169,068 research outputs found

    Transparent and scalable client-side server selection using netlets

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    Replication of web content in the Internet has been found to improve service response time, performance and reliability offered by web services. When working with such distributed server systems, the location of servers with respect to client nodes is found to affect service response time perceived by clients in addition to server load conditions. This is due to the characteristics of the network path segments through which client requests get routed. Hence, a number of researchers have advocated making server selection decisions at the client-side of the network. In this paper, we present a transparent approach for client-side server selection in the Internet using Netlet services. Netlets are autonomous, nomadic mobile software components which persist and roam in the network independently, providing predefined network services. In this application, Netlet based services embedded with intelligence to support server selection are deployed by servers close to potential client communities to setup dynamic service decision points within the network. An anycast address is used to identify available distributed decision points in the network. Each service decision point transparently directs client requests to the best performing server based on its in-built intelligence supported by real-time measurements from probes sent by the Netlet to each server. It is shown that the resulting system provides a client-side server selection solution which is server-customisable, scalable and fault transparent

    Loosening the notions of compliance and sub-behaviour in client/server systems

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    In the context of "session behaviors" for client/server systems, we propose a weakening of the compliance and sub-behaviour relations where the bias toward the client (whose "requests" must be satisfied) is pushed further with respect to the usual definitions, by admitting that "not needed" output actions from the server side can be "skipped" by the client. Both compliance and sub-behaviour relations resulting from this weakening remain decidable, though the proof of the duals-as-minima property for servers, on which the decidability of the sub-behaviour relation relies, requires a tighter analysis of client/server interactions.Comment: In Proceedings ICE 2014, arXiv:1410.701

    Large closed queueing networks in semi-Markov environment and its application

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    The paper studies closed queueing networks containing a server station and kk client stations. The server station is an infinite server queueing system, and client stations are single-server queueing systems with autonomous service, i.e. every client station serves customers (units) only at random instants generated by a strictly stationary and ergodic sequence of random variables. The total number of units in the network is NN. The expected times between departures in client stations are (Nμj)1(N\mu_j)^{-1}. After a service completion in the server station, a unit is transmitted to the jjth client station with probability pjp_{j} (j=1,2,...,k)(j=1,2,...,k), and being processed in the jjth client station, the unit returns to the server station. The network is assumed to be in a semi-Markov environment. A semi-Markov environment is defined by a finite or countable infinite Markov chain and by sequences of independent and identically distributed random variables. Then the routing probabilities pjp_{j} (j=1,2,...,k)(j=1,2,...,k) and transmission rates (which are expressed via parameters of the network) depend on a Markov state of the environment. The paper studies the queue-length processes in client stations of this network and is aimed to the analysis of performance measures associated with this network. The questions risen in this paper have immediate relation to quality control of complex telecommunication networks, and the obtained results are expected to lead to the solutions to many practical problems of this area of research.Comment: 35 pages, 1 figure, 12pt, accepted: Acta Appl. Mat

    The development of a Java based GIS viewing tool : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Technology in Information Engineering at Massey University

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    Geographic Information Systems (GIS) industry sources quote the ratio of power users to casual users at 1000:1, within New Zealand this figure has been found to be 30:1. The casual user is often under-supported, with slow and cumbersome viewing tools. This project implements a full data download system in Java for use with Genasys (New Zealand) GIS software. Three components were developed; a vector data handler, an image download system, and a database client. These components were integrated to form a powerful client that offered a significant performance increase over the "server based" client. The image download system outperformed the "server based" client by over 400%. The vector data handler outperformed the "server based" client by over 50%, while the database client was over 250% quicker. GIS users rated all components to be of significant benefit, offering improved performance over their current GIS viewing tools. The work completed in this thesis provides Genasys (New Zealand) a useful tool to enable powerful, fast and stable Java based GIS viewing clients. Keywords: GIS, Java, computer graphics, image pyramid

    Client-Server Computing: Getting your Feet Wet

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    Tremendous growth of client-server (C-S) computing is expected throughout the 1990s. Computer information systems (CIS) curricula are faced with the ongoing challenge of providing client-server instruction while technologies and methodologies are still evolving. To keep pace with this dynamic environment, faculty must begin building initial client-server experiences into the CIS curriculum. The purpose of this paper is to describe one institution\u27s experiences getting its client-server feet wet. First, fundamental concepts of client-server are considered. Second, basic questions about introducing C-S to the CIS curriculum are addressed. Next, the introduction of client-server computing at Western Carolina University is described. Finally, future client-server changes are considered

    Improving SQL Server Perform

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    With the development of client server technology and multilayer architectures the systems ef-ficiency issue has been increasingly discussed. Lacking knowledge in optimization methods and tools offered by DBMS's, database administrators and developers of applications based on Microsoft technologies cannot optimally design and service performing systems. In this article we review the objectives that should be considered (in order) to improve performance of SQL Server instances and we describe the techniques used to optimize queries. Also, we explain and illustrate the new optimization features offered by SQL Server 2008.Query, Optimization, SQL Server

    An experimental study of client-side Spotify peering behaviour

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    Spotify is a popular music-streaming service which has seen widespread use across Europe. While Spotify’s server-side behaviour has previously been studied, little is known about the client-side behaviour. In this paper, we describe an experimental study where we collect packet headers for Spotify traffic over multiple 24-hour time frames at a client host. Two distinct types of behaviour are observed, when tracks are being downloaded, and when the client is only serving requests from other peers. We also note wide variation in connection lifetimes, as seen in other studies of peer-to-peer systems. These findings are relevant for improving Spotify itself, and for the designers of other hybrid peer-to-peer and server-based distribution architectures
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