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Flocks, herds, and schools: a distributed behavioral model
 Computer Graphics
, 1987
"... The aggregate motion of a flock of birds, a herd of land animals, or a school of fish is a beautiful and familiar part of the natural world. But this type of complex motion is rarely seen in computer animation. This paper explores an approach based on simulation as an alternative to scripting the pa ..."
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Cited by 808 (4 self)
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The aggregate motion of a flock of birds, a herd of land animals, or a school of fish is a beautiful and familiar part of the natural world. But this type of complex motion is rarely seen in computer animation. This paper explores an approach based on simulation as an alternative to scripting the paths of each bird individually. The simulated flock is an elaboration of a particle system, with the simulated birds being the particles. The aggregate motion of the simulated flock is created by a distributed behavioral model much like that at work in a natural flock; the birds choose their own course. Each simulated bird is implemented as an independent actor that navigates according to its local perception of the dynamic environment, the laws of simulated physics that rule its motion, and a set of behaviors programmed into it by the "animator. " The aggregate motion of the simulated flock is the result of the dense interaction of the relatively simple behaviors of the individual simulated birds.
Service Disciplines for Guaranteed Performance Service in PacketSwitching Networks
 Proceedings of the IEEE
, 1995
"... While today’s computer networks support only besteffort service, future packetswitching integratedservices networks will have to support realtime communication services that allow clients to transport information with performance guarantees expressed in terms of delay, delay jitter, throughput, ..."
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Cited by 510 (3 self)
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While today’s computer networks support only besteffort service, future packetswitching integratedservices networks will have to support realtime communication services that allow clients to transport information with performance guarantees expressed in terms of delay, delay jitter, throughput, and loss rate. An important issue in providing guaranteed performance service is the choice of the packet service discipline at switching nodes. In this paper, we survey several service disciplines that are proposed in the literature to provide perconnection endtoend peqormance guarantees in packetswitching networks. We describe their mechanisms, their similarities and differences, and the performance guarantees they can provide. Various issues and tradeoffs in designing service disciplines for guaranteed performance service are discussed, and a general framework for studying and comparing these disciplines are presented. I.
Synchronization and linearity: an algebra for discrete event systems
, 2001
"... The first edition of this book was published in 1992 by Wiley (ISBN 0 471 93609 X). Since this book is now out of print, and to answer the request of several colleagues, the authors have decided to make it available freely on the Web, while retaining the copyright, for the benefit of the scientific ..."
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Cited by 249 (10 self)
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The first edition of this book was published in 1992 by Wiley (ISBN 0 471 93609 X). Since this book is now out of print, and to answer the request of several colleagues, the authors have decided to make it available freely on the Web, while retaining the copyright, for the benefit of the scientific community. Copyright Statement This electronic document is in PDF format. One needs Acrobat Reader (available freely for most platforms from the Adobe web site) to benefit from the full interactive machinery: using the package hyperref by Sebastian Rahtz, the table of contents and all LATEX crossreferences are automatically converted into clickable hyperlinks, bookmarks are generated automatically, etc.. So, do not hesitate to click on references to equation or section numbers, on items of thetableofcontents and of the index, etc.. One may freely use and print this document for one’s own purpose or even distribute it freely, but not commercially, provided it is distributed in its entirety and without modifications, including this preface and copyright statement. Any use of thecontents should be acknowledged according to the standard scientific practice. The
Limits on Interconnection Network Performance
 IEEE Transactions on Parallel and Distributed Systems
, 1991
"... As the performance of interconnection networks becomes increasingly limited by physical constraints in highspeed multiprocessor systems, the parameters of highperformance network design must be reevaluated, starting with a close examination of assumptions and requirements. This paper models networ ..."
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Cited by 177 (4 self)
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As the performance of interconnection networks becomes increasingly limited by physical constraints in highspeed multiprocessor systems, the parameters of highperformance network design must be reevaluated, starting with a close examination of assumptions and requirements. This paper models network latency, taking both switch and wire delays into account. A simple closed form expression for contention in buffered, direct networks is derived and is found to agree closely with simulations. The model includes the effects of packet size and communication locality. Network analysis under various constraints (such as fixed bisection width, fixed channel width, and fixed node size) and under different workload parameters (such as packet size, degree of communication locality, and network request rate) reveals that performance is highly sensitive to these constraints and workloads. A twodimensional network has the lowest latency only when switch delays and network contention are ignored, but...
Proportional Differentiated Services: Delay Differentiation and Packet Scheduling
 IEEE/ACM Transactions on Networking
, 1999
"... The proportional differentiation model provides the network operator with the `tuning knobs' for adjusting the perhop qualityofservice (QoS) ratios between classes, independent of the class loads. This paper applies the proportional model in the differentiation of queueing delays, and investigate ..."
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Cited by 163 (6 self)
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The proportional differentiation model provides the network operator with the `tuning knobs' for adjusting the perhop qualityofservice (QoS) ratios between classes, independent of the class loads. This paper applies the proportional model in the differentiation of queueing delays, and investigates appropriate packet scheduling mechanisms. Starting from the proportional delay differentiation (PDD) model, we derive the average queueing delay in each class, show the dynamics of the class delays under the PDD constraints, and state the conditions in which the PDD model is feasible. The feasibility model of the model can be determined from the average delays that result with the strict priorities scheduler. We then focus on scheduling mechanisms that can implement the PDD model, when it is feasible to do so. The proportional average delay (PAD) scheduler meets the PDD constraints, when they are feasible, but it exhibits a pathological behavior in short timescales. The waiting time priority (WTP) scheduler, on the other hand, approximates the PDD model closely, even in the short timescales of a few packet departures, but only in heavy load conditions. PAD and WTP serve as motivation for the third scheduler, called hybrid proportional delay (HPD). HPD approximates the PDD model closely, when the model is feasible, independent of the class load distribution. Also, HPD provides predictable delay differentiation even in short timescales.
The FourierSeries Method For Inverting Transforms Of Probability Distributions
, 1991
"... This paper reviews the Fourierseries method for calculating cumulative distribution functions (cdf's) and probability mass functions (pmf's) by numerically inverting characteristic functions, Laplace transforms and generating functions. Some variants of the Fourierseries method are remarkably easy ..."
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Cited by 149 (51 self)
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This paper reviews the Fourierseries method for calculating cumulative distribution functions (cdf's) and probability mass functions (pmf's) by numerically inverting characteristic functions, Laplace transforms and generating functions. Some variants of the Fourierseries method are remarkably easy to use, requiring programs of less than fifty lines. The Fourierseries method can be interpreted as numerically integrating a standard inversion integral by means of the trapezoidal rule. The same formula is obtained by using the Fourier series of an associated periodic function constructed by aliasing; this explains the name of the method. This Fourier analysis applies to the inversion problem because the Fourier coefficients are just values of the transform. The mathematical centerpiece of the Fourierseries method is the Poisson summation formula, which identifies the discretization error associated with the trapezoidal rule and thus helps bound it. The greatest difficulty is approximately calculating the infinite series obtained from the inversion integral. Within this framework, lattice cdf's can be calculated from generating functions by finite sums without truncation. For other cdf's, an appropriate truncation of the infinite series can be determined from the transform based on estimates or bounds. For Laplace transforms, the numerical integration can be made to produce a nearly alternating series, so that the convergence can be accelerated by techniques such as Euler summation. Alternatively, the cdf can be perturbed slightly by convolution smoothing or windowing to produce a truncation error bound independent of the original cdf. Although error bounds can be determined, an effective approach is to use two different methods without elaborate error analysis. For this...
RateControlled Service Disciplines
, 1994
"... We propose a class of nonworkconserving service disciplines, called the RateControlled Service Disciplines. When coupled with suitable admission control algorithms, RateControlled Service Disciplines can provide endtoend deterministic and statistical performance guarantees on a perconnectio ..."
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Cited by 141 (10 self)
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We propose a class of nonworkconserving service disciplines, called the RateControlled Service Disciplines. When coupled with suitable admission control algorithms, RateControlled Service Disciplines can provide endtoend deterministic and statistical performance guarantees on a perconnection basis in an arbitrary topology packetswitching network. The key feature of a ratecontrolled service discipline is the separation of the server into two components: a ratecontroller and a scheduler. This separation makes it possible to obtain endtoend performance characteristics by applying single node analysis at each switch. It also has several other distinct advantages: it decouples the allocation of bandwidths and delay bounds, uniformly distributes the allocation of buffer space inside the network to prevent packet loss, and allows arbitrary combinations of ratecontrol policies and packet scheduling policies. Ratecontrolled service disciplines provide a general framework w...
Information Theory and Communication Networks: An Unconsummated Union
 IEEE Trans. Inform. Theory
, 1998
"... Information theory has not yet had a direct impact on networking, although there are similarities in concepts and methodologies that have consistently attracted the attention of researchers from both fields. In this paper, we review several topics that are related to communication networks and that ..."
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Cited by 133 (5 self)
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Information theory has not yet had a direct impact on networking, although there are similarities in concepts and methodologies that have consistently attracted the attention of researchers from both fields. In this paper, we review several topics that are related to communication networks and that have an information theoretic flavor, including multiaccess protocols, timing channels, effective bandwidth of bursty data sources, deterministic constraints on datastreams, queueing theory, and switching networks. Keywords Communication networks, multiaccess, effective bandwidth, switching I. INTRODUCTION Information theory is the conscience of the theory of communication; it has defined the "playing field" within which communication systems can be studied and understood. It has provided the spawning grounds for the fields of coding, compression, encryption, detection, and modulation and it has enabled the design and evaluation of systems whose performance is pushing the limits of wha...
Performance and Stability of Communication Networks via Robust Exponential Bounds
 IEEE/ACM Transactions on Networking
, 1993
"... We propose a new way for evaluating the performance of packet switching communication networks under a fixed (session based) routing strategy. Our approach is based on properly bounding the probability distribution functions of the system input processes. The bounds we suggest, which are decaying ex ..."
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Cited by 124 (3 self)
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We propose a new way for evaluating the performance of packet switching communication networks under a fixed (session based) routing strategy. Our approach is based on properly bounding the probability distribution functions of the system input processes. The bounds we suggest, which are decaying exponentials, possess three convenient properties: When the inputs to an isolated network element are all bounded, they result in bounded outputs, and assure that the delays and queues in this element have exponentially decaying distributions; In some network settings bounded inputs result in bounded outputs; Natural traffic processes can be shown to satisfy such bounds. Consequently, our method enables the analysis of various previously intractable setups. We provide sufficient conditions for the stability of such networks, and derive upper bounds for the interesting parameters of network performance. 1 Introduction In this paper we consider data communication networks, and the problem of ev...
Congestion Control With Explicit Rate Indication
 PROC. ICC'95
, 1995
"... As the speed and the dynamic range of computer networks evolve, the issue of efficient traffic management becomes increasingly important. This work describes an approach to traffic management using explicit rate information provided to the source by the network. We present an asynchronous distribute ..."
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Cited by 122 (15 self)
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As the speed and the dynamic range of computer networks evolve, the issue of efficient traffic management becomes increasingly important. This work describes an approach to traffic management using explicit rate information provided to the source by the network. We present an asynchronous distributed algorithm for optimal rate calculation across the network, where optimality is understood in the maxmin sense. The algorithm quickly converges to the optimal rates and is shown to be wellbehaved in transience. 1 Introduction 1.1 Background In the past decade several mechanisms for congestion control have been developed and implemented. DECbit [34] and Slow Start [20] are perhaps the best known. Both of these schemes were developed for connectionless networks with window flow control, in which the routers had no knowledge of the individual flows and their demands, the routes changed frequently and the header space was scarce. With the rapid increase of the ratio of propagation delay to...