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Advanced Distributed Simulation Research Consortium



Parallel and Distributed Evaluation, Visualization, and AI Reasoning to Advanced DIS Technology






September 29, 1998 - September 28, 1999



Army Research Office

Grant No. DAAH04-95-1-0250


Grambling State University

Department of Mathematics and Computer Science

Grambling, LA 71245



Table of Contents


1. Project Progress Reports from Task Teams


1.1 ADS Architecture Design and Evaluation (ADS-ADE) Task 2 - 23

Coordinator: Ratan K. Guha


1.2 ADS Visualization and Synthetic Environment (ADS-VSE) Task 24 - 46

Coordinator: Patrick Bobbie


1.3 ADS Knowledge Base Systems (ADS-KBS) Task 47 - 63

Coordinator: Richard Al󼯰>


1.4 Student Outreach and Training Program Task 64 - 65

Coordinator: Muddapu Balaram


2. Publications, Presentations and Personnel


2.1 ADS Architecture Design and Evaluation (ADS-ADE) Task 67 - 69

Coordinator: Ratan K. Guha


2.2 ADS Visualization and Synthetic Environment(ADS-VSE) Task 70 - 71

Coordinator: Patrick Bobbie


2.3 ADS Knowledge Base Systems (ADS-KBS) Task 72 - 74

Coordinator: Richard Al󼯰>


2.4 Student Outreach and Training Program (ADS-KBS) Task 75 - 76

Coordinator: Muddapu Balaram



Appendix: Publication Abstracts 77 - 93




















1.1 ADS Architecture Design and Evaluation (ADS-ADE) Task


Task Coordinator: Ratan K. Guha




Objectives and Significance:

The main objectives of the research performed by the ADS Architecture Design and Evaluation team are: (1) to develop techniques to model/evaluate the performance of large scale ADS systems, (2) to develop algorithms, based on DoD High Level Architecture (HLA), for improving the scalability and reducing the bandwidth requirement of distributed simulation systems, and (3) to improve solution techniques used by tools for the modeling and performance evaluation of DIS systems.


Specifically, the main objective for the fourth year of this project was to continue our research in (1) advanced networking technology, (2) synchronization problem of distributed systems, (3) relevance filtering, and (4) plan research activities and gather relevant information on integration-driven software reuse practices and open platforms and tools for implementing it. For general purpose tools, we have worked on developing easily accessible interval computation software which can reliably perform fundamental interval arithmetic, set operation and bound elementary interval functions.


In networking technology, one project aims at developing and evaluating methodologies that can be used for the conformance testing of the implementations of protocols for concurrent interactions. In another project, we extend our previous work to design efficient channel reservation schemes for two dimensional networks based on the rapidly evolving technology of mobile positioning. We are also evaluating the impact of porting distributed applications to state-of-the-art gigabit ATM networks. For internet applications, we evaluate various web architectures to improve the performance of client's information access time. For synchronization problem of distributed systems, we extend our triangular level coteries to trapezoidal and incomplete triangular level coteries and develop an algebraic method for generating coteries. The successful implementation of efficient relevance filtering in network gateways would help solve one of the challenges facing the design of highly scalable DIS and HLA systems.


In software development, our aim is to provide support to object-oriented developers and managers to foster better design and more reusable code. The emerging integration-based reuse technology holds good promise for increasing productivity and reducing the overhead of source modification and re-verification. Our software tool projects improve the performance of a generic non-linear global optimization interval software, develop a standard for interval basic linear algebra software, and an online interval calculator.


Army Relevance:

Conformance testing verifies that DIS/HLA products comply with their specifications. Conformance testing also provides safeguard against implementation errors as well as incompatibility among different implementations.


Wireless and mobile communication technologies will continue to play increasingly important role in the various functions of armed forces. The development of efficient channel assignment and handoff protocols is of one of the critical problems facing the designers of third generation wireless systems. We have extended our linear topology schemes into general two-dimensional channel reservation schemes based on global positioning. Our research addresses the real-time performance issues of handoff protocols and seeks to develop efficient channel assignment and handoff schemes suitable for the delivery of UAV-collected imagery to/from mobile tactical vehicles and the delivery of location-based video/audio data to mobile users. Efficient handoff designs will also help the effort to incorporate live vehicles in military simulation training exercises.


Standard coding and documentation facilitate the software reuse process but do not offset the overhead of acquiring a deep understanding of the source code. Integration-driven software seeks to generate easy-to-use open platforms for the integration of software tools and applications. The ultimate goal of this paradigm is to develop software components that can be reused without change. Software components that need to be extensively modified before reuse will require re-verification which could be a time consuming and costly task. The integration-based reuse approach is promising and seems to have good potential for increasing software productivity and reducing the cost and time of software development.


The research on filtering and routing spaces is crucial to the scalability of HLA currently being developed under the auspices of the Defense Modeling and Simulation Office as the DoD-wide standard for simulation. The results of this research have provided good insight into the behavior of relevance filtering schemes, their real-time performance and their reliability. With this insight, the development of reliable and efficient filtering methods is greatly enhanced.


For synchronization in a distributed system, the special class of non-token-based algorithm, known as the quorum based approach, requires each process to only exchange messages with a subset of specific nodes in the distributed system. The quorum-based approach is attractive due to its well-defined concept, low message overhead, and its capability to tolerate both the site and link failures. The development of this concept will contribute to the efficiency and fault tolerance capabilities of HLA systems.



Several teams have been formed to work on several sub-tasks. Areas of accomplishments include Petri net models to check certain types of illegal behavior by a DIS/HLA station connected to an FDDI LAN, real-time protocols for channel assignments and handoff handling in mobile cellular environments, trapezoidal and incomplete triangular level quorums for distributed mutual exclusion, relevance document filtering, an online interval calculator, and a parallel global optimization software tool. During the past year, we have also been gathering information about emerging new practices for software reuse and have been planning for performing research and experiments on integration-based tools for software reuse.


Planned Activities:

The planned activities of each ADS-ADE sub-task are described in the individual reports given on the following pages.


Conformance Testing of Concurrent Protocol Implementations


M. Bassiouni and R. Guha(UCF)

M. Balaram and Y. Reddy (GSU)



Research Objectives and Significance:

This project aims at developing and evaluating methodologies that can be used for the conformance testing of the implementations of protocols for concurrent interactions. The two main paradigms used in our research are Finite State Machine (FSM) and Petri nets. Our investigation involves two steps. We first develop models for the passive testing mode. Next, we extend these models to the mode of active conformance testing. In this latter mode, an external tester is used to apply a sequence of inputs to the station under test (SUT) and verify that it behaves as its specification describes. The tester drives the SUT into different states and examines its behavior in response to the various conditions induced by the test sequence.


Army Relevance:

Distributed interactive simulation (DIS) and High Level Architecture (HLA) systems rely on the real-time interconnection of large numbers of simulation entities. Conformance testing is needed to verify that DIS/HLA products comply with their specifications. Conformance testing also provides safeguard against implementation errors as well as incompatibility among different implementations.



We have examined the issue of applying Finite State Machine (FSM) models to verify the adherence of DIS/HLA simulators to some of the interactions specified by their standards. We have also investigated Petri-net models as basis for the compliance testing of concurrent and networked protocols. Below, we illustrate our approach for applying Petri-nets on a real-life example of a complex network protocol, namely, the Fiber Distributed Data Interface (FDDI).


The FDDI Media Access Control (MAC) protocol uses a timed token algorithm to arbitrate access to the transmission medium. Access to the physical medium is controlled by passing a token around the FDDI ring. The token gives the station which receives it the opportunity to transmit a frame of data (or a sequence of frames) onto the ring. For the purpose of illustration, we shall assume that the station being tested does not transmit synchronous data and we will therefore limit our discussion to aspects of the FDDI protocol that are relevant to asynchronous transmission.


The implementation of the FDDI MAC protocol is accomplished via a set of timers and counters that are used to control the transmission of data frames. The following are the important timers/counters maintained (locally) by each node on the network.


? Token-Rotation Timer (TRT) is used to control the station's access to the network.

? LateCt: is a counter used to indicate the number of times the timer TRT has expired since the token was last received by this station.

? Token-Holding Timer (THT) is used to control the amount of asynchronous data that can be transmitted by the station.


A token arriving at a given station is considered to be an early token if LateCt = 0. Otherwise, the token is considered to be a late token. The FDDI access protocol can be simply described as follows. A token arriving before TRT times out (i.e., an early token) can be used for asynchronous transmissions. A late token allows the transmission of synchronous data but cannot be used for asynchronous transmission.


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