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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## Abstract

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 |
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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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