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Optimal Mobile Agent Protocols for Searching a Black Hole in Arbitrary Networks

Dobrev, Stefan and Flocchini, Paola and Prencipe, Giuseppe and Santoro, Nicola (2004) Optimal Mobile Agent Protocols for Searching a Black Hole in Arbitrary Networks. Technical Report del Dipartimento di Informatica . Università di Pisa, Pisa, IT.

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    Consider a networked environment, supporting mobile agents, where there is a black hole: a harmful host that disposes of visiting agents upon their arrival, leaving no observable trace of such a destruction. The black hole search problem is the one of assembling a team of asynchronous mobile agents, executing the same protocol and communicating by means of whiteboards, to successfully identify the location of the black hole; we are concerned with solutions that are generic (i.e., topology-independent). We establish tight bounds on the size of the team (i.e., the number of agents), and the cost (i.e., the number of moves) of a size-optimal solution protocol. These bounds depend on the a priori knowledge the agents have about the network, and on the consistency of the local labellings. In particular, we prove that: with topological ignorance $\Delta+1$ agents are needed and suffice, and the cost is $\Theta(n^2)$, where $\Delta$ is the maximal degree of a node and $n$ is the number of nodes in the network; with topological ignorance but in presence of sense of direction only $two$ agents suffice and the cost is $\Theta(n^2)$; and with complete topological knowledge only $two$ agents suffice and the cost is $\Theta(n \log n)$. All the upper-bound proofs are constructive.

    Item Type: Book
    Uncontrolled Keywords: Mobile Agents, Malicious Host, Distributed Search, Topological Knowledge
    Subjects: Area01 - Scienze matematiche e informatiche > INF/01 - Informatica
    Divisions: Dipartimenti (until 2012) > DIPARTIMENTO DI INFORMATICA
    Depositing User: dott.ssa Sandra Faita
    Date Deposited: 09 Dec 2014 10:59
    Last Modified: 09 Dec 2014 10:59
    URI: http://eprints.adm.unipi.it/id/eprint/2129

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