Copyright (C) 1998 Institute of Electrical and Electronics Engineers. Reprinted from IEEE Network, Vol 12, no. 3, May/June 1998, pp. 61-65.

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This work is partly supported by the Defense Advanced Research Projects Agency through FBI contract #J-FBI-95-185 entitled Large-Scale Active Middleware. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the Department of the Army, the Defense Advanced Research Projects Agency, or the U.S. Government.