We present a system for secure telephone conferences (stc) over the internet. the system ensures participant authentication via x.509 certificates, such that every participant of a conference is informed about every o...
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ISBN:
(纸本)0769526403
We present a system for secure telephone conferences (stc) over the internet. the system ensures participant authentication via x.509 certificates, such that every participant of a conference is informed about every other participant. Also, all signaling and media data are encrypted, to ensure confidentiality. the system builds upon the open source telephone server asterisk and standard IP softphones. those software products are used unaltered. Stc client and server processes reside with softphones and server, respectively, to realize secure conferences. Experiments with our prototype show that the additional network and processor load is low, and that the system scales well for more than 10 participants.
Reliable distributed data storage systems have to employ redundancy codes to tolerate the loss of storages. Many appropriate codes and algorithms can be found in the literature, but efficient schemes for tolerating se...
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ISBN:
(纸本)0769526403
Reliable distributed data storage systems have to employ redundancy codes to tolerate the loss of storages. Many appropriate codes and algorithms can be found in the literature, but efficient schemes for tolerating several storage failures and their embedding in a distributed system are still research issues. In this paper, a variety of redundancy schemes are compared that got implemented in a distributed storage system. All schemes are based on parity and Reed/Solomon and are integrated in the storage system NetRAID. this system allows to configure several user-specified layouts. A performance and reliability analysis of several data and redundancy layouts is presented that combines analytical and experimental results. In a detail, we present performance results for an optimized Reed/Solomon implementation and give an outline for speeding up encoding and recovery by reconfigurable hardware employed in the distributed storage system.
distributed Hash Tables (DHTs) provide a scalable mechanism for mapping identifiers to socket addresses. As each peer in the network can initiate lookup requests, a DHT has to process concurrently a potentially very l...
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ISBN:
(纸本)0769526403
distributed Hash Tables (DHTs) provide a scalable mechanism for mapping identifiers to socket addresses. As each peer in the network can initiate lookup requests, a DHT has to process concurrently a potentially very large number of requests. In this paper, we look at congestion control for DHTs. Our goal is to control the flow of lookup requests that are routed in the overlay network. We first show that congestion control is essential for certain applications with high lookup rates. We then present two congestion control mechanisms for DHTs and compare their performances in different network conditions.
this paper gives a definition of the communication overhead among nodes in task scheduling and resource management in Grid environment, presents rules of building QoS Routing Tree based on the QoS routing algorithm, p...
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ISBN:
(纸本)9780769526942
this paper gives a definition of the communication overhead among nodes in task scheduling and resource management in Grid environment, presents rules of building QoS Routing Tree based on the QoS routing algorithm, proposes grid heap-sort algorithm and QoS routing algorithm, and designs a scheme of grid task scheduling withthe help of them. the results of its correlative experiment indicate that this design can guarantee quality of service in Grid better.
Flooding and random walk are two basic mechanisms for blind search in unstructured peer-to-peer overlays. Although these mechanisms have been widely studied experimentally and via simulations, they have not been analy...
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ISBN:
(纸本)0769526403
Flooding and random walk are two basic mechanisms for blind search in unstructured peer-to-peer overlays. Although these mechanisms have been widely studied experimentally and via simulations, they have not been analytically modeled. Time overhead, message overhead, and success rate are often used as metrics for search schemes. this paper shows that node coverage is an important metric to estimate performance metrics such as the message efficiency, success rate, and object recall of a blind search. the paper then presents two simple models to analyze node coverage in random graph overlays. these models are useful to set query parameters, evaluate search efficiency, and to estimate object replication on a statistical basis.
DNA sequence assembly is a fundamental part of biological computing. However, most of the large-scale sequence assemblies require intensive computing power and huge storage. To speed up the assembly process, we here p...
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ISBN:
(纸本)0769526950
DNA sequence assembly is a fundamental part of biological computing. However, most of the large-scale sequence assemblies require intensive computing power and huge storage. To speed up the assembly process, we here propose a method for large-scale DNA sequence assembly by using computing grid the central idea of our method is to first cluster the input of fragment set into many non-intersected subsets using k-mers and then to distribute them to all nodes of the grid-computing system. Our method has accuracy of more than 92% on the test data sets under the simulated grid-computing system but costing shorter time and lower storage. Our method can efficiently process large-scale DNA sequence assembly by taking advantage of huge storage and computing capacity of computing gird.
Grid computing systems (machines) pool together the resources of a heterogeneous collection of computing systems that are widely distributed, possibly around the globe, to create a virtual computing organization. User...
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ISBN:
(纸本)9780769526942
Grid computing systems (machines) pool together the resources of a heterogeneous collection of computing systems that are widely distributed, possibly around the globe, to create a virtual computing organization. Users can "draw" resources either from local or from remote computing resources to execute their jobs. We only consider such a system in tree networks, and study a basic allocation problem: given a set of jobs, each demanding bandwidth and a set of cumulative computing resources and yielding profits corresponding to different machines, determine which feasible subset of jobs yields the maximum total profit.
Modern distributed information systems handle increasingly critical data and computation, but there is no systematic way to assess whether a given part of the system can be entrusted with such data and computation on ...
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ISBN:
(纸本)0769526403
Modern distributed information systems handle increasingly critical data and computation, but there is no systematic way to assess whether a given part of the system can be entrusted with such data and computation on a continuous basis. In a highly interconnected networked environment, components with varying levels of trustworthiness must interact with each other. Occurrence and spread of attack induced failure imply that hosts once trusted cannot remain equally trusted all the time. System components and human operators can benefit from a scheme that assesses the trustworthiness of hosts i.e., the confidence that individual hosts are not corrupt, on a continuous basis by adjusting and adapting their behavior when a host's trustworthiness diminishes. In this work in progress report we present an accusation based trust assessment scheme.
Large-scale distributed systems, e.g., Grid or P2P networks, are targets for large-scale attacks. Unfortunately, few existing systems support propagation of alerts during the attack itself while also suppressing disru...
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ISBN:
(纸本)0769526403
Large-scale distributed systems, e.g., Grid or P2P networks, are targets for large-scale attacks. Unfortunately, few existing systems support propagation of alerts during the attack itself while also suppressing disruptive alerts from faulty or malicious sources. this paper proposes the "ContagAlert" protocol, which uses contagion spreading behavior to spread alerts. ContagAlert rapidly propagates alerts during attacks while also suppressing disruptive alerts. the core contagion protocols in the system are completely localized, but result in desired behavior at the network scale. We analyze and evaluate our protocol with synthetic simulations and in both Internet worm and DoS attack scenarios.
We propose to use W3C Web Services and recently emerging scientific workflow technologies for geospatial data processing in distributed and heterogeneous computation environments. the Web service technology provides p...
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ISBN:
(纸本)9780769526942
We propose to use W3C Web Services and recently emerging scientific workflow technologies for geospatial data processing in distributed and heterogeneous computation environments. the Web service technology provides platform independence and greater interoperability;the scientific workflow technology provides software reuse and visual programming. We demonstrate the feasibility of the proposed approach using storm dynamics tracking from weather radar data as an example. Technical details of algorithm development, Web services publishing, workflow composition and execution for the demonstrative example are discussed.
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