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Traditionally, it had been assumed that the efficiency requirements of TCP dictate that the buffer size at the router must be of the order of the bandwidth-delay (<i>C</i> &#215; RTT) product. Recently, this assumption was questioned in a number of papers, and the rule was shown to be conservative for certain traffic models. In particular, by appealing to(More)
— A necessary and sufficient condition is given for the exact reduction of systems modeled by linear fractional transformations (LFT's) on structured operator sets. This condition is based on the existence of a rank-deficient solution to either of a pair of linear matrix inequalities which generalize Lyapunov equations; the notion of Gramians is thus also(More)
—Error-bounds are developed for balanced truncation of linear time-varying systems, leading to an extension of the " twice the sum of the tail " formulas, well known in the time-invariant case. The approach relies on an operator-theoretic framework for analysis of linear time-varying systems. This provides a multivariable notion of frequency for such(More)
— This paper introduces a new method for reducing large directed graphs to simpler graphs with fewer nodes. The reduction is carried out through node and edge aggregation, where the simpler graph is representative of the original large graph. Representativeness is measured using a metric defined herein, which is motivated by thermodynamic free energy and(More)
We present model reduction methods with guaranteed error bounds for systems represented by a Linear Fractional Transformation (LFT) on a repeated scalar uncertainty structure. These reduction methods can be interpreted either as doing state order reduction for multi-dimensionalsystems, or as uncertainty simpliication in the case of uncertain systems, and(More)
In this paper, we evaluate the performance of both real and virtual queue-based marking schemes designed for use at routers in the Internet. Using fluid flow models, we show via analysis and simulations that Virtual Queue (VQ)-based marking schemes outperform Real Queue (RQ)-based marking schemes in terms of robustness to disturbances and the ability to(More)