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Distributed Simulation and Real-Time Applications, 2002. Proceedings. Sixth IEEE International Workshop on

Date 13-13 Oct. 2002

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  • Proceedings Sixth IEEE International Workshop on Distributed Simulation and Real-Time Applications. DS-RT 2002

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    Page(s): 167
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    Freely Available from IEEE
  • An implementation of a distributed algorithm for detection of local knots and cycles in directed graphs based on the CSP model and Java

    Page(s): 143 - 150
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB) |  | HTML iconHTML  

    Cycles and knots in directed graphs are problems that can be associated with deadlocks in database and communication systems. Many algorithms to detect cycles and knots in directed graphs were proposed. Boukerche and Tropper (1998) have proposed a distributed algorithm that solves the problem in a efficient away. Their algorithm has a message complexity of 2 m vs. (at least) 4 m for the Chandy and Misra algorithm, where m is the number of links in the graph, and requires O (n log n) bits of memory, where n is the number of nodes. We have implemented Boukerche and Tropper's algorithm according to the construction of processes of the CSP model. Our implementation was done using JCSP, an implementation of CSP for Java, and the results are presented. View full abstract»

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  • ACE/2: a scalable modular SATCOM system emulator

    Page(s): 119 - 126
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB) |  | HTML iconHTML  

    Simulation is widely used to evaluate the performance of telecommunication services. One interesting case is the access to the Internet through satellites, where a critical parameter is the quality of service perceived by the users (P-QoS). Unfortunately, TCP, the data transport protocol of the Internet, reacts to packet losses decreasing the packet transmission rate. This is perfectly suited to reduce congestion, the main reason of losses in terrestrial networks, but it further decreases the performance when losses are due to transmission errors, as in satellite links. The problem is made more complex by the interaction between TCP and the applications used to surf the Internet. To address this problem the Italian Space Agency (ASI) financed a two-year research program, during which two SATCOM system emulators, dubbed ACE and ACE/2, respectively, where built. This paper describes the second emulator, an enhanced version of the first one. View full abstract»

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  • Using a software architecture description language to model the architecture and run-time performance of a federate

    Page(s): 85 - 92
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (390 KB) |  | HTML iconHTML  

    Software architecture is high-level software design, dealing with the structure and organization of software systems. A software architecture is defined in terms of computational components and interactions among those components. Architecture description languages (ADLs) represent architecture-level software designs. Different ADLs often have different intents; e.g., Rapide supports architecture simulation and Acme is intended to be both an ADL and an ADL interchange format. Experimental applications of two ADLs were conducted to determine the effectiveness of ADLs for architecture-level analysis of simulation systems; one of them is reported. Acme was used to model the architecture of ModSAF and to analyze its run-time performance. The model was used to analyze execution time at the component and federate levels and to estimate the maximum number of internal and external simulation entities that could be supported by the ModSAF architecture. The experiment showed that ADLs could model important features of simulation system architectures. View full abstract»

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  • Automatic construction of Hierarchical Federations Architecture

    Page(s): 50 - 57
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB) |  | HTML iconHTML  

    The High Level Architecture allows simulation components of various types to be joined together into a federation to create a common virtual environment. However with the increased complexity of simulations, not all user requirements can be satisfied by a flat federation. The requirement of selective information hiding naturally suggests a Hierarchical Federations Architecture (HFA) where federations are organized into hierarchies so that a federation appears as a federate in an upper level federation. In order to provide reusability and interoperability at the federation level, a federation should be able to participate in different super-federations without requiring code modification. We present an approach to automatically construct the HFA. We describe the information that must be provided by the participating user federations and how this is used to construct the Universal Object Model (UOM) used by the super-FOMs (the FOMs of super-federations). We show how the structure for selective information hiding is generated from the user information and how gateway federates are automatically constructed to support super-FOM independence. View full abstract»

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  • An overhead reducing technique for Time Warp

    Page(s): 95 - 102
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    We introduce a technique that reduces the number of state savings and the maximum memory needed for the Time Warp. We present a technique to determine if an event is safe or not. If an event execution is safe, no state saving is carried out. The technique discards some saved states even though the time stamps are larger than the GVT. We prove that the technique is correct under both the aggressive and lazy cancellation scheme. This technique can be implemented with minimal additional overhead. Benchmark results on circuit simulation show that the mechanism can reduce the number of state savings and maximum memory size significantly. The technique is applicable to hardware simulation, network simulation and other systems that have fixed interconnection. View full abstract»

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  • Trade-offs in overhead vs effectiveness of causality inconsistency tracking for preemptive rollback in optimistic simulation

    Page(s): 63 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (310 KB) |  | HTML iconHTML  

    We discuss and compare three different causality inconsistency tracking mechanisms in support of preemptive rollback in optimistic parallel simulation on myrinet clusters. These mechanisms exhibit different communication/processing overhead and also different effectiveness in revealing causality inconsistency of the currently executed simulation event. By the results of an empirical study on a classical simulation benchmark we have found some trade-offs between these mechanisms, pointing out indications of application contexts for which each mechanism is expected to be well tailored. View full abstract»

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  • Distributed simulation of timed coloured Petri nets

    Page(s): 159 - 166
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB) |  | HTML iconHTML  

    This paper introduces a coloured Petri nets formalism-TCPN-which is suitable for modelling and simulation of complex systems. Novel in TCPN is (i) a timing model which accommodates both unordered and ordered (queue) places; (ii) the adoption of Java as the net inscription language. TCPN is supported by a graphical tool-RAINBOW-which allows model design, testing and simulation. A large TCPN model can be split into regions (subnets) whose execution is assigned to different LP/processors of a networked simulator. Distributed simulation relies on TUTW, an agent-based time warp algorithm capable of exploiting temporal uncertainty for improving simulation performance. The paper describes TCPN and its distributed execution kernel. The practical use of TCPN is demonstrated through an example and experimental results. View full abstract»

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  • The design of the distributed ABELS brokering system

    Page(s): 151 - 158
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    Many simulations and other applications need to interact seamlessly with distributed data resources. The Agent-Based Environment for Linking Simulations (ABELS) allows the formation of a dynamic "data and simulation cloud" that links a heterogeneous collection of networked resources. ABELS consists of three major types of components: user entities that serve as data producers and/or consumers, a brokering system for organizing and linking the various participants, and generic local agents that connect simulations and data resources to the cloud of participants. This paper presents the design of the distributed brokering system, which is implemented using Java and Sun Microsystems' Jini technology. View full abstract»

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  • Software design for implementation of the Selectively Reliable Multicast Protocol

    Page(s): 103 - 107
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB) |  | HTML iconHTML  

    The Selectively Reliable Multicast transport Protocol (SRMP) supports a mix of reliable and best-effort multicast by taking advantage of the specific requirements of distributed virtual simulation. It serves as the transport layer of a protocol stack with Internet Protocol multicast, and has been demonstrated to support distributed simulation with significantly lower demands on the network than that generated by use of multiple TCP connections. We address the iterative design and prototyping process used to develop the current implementation of SRMP. We begin with a review of the principles involved in SRMP. We then focus on two major aspects of the SRMP implementation software design, inter-process communication and process concurrency (threading), which were developed using an iterative or spiral development model. The earliest prototypes we developed showed disappointingly poor performance. Inter-process communication went through three distinct iterations before arriving at an efficient implementation; threading required two iterations for the basic SRMP functionality, and a third for implementation of heartbeats and bundling. We describe how the iterative development process has produced an efficient and effective implementation, and can be expected to yield similar results with ongoing enhancements to SRMP. View full abstract»

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  • On scheduling 3D model transmission in network virtual environments

    Page(s): 127 - 133
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    View dependent 3D-geometry streaming allows navigation of large virtual environments without requiring replication of the entire database at the client. We present scheduling policies for optimal transmission of multiple multiresolution 3D-geometry objects over congested network links. Using multiresolution objects allows smooth adaptation of the visual quality of the graphics environment with network bandwidth fluctuations. A greedy scheduling policy is used for minimizing the visual error received at the client. The performance is further increased using a look-ahead scheduling policy. Finally a scheduling policy using multicast transmission of 3D models is presented. The scheduling policy combines unicast and multicast transmissions in order to provide optimal visual quality of the virtual environment rendered at the client. View full abstract»

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  • A load management system for running HLA-based distributed simulations over the grid

    Page(s): 7 - 14
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB) |  | HTML iconHTML  

    Running a large-scale distributed simulation may need a large amount of computing resources at geographically different locations. These resources may be from different organizations. The simulation may run for a long period of time and the availability and amount of computing resources available may change during the course of simulation execution. Therefore, coordinating and managing resources for distributed simulation to complete the simulation efficiently and effectively is a critical issue. This paper describes a load management system for HLA-based distributed simulation. The system is constructed on top of a grid computing environment supported by Globus. The overall structure of the system is presented in the paper and how the system saves and restores a federate is also discussed in detail. View full abstract»

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  • Enhancing the DiffServ architecture of a simulation environment

    Page(s): 108 - 115
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (354 KB) |  | HTML iconHTML  

    Simulation has always been a valuable tool for experimentation and validation of models, architectures and mechanisms in the field of networking. In the case of the DiffServ framework, simulation is even more valuable, due to the fact that an analytical approach of mechanisms and services is infeasible because of the aggregation and multiplexing of flows. In this work, we have extended the functionality of a widely used simulation environment towards the direction of realistic traffic generation and a series of mechanisms defined by the DiffServ architecture. The modules created are being presented and a case study of a simulation scenario that exploits the functionality provided by them is described. View full abstract»

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  • Modular HLA RTI services: the GRIDS approach

    Page(s): 15 - 22
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (325 KB) |  | HTML iconHTML  

    The Generic Runtime Infrastructure for Distributed Simulation (GRIDS) has been developed to investigate modularity issues in distributed simulation. It could be argued that although the HLA RTI is a widespread solution to distributed simulation, it cannot include all possible services. This paper investigates an approach to extending the distributed simulation services available in the HLA RTI. One example of this is bridging support for HLA/DIS legacy integration. This paper therefore presents GRIDS, how GRIDS can be used to provide modular service support for the HLA RTI, and a case study on legacy integration to demonstrate our approach. View full abstract»

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  • Nautilus-the environment for training and testing

    Page(s): 134 - 139
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (337 KB) |  | HTML iconHTML  

    The paper describes an experimental Web-based environment for teaching and testing. The application named Nautilus has been developed using Virtual Reality Modeling Language (VRML) and Java language with two special libraries: DILEWA and Vrmlworld. Although the resulting system is intended for low-level virtual reality systems without specialized hardware support it is powerful enough to accurately simulate various situations and scenarios. The currently implemented multi-user environment for training and testing of yacht captains serves as an experimental workbench for creation of general applications where a developer combines a simulated environment from simpler simulation elements. Design and implementation of the system are presented together with several practical observations concerning efficiency of the real-time rendering and the level of implementation difficulty. View full abstract»

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  • Performance trade-off in distributed simulation

    Page(s): 77 - 84
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    We extend our previous work on formalizing event orderings using partial order set and its application in space analysis in distributed simulation. We focus on the time and space trade-off in exploiting event parallelism. Event parallelism is divided into inherent (problem) parallelism, event ordering parallelism and effective event parallelism. Firstly, we analyze the performance cost of varying event ordering parallelism on memory requirement in open and closed systems. Secondly, we study the effects of interconnection topology of a physical system on exploitable event ordering parallelism. Measurements were obtained from a time-space analyzer that we have developed. View full abstract»

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  • A next-generation Internet federation object model for the HLA

    Page(s): 43 - 49
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB) |  | HTML iconHTML  

    This paper reports on development of a Web-based capability for distributed simulation in large-scale virtual environments that has been developed collaboratively by the Naval Postgraduate School and George Mason University. The work brings together several Years of effort in DIS-Java-VRML and the Virtual Reality Transfer Protocol on the part of NPS with a similar period of effort by GMU in selectively reliable multicast for distributed virtual simulation combined with Java-based middleware for use with the DoD High Level Architecture (HLA) for modeling and simulation. We describe the capability we have created for simulations of military and other highly interactive, physics-based models to operate in three-dimensional visualization over advanced Internet facilities. The major components of our system are described in detail, with the intent of creating interest in their use by the academic community. View full abstract»

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  • Performance evaluation of real time schedulers for a multicomputer

    Page(s): 71 - 76
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    This paper considers work in the context of the CRUX project, which aims at the conception of a complete environment for parallel programming, in the development of a postgraduate course in Computer Science of Santa Catarina Federal University. This paper discusses a performance evaluation of several scheduling algorithms of real time systems found in the bibliography, about a simulation model that represents the processing as the communication of this multicomputer. The objective was to quantify the effect of the scheduling algorithm and other factors about some metrics of selected performance, in order to verify the applicability of CRUX in real time systems. View full abstract»

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  • Bridging the HLA: problems and solutions

    Page(s): 33 - 42
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    The High-Level Architecture (HLA) provides a common architecture for distributed modeling and simulation. In its original form, HLA allows a number of simulations to be joined together into a federation using a single run time infrastructure. Recently there has been interest in joining multiple federations together using a mediating unit, called an HLA "bridge." This paper presents the results of an in-depth study of the feasibility of an HLA bridge in the context of the current HLA interface specification. Problems and solutions are discussed and illustrated using particular HLA services. View full abstract»

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  • PERFOSIM: a performance evaluation tool for HLA distributed simulations

    Page(s): 23 - 30
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    With distributed simulation, existing simulations, even from different disciplines, can be reused or made to interoperate. The efficiency of this technique is, however, not firmly established and depends on the ability to satisfy a number of requirements, especially concerning simulation performance. The performance depends to a large extent on the structure and scaling of architectural components of the simulation execution platform. In this paper, we present an approach to address this problem: the design of models to capture the main characteristics of distributed simulations, run-time infrastructures and network architectures, and the development of a tool to predict performances. This tool, which is a simulator of HLA simulations, is written using HLA, and is evaluated on three test applications. View full abstract»

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