Specification of initial connection handling in TCP using structured Petri nets

This paper uses structured Petri nets to specify how connection establishment is handled by the DoD Transmission Control Protocol. The purpose of this paper is to demonstrate an alternate specification technique by examining its application to a portion of a protocol of reasonable complexity.Initially we briefly present the semantics of structured Petri nets. Following this, a terse discussion of the problems of establishing connections in a network takes place. This discussion centers on the use of the three-way handshake, which is used by TCP, as a solution for many of these problems. Finally, the specification of the three-way handshake used in TCP is made. The specification is presented in three sections: first, a general set of notes concerning the nature of this particular specification is discussed; second, the data definitions of the specification are given; and, third, the actual nets themselves are presented.This paper is condensed from a portion of the author's dissertation, which is still in preparation. In the interests of brevity, some components of the specification, such a retransmission handling, have been omitted. Interested readers should contact the author for a more detailed paper

Correcting soft errors online in fast fourier transform

While many algorithm-based fault tolerance (ABFT) schemes have been proposed to detect soft errors offline in the fast Fourier transform (FFT) after computation finishes, none of the existing ABFT schemes detect soft errors online before the computation finishes. This paper presents an online ABFT scheme for FFT so that soft errors can be detected online and the corrupted computation can be terminated in a much more timely manner. We also extend our scheme to tolerate both arithmetic errors and memory errors, develop strategies to reduce its fault tolerance overhead and improve its numerical stability and fault coverage, and finally incorporate it into the widely used FFTW library - one of the today's fastest FFT software implementations. Experimental results demonstrate that: (1) the proposed online ABFT scheme introduces much lower overhead than the existing offline ABFT schemes; (2) it detects errors in a much more timely manner; and (3) it also has higher numerical stability and better fault coverage

Transport systems research vehicle color display system operations manual

A recent upgrade of the Transport Systems Research Vehicle operated by the Advanced Transport Operating Systems Program Office at the NASA Langley Research Center has resulted in an all-glass panel in the research flight deck. Eight ARINC-D size CRT color displays make up the panel. A major goal of the display upgrade effort was ease of operation and maintenance of the hardware while maintaining versatility needed for flight research. Software is the key to this required versatility and will be the area demanding the most detailed technical design expertise. This document is is intended to serve as a single source of quick reference information needed for routine operation and system level maintenance. Detailed maintenance and modification of the display system will require specific design documentation and must be accomplished by individuals with specialized knowledge and experience

Demystifying Digital Records Processing... Step by Step, Byte by Byte

After briefly providing some background information on the acquisition of a digital processing workstation and the development of digital records processing workflows, this hands-on work session will provide an overview of at least one possible workflow for accessioning and processing born digital archival records. Attendees will walk through the process themselves and learn how to use specific (free) tools to better understand and process the materials at hand. Some possible tasks could include documenting basic file structure for ingesting and processing digital files, generating basic metadata about files (e.g. identify the number, size, and types/formats of files), identifying duplicate files and/or empty directories, and creating checksums (as a baseline for preservation). Come and take the next step with us

Generic Ada code in the NASA space station command, control and communications environment

The results of efforts to apply powerful Ada constructs to the formatted message handling process are described. The goal of these efforts was to extend the state-of-technology in message handling while at the same time producing production-quality, reusable code. The first effort was initiated in September, 1984 and delivered in April, 1985. That product, the Generic Message Handling Facility, met initial goals, was reused, and is available in the Ada Repository on ARPANET. However, it became apparent during its development that the initial approach to building a message handler template was not optimal. As a result of this initial effort, several alternate approaches were identified, and research is now on-going to identify an improved product. The ultimate goal is to be able to instantly build a message handling system for any message format given a specification of that message format. The problem lies in how to specify the message format, and one that is done, how to use that information to build the message handler. Message handling systems and message types are described. The initial efforts, its results and its shortcomings are detailed. The approach now being taken to build a system which will be significantly easier to implement, and once implemented, easier to use, is described. Finally, conclusions are offered

A functional video-based anthropometric measuring system

A high-speed anthropometric three dimensional measurement system using the Selcom Selspot motion tracking instrument for visual data acquisition is discussed. A three-dimensional scanning system was created which collects video, audio, and performance data on a single standard video cassette recorder. Recording rates of 1 megabit per second for periods of up to two hours are possible with the system design. A high-speed off-the-shelf motion analysis system for collecting optical information as used. The video recording adapter (VRA) is interfaced to the Selspot data acquisition system