264 research outputs found

    Spacelab system analysis: A study of the Marshall Avionics System Testbed (MAST)

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    An analysis of the Marshall Avionics Systems Testbed (MAST) communications requirements is presented. The average offered load for typical nodes is estimated. Suitable local area networks are determined

    Spacelab system analysis: A study of communications systems for advanced launch systems

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    An analysis of the required performance of internal avionics data bases for future launch vehicles is presented. Suitable local area networks that can service these requirements are determined

    Space Station Freedom data management system growth and evolution report

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    The Information Sciences Division at the NASA Ames Research Center has completed a 6-month study of portions of the Space Station Freedom Data Management System (DMS). This study looked at the present capabilities and future growth potential of the DMS, and the results are documented in this report. Issues have been raised that were discussed with the appropriate Johnson Space Center (JSC) management and Work Package-2 contractor organizations. Areas requiring additional study have been identified and suggestions for long-term upgrades have been proposed. This activity has allowed the Ames personnel to develop a rapport with the JSC civil service and contractor teams that does permit an independent check and balance technique for the DMS

    Advanced information processing system: The Army fault tolerant architecture conceptual study. Volume 2: Army fault tolerant architecture design and analysis

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    Described here is the Army Fault Tolerant Architecture (AFTA) hardware architecture and components and the operating system. The architectural and operational theory of the AFTA Fault Tolerant Data Bus is discussed. The test and maintenance strategy developed for use in fielded AFTA installations is presented. An approach to be used in reducing the probability of AFTA failure due to common mode faults is described. Analytical models for AFTA performance, reliability, availability, life cycle cost, weight, power, and volume are developed. An approach is presented for using VHSIC Hardware Description Language (VHDL) to describe and design AFTA's developmental hardware. A plan is described for verifying and validating key AFTA concepts during the Dem/Val phase. Analytical models and partial mission requirements are used to generate AFTA configurations for the TF/TA/NOE and Ground Vehicle missions

    Message-Bundle Converting in Intenet Protocol Multicast-Based High Level Architecture Exercises

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    The Department of Defense is pushing for more wide-spread and realistic interactive training simulations which increases the demand on network capacity and resources. While network bandwidth is a measurable resource, packet bandwidth, or the number of packets-per-second (Pk/s) a host can handle, is a shifting commodity. This research analyzes host performance characteristics under varying data loads. The hosts include SGI single and multi-processor systems and Intel Pentium platforms using both Windows 95 and Linux Operating Systems. The networking media covers Ethernet, ATM and FDDI. For the ATM network, both AAL5 and IP over ATM were analyzed. With the data from this research, a system is proposed and developed that takes individual messages and bundles them into multi-message packets. This bundling process overcomes the 5,000 Pk/s limitation, reduces the CPU network handling time and introduces a flow-control mechanism at the local network level. While the idea of bundling messages to increase CPU efficiency is not new, there are no current methods of bundling within the new High Level Architecture (HLA). This proposed process is a novel approach to introduce flow control, priority message handling and increase address space while utilizing bundled data delivery. For traditional network delivery, typical CPU usage from network data varies as a function of traffic load, ranging from 5% at 500 messages-per-second to over 80% at 4,000 messages-per-second. The new bundling process requires 10% at 500 messages-per-second but only increases to 13% at 4,000 messages-per-second

    The TurboLAN project. Phase 1: Protocol choices for high speed local area networks. Phase 2: TurboLAN Intelligent Network Adapter Card, (TINAC) architecture

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    The hardware and the software architecture of the TurboLAN Intelligent Network Adapter Card (TINAC) are described. A high level as well as detailed treatment of the workings of various components of the TINAC are presented. The TINAC is divided into the following four major functional units: (1) the network access unit (NAU); (2) the buffer management unit; (3) the host interface unit; and (4) the node processor unit

    Technology Directions for the 21st Century

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    New technologies will unleash the huge capacity of fiber-optic cable to meet growing demands for bandwidth. Companies will continue to replace private networks with public network bandwidth-on-demand. Although asynchronous transfer mode (ATM) is the transmission technology favored by many, its penetration will be slower than anticipated. Hybrid networks - e.g., a mix of ATM, frame relay, and fast Ethernet - may predominate, both as interim and long-term solutions, based on factors such as availability, interoperability, and cost. Telecommunications equipment and services prices will decrease further due to increased supply and more competition. Explosive Internet growth will continue, requiring additional backbone transmission capacity and enhanced protocols, but it is not clear who will fund the upgrade. Within ten years, space-based constellations of satellites in Low Earth orbit (LEO) will serve mobile users employing small, low-power terminals. 'Little LEO's' will provide packet transmission services and geo-position determination. 'Big LEO's' will function as global cellular telephone networks, with some planning to offer video and interactive multimedia services. Geosynchronous satellites also are proposed for mobile voice grade links and high-bandwidth services. NASA may benefit from resulting cost reductions in components, space hardware, launch services, and telecommunications services

    Multimedia performance evaluation of ethernet and token ring media access protocols: a network comparison

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    This paper and accompanying project examines which type of time-division multiplexing media access protocol, the Carrier Sense Multiple Access (CSMA) of Ethernet or the token passing of token ring, is best able to fulfill the stringent isochronous performance demands required of today's resource-hungry multimedia networks, specifically the requirements of high throughput, low latency and jitter, and minimal error rates. Using performance bounds accepted by other researchers as sufficient to ensure quality isochronous transmission, that of (1) the throughput rate being equal to or less than the playback rate; (2) the latency in transmitting each packet ranging from 20 to 400 milliseconds and the variance or jitter being less than 80 milliseconds; and (3) the rate of lost packets ranging from 0.01--1.001, this paper approaches a solution first from the theoretical and then integrates into the final conclusion an analytical, C++ software evaluation test component that models network performance under optimum conditions. The immediate benefit of the entire study is the identification of one media access protocol, Ethernet or Token Ring, over its counterpart as being superior for isochronous applications as defined by the above performance requirements, and the long-term consequence of this identification will be facilitating for future network designers, including those of digital libraries, the selection of the best network architecture for their multimedia environments

    Future benefits and applications of intelligent on-board processing to VSAT services

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    The trends and roles of VSAT services in the year 2010 time frame are examined based on an overall network and service model for that period. An estimate of the VSAT traffic is then made and the service and general network requirements are identified. In order to accommodate these traffic needs, four satellite VSAT architectures based on the use of fixed or scanning multibeam antennas in conjunction with IF switching or onboard regeneration and baseband processing are suggested. The performance of each of these architectures is assessed and the key enabling technologies are identified
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