A dynamic multiple copy approach for time-constrained communication

Messages in a real-time system have deadlines. The system incurs a recovery cost whenever a message misses its deadline. The scheme proposed in this paper reduces the expected cost incurred by the system as result of messages missing their deadlines. The proposed scheme is intended for distributed systems with a point{to{point inter-connection topology that support a virtual cut-through message passing scheme. In the proposed approach, nodes adaptively send multiple copies of messages through a set of dis-joint routes to increase the probability of meeting their deadlines. A message is replicated only when the time remaining to its deadline is below a pre-computed threshold. An oo{ line algorithm for eeciently computing the number of copies to be sent and the deadline thresholds is presented in this paper. The algorithm guarantees that the system never becomes overloaded as a result of message replication. Simulation results indicate that the reductions in the expected cost due to missed message deadlines are substantial as a result of using the proposed scheme. Any opinions, ndings, and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reeect the views of NSF.

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