74 research outputs found

    Findings of a comparison of five filing protocols

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    Filing protocols are essential for the management and dissemination of shared information within computer systems. This is a survey of the current state of the art in filing protocols. Five popular filing protocols were selected and subjected to a rigorous comparison. FTAM, FTP, UNIX rep, XNS Filing, and NFS are compared in the following areas: exported interface, concurrency control, access control, error recovery, and performance. The coverage of background material includes a taxonomy and a brief history of filing protocols

    Open Source in Imaging Informatics

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    The open source community within radiology is a vibrant collection of developers and users working on scores of collaborative projects with the goal of promoting the use of information technology within radiology for education, clinical, and research purposes. This community, which includes many commercial partners, has a rich history in supporting the success of the digital imaging and communication in medicine (DICOM) standard and today is pioneering interoperability limits by embracing the Integrating the Healthcare Enterprise. This article describes only a small portion of the more successful open source applications and is written to help end users see these projects as practical aids for the imaging informaticist and picture archiving and communication system (PACS) administrator

    CERN UNIX user guide

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    An application of an ethernet based protocol for communication and control in automated manufacturing

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    The exchange of information in the industrial environment is essential in order to achieve complete integration and control of manufacturing processes. At present the majority of devices present in the shop floor environment are still used as stand alone machines. They do not take advantage of the possibilities offered by a communication link to improve the manufacturing process. The subject of this research has been centered on the development of a simple, flexible and inexpensive support system for communication and control of manufacturing processes. As a result, a system with these features has been proposed and implemented on a simulated workcell. The area footwear manufacturing was chosen for modelling the workcell. The components of the manufacturing support system were developed using an object oriented approach which allowed modularity and software reuse. In order to achieve communication between the components, a communication protocol was developed following the process defined in the rapid protocol implementation framework. Ethernet was selected for implementing the lower levels of the protocol. Java, a new object oriented programming language used for the implementation of the system, showed that it could became a promising language for the implementation of manufacturing applications. In particular the platform independence feature of the language allows the immediate porting of applications to systems with different features. The manufacturing cell simulation had shown that the times associated with the manufacturing support system operations are compatible for its use in applications where the response times are in the order of one second

    Natural language software registry (second edition)

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    Research into software executives for space operations support

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    Research concepts pertaining to a software (workstation) executive which will support a distributed processing command and control system characterized by high-performance graphics workstations used as computing nodes are presented. Although a workstation-based distributed processing environment offers many advantages, it also introduces a number of new concerns. In order to solve these problems, allow the environment to function as an integrated system, and present a functional development environment to application programmers, it is necessary to develop an additional layer of software. This 'executive' software integrates the system, provides real-time capabilities, and provides the tools necessary to support the application requirements

    The interaction network : a performance measurement and evaluation tool for loosely-coupled distributed systems

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    Much of today's computing is done on loosely-coupled distributed systems. Performance issues for such systems usually involve interactive performance, that is, system responsiveness as perceived by the user. The goal of the work described in this thesis has been to develop and implement tools and techniques for the measurement and evaluation of interactive performance in loosely-coupled distributed systems. The author has developed the concept of the interaction network, an acyclic directed graph designed to represent the processing performed by a distributed system in response to a user input. The definition of an interaction network is based on a general model of a loosely-coupled distributed system and a general model of user interactions. The author shows that his distributed system model is a valid abstraction for a wide range of present-day systems. Performance monitors for traditional time-sharing systems reported performance information, such as overall resource utilisations and queue lengths, for the system as a whole. Performance problems are now much more difficult, because systems are much more complex. Recent monitors designed specifically for distributed systems have tended to present performance information for execution of a distributed program, for example the time spent in each of a program's procedures. In the work described in this thesis, performance information is reported for one or more user interactions, where a user interaction is defined to be a single user input and all of the processing performed by the system on receiving that input. A user interaction is seen as quite different from a program execution; a user interaction includes the partial or total execution of one or more programs, and a program execution performs work as part of one or more user interactions. Several methods are then developed to show how performance information can be obtained from analysis of interaction networks. One valuable type of performance information is a decomposition of response time into times spent in each of some set of states, where each state might be defined in terms of the hardware and software resources used. Other performance information can be found from displays of interaction networks. The critical path through an interaction network is then defined as showing the set of activities such that at least one must be reduced in length if the response time of the interaction is to be reduced; the critical path is used in both response time decompositions and in displays of interaction networks. It was thought essential to demonstrate that interaction networks could be recorded for a working operating system. INMON, a prototype monitor based on the interaction network concept, has been constructed to operate in the SunOS environment. INMON consists of data collection and data analysis components. The data collection component, for example, involved the adding of 53 probes to the SunOS operating system kernel. To record interaction networks, a high-resolution global timebase is needed. A clock synchronisation program has been written to provide INMON with such a timebase. It is suggested that the method incorporates a number of improvements over other clock synchronisation methods. Several experiments have been performed to show that INMON can produce very detailed performance information for both individual user interactions and groups of user interactions, with user input being made through either character-based or graphical interfaces. The main conclusion reached in this thesis is that representing the processing component of a user interaction in an interaction network is a very valuable way of approaching the problem of measuring interactive performance in a loosely-coupled distributed system. An interaction network contains a very detailed record of the execution of an interaction and, from this record, a great deal of performance (and other) information can be derived. Construction of INMON has demonstrated that interaction networks can be identified, recorded, and analysed

    Network Attack Analysis Using Honeypots

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    Práce se zabývá bezpečností počítačových sítí za využití technologie honeypotů, jakožto nástroje účelných nástrah pro útočníky. Blíže popisuje základní myšlenky a výhody a nevýhody tohoto konceptu. Zaměřuje se na honeypot s nízkou interakce Honeyd, jeho funkčnost a možná rozšíření. V rámci praktické části je zde popsán princip implementace rozšiřujících servisních skriptů Honeyd v podobě simulace chování červa Conficker. Dále se zabývá vytvořením automatizovaného skriptu analýzy, zpracování útoků a vyhodnocení dat, získaných v průběhu skutečného nasazení honeypotu v síti Internet.This text deals with computer network security using honeypot technology, as a tool of intentional trap for attackers. It closely describes basic thoughts, together with advantages and disadvantages of this concept. The main aim is a low interaction honeypot Honeyd, its functionality and possible extensional features. As a practical part of the text there is a description of principles of implementation Honeyd service scripts, which are represented as a simulation of behavior of computer worm Conficker. Further it describes creation of automated script used for analysis and processing of gathered data, captured during actual deployment of Honeyd in Internet network.

    Supporting distributed computation over wide area gigabit networks

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    The advent of high bandwidth fibre optic links that may be used over very large distances has lead to much research and development in the field of wide area gigabit networking. One problem that needs to be addressed is how loosely coupled distributed systems may be built over these links, allowing many computers worldwide to take part in complex calculations in order to solve "Grand Challenge" problems. The research conducted as part of this PhD has looked at the practicality of implementing a communication mechanism proposed by Craig Partridge called Late-binding Remote Procedure Calls (LbRPC). LbRPC is intended to export both code and data over the network to remote machines for evaluation, as opposed to traditional RPC mechanisms that only send parameters to pre-existing remote procedures. The ability to send code as well as data means that LbRPC requests can overcome one of the biggest problems in Wide Area Distributed Computer Systems (WADCS): the fixed latency due to the speed of light. As machines get faster, the fixed multi-millisecond round trip delay equates to ever increasing numbers of CPU cycles. For a WADCS to be efficient, programs should minimise the number of network transits they incur. By allowing the application programmer to export arbitrary code to the remote machine, this may be achieved. This research has looked at the feasibility of supporting secure exportation of arbitrary code and data in heterogeneous, loosely coupled, distributed computing environments. It has investigated techniques for making placement decisions for the code in cases where there are a large number of widely dispersed remote servers that could be used. The latter has resulted in the development of a novel prototype LbRPC using multicast IP for implicit placement and a sequenced, multi-packet saturation multicast transport protocol. These prototypes show that it is possible to export code and data to multiple remote hosts, thereby removing the need to perform complex and error prone explicit process placement decisions
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