Página 1 dos resultados de 492 itens digitais encontrados em 0.019 segundos

Simulation studies of a wide area health care network.

McDaniel, J. G.
Fonte: American Medical Informatics Association Publicador: American Medical Informatics Association
Tipo: Artigo de Revista Científica
Publicado em //1994 EN
Relevância na Pesquisa
46%
There is an increasing number of efforts to install wide area health care networks. Some of these networks are being built to support several applications over a wide user base consisting primarily of medical practices, hospitals, pharmacies, medical laboratories, payors, and suppliers. Although on-line, multi-media telecommunication is desirable for some purposes such as cardiac monitoring, store-and-forward messaging is adequate for many common, high-volume applications. Laboratory test results and payment claims, for example, can be distributed using electronic messaging networks. Several network prototypes have been constructed to determine the technical problems and to assess the effectiveness of electronic messaging in wide area health care networks. Our project, Health Link, developed prototype software that was able to use the public switched telephone network to exchange messages automatically, reliably and securely. The network could be configured to accommodate the many different traffic patterns and cost constraints of its users. Discrete event simulations were performed on several network models. Canonical star and mesh networks, that were composed of nodes operating at steady state under equal loads, were modeled. Both topologies were found to support the throughput of a generic wide area health care network. The mean message delivery time of the mesh network was found to be less than that of the star network. Further simulations were conducted for a realistic large-scale health care network consisting of 1...

A network model for wide area access to structural information.

Dailey, D. J.; Eno, K.; Zick, G. L.; Brinkley, J. F.
Fonte: American Medical Informatics Association Publicador: American Medical Informatics Association
Tipo: Artigo de Revista Científica
Publicado em //1993 EN
Relevância na Pesquisa
55.78%
Structural information in medicine is information about the physical body. Recent advances in medical imaging and biotechnology have greatly increased the amount and importance of structural information, and advances in networking envisioned by the High Performance Computing and Communication Initiative (HPCC) will allow this kind of information to be delivered to remote clients over wide area networks. One of the most important factors determining the usability of such a client-server configuration is the time delay between the request for information from the server, and its presentation to the user at the client. In this paper we present a model for predicting the performance of a structural information client based on the ping time, a simple, unobtrusive network measurement. Preliminary results suggest that the relationship between ping time and transfer time for large files is linear, which if borne out by more data, will allow the performance of structural information clients at remote sites to be predicted without the expense of installing them first. At the same time, such a model will be useful for planning improvements to the network in those sites which could most benefit by wide area access to structural information.

TCP/IP Optimization over Wide Area Networks: Implications for Teleradiology

Langer, Steve G.; French, Todd; Segovis, Colin
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
65.82%
Radiology examinations are large. The advent of fast volume imaging is making that statement truer every year. PACS are based on the assumption of fast local networking and just-in-time image pull to the desktop. On the other hand, teleradiology has been developed on a push model to accommodate the challenges of moderate bandwidth, high-latency wide area networks (WANs). Our group faced the challenging task of creating a PACS environment that felt local, while pulling images across a 3,000-mile roundtrip WAN link. Initial tests showed WAN performance lagging local area network (LAN) performance by a factor of 30 times. A 16-month journey of explorations pulled the WAN value down to only 1.5 times slower than the LAN.

A one-round algorithm for virtually synchronous group communication in wide area networks

Khazan, Roger Igor
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 165 p.; 8163207 bytes; 8163016 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
65.82%
Group communication services, and especially those that implement Virtual Synchrony semantics, are powerful middleware systems that facilitate the development of fault-tolerant distributed applications. In this thesis, we present a high quality, theoretical design of a group communication service that implements Virtual Synchrony semantics and is aimed for deployment in wide-area networks (WANs). The design features a novel algorithm for implementing Virtual Synchrony semantics; the algorithm is more appropriate for WANs than the existing solutions because it involves fewer rounds of communication and operates in a scalable WAN-oriented architecture. The high quality of the design refers to the level of formality and rigor at which it is done: The design includes formal and precise specifications, algorithms, correctness proofs, and performance analyses. We develop the necessary supporting theory and methodology required for producing and evaluating this design. In particular, we develop a formal, inheritance-based, methodology that supports incremental construction of specifications, models, and proofs. This methodology helps us manage the complexity of the design and makes it evident which part of the algorithm implements which property of the system. We also develop new...

Quality of service analysis for audio over cellular voice networks and cellular wireless wide area networks

Malik, Omair S. (Omair Safwan)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 51, [5] p.
ENG
Relevância na Pesquisa
65.89%
Cellular Wireless Wide Area Networks (WWANs) are most prevalent and offer high-bandwidth data transfer. We believe WWANs can be availed for voice communications employing Voice Over IP technologies. Such a communication will be of better quality and offer higher resilience compared to voice communication over a cellular phone (using cellular voice networks). We present a Quality of Service analysis of one-way voice communication over cellular voice networks and cellular WWANs. By studying different quality metrics we test if WWANs offer a better solution for voice communications compared to traditional cellular voice networks. We also study if employing more than one WWANs or cellular voice networks leads to a higher resilience in voice communication.; by Omair S. Malik.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.; Includes bibliographical references (p. 51-[55]).

Wide Area Filesystem Performance using Lustre on the TeraGrid

Simms, Stephen C.; Pike, Gregory G.; Balog, Douglas
Fonte: Universidade de Indiana Publicador: Universidade de Indiana
Tipo: Relatório
EN_US
Relevância na Pesquisa
55.71%
In: Proceedings of TeraGrid 2007. (Madison, WI, 2007); Today???s scientific applications demand computational resources that can be provided only by parallel clusters of computers. Storage subsystems have responded to the increased demand for high-throughput disk access by moving to network attached storage. Emerging Cyberinfrastructure strategies are leading to geographically distributed computing resources such as the National Science Foundation???s TeraGrid. One feature of the TeraGrid is a dedicated national network with WAN bandwidth on the same scale as machine room bandwidth. A natural next step for storage is to export file systems across wide area networks to be available on diverse resources. In this paper we detail our testing with the Lustre file system across the TeraGrid network. On a single 10 Gbps WAN link we achieved single host performance approaching 700 MB/s for single file writes and 1GB/s for two simultaneous file writes with minimal tuning.; This material is based upon work supported by the National Science Foundation under the following programs: Terascale Extensions and TeraGrid Operations (Extensible Terascale Facility). Support for the Data Capacitor project provided by the National Science Foundation is gratefully acknowledged and appreciated (CNS- 0521433).

Empowering Bioinformatics Workflows Using the Lustre Wide Area File System across a 100 Gigabit Network

Simms, Stephen; Seiffert, Kurt
Fonte: Universidade de Indiana Publicador: Universidade de Indiana
Tipo: Conferência ou Objeto de Conferência
EN_US
Relevância na Pesquisa
55.71%
Presented at BioITWorld Cloud Summit September 11-13, 2012.; Managing the profusion and accumulated volumes of life-science data is cumbersome; transferring them can require anything from shipping a hard drive to paying a graduate student to babysit transfers. Indiana University???s Data Capacitor solves this problem by exporting a high-performance Lustre file system across wide area networks to multiple locations. A mounted file system lets researchers run simple and familiar commands without having to contend with special tools for data transfer. Moreover, multiple mounts let researchers compute against their data from anywhere. To meet the insatiable bandwidth demands of life scientists, network infrastructure providers are increasingly offering 100 Gigabit circuits. IU recently used Lustre across a 100 Gigabit network spanning 2,300 miles to demonstrate application performance across a great distance. This presentation will describe the Data Capacitor cyber infrastructure and associated work, explore future use cases applicable to bioinformatics, and explain how the National Center for Genome Analysis Support (NCGAS) at Indiana University intends to integrate the Data Capacitor into their workflows.

Analysis of possibilities to use information from NetFlow protocol for improvement of performance of Wide Area Network

Escat Juanes, Pablo
Fonte: Universidade Autônoma de Madrid Publicador: Universidade Autônoma de Madrid
Tipo: Trabalho de Conclusão de Curso
ENG
Relevância na Pesquisa
55.82%
The main goal of this project is to analyze the data regarding to the connections of the Wide Area Networks (WAN) with the networks of Akademia Górniczo-Hutnicza (AGH University), and therefore try to obtain possibilities of optimizimization. Due to this, by analyzing the dumps of the connections, we will collect the characteristics of this network, and therefore to try to figure out how to resolve the troubleshooting this connections encountered. This document contains the obtained results of a deep analyze of the traffic produced on a WAN and along it (campus network), and also the methods and tools that have been used during the development of it. Once shown the results of the analyze, the study of possible solutions, deducted from previous studies will be presented, showing all the possibilities that might perform somehow the WAN and also the possible drawbacks of them.; El principal objetivo de este proyecto es analizar la información relacionada con las conexiones que las Redes de Área Extensa (WAN) realizan con la red de la Universidad AGH de Cracovia,en Polonia, y de ahí obtener posibilidades de optimización. Es por ello que, mediante análisis de los registros de las conexiones, recogeremos las características de nuestra red...

Converged optical Ethernet technologies in the LAN, MAN and SAN: novel architectures, performance analysis and energy efficiency; Convergencia de tecnologías ópticas y Ethernet en LAN, MAN y SAN: nuevas arquitecturas, análisis de prestaciones y eficiencia energética

Rodríguez de los Santos López, Gerson
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado
SPA
Relevância na Pesquisa
46.05%
The development of Information Technologies in the last decades, especially the last two, together with the introduction of computing devices to the mainstream consumer market, has had the logical consequence of the generalisation of the Internet access. The explosive development of the smartphone market has brought ubiquity to that generalisation, to the point that social interaction, content sharing and content production happens all the time. Social networks have all but increased that trend, maximising the diffusion of multimedia content: images, audio and video, which require high network capacities to be enjoyed quickly. This need for endless bandwidth and speed in information sharing brings challenges that affect mainly optical Metropolitan Area Networks (MANs) and Wide Area Networks (WANs). Furthermore, the wide spreading of Ethernet technologies has also brought the possibility to achieve economies of scale by either extending the reach of Ethernet Local Area Networks (LANs) to the MAN and WAN environment or even integrating them with Storage Area Networks (SANs). Finally, this generalisation of telecommunication technologies in every day life has as a consequence an important rise in energy consumption as well. Because of this...

Architecture and protocols for a decentralized group membership service for wide-area networks

Shukla, Shridhar B.; Neely, David S.; Kostrivas, John
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Relatório Formato: iv, 27 p. : ill. ; 28 cm.
Relevância na Pesquisa
55.71%
Entities cooperating as a group become simpler to construct if they possess access to a membership service to manage and administer the membership information of such groups. This report describes the architecture and design of a wide-area group membership service. Unlike any known membership service, the semce is based on a completely decentralized protocol executed by a hierarchy of servers. This hierarchy permits a clear separation between the membership service infrastructure and support for application groups, permitting global scaleability. The membership protocol itself is executed by a core set of membership servers identified in a group-specific manner, permitting a separate name space, membership scope and partition handling for each group. We describe a suitable application programmer's interface and provide correctness arguments for the protocol. A working implementation of the basic membership protocol is described.

Introduction to human factors and wide area networking.

Clarke, John Gordon
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: 112 p.;28 cm.
EN_US
Relevância na Pesquisa
55.71%
The Human-Systems Interaction Course taught at the Naval Postgraduate School is an introduction to the human-systems interface, that part of the system which the human uses to provide input to and receive feedback from the system. This thesis will provide a basic introduction to those factors which must be considered when designing today's complex military systems. Additionally, the thesis will provide an introduction to the Internet - - a worldwide network of computers and smaller networks. Students will use the Internet to gather information, access remote programs, and communicate with other personnel around the world. This thesis in only an introduction to both of these complex topics; further research is possible into any of the topics discussed. Appendix A provides a number of basic exercises intended to introduce the concepts discussed in the body of the thesis.; Captain, United States Air Force

Scheduling and management of real-time communication in point-to-point wide area networks

Pope, Cheryl Lynn
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 1345737 bytes; 73076 bytes; application/pdf; application/pdf
Publicado em //2003 EN
Relevância na Pesquisa
65.94%
Applications with timing requirements, such as multimedia and live multi-user interaction, are becoming more prevalent in wide area networks. The desire to provide more predictable performance for such applications in packet switched wide area networks is evident in the channel management provided by Asynchronous Transfer Mode (ATM) networks and in the extensions to the Internet protocols proposed by the Internet Engineering Task Force (IETF) working groups on integrated and differentiated service. The ability to provide guarantees on the performance of traffic flows, such as packet delay and loss characteristics, relies on an accurate model of the traffic arrival and service at each node in the network. This thesis surveys the work in bounding packet delay based on various proposed queuing disciplines and proposes a method for more accurately defining the traffic arrival and worst case backlog experienced by packets. The methods are applied to the first in first out (FIFO) queuing discipline to define equations for determining the worst case backlog and queuing delay in multihop networks. Simulation results show a significant improvement in the accuracy of the delay bounds over existing bounds published in the literature. An improvement of two orders of magnitude can be realised for a ten hop path and the improvement increases exponentially with the length of the path for variable rate network traffic. The equations derived in the thesis also take into consideration the effect of jitter on delay...

Flexible application driven network striping over Wireless Wide Area Networks

Qureshi, Asfandyar
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 161 p.; 10306058 bytes; 10313618 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
55.71%
Inverse multiplexing, or network striping, allows the construction of a high-bandwidth virtual channel from a collection of multiple low-bandwidth network channels. Striping systems usually employ a packet scheduling policy that allows applications to be oblivious of the way in which packets are routed to specific network channels. Though this is appropriate for many applications, many other applications can benefit from an approach that explicitly involves the application in the determination of the striping policy. Horde is middleware that facilitates flexible striping over Wireless Wide Area Network (WWAN) channels. Horde is unusual in that it separates the striping policy from the striping mechanism. It allows applications to describe network Quality-of-Service (QoS) objectives that the striping mechanism attempts to satisfy. Horde can be used by a set of data streams, each with its own QoS policy, to stripe data over a set of WWAN channels. The WWAN QoS variations observed across different channels and in time, provide opportunities to modulate stream QoS through scheduling. The key technical challenge in Horde is giving applications control over certain aspects of the data striping operation while at the same time shielding the application from low-level details. Horde exports a set of flexible abstractions replacing the application's network stack. Horde allows applications to express their policy goals as succinct network-QoS objectives. Each objective says something...

Verifying the Correctness of Wide-Area Internet Routing

Feamster, Nick; Balakrishnan, Hari
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Formato: 14 p.; 28764880 bytes; 1265172 bytes; application/postscript; application/pdf
EN_US
Relevância na Pesquisa
55.78%
Several studies have shown that wide-area Internet routing is fragile, with failures occurring for a variety of reasons. Routing fragility is largely due to the flexible and powerful ways in which BGP can be configured to perform various tasks, which range from implementing the policies of commercial relationships to configuring backup paths. Configuring routers in an AS is like writing a distributed program, and BGP's flexible configuration and today's relatively low-level configuration languages make the process error-prone. The primary method used by operators to determine whether their complex configurations are correct is to try them out in operation.We believe that there is a need for a systematic approach to verifying router configurations before they are deployed. This paper develops a static analysis framework for configuration checking, and uses it in the design of rcc, a ``router configuration checker''. rcc takes as input a set of router configurations and flags anomalies and errors, based on a set of well-defined correctness conditions. We have used rcc to check BGP configurations from 9 operational networks, testing nearly 700 real-world router configurations in the process. Every network we analyzed had configuration errors...

Wide-area Wireless Communication Challenges for the Internet of Things

Dhillon, Harpreet S.; Huang, Howard; Viswanathan, Harish
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/04/2015
Relevância na Pesquisa
45.97%
Aided by the ubiquitous wireless connectivity, declining communication costs, and the emergence of cloud platforms, the deployment of Internet of Things (IoT) devices and services is accelerating. Most major mobile network operators view machine-to-machine (M2M) communication networks for supporting IoT as a significant source of new revenue. In this paper, we motivate the need for wide-area M2M wireless networks, especially for short data packet communication to support a very large number of IoT devices. We first present a brief overview of current and emerging technologies for supporting wide area M2M, and then using communication theory principles, discuss the fundamental challenges and potential solutions for these networks, highlighting tradeoffs and strategies for random and scheduled access. We conclude with recommendations for how future 5G networks should be designed for efficient wide-area M2M communications.

Split Architecture for Large Scale Wide Area Networks

John, Wolfgang; Devlic, Alisa; Ding, Zhemin; Jocha, David; Kern, Andras; Kind, Mario; Köpsel, Andreas; Nordell, Viktor; Sharma, Sachin; Sköldström, Pontus; Staessens, Dimitri; Takacs, Attila; Topp, Steffen; Westphal, F. -Joachim; Woesner, Hagen; Gladis
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/02/2014
Relevância na Pesquisa
65.88%
This report defines a carrier-grade split architecture based on requirements identified during the SPARC project. It presents the SplitArchitecture proposal, the SPARC concept for Software Defined Networking (SDN) introduced for large-scale wide area networks such as access/aggregation networks, and evaluates technical issues against architectural trade-offs. First we present the control and management architecture of the proposed SplitArchitecture. Here, we discuss a recursive control architecture consisting of hierarchically stacked control planes and provide initial considerations regarding network management integration to SDN in general and SplitArchitecture in particular. Next, OpenFlow extensions to support the carrier-grade SplitArchitecture are discussed. These are: a) Openness & Extensibility; b) Virtualization; c) OAM; d) Resiliency approaches; e) Bootstrapping and topology discovery; f) Service creation; g) Energy-efficient networking; h) QoS aspects; and i) Multilayer aspects. In addition, we discuss selected deployment and adoption scenarios faced by modern operator networks, such as service creation scenarios and peering aspects, i.e., how to interconnect with legacy networks. Finally, we indicate how our SplitArchitecture approach meets carrier grade scalability requirements in access/aggregation network scenarios; Comment: This is the public deliverable D3.3 of the EU FP7 SPARC project (ICT-258457) - "Split Architecture for Carrier Grade Networks". Original Deliverable published at http://www.fp7-sparc.eu/

MPWide: a light-weight library for efficient message passing over wide area networks

Groen, Derek; Rieder, Steven; Zwart, Simon Portegies
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/12/2013
Relevância na Pesquisa
65.78%
We present MPWide, a light weight communication library which allows efficient message passing over a distributed network. MPWide has been designed to connect application running on distributed (super)computing resources, and to maximize the communication performance on wide area networks for those without administrative privileges. It can be used to provide message-passing between application, move files, and make very fast connections in client-server environments. MPWide has already been applied to enable distributed cosmological simulations across up to four supercomputers on two continents, and to couple two different bloodflow simulations to form a multiscale simulation.; Comment: accepted by the Journal Of Open Research Software, 13 pages, 4 figures, 1 table

A Comparison of wide area network performance using virtualized and non-virtualized client architectures

Gustafson, John
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
75.88%
The goal of this thesis is to determine if there is a significant performance difference between two network computer architecture models. The study will measure latency and throughput for both client-server and virtualized client architectures. In the client server environment, the client computer performs a significant portion of the work and frequently requires downloading uploading files to and from a remote location. Virtual client architecture turns the client machine into a terminal, sending only keystrokes and mouse clicks and receiving only display pixel or sound changes. I accomplished the goal of comparing these architectures by comparing completion times for ping reply, file download, a small set of common work tasks, and a moderately large SQL database query. I compared these tasks using simulated wide area network, local area network, and virtual client network architectures. The study limits the architecture to one where the virtual client and server are in the same data center.

Improved Lightpath (Wavelength) Routing in Large WDM Networks

Liang, Weifa; Shen, Xiaojun
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
75.85%
We address the problem of efficient circuit switching in wide area networks. The solution provided is based on finding optimal routes for lightpaths and semilightpaths. A lightpath is a fully optical transmission path, while a semilightpath is a transmission path constructed by chaining several lightpaths together, using wavelength conversion at their junctions. The problem thus is to find an optimal lightpath/semilightpath in the network in terms of the cost of wavelength conversion and the cost of using the wavelengths on links. In this paper, we first present an efficient algorithm for the problem which runs in time O(k2n + km + kn log(kn)), where n and m are the number of nodes and links in the network, and k is the number of wavelengths. We then analyze that the proposed algorithm requires O(d2nk02 + mk0 log n) time for a restricted version of the problem in which the number of available wavelengths for each link is bounded by k0 and k0 = o(n), where d is the maximum in-degree or out-degree of the network. It is surprising to have found that the time complexity for this case is independent of k. It must be mentioned that our algorithm can be implemented efficiently in the distributed computing environment. The distributed version requires O(kn) time and O(km) messages. Compared with a previous O(k2n + kn2) time algorithm...

Finding multiple routing paths in wide-area WDM networks

Liang, Weifa; Shen, Xiaojun
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
75.92%
In this paper a multiple routing path problem in wide area Wavelength Division Multiplexing (WDM) networks is considered, which is to find K edge-disjoint lightpaths/semilightpaths from a source to a destination, if they exist, such that they meet some specified optimization objective. Two versions of the problem are studied. One is to minimize the total cost of the K paths, and the other is to minimize the cost of the maximum cost one among the K paths. An efficient algorithm for the first version is proposed, which takes O(kK(kn+m+nlog(kn))) time and delivers an exact solution, where n, m, and k are the number of nodes, links and wavelengths in the network, respectively. The second version of the problem is shown to be NP-hard, instead an approximation algorithm is devised which delivers a solution within K times of the optimum, where K≥2.