User requirements for geo-collaborative work with spatio-temporal data in a web-based virtual globe environment

Web-based tools developed in the last couple of years offer unique opportunities to effectively support scientists in their effort to collaborate. Communication among environmental researchers often involves not only work with geographical (spatial), but also with temporal data and information. Literature still provides limited documentation when it comes to user requirements for effective geo-collaborative work with spatio-temporal data. To start filling this gap, our study adopted a User-Centered Design approach and first explored the user requirements of environmental researchers working on distributed research projects for collaborative dissemination, exchange and work with spatio-temporal data. Our results show that system design will be mainly influenced by the nature and type of data users work with. From the end-users' perspective, optimal conversion of huge files of spatio-temporal data for further dissemination, accuracy of conversion, organization of content and security have a key role for effective geo-collaboration.     

Optimal distribution of a hierarchy of network management agents

In this paper, we consider several mathematical and algorithmic problems which arise naturally in the optimal deployment of modern network management systems. Specifically, we will consider the problem of minimizing the total communication costs within an architecture consisting of a distributed hierarchy of cooperating intelligent agents. We consider several communication cost models, and describe provable optimal schemes for distributing agents among machines in each of these models.     

Analysis of mobile agents in network fault management

Network domains have become more and more advanced in terms of their size, complexity and the level of heterogeneity. Comprehensive fault management is the most significant challenge in network management. Fault management can help increase the availability of the network by quickly identifying the faults and then, proactively, start the recovery process. Current centralized configured network management systems suffer from problems such as insufficient scalability, availability and flexibility as networks become more distributed. Mobile agents (MAs), with integral intelligence, can present a reasonable new technology that will help to achieve distributed management, several researchers have embraced these approaches. In this paper, we introduce a general analytical model for network management client/server (CS) and MA paradigms. We express how to build up an analytical framework, which can be used to quantitatively assess the performances of the MA and CS paradigms under different scenarios. We present some numerical and experimental results that demonstrate the applicability of our proposed framework, which will be based on a combination of MA and CS schemes called Adaptive Intelligent Mobile Agent.     

Experiences of designing a sophisticated network monitor

This paper describes the design of a network monitor that captures connections information in a network. The real-time performance requirement makes the design significantly more challenging than that of a simple monitor that only counts packet types. Although we developed the monitor for DECnet, most of the lessons we learned are protocol-independent and are thus applicable to designing such a monitor for a different protocol. In addition to reviewing the functionality, we report a first-cut performance evaluation of the monitor software. We also describe some of our early experiences in using the monitor and review some current applications of the monitor in the areas of network configuration planning and performance management.     

基于用户的大型网络应用信息审计系统

以一个网络管理项目为背景,结合大型企业网络办公管理的现实问题和需求,提出了一个基于用户管理的大型网络管理系统的解决方案。系统详细描述了该项目的功能结构和体系设计,尤其重点介绍了数据信息收集和处理的设计方案以及数据库结构设计和最终的实现方法。     

A Grid resource brokering strategy based on resource and network performance in Grid

To achieve high performance distributed data access and computing in Grid environment, monitoring of resource and network performance is vital. Our proposed Grid network monitoring architecture is modeled by the Grid scheduler. The proposed Grid network monitoring retrieves network metrics using sensors as network monitoring tools. The mobile agents are migrated to start the sensors to measure the network metrics in all Grid Resources from the Resource Broker. The raw data provided by the monitoring tools is used to produce a high level view of the Grid through the set of internal cost functions. The network cost function is formed by combining various network metrics such as bandwidth, Round Trip Time, jitter and packet loss to measure the network performance. This paper presents the Grid Resource Brokering strategy which analyzes the network metrics along with the resource metrics for the selection of the Grid resource to submit the job and the proposed approach is integrated with CARE Resource Broker (CRB) for job submission. The experimental results are evident for the minimization of job completion time for the submitted job. The simulation results also prove that the more number of jobs are completed with the proposed strategy which influences the better utilization of the Grid resources.     

Network management in a local computer network

The functions and structure of the network management subsystem of the GAMMA-NET, a local computer network at the University of Tsukuba, are presented. The network management subsystem is an integrated subsystem that offers a convenient man-machine interface for the network users during the execution of required jobs, and levels the workload throughout the system, as well as managing the network operations.     

Replica Placement Strategies in Data Grid

Replication is a technique used in Data Grid environments that helps to reduce access latency and network bandwidth utilization. Replication also increases data availability thereby enhancing system reliability. The research addresses the problem of replication in Data Grid environment by investigating a set of highly decentralized dynamic replica placement algorithms. Replica placement algorithms are based on heuristics that consider both network latency and user requests to select the best candidate sites to place replicas. Due to dynamic nature of Grid, the candidate site holds replicas currently may not be the best sites to fetch replicas in subsequent periods. Therefore, a replica maintenance algorithm is proposed to relocate replicas to different sites if the performance metric degrades significantly. The study of our replica placement algorithms is carried out using a model of the EU Data Grid Testbed 1 [Bell et al. Comput. Appl., 17(4), 2003] sites and their associated network geometry. We validate our replica placement algorithms with total file transfer times, the number of local file accesses, and the number of remote file accesses.     

面向业务的SDN网络带宽保障研究

随着云计算、大数据技术的蓬勃发展,部署于数据中心的网络业务随之也越来越多,为了确保用户的良好体验以及服务提供商的经济收益,对业务带宽的高效保障逐渐成为研究的热点。基于SDN将控制和转发相分离的技术优势,提出一面向业务的带宽保障方法,该方法首先将多种业务进行了粗粒度分类,以此为基础提出了ATBG（Application-towards Bandwidth Guarantee）算法,并通过集中式的调度控制,实现了多业务不同优先级的带宽高效保障。利用floodlight+mininet模拟环境验证了文中所提方法的有效性。     

基于用户管理的网络计费系统

主要研究网络管理技术在校园网中应用,并结合校园网用户管理特点设计了一套综合网络计费管理系统。     

计算网格中统一的用户管理研究

分析了在计算网格中用户管理要解决的问题，描述了用户分类和用户权限限制，提出了一个统一的用户管理系统，并且详细论述了用户管理的一些关键技术实现，包括用户管理流程、记账机制、标识协议设计和访问远程集群几方面，并已在研制的计算网格JobCenter-Grid中加以实现。     

The network weather service: a distributed resource performance forecasting service for metacomputing

The goal of the Network Weather Service is to provide accurate forecasts of dynamically changing performance characteristics from a distributed set of metacomputing resources. Providing a ubiquitous service that can both track dynamic performance changes and remain stable in spite of them requires adaptive programming techniques, an architectural design that supports extensibility, and internal abstractions that can be implemented efficiently and portably. In this paper, we describe the current implementation of the NWS for Unix and TCP/IP sockets and provide examples of its performance monitoring and forecasting capabilities.     

一种面向电冰箱测试的计算机网格系统

介绍了一种电冰箱测试计算机网格系统。利用该网格系统，把企业遍布在全国、分布在Internet上的各电冰箱测试系统，整合为一台虚拟计算机上的电冰箱测试系统，实现整个企业冰箱测试的统一监控、查询、统计分析，为企业冰箱质量的宏观控制提供可靠依据，给电冰箱生产相关企业提供了一种计算机网格应用模型。     

Implementation of a CMIP-based network management system

This paper discusses the experiences of the Provisioning And Monitoring (PAM) laboratory at NYNEX Science and Technology in incorporating the Common Management Information Protocol (CMIP) and the Telecommunications Management Network (TMN) concepts into a network management system developed to manage a network of broadband ATM switches supporting a CMIP interface, as well as a legacy switching platform supporting both a proprietary interface and the Simple Network Management Protocol (SNMP) interface. The primary focus of the discussion will be on the implementation issues pertaining to the CMIP interface and the TMN object model; in particular their complexities and the approaches used to manage that complexities while retaining their functionalities.     

Fault Management in Distributed Systems: A Policy-Driven Approach

Managing the availability and performance of a distributed system involves monitoring the behavior of the system, identifying system problems, and correcting those problems. Each of these tasks requires some expertise, such as an understanding of the mechanics of the underlying system components. As the size and complexity of these systems increases, and the number of distributed applications executing on these systems increases, managing the availability and performance of distributed systems becomes more difficult. Little research has focused on embedding systems management expertise into a management application for a distributed system. In this paper we describe a rule-based management application for a commercially available distributed computing environment that is capable of monitoring the distributed system, detecting system service-related performance and availability problems, and generating corrective actions to correct the problems.     

Supply chain network design under oligopolistic price and service level competition with foresight

In this paper a new bi-level model for designing the network structure of a competitive supply chain (SC) is presented with anticipating variable prices and service levels competition in markets under stochastic price and service level dependent elastic demands with the presence of existing, external rivals. The network structure of the new entrant SC would be designed under the limited production capacity of its producers in a way to maximize its future capturable profit in the competitive markets. The network of the new SC is assumed to be set “once and for all” but further price and service level adjustments are possible. Outer part of this bi-level model deals with strategic decisions of SC network design. Given the SC network structure assigned by the outer model in each iteration, the inner equilibrium model determines the equilibrium retail prices and service levels. Finally, we illustrate the model through several numerical examples.     

Securing the distributed word processing network

There has been little concern for the security of stand-alone and shared-logic word processor systems although the threats are there and the loss from breaches of security can be very expensive. Word processors usually store processed information rather than data and modification or destruction of a document can lead to poor or delayed decisions. Inherent controls of paper-based systems are lost when the typing function is automated. Word processing networks are particularly vulnerable with reliance placed on the software system to secure documents. The weakest configuration in distributed word processing systems is in moderate size networks which cannot justify sophisticated hardware to support sophisticated operating systems and security software. Therefore, either additional physical security for each terminal or a more sophisticated authorization routine must be provided. The first is nearly impossible and the second rarely exists on these systems. As the trend toward hard disks for these units continues, the best solution may be the inclusion of a cryptographic routine.     

网格用户管理体系结构的研究与设计

在网格系统的研究中,相对于资源(客体)管理而言,对网格用户(主体)管理的研究相对薄弱．网格用户的表示、命名以及网格用户管理的功能及体系结构的确定对实现一个实用的网格用户管理系统非常重要．首先论述了网格用户管理的特点、范围及内容,提出了网格用户的表示及命名方法,描述了网格用户的全生命周期状态图．在此基础上提出了一个网格用户管理体系结构,并实现了一个实用系统VegaGUS．最后给出了该实用系统的性能指标及评价,该系统有效地解决了网格用户管理的关键问题．     

User utility discovery for priority-based network resource pricing

While equilibrium analysis has been commonly used for network pricing under the assumption that user utility functions are precisely known, many researchers have criticized the validity of the assumption. In this paper, we propose a solution for bridging the gap between the existing theoretical work on optimal pricing and the unavailability of precise user utility information in real networks. In the proposed method, the service provider obtains increasingly more accurate estimates of user utility functions by iteratively changing the prices of service levels and observing the users’ service-level choices under various prices. Our study’s contribution is twofold. First, we have developed a general principle for estimating user utility functions. Especially, we present the utility estimation for dynamic user population. Second, we have developed a method for setting prices that can optimize the extraction of information about user utility functions. The extensive simulation results demonstrate the effectiveness of our method.     

Parallel extraction and simplification of large isosurfaces using an extended tandem algorithm

In order to deal with the common trend in size increase of volumetric datasets, in the past few years research in isosurface extraction has focused on related aspects such as surface simplification and load-balanced parallel algorithms.We present a parallel, block-wise extension of the tandem algorithm [Attali D, Cohen-Steiner D, Edelsbrunner H. Extraction and simplification of iso-surfaces in tandem. In: SGP ’05: Proceedings of the third Eurographics symposium on Geometry processing. Aire-la-Ville, Switzerland: Eurographics Association; 2005. p. 139-148], which simplifies on the fly an isosurface being extracted. Our approach minimizes the overall memory consumption using an adequate block splitting and merging strategy along with the introduction of a component dumping mechanism that drastically reduces the amount of memory needed for particular datasets such as those encountered in geophysics. As soon as detected, surface components are migrated to the disk along with a meta-data index (oriented bounding box, volume, etc.) that permits further improved exploration scenarios (small component removal or particularly oriented component selection for instance).For ease of implementation, we carefully describe a master and worker algorithm architecture that clearly separates the four required basic tasks. We show several results of our parallel algorithm applied on a geophysical dataset of size 7000×1600×2000.