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24
A Framework for Simulationbased Network Control via Hindsight Optimization
 39th IEEE Conf. on Decision and Control
, 2000
"... We describe a novel approach for designing network control algorithms that incorporate traffic models. Traffic models can be viewed as stochastic predictions about the future network state, and can be used to generate traces of potential future network behavior. Our approach is to use such traces to ..."
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Cited by 20 (10 self)
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We describe a novel approach for designing network control algorithms that incorporate traffic models. Traffic models can be viewed as stochastic predictions about the future network state, and can be used to generate traces of potential future network behavior. Our approach is to use such traces to heuristically evaluate candidate control actions using a technique called hindsight optimization. In hindsight optimization, the finitehorizon "utility" achievable from a given system state is estimated by averaging estimates obtained from a number of traces starting at the state. For each trace, the utility value of the state is estimated by determining the optimal "hindsight control"  this is the control that would be applied by an optimal controller that somehow "knew" the whole trace beforehand  and then measuring the utility obtained under that control. Averaging over many samples then gives a simulationbased "hindsightoptimal" utility for the starting state that upper bounds the true...
Burstlevel Congestion Control Using Hindsight Optimization
, 2000
"... We consider the burstlevel congestioncontrol problem in a communication network with multiple traffic sources, each modeled as a fullycontrollable stream of fluid traffic. The controlled traffic shares a common bottleneck node with highpriority cross traffic described by a Markovmodulated fluid ..."
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Cited by 12 (5 self)
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We consider the burstlevel congestioncontrol problem in a communication network with multiple traffic sources, each modeled as a fullycontrollable stream of fluid traffic. The controlled traffic shares a common bottleneck node with highpriority cross traffic described by a Markovmodulated fluid (MMF). Each controlled source is assumed to have a unique roundtrip delay. The goal is to maximize a linear combination of the throughput, delay, traffic loss rate, and a fairness metric at the bottleneck node. We introduce a simulationbased congestioncontrol scheme capable of performing effectively under rapidlyvarying cross traffic by making use of the provided MMF model of that variation. In our scheme, the control problem is posed as a finitehorizon Markov decision process and is solved heuristically using a technique called Hindsight Optimization. We provide a detailed derivation of our congestioncontrol algorithm based on this technique. Our empirical study shows that the control scheme performs sign...
A Simple, Scalable, and Stable Explicit Rate Allocation Algorithm for MAXMIN Flow Control with Minimum Rate Guarantee
 IEEE/ACM Trans. Networking
, 2001
"... In this paper, we present a novel controltheoretic explicit rate (ER) allocation algorithm for the MAXMIN flow control of elastic traffic services with minimum rate guarantee in the setting of the ATM available bit rate (ABR) service. The proposed ER algorithm is simple in that the number of oper ..."
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Cited by 11 (1 self)
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In this paper, we present a novel controltheoretic explicit rate (ER) allocation algorithm for the MAXMIN flow control of elastic traffic services with minimum rate guarantee in the setting of the ATM available bit rate (ABR) service. The proposed ER algorithm is simple in that the number of operations required to compute it at a switch is minimized, scalable in that pervirtual circuit (VC) operations including perVC queueing, perVC accounting, and perVC state management are virtually removed, and stable in that by employing it, the user transmission rates and the network queues are asymptotically stabilized at a unique equilibrium point at which MAXMIN fairness with minimum rate guarantee and target queue lengths are achieved, respectively. To improve the speed of convergence, we normalize the controller gains of the algorithm by the estimate of the number of locally bottlenecked VCs. The estimation scheme is also computationally simple and scalable since it does not require perVC accounting either. We analyze the theoretical performance of the proposed algorithm and verify its agreement with the practical performance through simulations in the case of multiple bottleneck nodes. We believe that the proposed algorithm will serve as an encouraging solution to the MAXMIN flow control of elastic traffic services, the deployment of which has been debated long due to their lack of theoretical foundation and implementation complexity. Index TermsAsymptotic decay rate, elastic traffic services, maxmin flow rate, scalibility, stability. I.
Congestion Control via Online Sampling
, 2001
"... We consider the congestioncontrol problem in a communication network with multiple traffic sources, each modeled as a fullycontrollable stream of fluid traffic. The controlled traffic shares a common bottleneck node with highpriority cross traffic described by a Markovmodulated fluid (MMF). Each c ..."
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Cited by 6 (1 self)
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We consider the congestioncontrol problem in a communication network with multiple traffic sources, each modeled as a fullycontrollable stream of fluid traffic. The controlled traffic shares a common bottleneck node with highpriority cross traffic described by a Markovmodulated fluid (MMF). Each controlled source is assumed to have a unique roundtrip delay. We wish to maximize a linear combination of the throughput, delay, traffic loss rate, and a fairness metric at the bottleneck node. We introduce an online samplingbased burstlevel congestioncontrol scheme capable of performing effectively under rapidlyvarying cross traffic by making explicit use of the provided MMF model of that variation. The control problem is posed as a finitehorizon Markov decision process and is solved heuristically using a technique called Hindsight Optimization. We provide a detailed derivation of our congestioncontrol algorithm based on this technique. The distinguishing feature of our scheme relative to conventional congestioncontrol schemes is that we exploit a stochastic model of the cross traffic. Our empirical study shows that our control scheme significantly outperforms the conventional proportionalderivative (PD) controller, achieving higher utlization, lower delay, and lower loss under reasonable fairness. The performance advantage of our scheme over the PD scheme grows as the rate variance of cross traffic increases, underscoring the effectiveness of our control scheme under variable cross traffic.
OnLine SamplingBased Control For Network Queueing Problems
, 2001
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Cited by 5 (2 self)
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A New Approach for Asynchronous Distributed Rate Control of Elastic Sessions in Integrated Packet Networks
 IEEE/ACM Trans. Networking
"... We develop a new class of asynchronous distributed algorithms for the explicit rate control of elastic sessions in an integrated packet network. Sessions can request for minimum guaranteed rate allocations (e.g., MCRs in the ATM context), and, under this constraint, we seek to allocate the maxmin f ..."
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Cited by 5 (0 self)
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We develop a new class of asynchronous distributed algorithms for the explicit rate control of elastic sessions in an integrated packet network. Sessions can request for minimum guaranteed rate allocations (e.g., MCRs in the ATM context), and, under this constraint, we seek to allocate the maxmin fair rates to the sessions. We capture the integrated network context by permitting the link bandwidths available to elastic sessions to be stochastically time varying. The available capacity of each link is viewed as some statistic of this stochastic process (e.g., a fraction of the mean, or a large deviations Equivalent Service Capacity (ESC)). For fixed available capacity at each link, we show that the vector of maxmin fair rates can be computed from the root of a certain vector equation. A distributed asynchronous stochastic approximation technique is then used to develop a provably convergent distributed algorithm for obtaining the root of the equation, even when the link flows and the ...
Congestion control for differentiatedservices using nonlinear control theory
 In Proceedings of the Sixth IEEE Symposium on Computers and Communications
, 2001
"... The growing demand of computer usage requires efficient ways of managing network traffic in order to avoid or at least limit the level of congestion in cases where increases in bandwidth are not desirable or possible. Using nonlinear control theory we developed and analysed a generic Integrated Dyn ..."
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Cited by 5 (4 self)
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The growing demand of computer usage requires efficient ways of managing network traffic in order to avoid or at least limit the level of congestion in cases where increases in bandwidth are not desirable or possible. Using nonlinear control theory we developed and analysed a generic Integrated Dynamic Congestion Control (IDCC) scheme for controlling traffic using information on the status of each queue in the network. The IDCC scheme is based on a nonlinear model of the network that is generated using fluid flow considerations. The methodology used is general and independent of technology, as for example TCP/IP or ATM. We assume a differentiatedservices network framework and formulate our control strategy in the same spirit as IP DiffServ for three types of services: Premium Service, Ordinary Service, and Best Effort Service. The three differentiated classes of traffic operate at each output port of a router/switch. An IDCC scheme is designed for each output port, and a powerful, simple to implement controller is designed and analysed. The IDCC methodology has been applied to an ATM network. We use OPNET simulations to demonstrate that the proposed control methodology achieves the desired behaviour of the network, and possesses important attributes, such as: stable and robust behaviour, high utilisation with bounded delay and loss performance, and good steady state and transient behaviour.
A Distributed Throttling Approach for Handling High Bandwidth Aggregates
 IEEE Trans. Parallel and Distributed Systems
, 2004
"... Publicaccess networks need to handle persistent congestion and overload caused by high bandwidth aggregates that may occur during times of flooding based DDoS attacks or flash crowds. The often unpredictable nature of these two activities can severely degrade server performance. Legitimate user re ..."
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Cited by 4 (1 self)
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Publicaccess networks need to handle persistent congestion and overload caused by high bandwidth aggregates that may occur during times of flooding based DDoS attacks or flash crowds. The often unpredictable nature of these two activities can severely degrade server performance. Legitimate user requests also suffer considerably when traffic from many different sources aggregates inside the network and causes congestion. This paper studies a “family ” of algorithms that “proactively ” protect a server from overload by installing rate throttles in a set of upstream routers. A controltheoretic approach is used to obtain an “optimal ” control setting that achieves throttling in a distributed and fair manner by taking important performance metrics into consideration, such as minimizing overall load variations. Using ns2 simulations, we show that our proposed algorithms (1) are highly adaptive by avoiding unnecessary control parameter configuration, (2) provide maxmin fairness for any number of throttling routers, (3) respond very quickly to network changes, (4) are extremely robust against extrinsic factors beyond the system control, and (5) are stable under given delay bounds. Most importantly, our approach provides a systematic way to handle high bandwidth aggregates by viewing them as a generic congestion control problem with relevance to many network applications. I.
The Effect of Uncertain TimeVariant Delays in ATM Networks with Explicit Rate Feedback: A Control Theoretic Approach
, 2001
"... A new, more realistic model for the Available BitRate traffic class in ATM network congestion control with explicit rate feedback is introduced and analyzed. This model is based on recent results by Ekanayake, regarding discrete time models for timevariant delays. The discrete time model takes int ..."
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Cited by 2 (1 self)
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A new, more realistic model for the Available BitRate traffic class in ATM network congestion control with explicit rate feedback is introduced and analyzed. This model is based on recent results by Ekanayake, regarding discrete time models for timevariant delays. The discrete time model takes into account the effect of timevariant buffer occupancy levels of ATM switches, thus treating the case of timevariant delays between a single congested node and the connected sources. For highly dynamic situations, such a model is crucial for a valid analysis of the resulting feedback system. The new model also handles the effects of the mismatch between the resource management cell rates and the variable bit rate controller sampling rate as well as buffer and rate nonlinearities. A brief stability study shows that an equilibrium in the buffer occupancy is impossible to achieve in the presence of timevariant forward path delays. Stability conditions for the case of timevariant delays in the return path are presented. Finally, illustrative examples are provided.
Resource Allocation And Congestion Control In Distributed Sensor Networks  A Network Calculus Approach
 In Proceedings of Fifteenth International Symposium on Mathematical Theory of Networks and Systems
, 2002
"... The establishment of the overall objectives of a distributed sensor network is a dynamic task so that it may sufficiently well `track' its environment. ..."
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Cited by 2 (0 self)
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The establishment of the overall objectives of a distributed sensor network is a dynamic task so that it may sufficiently well `track' its environment.