Searching for a black hole in tree networks

  • Authors:

  • Jurek Czyzowicz;Dariusz Kowalski;Euripides Markou;Andrzej Pelc

  • Affiliations:

  • Département d'informatique, Université du Québec en Outaouais, Hull, Québec, Canada;Max-Planck-Institut für Informatik, Saarbrücken, Germany;Département d'informatique, Université du Québec en Outaouais, Hull, Québec, Canada;Département d'informatique, Université du Québec en Outaouais, Hull, Québec, Canada

  • Venue:
  • OPODIS'04 Proceedings of the 8th international conference on Principles of Distributed Systems
  • Year:
  • 2004

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Abstract

A black hole is a highly harmful stationary process residing in a node of a network and destroying all mobile agents visiting the node, without leaving any trace. We consider the task of locating a black hole in a (partially) synchronous tree network, assuming an upper bound on the time of any edge traversal by an agent. The minimum number of agents capable to identify a black hole is two. For a given tree and given starting node we are interested in the fastest possible black hole search by two agents. For arbitrary trees we give a 5/3-approximation algorithm for this problem. We give optimal black hole search algorithms for two “extreme” classes of trees: the class of lines and the class of trees in which any internal node (including the root which is the starting node) has at least 2 children.