Stochastic Optimization of Distributed Sampling System Placement for Passive Measurement *

Abstract. Flow-level traffic measurement is important for network traffic accounting, traffic engineering, and network security. However, flow-level measurement in high speed networks poses great challenges due to the requirements of high packet processing speed and large memory size (high time/space complexity). To reduce these demanding requirements, sampling is usually used and samplers are deployed in the network. But sampling incurs information loss. To address this issue, this paper studies the tradeoff between sampling loss and complexity in distributed sampling system. We formulate the distributed sampling problem as a constrained optimization problem; specifically, maximizing the measurement coverage (i.e., the percentage of sampled traffic among the total traffic) and minimizing the complexity/budget. Considering the stochastic nature of traffic flows, we further formulate the optimization problem under two stochastic criteria: Stochastic Expected Value Optimization criterion (which is concerned with average performance) and Stochastic Chance Constrained Optimization criterion (which is concerned with the distribution of performance measure). Then we propose a Hybrid Intelligent algorithm to decide the optimal deployment strategy for monitors ’ placement and the sampling rate at each monitor. Equipped with the proposed algorithm, we are able to address the optimal tradeoff between measurement coverage and deployment cost for networks with random traffic, which has not been studied before. The extensive simulations an