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<p><b>Abstract</b>—A real-time stream is said to have (<it>m</it>, <it>k</it>)-firm deadlines if at least <it>m</it> out of any <it>k</it> consecutive customers from the stream must meet their respective deadlines. Such a stream is said to have encountered a <it>dynamic failure</it> if fewer than <it>m</it> out of any <it>k</it> consecutive customers meet their deadlines. Hamdaoui and Ramanathan recently proposed a scheduling policy called Distance Based Priority (DBP) in which customers are serviced with a higher priority if their streams are closer to a dynamic failure. In terms of reducing the probability of dynamic failure, Hamdaoui and Ramanathan also showed, using simulation, that the DBP policy is better than a policy in which all customers are serviced at the same priority level.</p><p>In this paper, an analytic model is developed for computing the probability of dynamic failure of a real-time stream for the DBP and the single priority schemes. This model is useful for providing statistical quality of service guarantees to real-time streams. The probability of dynamic failure computed using this model is compared to the results from a discrete-event simulator. The comparison shows that the model is accurate for low and moderate loads.</p>
Real-time systems, dynamic failure, priority queues, analytic modeling, quality of service guarantees.
Parameswaran Ramanathan, Moncef Hamdaoui, "Evaluating Dynamic Failure Probability for Streams with (m, k)-Firm Deadlines", IEEE Transactions on Computers, vol. 46, no. , pp. 1325-1337, December 1997, doi:10.1109/12.641933
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