Download or read book Resolving Network Congestion in Mobile Computing Using Coda File System written by Temidayo Oluwafunke Ogunniyi and published by . This book was released on 2009 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: With this research, we focus on utilizing a distributed file system to combat congestion problems in wireless networks. The Coda file system is our choice of a distributed file system, as it offers several services, such as data pre-fetching, hoarding of files, disconnected operation and data consistency.

Download or read book Replicated Data Management for Mobile Computing written by Terry Douglas and published by Morgan & Claypool Publishers. This book was released on 2008-06-08 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Managing data in a mobile computing environment invariably involves caching or replication. In many cases, a mobile device has access only to data that is stored locally, and much of that data arrives via replication from other devices, PCs, and services. Given portable devices with limited resources, weak or intermittent connectivity, and security vulnerabilities, data replication serves to increase availability, reduce communication costs, foster sharing, and enhance survivability of critical information. Mobile systems have employed a variety of distributed architectures from client–server caching to peer-to-peer replication. Such systems generally provide weak consistency models in which read and update operations can be performed at any replica without coordination with other devices. The design of a replication protocol then centers on issues of how to record, propagate, order, and filter updates. Some protocols utilize operation logs, whereas others replicate state. Systems might provide best-effort delivery, using gossip protocols or multicast, or guarantee eventual consistency for arbitrary communication patterns, using recently developed pairwise, knowledge-driven protocols. Additionally, systems must detect and resolve the conflicts that arise from concurrent updates using techniques ranging from version vectors to read–write dependency checks. This lecture explores the choices faced in designing a replication protocol, with particular emphasis on meeting the needs of mobile applications. It presents the inherent trade-offs and implicit assumptions in alternative designs. The discussion is grounded by including case studies of research and commercial systems including Coda, Ficus, Bayou, Sybase’s iAnywhere, and Microsoft’s Sync Framework. Table of Contents: Introduction / System Models / Data Consistency / Replicated Data Protocols / Partial Replication / Conflict Management / Case Studies / Conclusions / Bibliography

Download or read book Exploiting Weak Connectivity in a Distributed File System written by Carnegie Mellon University. Computer Science Department and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "Weak connectivity, in the form of intermittent, low- bandwidth, or expensive networks is a fact of life in mobile computing. For the foreseeable future, access to cheap, high-performance, reliable networks, or strong connectivity will be limited to a few oases, such as work or home, in a vast desert of weak connectivity. The design of distributed file systems has traditionally been based on an assumption of strong connectivity. Yet, to provide ubiquitous data access, it is vital that distributed file systems make effective use of weak connectivity. This dissertation describes the design, implementation, and evaluation of weakly connected operation in the Coda File System. The starting point of this work is disconnected operation, in which a file system client operates using data in its cache during server or network failures. Disconnected clients suffer from many limitations: updates are not visible to other clients, cache misses may impede progress, updates are at risk from client loss or damage, and the danger of update conflicts increases as disconnections are prolonged. Weak connectivity provides an opportunity to alleviate these limitations. Coda's strategy for weakly connected operation is best characterized as application-transparent adaptation. The system bears full responsibility for coping with the demands of weak connectivity. This approach preserves upward compatibility by allowing applications to run unchanged. Coda provides several mechanisms for weakly connected operation motivated by actual experience. The foundation of adaptivity in this system is the communications layer, which derives and supplies information on network conditions to higher system layers. The rapid cache validation mechanism enables the system to recover quickly in intermittent environments. The trickle reintegration mechanism insulates the user from poor network performance by propagating updates to servers asynchronously. The cache miss handling mechanism alerts the user to potentially lengthy service times and provides opportunities for intervention. A quantitative evaluation of these mechanisms, based on controlled experimentation and empirical data gathered from the deployed system in everyday use, shows that Coda is able to provide good performance even when network bandwidth varies over four orders of magnitude -- from modem speeds to Lan speeds."

Download or read book Network aware Adaptation in Mobile File Systems written by Benjamin Atkin and published by . This book was released on 2004 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Exploiting Weak Connectivity for Mobile File Access written by Lily B. Mummert and published by . This book was released on 1995 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "Weak connectivity, in the form of intermittent, low- bandwidth, or expensive networks is a fact of life in mobile computing. In this paper, we describe how the Coda File System has evolved to exploit such networks. The underlying theme of this evolution has been the systematic introduction of adaptivity to eliminate hidden assumptions about strong connectivity. Many aspects of the system, including communication, cache validation, update propagation and cache miss handling have been modified. As a result, Coda is able to provide good performance even when network bandwidth varies over four orders of magnitude -- from modem speeds to LAN speeds."

Download or read book Exploiting Weak Connectivity in a Distributed File System written by Carnegie-Mellon University. Computer Science Dept and published by . This book was released on 1996 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "Weak connectivity, in the form of intermittent, low- bandwidth, or expensive networks is a fact of life in mobile computing. For the foreseeable future, access to cheap, high-performance, reliable networks, or strong connectivity will be limited to a few oases, such as work or home, in a vast desert of weak connectivity. The design of distributed file systems has traditionally been based on an assumption of strong connectivity. Yet, to provide ubiquitous data access, it is vital that distributed file systems make effective use of weak connectivity. This dissertation describes the design, implementation, and evaluation of weakly connected operation in the Coda File System. The starting point of this work is disconnected operation, in which a file system client operates using data in its cache during server or network failures. Disconnected clients suffer from many limitations: updates are not visible to other clients, cache misses may impede progress, updates are at risk from client loss or damage, and the danger of update conflicts increases as disconnections are prolonged. Weak connectivity provides an opportunity to alleviate these limitations. Coda's strategy for weakly connected operation is best characterized as application-transparent adaptation. The system bears full responsibility for coping with the demands of weak connectivity. This approach preserves upward compatibility by allowing applications to run unchanged. Coda provides several mechanisms for weakly connected operation motivated by actual experience. The foundation of adaptivity in this system is the communications layer, which derives and supplies information on network conditions to higher system layers. The rapid cache validation mechanism enables the system to recover quickly in intermittent environments. The trickle reintegration mechanism insulates the user from poor network performance by propagating updates to servers asynchronously. The cache miss handling mechanism alerts the user to potentially lengthy service times and provides opportunities for intervention. A quantitative evaluation of these mechanisms, based on controlled experimentation and empirical data gathered from the deployed system in everyday use, shows that Coda is able to provide good performance even when network bandwidth varies over four orders of magnitude -- from modem speeds to Lan speeds."

Download or read book Improving Data Consistency for Mobile File Access Using Isolation only Transactions written by Carnegie-Mellon University. Computer Science Dept and published by . This book was released on 1996 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "Disconnected operation based on optimistic replication has been demonstrated as an effective technique enabling mobile computers to access shared data in distributed file systems. To guard against inconsistencies resulted from partitioned data sharing, past research has focused on detecting and resolving write/write conflicts. However, experience shows that undetected read/write conflicts pose a subtle but serious threat to data integrity in mobile file access. Solving this problem is critical for the future success of mobile computing. This dissertation shows that isolation-only transaction (IOT), an upward compatible transaction mechanism for the Unix File System, is a viable solution to this problem. The central idea of the IOT model is imposing serializability-based isolation requirements on partitioned transaction executions. Transactions executed on a disconnected client stay in a tentative state until the client regains connection to relevant servers. They are committed to the servers as soon as they pass consistency validation. Invalidated transactions are automatically or manually resolved to ensure global consistency. Powerful resolution mechanisms such as automatic transaction re-execution and application specific resolver invocation can transparently resolve conflicts for many common Unix applications. In addition, a concise conflict representation scheme enables application semantics to be smoothly integrated for only conflict resolution and consistency validation. The practical usability of IOT is further enhanced by a flexible interactive interface, full compatibility with existing Unix applications, and the ability to retain overall file system scalability, security and transparency. A working IOT implementation in the Coda file system has been developed and used in experiments in software development and document processing applications. Quantitative evaluation based on controlled experiments and trace-driven simulations establish that the IOT model is scalable and incurs modest performance and resource overhead. The main contributions of this thesis research are the following: the design of an isolation-only transaction model specialized for improving mobile file consistency while preserving upward compatibility with existing Unix applications; the development of a working IOT implementation in the Coda file system; experimentation and evaluation demonstrating the feasibility and practicality of the IOT model."

Download or read book Flexible and Safe Resolution of File Conflicts written by Puneet Kumar and published by . This book was released on 1994 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "In this paper we describe the support provided by the Coda File System for transparent resolution of conflicts arising from concurrent updates to a file in different network partitions. Such partitions often occur in mobile computing environments. Coda provides a framework for invoking customized pieces of code called application- specific resolvers (ASRs) that encapsulate the knowledge needed for file resolution. If resolution succeeds, the user notices nothing more than a slight performance delay. Only if resolution fails does the user have to resort to manual repair. Our design combines a rule-based approach to ASR selection with transactional encapsulation of ASR execution. This paper shows how such an approach leads to flexible and efficient file resolution without loss of security or robustness."

Download or read book Proceedings of the Annual ACM Symposium on Principles of Distributed Computing written by and published by . This book was released on 1996 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Proceedings of the Fifteenth Annual ACM Symposium on Principles of Distributed Computing written by ACM Special Interest Group for Automata and Computability Theory and published by Association for Computing Machinery (ACM). This book was released on 1996 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Remote Access to Distributed File Systems written by Lawrence Bruce Huston and published by . This book was released on 1995 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Peterson s Graduate Programs in Engineering and Applied Sciences 1996 written by Peterson's Guides and published by Peterson Nelnet Company. This book was released on 1995-12-10 with total page 1518 pages. Available in PDF, EPUB and Kindle. Book excerpt: Graduate students depend on this series and ask for it by name. Why? For over 30 years, it's been the only one-stop source that supplies all of their information needs. The new editions of this six-volume set contain the most comprehensive information available on more than 1,500 colleges offering over 31,000 master's, doctoral, and professional-degree programs in more than 350 disciplines.New for 1997 -- Non-degree-granting research centers, institutes, and training programs that are part of a graduate degree program.Five discipline-specific volumes detail entrance and program requirements, deadlines, costs, contacts, and special options, such as distance learning, for each program, if available. Each Guide features "The Graduate Adviser", which discusses entrance exams, financial aid, accreditation, and more.Interest in these fields has never been higher! And this is the source to the 3,400 programs currently available -- from bioengineering and computer science to construction management.

Download or read book MOBICOM written by and published by . This book was released on 2000 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Building Secure and Reliable Network Applications written by Kenneth P. Birman and published by Prentice Hall. This book was released on 1996 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fundamentals of Mobile and Pervasive Computing written by Frank Adelstein and published by McGraw Hill Professional. This book was released on 2005-01-20 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authoritative, general reference that has been sorely missing in the field of mobile computing This book teaches all the main topics via the hottest applications in a rapidlygrowing field. "Big picture" explanations of ad hoc networks and service discovery Exercises, projects, and solutions to illustrate core concepts Extensive wireless security methodologies

Download or read book Third Workshop on Workstation Operating Systems April 23 24 1992 Key Biscayne Florida written by and published by . This book was released on 1992 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Proceedings written by and published by . This book was released on 1992 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: