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Queue Dynamics with Window Flow Control
, 2010
"... This paper develops a new model that describes the queueing process of a communication network when data sources use window flow control. The model takes into account the burstiness in subroundtrip time (RTT) timescales and the instantaneous rate differences of a flow at different links. It is ge ..."
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Cited by 8 (4 self)
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This paper develops a new model that describes the queueing process of a communication network when data sources use window flow control. The model takes into account the burstiness in subroundtrip time (RTT) timescales and the instantaneous rate differences of a flow at different links. It is generic and independent of actual source flow control algorithms. Basic properties of the model and its relation to existing work are discussed. In particular, for a general network with multiple links, it is demonstrated that spatial interaction of oscillations allows queue instability to occur even when all flows have the same RTTs and maintain constant windows. The model is used to study the dynamics of delaybased congestion control algorithms. It is found that the ratios of RTTs are critical to the stability of such systems, and previously unknown modes of instability are identified. Packetlevel simulations and testbed measurements are provided to verify the model and its predictions.
Window Flow Control: Macroscopic Properties from Microscopic Factors
, 2008
"... This paper studies window flow control focusing on bridging the gap between microscopic factors such as burstiness in subRTT timescales, and observable macroscopic properties such as steady state bandwidth sharing and flow level stability. Using new models, we analytically capture notable effects ..."
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Cited by 6 (6 self)
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This paper studies window flow control focusing on bridging the gap between microscopic factors such as burstiness in subRTT timescales, and observable macroscopic properties such as steady state bandwidth sharing and flow level stability. Using new models, we analytically capture notable effects of microscopic behavior on macroscopic quantities. For lossbased protocols, we calculate the loss synchronization rate for different flows and use it to quantitatively explain the unfair bandwidth sharing between paced and unpaced TCP flows. For delaybased protocols, we show that the ratios of round trip delays are critical to the stability of the system. These results deepen the fundamental understanding of congestion control systems. Packet level simulations are used to verify our theoretical claims.
On the Validity of Flowlevel TCP Network Models for Grid and Cloud Simulations
, 2013
"... Researchers in the area of grid/cloud computing perform many of their experiments using simulations that must capture network behavior. In this context, packetlevel simulations, which are widely used to study network protocols, are too costly given the typical large scales of simulated systems and ..."
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Cited by 4 (1 self)
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Researchers in the area of grid/cloud computing perform many of their experiments using simulations that must capture network behavior. In this context, packetlevel simulations, which are widely used to study network protocols, are too costly given the typical large scales of simulated systems and applications. An alternative is to implement network simulations with less costly flowlevel models. Several flowlevel models have been proposed and implemented in grid/cloud simulators. Surprisingly, published validations of these models, if any, consist of verifications for only a few simple cases. Consequently, even when they have been used to obtain published results, the ability of these simulators to produce scientifically meaningful results is in doubt. This work evaluates these stateoftheart flowlevel network models of TCP communication via comparison to packetlevel simulation. While it is straightforward to show cases in which previously proposed models lead to good results, instead we follow the critical method, which places model refutation at the center of the scientific activity, and we systematically seek cases that lead to invalid results. Careful analysis of these cases reveal fundamental flaws and also suggest improvements. One contribution of this work is that these improvements lead to a new model that, while far from being perfect, improves upon all previously proposed models in the context of simulation of grids or clouds. A more important contribution, perhaps, is provided by the pitfalls and unexpected behaviors encountered in this work, leading to a number
Design, Analysis and Performances of ChemicalInspired Rate Controllers in Packet Networks
, 2013
"... In computer networks, a Distributed Rate Controller (DRC) must quickly propagate changes of inflow rates and let participating sites converge to their admissible rate. In this paper we introduce a family of DRCs where controllers can be easily customized whereas their performance and dynamics are st ..."
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In computer networks, a Distributed Rate Controller (DRC) must quickly propagate changes of inflow rates and let participating sites converge to their admissible rate. In this paper we introduce a family of DRCs where controllers can be easily customized whereas their performance and dynamics are strictly predictable. Borrowing from engineering methods in Chemistry, we show how to derive a deterministic mathematical model of the network flow that can be analyzed through standard tools of (linear) system theory. We also report on simulation and native experimental results that validate our theoretical approach.
Stability and Robustness Conditions using Frequency Dependent Half Planes
"... AbstractThis paper presents a sufficient condition that establishes closed loop stability for linear time invariant dynamical systems with transfer functions that are analytic in the open right half complex plane. The condition is suitable for analyzing a large class of highly complex, possibly in ..."
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AbstractThis paper presents a sufficient condition that establishes closed loop stability for linear time invariant dynamical systems with transfer functions that are analytic in the open right half complex plane. The condition is suitable for analyzing a large class of highly complex, possibly interconnected, systems. The result is based on bounding Nyquist curves by using frequency dependent half planes. It provides (usually nontrivial) robustness guarantees for the provably stable systems and generalizes to the multidimensional case using matrix field of values. Concrete examples illustrate the applications of the condition. From our condition, it is easy to derive a relaxed version of the classical result that the interconnection of a positive real and strictly positive real linear system under feedback is closed loop stable.
49th IEEE Conference on Decision and Control
"... Nonlinear statedependent delay modeling and stability analysis of internet congestion control ..."
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Nonlinear statedependent delay modeling and stability analysis of internet congestion control