27240142
Two optimal peer selection problems
Many peer computers today participate in peer-to-peer file sharing applications in which the computers contribute storage and bandwidth resources. Of course, applications can only harness the resource pool if peers make available their surplus resources to them. It is widely documented, however, that the P2P systems are havens for "free riders": a significant fraction of users do not contribute any resources, and a minute fraction of users contribute the majority of the resources. Clearly, to improve the performance of existing P2P file sharing systems, and to enable new classes of P2P applications, a compelling incentive system needs to be put in place.
1908016
Optimal peer selection for P2P downloading and streaming
In a P2P system, a client peer may select one or more server peers to download a specific file. In a P2P resource economy, the server peers charge the client for the downloading. A server peer's price would naturally depend on the specific object being downloaded, the duration of the download, and the rate at which the download is to occur. The optimal peer selection problem is to select, from the set of peers that have the desired object, the subset of peers and download rates that minimizes cost. In this paper we examine a number of natural peer selection problems for both P2P downloading and P2P streaming. For downloading, we obtain the optimal solution for minimizing the download delay subject to a budget constraint, as well as the corresponding Nash equilibrium. For the streaming problem, we obtain a solution that minimizes cost subject to continuous playback while allowing for one or more server peers to fail during the streaming process. The methodologies developed in this paper are applicable to a variety of P2P resource economy problems.
14410544
Fluid modeling of pollution proliferation in P2P networks
P2P systems are highly vulnerable to pollution attacks in which attackers inject multiple versions of corrupted content into the system, which is then further proliferated by unsuspecting users. However, to our knowledge, there are no closed-form solutions that describe this phenomenon, nor are there models that describe how the injection of multiple versions of corrupted content impacts a clients' ability to receive a valid copy. In this paper we develop a suite of fluid models that model pollution proliferation in P2P systems. These fluid models lead to systems of non-linear differential equations. We obtain closed-form solutions for the differential equations; for the remaining models, we efficiently solve the differential equations numerically. The models capture a variety of user behaviors, including propensity for popular versions, abandonment after repeated failure to obtain a good version, freeloading, and local version blacklisting. Our analysis reveals intelligent strategies for attackers as well as strategies for clients seeking to recover non-polluted content within large-scale P2P networks.
14817913
The FastTrack overlay: A measurement study
Both in terms of number of participating users and in traffic volume, FastTrack is one of the most important applications in the Internet today. Nevertheless, because FastTrack is proprietary and uses encryption, little is understood about FastTrack's overlay structure and dynamics, its messaging protocol, and its index management. We have built two measurement apparatus--the FastTrack Sniffing Platform and the FastTrack Probing Tool--to unravel many of the mysteries behind FastTrack. We deploy the apparatus to study FastTrack's overlay structure and dynamics, its neighbor selection, its use of dynamic port numbers to circumvent firewalls, and its index management. Although this study does not fully solve the FastTrack puzzle, it nevertheless leads to a coherent description of FastTrack and its overlay. Furthermore, we leverage the measurement results to set forth a number of key principles for the design of a successful unstructured P2P overlay. The measurement results and resulting design principles in this paper should be useful for future architects of P2P overlay networks as well as for engineers managing ISPs.
8733679
Stochastic Fluid Theory for P2P Streaming Systems
We develop a simple stochastic fluid model that seeks to expose the fundamental characteristics and limitations of P2P streaming systems. This model accounts for many of the essential features of a P2P streaming system, including the peers' realtime demand for content, peer churn (peers joining and leaving), peers with heterogeneous upload capacity, limited infrastructure capacity, and peer buffering and playback delay. The model is tractable, providing closed-form expressions which can be used to shed insight on the fundamental behavior of P2P streaming systems. The model shows that performance is largely determined by a critical value. When the system is of moderate-to-large size, if a certain ratio of traffic loads exceeds the critical value, the system performs well; otherwise, the system performs poorly. Furthermore, large systems have better performance than small systems since they are more resilient to bandwidth fluctuations caused by peer churn. Finally, buffering can dramatically improve performance in the critical region, for both small and large systems. In particular, buffering can bring more improvement than can additional infrastructure bandwidth.
14392689
Composition trust bindings in pervasive computing service composition
In pervasive computing, devices or peers may implement or compose services using services from other devices or peers, and may use components from various sources. A composition trust binding is a prescriptive set of rules which defines the combination of allowable components for a particular service or application. Composition trust bindings can be used to protect both the service invocation path as well as the content handling path. The subsidiary relationships addressed by a composition trust binding are typically transparent today, but represent potential security exposure in pervasive computing systems because the subsidiary services or components may have security vulnerabilities. We define the composition trust binding and illustrate its use in the context of rights management and distributed search in personal content publishing. We compare this approach to existing authentication and authorization methods in service composition
36631591
Video as an image data source: efficient representations and applications
The two fundamental advantages of video over still imagery are: (i) the ability capture temporal information, and (ii) the ability to acquire a continuously varying set of views of a scene. These advantages are obtained, however, at the cost of vastly increased amount of data. This paper describes an approach to video representation that is based on frame-to-frame alignment, mosaic construction, and 3D parallax recovery. The basic motivation behind our approach is to enable rapid access to the contents, while maintaining the data in a form as close to the source as possible. This representation supports a wide variety of applications that involve transmission, storage, visualization, retrieval, analysis, and manipulation of video sequences.
205912378
The architecture of Efficient Multi-Core Processors: A Holistic Approach
Abstract The most straightforward methodology for designing a multi-core architecture is to replicate an off-the-shelf core design multiple times, and then connect the cores together using an interconnect mechanism. However, this methodology is “multi-core oblivious” as subsystems are designed/optimized unaware of the overall chip-multiprocessing system they would become parts of. The chapter demonstrates that this methodology is inefficient in terms of area/power. It recommends a holistic approach where the subsystems are designed from the ground up to be effective components of a complete system. The inefficiency in “multi-core oblivious” designs comes from many sources. Having multiple replicated cores results in an inability to adapt to the demands of execution workloads, and results in either underutilization or overutilization of processor resources. Single-ISA (instruction-set architecture) heterogeneous multi-core architectures host cores of varying power/performance characteristics on the die, but all cores are capable of running the same ISA. Such a processor can result in significant power savings and performance improvements if the applications are mapped to cores judiciously. The paper also presents holistic design methodologies for such architectures. Another source of inefficiency is blind replication of over-provisioned hardware structures. Conjoined-core chip multiprocessing allows adjacent cores of a multi-core architecture to share some resources. This can result in significant area savings with little performance degradation. Yet another source of inefficiency is the interconnect. The interconnection overheads can be very significant for a “multi-core oblivious” multi-core design—especially as the number of cores increases and the pipelines get deeper. The paper demonstrates the need to co-design the cores, the memory and the interconnection to address the inefficiency problem, and also makes several suggestions regarding co-design.
5063744
Translator Design to Model Cpp Files
The most reliable and accurate description of the actual behavior of a software system is its source code. However, not all questions about the system can be answered directly by resorting to this repository of information. What the reverse engineering methodology aims at is the extraction of abstract, goal-oriented "views" of the system, able to summarize relevant properties of the computation performed by the program. While concentrating on reverse engineering we had modeled the C++ files by designing the translator. E all want to build software that makes things better, avoiding the bad things that lurk in the shadow of failed efforts. To succeed we need discipline when software is designed and built. We need an engineered approach. The usefulness of an abstract system model was already recognized in the 1970s, when structured methods were proposed as software development methods. These methods offered Entity-Relationship diagrams (1) to model the data aspect of a system, and data flow diagrams or functional decomposition techniques to model the functional, behavioral aspect of a system. The main drawbacks of these structured approaches were the often missing horizontal consistency between the data and behavior part within the overall system model, and the vertical mismatch of concepts between the real world domain and the model as well as between the model and the implementation. As a solution to these drawbacks, the concept of an abstract data type, where data and behavior of objects are closely coupled, became popular within the 1980s. This concept then formed the base for the object-oriented paradigm. In particular, object-oriented languages like C++ or Java have become the de facto standard for programming (10). The same holds for the analysis and design phases within a software development process, where object-oriented modeling approaches are becoming more and more the standard ones. The success of object-oriented modeling approaches was hindered in the beginning of the 90s due to the fact that surely more than fifty object-oriented modeling approaches claimed to be the right one. This so-called method war came to an end by an industrial initiative, which pushed the development of the meanwhile standardized object-oriented modeling language UML (Unified Modeling Language) (8). But, despite the fact that it has been standardized, UML is still a moving target.
44489135
Software Energy Optimization of Real Time Preemptive Tasks by Minimizing Cache-Related Preemption Costs
An attempt has been made to optimize the software energy of real time preemptive tasks by minimizing the cache related preemption costs which are primarily incurred due to the inter-task interference in the cache. We have presented an algorithm that outputs an "optimum" task layout which reduces the overall inter-task interference in cache and thus reduces the preemption costs of each task of a given task set. We have compared the result of our estimated layout with that of the random layout generated for benchmark examples for demonstrating the performance of our algorithm.
26545951
Placement of scattering bars in binary and attenuated phase shift mask for damascene trench patterning
Abstract Scattering bars have been very effective technique to increase the common lithography process window for patterns with design rules 0.18 μm and below. This paper studies the placement of scattering bars in binary and attenuated phase shift mask in damascene trench patterning. Different partial coherence values are used to compare the scattering bar effect in binary and 8% attenuated phase shift mask. At low partial coherence ( σ ) the trench size has been found more sensitive to scattering bar parameters than at high σ . Scattering bar separation is found more effective than size to affect the trench critical dimension (CD). At low partial coherence a deep valley or ‘V’ shaped CD trend is found in scattering bar separation versus CD curve. CD dip is more using APSM as compared to binary mask. The process latitude is poor at valley as compared to top. Also, 3 sigma CD variation and range is higher at valley as compared to other separations of the scattering bars.