A Survey of Process Migration Mechanisms

We define process migration as the transfer of a sufficient amount of a process's state from one machine to another for the process to execute on the target machine. This paper surveys proposed and implemented mechanisms for process migration. We pay particular attention to the designer's goals, such as performance, load-balancing, and reliability. The effect of operating system design upon the ease of implementation is discussed in some detail; we conclude that message-passing systems simplify designs for migration

Multicast communications in distributed systems

PhD ThesisOne of the numerous results of recent developments in communication networks and distributed systems has been an increased interest in the study of applications and protocolsfor communications between multiple, as opposed to single, entities such as processes and computers. For example, in replicated file storage, a process attempts to store a file on several file servers, rather than one. MUltiple entity communications, which allow one-to-many and many-to-one communications, are known as multicast communications. This thesis examines some of the ways in which the architectures of computer networks and distributed systems can affect the design and development of multicast communication applications and protocols.To assist in this examination, the thesis presents three contributions. First, a set of classification schemes are developed for use in the description and analysis of various multicast communication strategies. Second, a general set of multicast communication primitives are presented, unrelated to any specific network or distributed system, yet efficiently implementable on a variety of networks. Third, the primitives are used to obtain experimental results for a study ofintranetwork and internetwork multicast communications.Postgraduate Scholarship, The Natural Sciences and Engineering Research Council of Canada: Overseas Research Student Award: the Committee of Vice-Chancellors and Principals of the Universities of the Uni ted Kingdom

An Efficient Reliable Broadcast Protocol

Many distributed and parallel applications can make good use of broadcast communication. In this paper we present a (software) protocol that simulates reliable broadcast, even on an unreliable network. Using this protocol, application programs need not worry about lost messages. Recovery of communication failures is handled automatically and transparently by the protocol. In normal operation, our protocol is more efficient than previously published reliable broadcast protocols. An initial implementation of the protocol on 10 MC68020 CPUs connected by a 10 Mbit/sec Ethernet performs a reliable broadcast in 1.5 msec

Approaches to Distributed UNIX Systems

This paper examines several approaches to developing a distributed version of the UNIX Operating system. Relevant UNIX concepts are introduced and brief overviews of a number of distributed UNIX implementations are provided. The major issues discussed are concurrency and file system architecture: 1. The multiprocessor designs examined have the common problem of implementing critical sections in the kernel; several approaches are studied. 2. The me system architectures studied reflect differing views as to how the UNIX name space should be implemented in a distributed environment, and what the names will refer to; the issue of transparency is central to both, and is examined in some detail

Policy issues in interconnecting networks

To support the activities of the Federal Research Coordinating Committee (FRICC) in creating an interconnected set of networks to serve the research community, two workshops were held to address the technical support of policy issues that arise when interconnecting such networks. The workshops addressed the required and feasible technologies and architectures that could be used to satisfy the desired policies for interconnection. The results of the workshop are documented

State of the art survey of network operating systems development

The results of the State-of-the-Art Survey of Network Operating Systems (NOS) performed for Goddard Space Flight Center are presented. NOS functional characteristics are presented in terms of user communication data migration, job migration, network control, and common functional categories. Products (current or future) as well as research and prototyping efforts are summarized. The NOS products which are revelant to the space station and its activities are evaluated

RK: A Real-Time Kernel for a Distributed System With Predictable Response

Robotics applications must execute in real-time. In addition, complex robotics applications include many physically distributed components such as manipulator arms and sensors. This paper presents the real-time kernel RK which is designed to facilitate the development of a distributed sensory system with multiple arms and sensors. The goal of the kernel is to support distributed applications that require predictable timing behavior. Our kernel design guarantees predictable response times by scheduling processes and communications based on timing constraints. In addition, the kernel provides a set of primitives that can be used to implement applications requiring predictable timing behavior. These primitives allow the specification of timing requirements that can be guaranteed in advance by the scheduler and the direct control of devices by application processes for faster and predictable feedback control. To illustrate the use of our kernel, this paper also describes a multiple sensory system which is being ported to our distributed test-bed

Empacotamento, multiplexagem e encriptação para TV

Mestrado em Engenharia Electrónica e TelecomunicaçõesO presente trabalho propõe-se a estudar e implementar um sistema de comunicação e encriptação para TV, ou seja transmissão de vídeo através da Internet de forma segura. Para tal, realiza-se inicialmente uma descrição da evolução da Internet, realiza-se uma descrição do modelo TCP/IP, ao nível da camada Rede, o protocolo IP (Internet Protocol) é utilizado não apenas para o endereçamento mas também para a interligação de redes de telecomunicações, com tecnologias heterogéneas nas camadas inferiores (ligação de dados e física). Acima da camada de rede, a informação é encapsulada e transportada pelos protocolos UDP (User Datagram Protocol) e RTP (Real Time Transport Protocol). O principal objectivo destes protocolos é identificar a existência de erros nos dados e associar informação de sincronismo e sequência. Esta informação permite ao receptor minimizar os efeitos dos erros de comunicação e sincronizar diferentes conteúdos de vídeo. Em seguida, introduz-se e define-se o conceito de interface socket em sistemas de comunicações. Descrevem-se os princípios e as funções desta interface necessária para a transmissão poder ocorrer. Logo de seguida são apresentados alguns protocolos de encriptação. Com base nestes princípios, propõe-se e descreve-se um algoritmo para a transmissão de vídeo, bem como a sua encriptação, de modo a oferecer algum tipo de segurança durante a transmissão. Finalmente, apresentam-se os resultados relativos de uma comunicação multimédia multiplexada em pacotes. ABSTRACT: This thesis explores and implements a communication system and encryption for TV, i.e. video transmission over the Internet in safe way. To achieve that goal, we first review the evolution of the Internet, then we made a description of the TCP/IP model, at the network layer, the IP (Internet Protocol) is used not only for addressing purposes, but also for the interconnection of diverse telecommunications networks, with heterogeneous technologies at lower layers (data link and physical). Above the network layer, the information is encapsulated and transported by UDP (User Datagram Protocol) and RTP (Real Time Transport Protocol) protocols. The main objective of these protocols is to signal any communications errors and to include synchronization information as well as inserting packet sequence numbers. Then, we introduced and defined the concept of socket interface in communications systems. We outline the basic principles and functions of this interface needed to support the transmission. Then, there are presented some encryption protocols. Based on these principles, it is proposed and described an algorithm for the video transmission and its encryption in order to provide some type of security during the transmission. Finally, we present the results for a multimedia communication encapsulated in packets