deterministic Rendezvous in Graphs

Cited by 42 publications

References 27 publications

Gathering of Mobile Agents in Asynchronous Byzantine Environments with Authenticated Whiteboards

Gathering of Mobile Agents in Asynchronous Byzantine Environments with Authenticated Whiteboards

Time versus space trade-offs for rendezvous in trees

Cooperating Mobile Agents

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