Internet heterogeneity is driving a new challenge in application development: adaptive software. Together with the increased Internet capacity and new access technologies, network congestion and the use of older technologies, wireless access, and peer-to-peer networking are increasing the heterogeneity of the Internet. Applications should provide gracefully degraded levels of service when network conditions are poor, and enhanced services when network conditions exceed expectations. Existing adaptive technologies, which are primarily end-to-end or proxy-based and often focus on a single deficient link, can perform poorly in heterogeneous networks. Instead, heterogeneous networks frequently require multiple, coordinated, and distributed remedial actions. Conductor: Distributed Adaptation for Heterogeneous Networks describes a new approach to graceful degradation in the face of network heterogeneity - distributed adaptation - in which adaptive code is deployed at multiple points within a network. The feasibility of this approach is demonstrated by conductor, a middleware framework that enables distributed adaptation of connection-oriented, application-level protocols. By adapting protocols, conductor provides application-transparent adaptation, supporting both existing applications and applications designed with adaptation in mind. Conductor: Distributed Adaptation for Heterogeneous Networks introduces new techniques that enable distributed adaptation, making it automatic, reliable, and secure. In particular, we introduce the notion of semantic segmentation, which maintains exactly-once delivery of the semantic elements of a data stream while allowing the stream to be arbitrarily adapted in transit. We also introduce a secure architecture for automatic adaptor selection, protecting user data from unauthorized adaptation. These techniques are described both in the context of conductor and in the broader context of distributed systems. Finally, this book presents empirical evidence from several case studies indicating that distributed adaptation can allow applications to degrade gracefully in heterogeneous networks, providing a higher quality of service to users than other adaptive techniques. Further, experimental results indicate that the proposed techniques can be employed without excessive cost. Thus, distributed adaptation is both practical and beneficial. Conductor: Distributed Adaptation for Heterogeneous Networks is designed to meet the needs of a professional audience composed of researchers and practitioners in industry and graduate-level students in computer science.

Disseminating Security Updates at Internet Scale describes a new system, "Revere", that addresses these problems. "Revere" builds large-scale, self-organizing and resilient overlay networks on top of the Internet to push security updates from dissemination centers to individual nodes. "Revere" also sets up repository servers for individual nodes to pull missed security updates. This book further discusses how to protect this push-and-pull dissemination procedure and how to secure "Revere" overlay networks, considering possible attacks and countermeasures. Disseminating Security Updates at Internet Scale presents experimental measurements of a prototype implementation of "Revere" gathered using a large-scale oriented approach. These measurements suggest that "Revere" can deliver security updates at the required scale, speed and resiliency for a reasonable cost. Disseminating Security Updates at Internet Scale will be helpful to those trying to design peer systems at large scale when security is a concern, since many of the issues faced by these designs are also faced by "Revere". The "Revere" solutions may not always be appropriate for other peer systems with very different goals, but the analysis of the problems and possible solutions discussed here will be helpful in designing a customized approach for such systems.

In 1775, Paul Revere, the folk hero of the American Revolution, galloped wildly on horseback through small towns to warn American colonists that the British were coming. In today's Internet age, how do we warn vast numbers of computers about impending cyber attacks?

Rapid and widespread dissemination of security updates throughout the Internet would be invaluable for many purposes, including sending early-warning signals, distributing new virus signatures, updating certificate revocation lists, dispatching event information for intrusion detection systems, etc. However, notifying a large number of machines securely, quickly, and with high assurance is very challenging. Such a system must compete with the propagation of threats, handle complexities in large-scale environments, address interruption attacks toward dissemination, and also secure itself.

Disseminating Security Updates at Internet Scale describes a new system, "Revere," that addresses these problems. "Revere" builds large-scale, self-organizing and resilient overlay networks on top of the Internet to push security updates from dissemination centers to individual nodes. "Revere" also sets up repository servers for individual nodes to pull missed security updates. This book further discusses how to protect this push-and-pull dissemination procedure and how to secure "Revere" overlay networks, considering possible attacks and countermeasures. Disseminating Security Updates at Internet Scale presents experimental measurements of a prototype implementation of "Revere" gathered using a large-scale oriented approach. These measurements suggest that "Revere" can deliver security updates at the required scale, speed and resiliency for a reasonable cost.

Disseminating Security Updates at Internet Scale is designed to meet the needs of researchers and practitioners in industry and graduate students in computer science. This book will also be helpful to those trying to design peer systems at large scale when security is a concern, since many of the issues faced by these designs are also faced by "Revere." The "Revere" solutions may not always be appropriate for other peer systems with very different goals, but the analysis of the problems and possible solutions discussed here will be helpful in designing a customized approach for such systems.

Internet heterogeneity is driving a new challenge in application development: adaptive software. Together with the increased Internet capacity and new access technologies, network congestion and the use of older technologies, wireless access, and peer-to-peer networking are increasing the heterogeneity of the Internet. Applications should provide gracefully degraded levels of service when network conditions are poor, and enhanced services when network conditions exceed expectations. Existing adaptive technologies, which are primarily end-to-end or proxy-based and often focus on a single deficient link, can perform poorly in heterogeneous networks. Instead, heterogeneous networks frequently require multiple, coordinated, and distributed remedial actions. Conductor: Distributed Adaptation for Heterogeneous Networks describes a new approach to graceful degradation in the face of network heterogeneity - distributed adaptation - in which adaptive code is deployed at multiple points within a network. The feasibility of this approach is demonstrated by conductor, a middleware framework that enables distributed adaptation of connection-oriented, application-level protocols. By adapting protocols, conductor provides application-transparent adaptation, supporting both existing applications and applications designed with adaptation in mind. Conductor: Distributed Adaptation for Heterogeneous Networks introduces new techniques that enable distributed adaptation, making it automatic, reliable, and secure. In particular, we introduce the notion of semantic segmentation, which maintains exactly-once delivery of the semantic elements of a data stream while allowing the stream to be arbitrarily adapted in transit. We also introduce a secure architecture for automatic adaptor selection, protecting user data from unauthorized adaptation. These techniques are described both in the context of conductor and in the broader context of distributed systems. Finally, this book presents empirical evidence from several case studies indicating that distributed adaptation can allow applications to degrade gracefully in heterogeneous networks, providing a higher quality of service to users than other adaptive techniques. Further, experimental results indicate that the proposed techniques can be employed without excessive cost. Thus, distributed adaptation is both practical and beneficial. Conductor: Distributed Adaptation for Heterogeneous Networks is designed to meet the needs of a professional audience composed of researchers and practitioners in industry and graduate-level students in computer science.

Computer systems consisting of many machines will be the norm within a few years. However, making a collection of machines appear as a single, coherent system - in which the location of files, servers, programs, or users is invisible to users who do not wish to know - is a very difficult problem. LOCUS, a distributed version of the popular operating system Unix, provides an excellent solution. It makes a collection of computers, whether they are workstations or mainframes, as easy to use as a single computer by providing a set of supports for the underlying network that is virtually invisible to users and - applications programs. This "network transparency" dramatically reduces the cost of developing and maintaining software, and considerably improves the user model of the system. It also permits a variety of system configurations, including diskless workstations, full duplex I/O to large mainframes, transparently shared peripherals, and incremental growth from one workstation to a large network including mainframes with no effect on applications software required to take advantage of the altered configurations.In addition to transparent, distributed operation, LOCUS features also include high performance and reliability; full Unix compatibility, support for heterogeneous machines and systems, automatic management of replicated file storage; and architectural extensions to support extensive interprocess communication and internetworking.Contents: The LOCUS Architecture. Distributed Operation and Transparency. The LOCUS Distributed Filesystem. Remote Tasking. Filesystem Recovery. Dynamic Reconfiguration of LOCUS. Heterogeneity. System Management. Appendixes: LOCUS Version Vector Mechnism. LOCUS Internal Network Messages.Gerald Popek is Professor of Computer Science at UCLA and President of Locus Computing Corporation in Santa Monica. The LOCUS Distributed System Architecture is included in the Computer Systems series, edited by Herb Schwetman.