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V. Liberatore
Pervasive Computing
QoS Assurances
*Objectives
nQoS protects from cross-traffic
nQoS does not protect from failures, interferences
*Worst-case
nIs it cross-traffic?
nIs it failures (e.g., network partition)?
nReasoning
*Reason about system timing
*Priorities make it easy
*QoS vs. fault-tolerance
nFailures as first class citizens
*Average-case
nNon-sense
nExacerbated by TCP
*Tail
nE.g., 99-percentile
nDoes not account for failure
nIt is not meant to account for failures
nMust be paired with middleware, fault-tolerance