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<i>Disconnected operation</i> is a mode of operation that enables a client to continue accessing critical data during temporary failures of a shared data repository. An important, though not exclusive, application of disconnected operation is in supporting portable computers. In this paper, we show that disconnected operation is feasible, efficient and(More)
Mobile computing continuously evolve through the sustained effort of many researchers. It seamlessly augments users' cognitive abilities via compute-intensive capabilities such as speech recognition, natural language processing, etc. By thus empowering mobile users, we could transform many areas of human activity. This article discusses the technical(More)
This paper discusses the challenges in computer systems research posed by the emerging field of pervasive computing. It first examines the relationship of this new field to its predecessors: distributed systems and mobile computing. It then identifies four new research thrusts: effective use of smart spaces, invisibility, localized scalability, and masking(More)
Coda is a file system for a large-scale distributed computing environment composed of Unix workstations. It provides resiliency to server and network failures through the use of two distinct but complementary mechanisms. One mechanism, server replication, stores copies of a file at multiple servers. The other mechanism, disconnected operation, is a mode of(More)
In this paper we show that application-aware adaptation, a collaborative partnership between the operating system and applications, offers the most general and effective approach to mobile information access. We describe the design of Odyssey, a prototype implementing this approach, and show how it supports concurrent execution of diverse mobile(More)
The loss behavior of wireless networks has become the focus of many recent research efforts. Although it is generally agreed that wireless communications experience higher error rates than wireline, the nature of these lossy links is not fully understood. This paper describes an effort to characterize the loss behavior of the AT&amp;T WaveLAN, a popular(More)
In this paper, we describe the design and implementation of PowerScope, a tool for profiling energy usage by applications. PowerScope maps energy consumption to program structure, in much the same way that CPU profilers map processor cycles to specific processes and procedures. Our approach combines hardware instrumentation to measure current level with(More)
The Information Technology Center (ITC), a collaborative effort between IBM and Carnegie-Mellon University, is in the process of creating</italic> Andrew, <italic>a prototype computing and communication system for universities. This article traces the origins of Andrew, discusses its goals and strategies, and gives an overview of the current status of its(More)
A summary of and historical perspective on work done to implement easy-to-share distributed file systems based on the Unix model are presented. Andrew and Coda are distributed Unix file systems that embody many of the recent advances in solving the problem of data sharing in large, physically dispersed workstation environments. The Andrew architecture is(More)
This paper presents the design and rationale of a distributed file system for a network of more than 5000 personal computer workstations. While scale has been the dominant design influence, careful attention has also been paid to the goals of location transparency, user mobility and compatibility with existing operating system interfaces. Security is an(More)