Showing papers on "Testbed published in 1986"

An Overview of the Army/DARPA Distributed Communications and Processing Experiment

Abstract: Emerging technologies in communications and information processing are having, and will continue to have, a significant effect on the way command and control (C2) is carried out on the battlefield of the future. One of these technologies is a packet-switched, internetwork, computer-communications system. This system concept allows for the interconnection of heterogeneous computers on heterogeneous networks, thereby providing for rapid, efficient, and reliable communications between processing elements-regardless of their physical location. This type of telecommunications architecture also allows automatic network reconfiguration when switching nodes or communications links fail. This permits system survivability in stressed environments. This communications system provides the means for passing time-critical information in a reliable and efficient fashion for purposes of C2. To achieve survivable C2, however, it is also necessary to integrate distributed software and data-processing technology with this telecommunications architecture technology. To achieve a survivable and effective C2capability, an experimental distributed command, control, and communications C3architecture has been evolved that blends these evolving communications and processing technologies with innovative concepts in tactical battle management. A joint Army/Defense Advanced Research Projects Agency (DARPA) Testbed, located at Fort Bragg, North Carolina, is being established to explore survivable C3concepts based on this architecture. This testbed, supported under the Army/DARPA Distributed Communications and Processing Experiment (ADDCOMPE), was started in late 1984. The ADDCOMPE testbed is leveraging the results of the earlier Army Data Distribution (ADDS) testbed also situated at Fort Bragg. However, ADDS primarily addressed communications; the ADDCOMPE program's emphasis is not only on communications but also on distributedprocessing environments (software and hardware) and distributed C2applications implemented over such an environment. In ADDCOMPE, the ADDS communications architecture is being taken as "available" technology but is being extended to include packet-switched, internetwork communications implemented over present-day Army communications systems. In this paper, an overview of the ADDCOMPE telecommunications architecture is presented and a discussion of the general philosophy for use of the ADDCOMPE testbed to support technology transfer to the Army is given. As this architecture is implemented, future papers will discuss its technical details, such as protocols used, throughput delay characteristics, and the like. Future papers will also provide technical discussions on the distributed-processing software (system and C2applications) developed for the testbed.

Software implementation of a recursive fault tolerance algorithm on a network of computers

Abstract: RAFT is a recursive algorithm for fault tolerance that uses a combination of dynamic space and time redundancy techniques for detecting faulty processors and recovering from errors. U* is a multicomputer testbed consisting of a network of AT&T 3B2 computers running a network operating system based on the UNIX system. This paper describes a software implementation of RAFT on U*, and demonstrates the effectiveness of a RAFT-like scheme for designing fault-tolerant multicomputer systems. Results of Monte Carlo experiments, conducted on this system that validated the theoretical basis of RAFT, are presented. Experimentally observed performance penalty, incurred due to fault tolerance, is also presented.

PACOSS program overview and status

Abstract: Many future civilian and military large space structures (LSS) will have as performance objectives stringent pointing accuracies, short settling times, relatively fast response requirements, or combinations thereof. Many of these structures will be large, light weight, and will exhibit high structural modal density at low frequency and within the control bandwidth. Although it is possible in principle to achieve structural vibration control through purely active means, experience with complex structures has shown that the realities of plant model inaccuracies and sensor/actuator dynamics frequently combine to produce substandard performance. A more desirable approach is to apply passive damping technology to reduce the active control burden. Development of the technology to apply this strategy is the objective of the PACOSS (Passive and Active Control OF Space Structures) program. A key element in the PACOSS program is the Representative System Article (RSA). The RSA is a generic paper system that serves as a testbed for damping and controls studies. It also serves as a basis for design of the smaller Dynamic Test Article (DTA), a hardware testbed for the laboratory validation of analysis and design practices developed under PACOSS.

An Introduction For Users

Abstract: Pan is a prototype and testbed for language-based editors and viewers. Its design addresses the needs of experienced users who manage complex objects such as large software systems. All of Pan''s components are multilingual, incremental, description-driven, customizable, and extensible. Viewing is facilitated by semantics-based browsing and an object model which integrates text and structure. Pan is intended to share information with other tools, allowing integration into a larger language, program, and document development environment.

MAGNET's Integrated Network Architecture

Abstract: The network architecture of NMAGNET, a testbed for integrated local area networks, is presented. The system architecture consists of integrated workstations, control and communication subsystems, and gateways. The network architecture incorporates this organization at the system level and represents an instance of the Integrated Reference Model previously proposed by the authors. It provides resource management, connection management and control, and user information flows in logically separate planes. Protocols supporting the control subsystem are organized in the (M)-Plane, while the protocols supporting the communication subsystem are embedded in the (C)-and (U)-Planes. The requlirements of the different traffic classes are quantified by a set of attributes to guarantee specified performance measures.

Performance measurement, modelling, and evaluation of integrated concurrency control and recovery algorithms in distributed database systems

Abstract: In this dissertation, the performance evaluation of integrated concurrency control and recovery mechanisms for distributed database systems is studied using a distributed testbed system. In addition, a queueing network model has been developed to analyze the two-phase locking scheme in the distributed testbed system. The combination of testbed measurement and analytical modelling provides an effective tool for understanding the performance of integrated concurrency control and recovery algorithms in distributed database systems. The design and implementation of the distributed testbed system, CARAT, are presented. The concurrency control and recovery algorithms implemented in CARAT include: a two-phase locking scheme with distributed deadlock detection, a distributed version of optimistic approach, before-image and after-image journalling mechanisms for transaction recovery, and a two-phase commit protocol. Many performance measurements have been conducted using a variety of workloads. In the workloads, there are four types of transactions: local read-only, local write, distributed read-only, and distributed write. The performance measures of the two-phase locking scheme with before-image journlling and the optimistic approach with after-image journalling are presented and analyzed. The major performance measures include transaction throughput, probability that a transaction is aborted, CPU utilization, and disk I/O rate. Basic parameter values, such as locking overhead, mean lock blocking time, and validation overhead, are also measured. A queueing network model is developed to analyze the performance of the CARAT system using the two-phase locking scheme with before-image journalling. The queueing model differs from previous analytical models in three major aspects. First, it is a model for distributed transaction processing. Second, it is more general and integrated than previous analytical models. Finally, this model reflects a functioning distributed database testbed system and is validated against performance measurements. The combination of testbed measurements and analytical modelling provides significant improvements in understanding the performance impacts of the concurrency control and recovery algorithms in distributed database systems.

Underwater Telerobotics and Virtual Reality: A New Technology Partnership

Abstract: : Despite major advances in autonomous vehicle technologies, human-control led ROVs (remotely-operated vehicles) continue to fill an important role in underwater work. To perform effectively, however, the human operator requires meaningful cues for spatial orientation, good workspace visibility, and tight feedback about manipulator behavior. These needs can be hard to support in actual undersea operations. Telerobot designers for space missions have addressed these challenges by presenting a graphic, virtual reality model of the workspace to the operator, who then performs tasks on this representation of the actual work site. Real-time graphic modeling can (1) maintain a continuous, clear depiction of the workspace that is largely independent of communications bandwidth, (2) allow arbitrary shading and perspective of the workspace, (3) provide integrated navigation and orienting cues, and (4) support a rich, multi-sensory feedback environment. The use of virtual reality technologies for operator interface design is being investigated at NCCOSC for undersea ROV applications. A general-purpose virtual reality testbed is described which involves a dedicated virtual reality system for underwater applications, together with a manipulator system and supporting software. The objectives of the testbed are to examine fundamental human performance and engineering issues connected with operating on a virtual workspace for real telerobotic tasks, and to benchmark emerging telerobotic technologies in a standardized test environment.

Between Laboratory and Field Trial: Experience with a Communications Services Testbed:

Abstract: To attempt to bridge the gap between laboratory and field trial, we at the Network Services Research Division of Bellcore have designed and implemented the Modular Integrated Communications Environment (MICE). The primary motivation for MICE is to provide a means for research on the design and evaluation of advanced communications services and user interface technologies for the public communications network in a realistic environment, but without the expense and overhead of field trials. Thus, MICE is a real system, providing reliable communications services to a community of friendly users, but permitting convenient experimental control over services and interfaces. MICE has been constructed entirely of commercially-available subsystems, with controlling software executing in the UNIX™ environment. MICE has processed over 50, 000 communications attempts to date; capabilities range from basic telephony to voice paging, voice mail, and integrated voice/data mail.

A Rewrite Rule Machine. Architectural Options and Testbed Facilities for the Rewrite Rule Machine.

Abstract: : The Rewrite Rule Machine (RRM) project unites advanced architectural concepts with advanced software concepts. The unification is achieved through a novel model of computation, called concurrent tree rewriting, which supports both ultra high level programming and extreme concurrency of execution. This report presents some options for RRM implementation. We expect to use custom VLSI design to place many small processors on a single chip. With a suitable high-level architecture, this will allow unprecedented concurrency, with many thousands of small processors cooperating on a preduction task. Our performance estimate for a reasonable prototype is one million MIPS. The proposed RM architecture is described at four different levels. The individual tokens that constitute trees are stored in cells, while nodes consist of many cells with a common controller. Clusters include many nodes sharing a common name space for tokens, and several clusters together constitute the network level. Scalability and fault tolerance are also discussed, as is a testbed to ease the validation of architectural concepts. (Author)

Design of testbed and emulation tools

Abstract: The research summarized in this report was concerned with the design of testbed and emulation tools suitable to assist in projecting, with reasonable accuracy, the expected performance of highly concurrent computing systems on large, complete applications. Such testbed and emulation tools are intended for the eventual use of those exploring new concurrent system architectures and organizations, either as users or as designers of such systems. While a range of alternatives was considered, a software-based set of hierarchical tools was chosen to provide maximum flexibility, to ease in moving to new computers as technology improves and to take advantage of the inherent reliability and availability of commercially available computing systems.

Versatile simulation testbed for rotorcraft speech I/O system design

Abstract: A versatile simulation testbed for the design of a rotorcraft speech I/O system is described in detail. The testbed will be used to evaluate alternative implementations of synthesized speech displays and speech recognition controls for the next generation of Army helicopters including the LHX. The message delivery logic is discussed as well as the message structure, the speech recognizer command structure and features, feedback from the recognizer, and random access to controls via speech command.

Sensor Driven Robot Systems Testbed

Abstract: Intelligent robot systeos which operate in a semiautonomous fashion (i.e. , the operator serves only as a high level supervisor) require the integration of sensors and mechanisms cour.)leA by intelligent software. since such robot syste.as operate in the real worl] with imperfect knowledge of that worll, error recovery is an important aspect of any control strategy. Configured with a 6 degree-of-freedom robot manipulator, two dimensional vision and force sensing, the Sensor driven Robot Systems Testbed offers an environment for the development of control concepts for intelligent machine systems. The Sensor Driven Robot Systems Testbed has led to the development of active sensing concepts using complementary sensors and a highly modular control software concept. Both concepts are currently being implemented within the testbed environment.

Design of a Testbed for Studying Rapidly Reconfigurable Tactical Communication Networks

Abstract: This paper describes the design of a testbed for studying rapidly reconfigurble ground and airborne tactical communication networks which use directed beam couplings between nodes The networks are subject to rapid changes in connectivity and topology caused by links fading in and out or by mobile users moving into and out of the directed beams Such networks, which provide improved security, jam resistance and probability of intercept, are viable candidates for tactical use in the 1990s The testbed has been designed around three major subsystems: the prototype network equipment, the monitor, and the stimulator The prototype network equipment consists of six nodes, with all required software, and direct wire connections between nodes The monitor subsystem records the significant arrival and departure times for each packet at each node It stores this data and processes it to determine appropriate performance parameters The stimulator subsystem generates packets and injects bit errors and link and node faults into the prototype network The testbed will be used to develop network architectures and protocols for constructing and reconfiguring networks and to study new types of adaptive routing algorithms and error control Most of the planned studies will make use of the ability of the network to measure transient network behavior

Graphical program to display a testbed block diagram with real-time data on an IBM personal computer

Abstract: A graphical program called TESTBED was written in Pascal in summer 1985 for NASA Lewis Research Center, Cleveland, Ohio. TESTBED displays on an IBM Personal Computer/XT a block diagram of the DC testbed for the power management and distribution system for the space station. When the testbed, which will contain photovoltaic arrays, batteries, and loads, is deployed in the field, it will be permanently connected to the IBM PC/XT via direct memory access. Sensors attached to the testbed in the field will continually collect and updata data in real time. The program will superimpose the real-time data on the block diagram of the testbed displayed on the screen of the IBM PC/XT. The program uses procedures contained in Metawindow, a software package of graphics utilities written by Metagraphics Corp., Mountain View, California.

Software fault-tolerance by design diversity DEDIX: A tool for experiments

Abstract: The use of multiple versions of a computer program, independently designed from a common specification, to reduce the effects of an error is discussed. If these versions are designed by independent programming teams, it is expected that a fault in one version will not have the same behavior as any fault in the other versions. Since the errors in the output of the versions are different and uncorrelated, it is possible to run the versions concurrently, cross-check their results at prespecified points, and mask errors. A DEsign DIversity eXperiments (DEDIX) testbed was implemented to study the influence of common mode errors which can result in a failure of the entire system. The layered design of DEDIX and its decision algorithm are described.

Dynamic production scheduling in computer-aided fabrication of integrated circuits

Abstract: The scheduling of a V.L.S.I. manufacturing facility is being studied using M.I.T.'s new V.L.S.I. Research Laboratory (V.R.L.) as a testbed. This paper describes the facility, outlines the scheduling methodology that is under investigation and presents the design of the initial preliminary scheduling system.

Rapid Prototyping using Local Area Network (LAN) Technologies

Abstract: An ethernet local area network and ISO/OSI transport and network layer software package was used to establish connectivity between functional components of an intergatewaying testbed. Standard interfaces were used to support session functions, thus, simplifying the coding effort on the variety of testbed hardware and insuring the portability of developed code. An overall thrust of the rapid prototyping effort was the minimizing of prototype specific code and efficiency modularization of software elements.

Use of High-Performance Workstations in Military Communications and ADP/Network Experiments

Abstract: Advances in high-performance computer workstation technology make it possible to merge traditionally distinct communications and automatic data processing functions into an integrated terminal device. The ADDCOMPE program has used these state-of-the-art, high-performance workstations to support distributed command, control, and communication (C3) in an active Army Testbed. These workstations are internetworked to provide a distributed processing and communications environment that forms the foundation for enduring survivable C3 concepts; and, at the same time, are used to test experimental concepts in advanced military automatic data processing and network communications.