Adaptation of the IBM 7535 robot for use as a slave in a hierarchical master/slave relationship

A new programming environment for the IBM 7535 robot is introduced. AML/E is replaced by a hierarchical control scheme involving a host and a subservient robot. Application programs are developed on the host, an IBM-PC XT, in an extended version of the “C” programming language. These extensions allow an application program to be composed of several concurrent processes, one of which is responsible for commanding the robot. To configure the robot as a slave in this relationship, a new operating system was developed for its controller. Written in the same language employed at the host level, it is structured as four concurrent processes managing the robot's resources. An interprocess message-passing scheme provides a path for master/slave communication. The resultant environment is believed to be superior to the original language AML/E for the following reasons: Concurrency, along with the data and control structures of “C,” is made available to the application programmer. Communication is well structured. The robot's operating system is documented, written in a high-level language, and open to the user for modification. Due to the significance of integrating the robot into more complex applications involving sensors, these characteristics are felt to be essential in future robots.     

A Local Network Based on the UNIX Operating System

The design and implementation of a local network operating ystem based on the UNIX¹operating system is described. UNIX has been extended to allow existing programs to access remote resources with no source program changes. Programs may access remote files, have a remote working directory, execute remote programs, and communicate with remote processes using the standard UNIX interprocess communication mechanism (pipe's). An efficient message-oriented interprocess communication mechanism and asynchronous I/O were added to the system to support the development of distributed applications and to make it easier to connect the local network to packet-switched networks.     

Configuration management in the Nexus distributed operating system

The paper describes the approach taken for configuration management in the Nexus distributed operating system. Nexus uses kernel-level support for monitoring the failure or termination status of distributed components of an application. Periodic user-level messages are not required for status monitoring. Group and dependency relationships between such components can be defined by the programmer for the purpose of configuration monitoring and management. An object belonging to a distributed application can be monitored by its host kernel for system-defined exception conditions. When any of these conditions arise, other objects are notified through signals or messages, as specified by the programmer.     

A predictable real-time kernel for distributed multisensor systems

The authors present a real-time kernel developed to support a distributed multisensor system encountered in robotics applications. To ensure predictability, the kernel provides services with bounded worst-case execution times. In addition, the kernel allows the programmer to specify timing constraints for process execution and interprocess communication. The kernel uses these timing constraints both for scheduling processes and for scheduling communications. To illustrate the kernel, the authors describe a multisensor system being developed on their distributed real-time system. They present the measured performance of kernel primitives along with conclusions and remarks regarding distributed real-time systems     

Distributed prototyping from validated specifications

We present vpl2cxx, a translator that automatically generates efficient, fully distributed C++ code from high-level system models specified in the mathematically well-founded VPL design language. As the Concurrency Workbench of the New Century (CWB-NC) verification tool includes a front-end for VPL, designers may use the full range of automatic verification and simulation checks provided by this tool on their VPL system designs before invoking the translator, thereby generating distributed prototypes from validated specifications. Besides being fully distributed, the code generated by vpl2cxx is highly readable and portable to a host of execution environments and real-time operating systems (RTOSes). This is achieved by encapsulating all generated code dealing with low-level interprocess communication issues in a library for synchronous communication, which in turn is built upon the adaptive communication environment (ACE) client-server network programming interface. Finally, example applications show that the performance of the generated code is very good, especially for prototyping purposes. We discuss two such examples, including the RETHER real-time Ethernet protocol for voice and video applications.     

Tutorial guide to Unix sockets for network communications

This paper presents a tutorial on the socket interprocess communication facility provided with 4.2 BSD Unix systems; sockets allow distributed applications to be developed between Unix hosts over a network. The use of the necessary system calls and supporting library routines is explained and illustrated by development of a simple socket application that provides a datagram-based remote command execution facility.     

A template-based approach to the generation of distributedapplications using a network of workstations

A computational model and system for the generation of distributed applications in a workstation environment are presented. The well-known RPC model is modified by a novel concept known as template attachment. A computation consists of a network of sequential procedures which have been encapsulated in templates. A small selection of templates is available from which a distributed application with the desired communication behavior can be rapidly built. The system generates all the required low-level code for correct synchronization, communication, and scheduling. This results in a system that is easy to use and flexible and can provide a programmer with the desired amount of control in using idle processing power over a network of workstations. The practical feasibility of the model has been demonstrated by implementing it for Unix-based workstation environments     

An Introduction to the V-System

A distributed operating system runs on Sun and VAXstation-II workstations connected by an Ethernet. Its distributed kernel provides inexpensive processes and fast interprocess communication.     

The Lynx distributed programming language: Motivation, design and experience

A programming language can provide much better support for interprocess communication than a library package can. Most message-passing languages limit this support to communication between the pieces of a single program, but this need not be the case. Lynx facilitates convenient, typesafe message passing not only within applications, but also between applications and among distributed collections of servers. Specifically, it addresses issues of compiler statelessness, late binding, and protection that allow run-time interaction between processes that were developed independently and that do not trust each other. Implementation experience with Lynx has yielded important insights into the relationship between distributed operating systems and language run-time support packages and into the inherent costs of high-level message-passing semantics.     

一种面向嵌入式系统的进程间消息信方法的设计

描述了具有典型意义的多CPU嵌入式系统的体系结构,详细介绍了一种应用于此种嵌入式系统的分布式操作系统进程间消息通信的方法,又将此方法和常用的分布式操作系统的进程间消息通信方法进行了比较。     

Perseus: Retrospective on a portable operating system

We describe the operating system Perseus, developed as part of a study into the issues of computer communications and their impact on operating system and programming language design. Perseus was designed to be portable by virtue of its kernel-based structure and its implementation in Pascal. In particular, machine-dependent code is limited to the kernel and most operating systems functions are provided by server processes, running in user mode. Perseus was designed to evolve into a distributed operating system by virtue of its interprocess communication facilities, based on message-passing. This paper presents an overview of the system and gives an assessment of how far it satisfied its original goals. Specifically, we evaluate its interprocess communication facilities and kernel-based structure, and discuss its portability. We close with a brief history of the project, pointing out major milestones and stumbling blocks.     

基于Win95的网络协议软件开发技术

网络协议软件的开发技术因为涉及到操作系统核心，所以大多没有公开的资料。以一个ＩＰ网关的实现为基础，阐述了网络协议软件在Ｗｉｎ９５中的开发方法。重点讨论了网络接口的实现，进程通信和内在管理等核心技术。     

An Application of Name Based Addressing to Low Level Distributed Algorithms

An interprocess communication structure for a distributed language is described which provides message level communication, multicast, and a generalized naming facility. The design is oriented to the needs of low level algorithms which, for example, might be used in a distributed operating system to support resource allocation or enhance reliability. The proposal is illustrated by programming several distributed algorithms from the literature. An implementation is described that takes advantage of physical multicast technology, and reduces to more conventional schemes for common communication paradigms.     

Link layer for cooperating processes on a LAN with enhanced communication services

Most local area networks support multicast and broadcast communication facilities among the network nodes. However, their use among processes has been limited by the lack of support in the distributed operating system kernel and by the limited requirements of traditional computer network applications. Some applications (e.g. operating in a multicast environment) and distributed algorithms require advanced associations among processes, whose support by the operating system kernel can take advantage of properly designed functions provided by the communication subsystem. This problem is examined in the context of an architecture for LANs, and enhanced protocols are described that can be provided by a communication subsystem based on a LAN. Virtual network protocols provide classes of service suited to a multicast environment. Their availability at communication subsystem layers offers higher layers a common framework for the implementation of a computing system with distributed control.     

A Parallel Processor Operating System Comparison

Three different operating system strategies for a parallel processor computer system are compared, and the most effective strategy for given job loads is determined. The three strategies compare uniprogramming versus multiprogramming and distributed operating systems versus dedicated processor operating systems. The level of evaluation includes I/O operations, resource allocation, and interprocess communication. The results apply to architectures where jobs may be scheduled to processors on the basis of processor availability, memory availability, and the availability of one other resource used by all jobs.     

MS LAN Manager 2.0网络操作系统及其特点

本文介绍了Microsoft公司的一个局网操作系统 LAN Manager V 2.0,对它的体系结构、组成、特点等作了简单说明,并与当今流行的另一局网操作系统,即Novell公司的NetWare在某些方面做了比较.     

Rollback recovery in distributed systems using loosely synchronizedclocks

A rollback recovery scheme for distributed systems is proposed. The state-save synchronization among processes is implemented by bounding clock drifts such that no state-save synchronization messages are required. Since the clocks are only loosely synchronized, the synchronization overhead can be negligible in many applications. An interprocess communication protocol which encodes state-save progress information within message frames is introduced to checkpoint consistent system states. A rollback recovery algorithm that will force a minimum number of nodes to roll back after failures is developed     

Communication facilities for distributed transaction-processingsystems

The study of communication designs in the context of the Raid system, a robust and adaptable distributed database system for transaction processing, is discussed. Related research work on local interprocess communication, remote interprocess communication, and communication protocols for both local area and wide area networks is briefly summarized. A series of experiments on the performance of the facilities available for building the Raid communication software is described. Raid's communication software, called Raidcomm, has evolved as a result of the knowledge gained both from other systems and from the authors' experiments. Several communication services and mechanisms that can be used to make Raid efficient are identified     

Parallel computing in networks of workstations with Paralex

Modern distributed systems consisting of powerful workstations and high-speed interconnection networks are an economical alternative to special-purpose supercomputers. The technical issues that need to be addressed in exploiting the parallelism inherent in a distributed system include heterogeneity, high-latency communication, fault tolerance and dynamic load balancing. Current software systems for parallel programming provide little or no automatic support towards these issues and require users to be experts in fault-tolerant distributed computing. The Paralex system is aimed at exploring the extent to which the parallel application programmer can be liberated from the complexities of distributed systems. Paralex is a complete programming environment and makes extensive use of graphics to define, edit, execute, and debug parallel scientific applications. All of the necessary code for distributing the computation across a network and replicating it to achieve fault tolerance and dynamic load balancing is automatically generated by the system. In this paper we give an overview of Paralex and present our experiences with a prototype implementation