HaTCh: a two-level caching scheme for estimating the number of active flows

In this paper, we present a Markov model to examine the capability of SRED in estimating the number of active flows. We show that the SRED cache hit rate can be used to quantify the number of active flows. We then propose a modified SRED scheme, called HaTCh (hash-based two-level caching), that uses hashing and a two-level caching mechanism to accurately estimate the number of active flows under various workloads. We formulate a preliminary Markov model of the proposed scheme to show its effectiveness in preventing the monopoly of misbehaving flows. Simulation results indicate that the proposed scheme provides better estimation of the number of active flows compared to SRED, stabilizes the estimation with respect to workload fluctuations, and prevents performance degradation by efficiently isolating the misbehaving flows.