AUTHENTICATED ISOLATION IN DEDUPLICATED STORAGE

Multi-tenancy, security, and deduplication are important features for distributed storage systems for either on premise or on cloud deployments. However, implementing these features can be difficult, as the features often do not play well together when building a performant system. Presented herein is a technique to provide a seamless, transparent deduplication system that incorporates all of these features without inter-dependence and without impacting performance

Exploring Design Configurations of System Models: From Simultaneous Simulation to Search Heuristics

Simulation is applied in numerous and diverse elds, such as manufacturing systems, communications and protocol design, nancial and economic engineering, operations research, design of transportation networks and systems, and so forth. The real utility of simulation lies in the ability to compare and evaluate alternative designs before actual implementation or deployment of a system. To perform a thorough analysis of a large number of congurations with varying system design parameter values, it is important to develop efficient simulation and design space exploration methods that can evaluate a large number of alternative system congurations quickly and accurately. In situations where it is practical to exhaustively explore design parameter space, we proposed a new approach, called Simultaneous Simulation of Alternative System Congurations (SSASC), to evaluate dependability models that combines adaptive uniformization in simulation with the SCMS technique. SSASC showed that a signicant speed-up can be achieved compared to traditional discrete-event simulation to evaluate all alternative congurations. The event set management using adaptive clock algorithm and efficient data structures to manage system model's state access and update enables ecient simulation. Using SSASC, design engineers can benet from quicker evaluation of their system designs with better accuracy (due to variance reduction) than traditional simulation approaches provide. In situations where complete design exploration is not practical, this dissertation provides an intelligent search space exploration technique to effieciently determine near optimal solutions. This dissertation provides a technique, called design solver (DS), to determine near-optimal designs using meta-search heuristics. DS achieves efficiency in exploring the design parameter space by first determining the parameter values that have major impact on the quality of the design solution, and then determining parameter values that further fine-tunes the quality of the design solution. That decomposition reduces the size of the search space, allowing DS algorithm to focus on the most relevant regions to achieve a near-optimal solution. In essence, this dissertation "develops algorithms and techniques that would enable an ecient methodology to compare large numbers of alternative configurations in order to speed-up the design evaluation and validation process"

Achieving Loss Discrimination with Congestion Avoidance in a Rate-based Protocol

The stability of the Internet depends on the presence of well-behaved flows. While TCP forms the majority of the traffic over the Internet, the Internet user community is also dedicated to supporting mobile devices over wireless networks. However, TCP is not well suited to support applications over lossy wireless networks. Ideally, these applications require a protocol that adapts to network conditions with the ability to discriminate congestion-based and transmission-based losses. In this paper, we present a rate-based transport protocol that is designed to support communication for mobile nodes using infrastructure-based wireless networks. We propose an end-to-end approach to loss discrimination based on network state estimation at the receiver. Discrimination is achieved by correlating short-term history of packet inter-arrival times with the loss. We also integrate a congestion avoidance algorithm to react to pending network congestion. Simulations of our protocol prototype show that rate-based protocols can provide better correlation to network conditions than ACK-clocked protocols. We provide extensive evaluation through simulation demonstrating that our protocol is well-behaved over a wide range of scenarios

Exploring Design Configurations of System Models: From Simultaneous Simulation to Search Heuristics

162 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.In essence, this dissertation "develops algorithms and techniques that would enable an efficient methodology to compare large numbers of alternative configurations in order to speedup the design evaluation and validation process". .U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Balancing Loss Discrimination and Congestion Control in a Rate-Based Protocol

The stability of the Internet depends on the presence of well-behaved flows. While TCP forms the majority of the tra#c over the Internet, the Internet user community is also dedicated to supporting mobile devices over wireless networks. However, TCP-like behavior is not well suited to support applications over lossy wireless networks. Ideally, these applications require a protocol that adapts to network conditions with the ability to discriminate congestion-based and transmission-based losses. In this thesi

Simultaneous Simulation of Alternative Configurations of Markovian System Models

Simulation is a useful tool for engineering systems, and it is used in numerous and diverse fields. Simulation of large systems can result in better designs and make the design process more efficient. One important use of simulation lies in comparing and choosing the best among different simulation models that represent competing or alternative designs before the actual deployment and implementation. We have developed the Simultaneous Simulation of Alternative System Configurations (SSASC) approach, which provides a methodology that exploits the structural similarity among the alternative configurations and results in an efficient simulation algorithm that evaluates alternative configurations of a system simultaneously. In addition, we designed and implemented an efficient data structure for simulation state management to speed up the SSASC algorithm. Our approach to simulation is orthogonal to parallel or distributed simulation. The resulting improved algorithm could form the basis of an efficient parallel simulation framework

Simultaneous simulation of alternative system configurations

Simulation to obtain reliability and availability estimates has been widely used by system designers to evaluate and compare alternative choices before making design decisions. However, traditionally that approach worked only if significant computer resources were available or designers accepted a significant time delay between design iterations. In this paper, we present an alternative approach to compute measures of interest for a family of models that represent alternative design choices that is significantly more efficient than the traditional approach. The new approach combines the existing single-clock multiple-system simulation with adaptive uniformization. We achieve the speedup by simulating all the alternative configurations of the discrete-event model simultaneously while amortizing the cost of enabled event set management. That allows us to explore and evaluate multiple configuration settings of a discrete-event model at the same time, significantly increasing the number of alternative versions of the model that are explored in a given amount of time

EFFICIENT STATE MANAGEMENT TO SPEED UP SIMULTANEOUS SIMULATION OF ALTERNATE SYSTEM CONFIGURATIONS

Simulation is a useful tool for engineering systems, and it is used in numerous and diverse fields. Simulation of large systems can result in better designs, and make the design process more efficient. One important use of simulation lies in comparing different simulation models that represent competing or alternative designs before the actual deployment and implementation. Simultaneous Simulation of Alternative System Configurations (SSASC) provides a methodology that exploits the structural similarity among the alternative configurations and results in an efficient simulation algorithm that evaluates alternative configurations of a system simultaneously. In this paper, we designed and implemented an efficient data structure for simulation state management to speed up SSASC. This approach is orthogonal to parallel or distributed simulation. The resulting improved algorithm could form the basis of an efficient parallel simulation framework