聚合通信模型的测试与分析

聚合通信的性能影响着大规模并行数值计算软件的整体效率,它是基于点对点消息传递实现的。可以通过选择点对点通信模型来描述聚合通信。一个恰当的模型可以为聚合通信算法提供精确的定量分析,有助于算法的设计与研究。论文通过对若干聚合通信典型算法的测试与分析,尝试比较与定量分析两种点对点通信模型对聚合通信的描述精度。     

Recovery of CFSM-based protocol and service design from protocol execution traces

Reverse engineering and design recovery are two important concepts for the evolutionary design of systems software. In particular, the reverse engineering of distributed software, such as communications software, is a very challenging practical problem. Most communications software is written without the use of formal methods and is often poorly documented. Consequently, to maintain or modify such software, relevant details of the original design need to be recovered from the executable software itself. This design recovery process involves either static analysis of the code or dynamic analysis of the software behaviour based on selected execution traces. In this paper, we use the dynamic trace analysis approach. Specifically, based on execution traces as represented at selected points of observation, we generate a higher level design representation consisting of communicating finite state machines (CFSMs) corresponding to the protocol design and service constraints. Further, the temporal and concurrent aspects of the protocol behaviour are also captured in the traces and are reflected in the recovered design.     

Alternatives to SNA

The advantages of changing from a network configured with IBM's preSNA equipment (hosts, host software, communications processors, terminals) to one using SNA are reviewed. Two viable alternatives to SNA are considered. One relies on data comunications architectures as developed by two vendors (NCR-Comten, CCl) of plug-compatible replacements for IBM's 3704/3705 communications controllers. Packet-switched public data networks provide a second alternative. Host software remains unchanged in both instances.     

Design of a multifunctional communications software package

Data communications and computer networks have undergone phenomenal growth, resulting in the proliferation of hardware, software, and communications protocols. However, as needs change and new technologies are developed existing software frequently becomes incapable of handling the new configurations and therefore obsolete. The design and implementation of a new data communications software package, Commpac, designed to address these problems, is described. The package is modular and multifunctional, and supports the hierarchy of point-to-point communications protocols. In addition, it has been designed to adapt to system changes and to provide the software resources necessary for the development of new modules to cope with these changes.     

A multicast interface for UNIX 4.3

The UNIX 4.3 operating system, like its predecessor UNIX 4.2, is designed to allow interprocess communications between pairs of processes using sockets — pairs of integers identifying specific hosts and ports — which are associated with a process. In this paper a software package which allows interprocess communications between many UNIX processes (as opposed to two) is presented.     

A collaborative P2P scheme for NAT Traversal Server discovery based on topological information

In the current Internet picture more than 70% of the hosts are located behind Network Address Translators (NATs). This is not a problem for the client/server paradigm. However, the Internet has evolved, and nowadays the largest portion of the traffic is due to peer-to-peer (p2p) applications. This scenario presents an important challenge: two hosts behind NATs (NATed hosts) cannot establish direct communications. The easiest way to solve this problem is by using a third entity, called Relay, that forwards the traffic between the NATed hosts. Although many efforts have been devoted to avoid the use of Relays, they are still needed in many situations. Hence, the selection of a suitable Relay becomes critical to many p2p applications. In this paper, we propose the Gradual Proximity Algorithm (GPA): a simple algorithm that guarantees the selection of a topologically close-by Relay. We present a measurement-based analysis, showing that the GPA minimizes both the delay of the relayed communication and the transit traffic generated by the Relay, being a QoS-aware and ISP-friendly solution. Furthermore, the paper presents the Peer-to-Peer NAT Traversal Architecture (P2P-NTA), which is a global, distributed and collaborative solution, based on the GPA. This architecture addresses the Relay discovery/selection problem. We have performed large-scale simulations based on real measurements, which validate our proposal. The results demonstrate that the P2P-NTA performs similarly to direct communications with reasonably large deployments of p2p applications. In fact, only 5% of the communications experience an extra delay that may degrade the QoS due to the use of Relays. Furthermore, the amount of extra transit traffic generated is only 6%. We also show that the P2P-NTA largely outperforms other proposals, where the QoS degradation affects up to more than 50% of the communications, and the extra traffic generated goes beyond 80%.     

Design and deployment of distributed numerical applications using .NET and component oriented programming

The common availability of multi-core and networked computers means that there is an increasing need for effective software development methods in order to harness this available power. This paper describes the use of component oriented methods both in the design and deployment of numerical software. The use of interfaces enables both isolation of areas of complexity and physical separation between client and server code. Three methods of deployment of distributed software are considered. Techniques developed for mobile agents were used to implement a method whereby hosts reside on various remote computers, and client programs then send assemblies (partially compiled code) to the hosts as required. The methods are applicable for both direct and iterative methods of equation solution.     

Switched memory for multiprocessor MC6809E systems

An increasing interest is being shown in the use of multimicroprocessor systems in a variety of applications. It is often desirable that the constituent processors have a fast communications link for the sharing of data and/or results. Both of these aims can be achieved by the sharing of blocks of memory between the two or more processors; this method has the added advantage of little, or in some cases no, software overhead. The design of a shared memory system for Motorola MC6809E microprocessors is presented.     

用通信服务器和MODEM实现远程联网和远程通信的连接

需要远程联网和远程通信的用户,多数需要利用ＭＯＤＥＭ在现有的电话公共交换网上实现。本文对如何选择、配置网络ＭＯＤＥＭ和通信服务器,以实现远程联网和远程通信的连接作了深入的讨论。     

基于多Agent的Web-BoxCAD系统的设计与实现

针对现有包装盒设计系统存在的主要问题,提出了基于多agent技术的Web-BoxCAD系统的解决方案.介绍了WebBoxCAD系统的主要功能和设计手段、MAS系统架构以及基于MVC的编程框架,并给出了关键技术的实现代码和演示示例,包括利用XML封装KQML消息实现多Agent间的通信,以SVG为中间文件实现标准文件转换,RGB和CMYK模式色彩空间转换以及利用Java3D实现包装盒的三维显示.有效地解决了包装盒设计系统中存在的问题,提高了包装盒设计的质量和效率.该系统对类似应用有一定参考价值.     

基于ARM智能电力协议转换器的设计

介绍如何使用ARM处理器实现一个电力规约串口协议转换的原理和设计过程。在设计中,软件主要是针对前台接受远程终端发来的命令启动抄表后台识别命令并开始抄指定的电表;在硬件设计中,使用PHLIPS公司的LPC2138处理器提高了系统的集成度和可靠性,采用uc/os-II操作系统进行任务的管理和调度,方便系统升级。     

基于三态调制的电力线载波通信的研究

电力线是目前分布最广的有线网络,利用电力线网络进行通信实现自动抄表是电力企业追切需求,但目前电力线载波通信的现状不能令人满意,针对电力线载波通信的现状,本文提出了一种基于三态脉冲位移相位调制的电力线载波通信的调制解调方式,利用RS编解码技术,通过信号检测算法的研究,实现了在相对恶劣环境下的电力线载波通信,并将软硬件开发设计完成的DEMO（实验样品）板进行了实验室模拟环境下的测试,由测试结果可知,此方案基本能满足电力载波抄表的要求,对目前电力线载波通信的研究有一定的参考价值。     

基于OPC技术的先进控制软件的集成

在石化行业应用先进控制技术的一个关键问题是如何实现先进控制软件与DCS系统之间可靠的数据通信以及运行平台的开发,应用OPC技术实现先进控制软件与DCS系统之间的无缝连接,使基于Windows平台的先进控制软件具有设备通用性和软件通用性,对于在石化行业广泛应用先进及优化控制具有重大意义一本阐述了基于OPC技术的先进控制软件的设计方法,并将该方法在石油大学胜华炼油厂催化车间进行了应用。     

基于GSM的车辆事故呼救中心软件平台设计

车辆事故呼救中心能在车辆发生事故时及时接收和处理事故信息,为实施救援挽救生命提供保障.呼救中心系统的搭建包括建立基站和呼救中心软件平台的设计.利用现已完善的GSM网络作为基站,采用Delphi软件平台设计开发出呼救中心系统,达到紧急呼救、定位、接收信息的功能,为建立呼救中心提供了通信及软件技术保障.     

移动IP隧道技术在Linux下的实现*

移动IP为移动主机在移动过程中保持其通信不间断提供了实现方法,隧道技术是移动IP的关键技术之一,当通信节点向移动节点发送数据报时,需要使用到隧道技术。介绍了移动IP中隧道技术的基本原理,并给出了一种在Linux系统下的实现方法,对于移动IP相关软件的研究和开发具有一定的借鉴作用。     

矿井下基于蓝牙技术的语音通讯控制器设计

提出一种基于蓝牙技术的矿井下无线语音通讯控制器设计方案,解决了蓝牙语音传输在特殊环境下容易受到外界干扰的问题;在语音通讯控制器系统结构中,采用ROK101 007蓝牙芯片做为无线通信模块,使用MSM7570芯片完成语音编解码;详细介绍了软、硬件的设计,使该语音通讯控制器达到本安型标准,从而适合在矿井下的特殊场合使用,经试用后,该语音通讯控制器传输话音清晰稳定。     

Avoiding a middleware muddle

Middleware is a layer of software that enables communications between software components regardless of the programming language in which the components are developed, the protocols used to communicate between components, or the platforms on which the components execute. To make sense of the middleware morass and to select the middleware best for you, the author recommends the following steps when constructing your system: identify what type of communication must occur; identify the communications model you will use to implement that communication type; using your communications model, identify the types of middleware you will use to implement the communication; and evaluate candidate products. The author examines each step in detail     

一种高性能处理器在主控单元中的应用

主控单元是新一代通信测控设备的信息控制中心,需要处理复杂的控制信息和运行嵌入式系统软件,要求采用的微处理器具有丰富的接口和较高的处理能力。MPC8265是FreeScale公司推出的高性能通信处理器,内部集成了高性能嵌入式PowerPC核和丰富的外部设备连接资源,适用于高端通信及网络产品的控制应用设计。首先描述了MPC8265的主要功能特性,并重点介绍了采用MPC8265通信处理器来设计一种通用的高性能主控单元,描述了其电路的设计原理和主要软硬件模块的参考设计。     

基于WIA—PA的数字仪表设计

以WIA—PA工业无线网．络技术为基础,采用集射频与微控制器于一体的无线单片机CC2431为核心控制器件,重点介绍了WIA—PA无线传感仪表硬件设计,简单介绍了系统软件的整体设计结构。该仪表实现了无线通信和显示功能,可广泛应用于工业无线网络现场。     

一种软件体系结构设计决策的建模工具

体系结构设计在整个软件生命周期中起到关键作用,而设计知识的蒸发会导致系统演化花费代价高、涉众之间交流出现障碍、体系结构制品的复用受到限制等问题,为此需要在软件体系结构层次对设计决策进行显式化的建模.基于一种以决策为中心的体系结构设计方法,实现了一个软件体系结构设计决策的建模工具.该工具帮助架构师对体系结构设计中的问题、方案、决策、理由等核心概念进行建模,完成从需求到体系结构的设计过程,并实现了自动化的候选体系结构方案的合成和部分设计理由的捕捉.该工具还提供了体系结构设计模型与设计决策之间的相互追踪性,以及帮助实现体系结构设计过程中设计决策知识的复用.