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22nd international workshop on principles of advanced and distributed simulation

作者： Toccaceli, Roberto Quaglia, Francesco Univ Roma La Sapienza Dipartimento Informat & Sistemist Rome Italy

ISBN: (纸本)9780769531595

In this article we focus on checkpoint/restore facilities for optimistic simulation objects with generic memory layout. Specifically, we present the design and implementation of a C library, named DyMeLoR (Dynamic Memory Logger and Restorer), that, beyond offering traditional services for dynamic memory allocation/release, additionally supports transparent checkpoint/restore of scattered simulation objects' states. DyMeLoR is well suited for being integrated within optimistic simulation platforms relying on kernel processes, each managing one or more simulation objects, as typical in most implementations of general purpose optimistic simulation platforms. From the point of view of efficiency, DyMeLoR has been designed in order to minimize memory consumption for meta-data describing the current layout of the simulation object's state, and to provide good trade-offs between the cost of meta-data manipulation and the cost of memory-to-memory data copies associated with checkpoint/restore tasks. Also, the library exhibits Piece-Wise-Deterministic (PWD) behavior, thus allowing the employment of (optimized) sparse checkpointing strategies each time the overlying application software complies with the PWD assumption. We also report the results of an experimental study where DyMeLoR is integrated within the ROme OpTimistic Simulator (ROOT-Sim), and is used to support optimistic simulation of a cellular system.

关键词： Dynamic storage simulating Metadata Loggers layouts cellular system Libraries Memory Memory

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Stochastic process models for packet/analytic-based network simulations 08

Stochastic process models for packet/analytic-based network ...

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22nd international workshop on principles of advanced and distributed simulation

作者： Cole, Robert G. Riley, George Cansever, Derya Yurcik, William Johns Hopkins Univ Dept Comp Sci Baltimore MD 21218 USA Johns Hopkins Univ Appl Phys Lab Baltimore MD 21218 USA Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA SI Int Inc Reston VA 20190 USA Univ Texas Dallas Dept Comp Sci Dallas TX USA

ISBN: (纸本)9780769531595

WE present our preliminary work that develops a new approach to hybrid packet/analytic network simulations for improved network simulation fidelity, scale, and simulation efficiency. Much work in the literature addresses this topic, including [10] [11] [81 [12] [13) and others. Current approaches rely upon models, which we refer to in this paper as Deterministic Fluid Models (9] [12], to address the analytic modeling aspects of these hybrid simulations. Instead we draw upon an extensive literature on stochastic models of queues and (eventually) networks of queues to implement a hybrid stochastic model/packet network simulation. We will refer to our approach as Stochastic Fluid Models throughout this paper. We outline our approach, present test cases, and present simulation results comparing the measured queue metrics from our approach for hybrid simulation to those of a deterministic fluid model hybrid simulation and a full packet-level simulation. We also discuss plans for future areas of research on this approach.

关键词： Event Driven simulations Hybrid simulation Models Network Models Stochastic Queues and Diffusion Equations

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Message from the program chair

Message from the program chair

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22nd workshop on principles of advanced and distributed simulation, PADS 2008

作者： Liu, Jason Florida International University Miami FL United States

No abstract available

ISBN: (纸本)9780769531595

No abstract available

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A Hybrid HLA Time Management Algorithm Based on Both Conditional and Unconditional Information 08

A Hybrid HLA Time Management Algorithm Based on Both Conditi...

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22nd international workshop on principles of advanced and distributed simulation

作者： Pan, Ke Turner, Stephen John Cai, Wentong Li, Zengxiang Nanyang Technol Univ Parallel & Distributed Comp Ctr Sch Comp Engn Singapore 639798 Singapore

ISBN: (纸本)9780769531595

The High-Level Architecture (HLA), which is the IEEE standard for distributed simulation, defines six service groups. The Time Management (TM) service group ensures a Time-Stamp-Ordered (TSO) message delivery sequence and correct time advancement of each simulation component (federate) in a HLA-based distributed simulation application (federation). To control time advancement of a federation, a distributed TM algorithm requires each regulating federate to periodically propagate its local time information to all constrained federates for their respective calculation of the Greatest Available Logical Time (GALT). The time information propagated is called conditional information or unconditional information depending on whether it can be guaranteed to be true conditionally or unconditionally. A traditional distributed TM algorithm can be either synchronous or asynchronous. In general, a synchronous algorithm utilizes conditional information while an asynchronous algorithm utilizes unconditional information. However, both synchronous and asynchronous algorithms have their own drawbacks and thus cannot be used for all federation scenarios. To resolve the drawback of each algorithm, this paper proposes a hybrid TM algorithm by combining synchronous and asynchronous algorithms. The three algorithms have been incorporated into a Run-Time Infrastructure (RTI) and experimental results show that the hybrid algorithm effectively combines the advantages of both synchronous and asynchronous algorithms. We also compare the proposed hybrid TM algorithm with the TM algorithm implemented in the Federated simulations Development Kit (FDK), which also uses both conditional and unconditional information. The hybrid TM algorithm is more scalable than FDK's TM algorithm with respect to the total number of federates in a federation, because FDK's TM algorithm has the overhead of redundant GALT calculations.

关键词： distributed simulation high-level architecture time management synchronous algorithm asynchronous algorithm hybrid algorithm conditional information unconditional information

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Time jails: A hybrid approach to scalable network emulation 08

Time jails: A hybrid approach to scalable network emulation

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22nd international workshop on principles of advanced and distributed simulation

作者： Grau, Andreas Maier, Steffen Herrmann, Klaus Rothermel, Kurt Inst Parallel & Distributed Syst IPVS D-70569 Stuttgart Germany

ISBN: (纸本)9780769531595

It is essential to evaluate the performance of newly developed distributed software and network protocols. Network emulation enables reproducible evaluation of unmodified real implementations. Software built for distributed systems, such as a large scale peer-to-peer system, requires evaluation scenarios with thousands of communicating nodes. Two approaches for scaling network emulation to such scenario sizes have been proposed in the literature: node virtualization and time virtualization. Node virtualization allows maximizing the utilization of standard hardware used for emulation experiments. Time virtualization enables trading experiment duration for virtually increased resources of the hardware. It stands to reason that a combination of those two approaches may increase scalability even further. However, in existing combinations, either node virtualization implies relatively high overhead or time virtualization requires modifications of the test subject implementation. In this paper, we present a novel hybrid approach called Time Virtualized Emulation Environment (TVEE). It integrates node virtualization with low overhead and time virtualization, which is transparent to the execution of test subjects. We introduce virtual time based on epochs to enable better dynamic hardware utilization during long lasting experiments. Additionally, a mechanism similar to soft timers ensures an accurate reproduction of network properties in the time virtualized emulation. Our evaluations show the accuracy and scalability of time virtualized network emulation. Comparing TCP throughput, TVEE outperforms other approaches using an event based virtual time by an order of magnitude.

关键词： network analog Virtualization Scalability distributed software Computer hardware Prisons EPOCH

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Mobility models for wireless networks: Challenges, pitfalls, and successes 08

Mobility models for wireless networks: Challenges, pitfalls,...

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22nd international workshop on principles of advanced and distributed simulation

作者： Towsley, Don Univ Massachusetts Dept Comp Sci Amherst MA 01003 USA

ISBN: (纸本)9780769531595

The performance of any mobile network is highly influenced by the mobility patterns of nodes in the network. In fact mobility behavior is the most important environmental factor that determines performance and influences network design. Thus it is important that we develop models that 1. accurately capture the mobility of nodes, while at the same time 2. are amenable to mathematical analysis and/or efficient simulation. In the past, the wireless networking community relied on simple models such as random walk [3] and random waypoint [2]. However, the first of these models was found to be too simplistic although very useful in analysis and simulation. The latter, on the other hand was widely accepted and used in simulations. However, recently it was disvcovered that practitioners had severely misued it in simulations [4]. That and the growing appreciation that random waypoint is unrealistic has led to significant activities recently focusing on the development of parsimonious and accurate models describing the movement of nodes in mobile wireless networks. These have included efforts to model connectivity within sparse mobile networks associated with people and vehicles, and with the movement of units in miliatary settings. This talk will provide some of the early history in modeling mobility, including some of the failures described above. The talk will then describe the more recent application of a wide range of techniques to account for mobility. These range from Markov chains to ODE-based fluid models [6], from the use of exponetial, lognormal, and heavy-tailed distributions [1]to geometric weighted Gaussian distributions for intercontact times [5], and from the use of discrete state models to continuous state PDE-based models. The goal of the talk is to provide a better understanding of the issues underlying the accurate modeling of mobiltiy, recent progress in addressing these issues and the challenges that different approaches place on simulation.

关键词： simulation mobility wireless network

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Proceedings - workshop on principles of advanced and distributed simulation, Pads 2008

Proceedings - Workshop on Principles of Advanced and Distrib...

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22nd workshop on principles of advanced and distributed simulation, PADS 2008

ISBN: (纸本)9780769531595

The proceedings contain 22 papers. The topics discussed include: time Jails: a Hybrid Approach to Scalable Network Emulation;Adaptive Model Update Algorithms for Remote Network Emulation;toward Scalable Routing Experiments with Real-Time Network simulation;modeling and simulation of Pedestrian Behaviors;parallel and distributed Spatial simulation of Chemical Reactions;secure Referee Selection for Fair and Responsive Peer-to-Peer Gaming;stochastic Process Models for Packet/Analytic-Based Network simulations;performance Analysis of Real Traffic Carried with Encrypted Cover Flows;an Algorithm Selection Approach for simulation Systems;Symbiotic simulation Systems: an Extended Definition Motivated by Symbiosis in Biology;evaluating the Performance of Real Time Videoconferencing in Ad Hoc Networks Through Emulation;and scalable versus Accurate Physical Layer Modeling in Wireless Network simulations.

关键词： Stochastic models

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A Hybrid HLA Time Management Algorithm Based on Both Conditional and Unconditional Information

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simulation-TRANSACTIONS OF THE SOCIETY FOR MODELING And simulation international 2009年第9期85卷 559-573页

作者： Pan, Ke Turner, Stephen John Cai, Wentong Li, Zengxiang Nanyang Technol Univ Parallel & Distributed Comp Ctr Sch Comp Engn Singapore 639798 Singapore

关键词： distributed simulation high-level architecture time management synchronous algorithm asynchronous algorithm hybrid algorithm conditional information unconditional information

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Scalability in the MASON Multi-agent simulation System 18

Scalability in the MASON Multi-agent Simulation System

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22nd IEEE/ACM international Symposium on distributed simulation and Real Time Applications (DS-RT)

作者： Wang, Haoliang Wei, Ermo Simon, Robert Luke, Sean Crooks, Andrew Freelan, David Spagnuolo, Carmine George Mason Univ Fairfax VA 22030 USA Univ Salerno Salerno Italy

ISBN: (纸本)9781538650486

This paper describes distributed MASON, a distributed version of the MASON agent-based simulation tool. distributed MASON is architected to take advantage of well known principles from Parallel and Discrete Event simulation, such as the use of Logical Processes (LP) as a method for obtaining scalable and high performing simulation systems. We first explain data management and sharing between LPs and describe our approach to load balancing. We then present both a local greedy approach and a global hierarchical approach. Finally, we present the results of our implementation of distributed MASON on an instance in the Amazon Cloud, using several standard multi-agent models. The results indicate that our design is highly scalable and achieves our expected levels of speed-up.

关键词： Load modeling Heating systems Two dimensional displays Schedules Computer bugs Geographic information systems Load management

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Models of Privacy Preserving Traffic Tunneling

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simulation-TRANSACTIONS OF THE SOCIETY FOR MODELING And simulation international 2009年第9期85卷 589-607页

作者： Nicol, David M. Schear, Nabil Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA Univ Illinois Informat Trust Inst Urbana IL 61801 USA Univ Illinois Dept Comp Sci Urbana IL 61801 USA

Encrypted protocols, such as Secure Socket Layer (SSL), are becoming more prevalent because of the growing use of e-commerce, anonymity services, and secure authentication. Likewise, traffic analysis is becoming more common because it is often the only way to analyze these protocols. Although there are many valid uses for traffic analysis (such as network policy enforcement and intrusion detection), it can also be used to maliciously compromise the secrecy or privacy of a user. While the payload can be strongly protected by encryption, analysis of traffic patterns can yield information about the type and nature of traffic. In this paper we use simulation and analytic models to examine the impact on user experience of a scheme that masks the behavior of real traffic by embedding it in synthetic, encrypted, cover traffic. Through simulation and an analytic model we investigate the effects on the user experience using disparate and similar traffic models. This point provides a novel context where we observe the synergy of simulation and analytic modeling. We show that a detailed simulation model of network traffic characteristics can be used to estimate the parameters of an analytic model of tunneling. We see that the accuracy of the model's predictions is directly dependent on the accuracy of parameters we obtain from the simulation. However, the simulation model does not need to have any concept of tunneling. Using simulation and analytic modeling together, we obtain an analysis whose whole is greater than the sum of its parts.

关键词： discrete-event simulation network modeling security traffic analysis

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