We present here the execution model of a policy-driven middleware for building secure distributed collaboration systems from their high level specifications. Our specification model supports nested collaboration activ...
详细信息
ISBN:
(纸本)0769515851
We present here the execution model of a policy-driven middleware for building secure distributed collaboration systems from their high level specifications. Our specification model supports nested collaboration activities, and uses role-based security policies and event count based coordination specification. From the specifications of a collaboration environment, appropriate policy modules are derived for enforcing security and coordination requirements. A policy-driven distributed middleware provides services to the users to join roles in an activity, perforin role specific operations, or create new, activities. We describe here the design challenges for the middleware and present the runtime structures and protocols supported by it for creating activities, roles, and objects.
Paxos, the de facto standard approach to solving distributed consensus, operates in two phases, each of which requires an intersecting quorum of nodes. Multi-Paxos reduces this to one phase by electing a leader but th...
详细信息
ISBN:
(纸本)9781450389334
Paxos, the de facto standard approach to solving distributed consensus, operates in two phases, each of which requires an intersecting quorum of nodes. Multi-Paxos reduces this to one phase by electing a leader but this leader is also a performance bottleneck. Fast Paxos bypasses the leader but has stronger quorum intersection requirements. In this paper we observe that Fast Paxos' intersection requirements can be safely relaxed, reducing to just one additional intersection requirement between phase-1 quorums and any pair of fast round phase-2 quorums. We thus find that the quorums used with Fast Paxos are larger than necessary, allowing alternative quorum systems to obtain new tradeoffs between performance and fault-tolerance.
The need for sharing is well known in a large number of distributed collaborative applications. These applications are difficult to develop for wide area (possibly, mobile) networks because of slow and unreliable conn...
详细信息
ISBN:
(纸本)0769515851
The need for sharing is well known in a large number of distributed collaborative applications. These applications are difficult to develop for wide area (possibly, mobile) networks because of slow and unreliable connections. For this purpose, we developed a platform called OB1WAN(1) that: i) allows the application to decide, in run-time, the mechanism by which objects should be invoked, remote method invocation or invocation on a local replica, ii) allows incremental replication of large object graphs, iii) allows the creation of dynamic clusters of data, and iv) provides hooks for the application programmer to implement a set of application specific properties such as relaxed transactional support or updates dissemination. These mechanisms allow an application to deal with situations that frequently occur in a (mobile) wide-area network, such as disconnections and slow links: i) as long as objects needed by an application (or by an agent) are colocated, there is no need to be connected to the network, and ii) it is possible to replace, in run-time, remote by local invocations on replicas, thus improving the performance and adaptability of applications. The prototype is developed in Java, is very small and simple to use, the performance results are very encouraging, and existing applications can be easily modified to take advantage of OB1WAN.
Named Data networking (ndN), a promising Future Internet Architecture design, requires new experimental applications to demonstrate its performance and feasibility. Through designing, implementing, and evaluating ndNM...
详细信息
ISBN:
(纸本)9781509044573
Named Data networking (ndN), a promising Future Internet Architecture design, requires new experimental applications to demonstrate its performance and feasibility. Through designing, implementing, and evaluating ndNMaze, i.e., an ndN version of a widely deployed peer-to-peer file-sharing application called IPMaze, we find that ndNMaze has a simpler system architecture with improved performance and flexibility. The innovative messaging mechanism anddistributed hash tables (DHT) in ndNMaze simplified the implementations of key system components such as user management, nearest neighbor discovery, file discovery and distributions. To systematically evaluate the performance, we simulate both versions with NS-3 simulator, and collect a broad range of performance metrics including hop count, data request latency, data request efficiency, and network transmission efficiency. Our experimental results show that ndNMaze achieves better performance than IPMaze due to the ndN's advantages in content-centric data distribution and sharing. Our work sheds light for distributed application design in ndN.
A spatio-textual similarity join searches a spatio-textual data collection and reports the object pairs that satisfy the specified spatial distance threshold and textual similarity threshold. However, when the data ow...
详细信息
ISBN:
(纸本)9781509044573
A spatio-textual similarity join searches a spatio-textual data collection and reports the object pairs that satisfy the specified spatial distance threshold and textual similarity threshold. However, when the data owner outsources the join computations to a third-party cloud service provider, the service provider may send incomplete or incorrect join results to the data owner. In this paper, we propose a pairwise authentication scheme, a cluster based scheme and an order and bound based scheme to authenticate the results of spatio-textual similarity joins. Extensive experiments on a real-world dataset verify the effectiveness and efficiency of our proposed schemes in terms of various performance metrics.
This paper proposes a replica control method based on a fairly assigned variation of numerical data that has weak consistency for loosely coupled systems managed or used by different organizations. This method dynamic...
详细信息
ISBN:
(纸本)0769515851
This paper proposes a replica control method based on a fairly assigned variation of numerical data that has weak consistency for loosely coupled systems managed or used by different organizations. This method dynamically distributes the variation of numerical data to replicas according to their demands while achieving fairness among them. By assigning the variation, a replica can determine the possibility that processed update transactions will be aborted and can notify a client of the possibility even when network partitioning happens. In addition, fairly assigning the variation of data to replicas enables the disadvantage among replicas caused by asynchronous update to be balanced among replicas. Fairness control for assigning the variation of data is performed by averaging the demands in the variation that are requested by, the replicas. Simulation showed that our system can achieve extremely, high fairness while processing update transactions at the maximum rate.
Context-aware mobile computing belongs to the field of ubiquitous computing. It aims to enable device to provide better service for people through applying available context information. In this paper, context-aware m...
详细信息
ISBN:
(纸本)9781424442331
Context-aware mobile computing belongs to the field of ubiquitous computing. It aims to enable device to provide better service for people through applying available context information. In this paper, context-aware mobile computing was elaborated Firstly, the history of definition of context was summarized, and then the new classification of human-centric context was proposed The acquiring and application of context information was generalized in the following part. On the basis, the issues in context-aware mobile computing were pointed out and finally the architecture of context-aware Q&A service was presented. Although the context-aware Q&A service can not solve all the issues introduced in this paper, it can be considered as an attempt to provide mobile service through mining of previously gathered context information sensed
We describe how to manage distributed file system caches based upon groups of files that are accessed together. We use file access patterns to automatically, construct dynamic groupings of files and then manage our ca...
详细信息
ISBN:
(纸本)0769515851
We describe how to manage distributed file system caches based upon groups of files that are accessed together. We use file access patterns to automatically, construct dynamic groupings of files and then manage our cache by fetching groups, rather than single files. We present experimental results, based on trace-driven workloads, demonstrating that grouping improves cache performance. At the file system client, grouping can reduce LRU demand fetches by 50 to 60%. At the server cache hit rate improvements are much more pronounced, but vary widely (20 to over 1200%) depending upon the capacity of intervening caches. Our treatment includes information theoretic results that justify our approach to file grouping.
In the near future, there will be increasingly powerful computers in smart cards, telephones, and other information appliances. This will create a massive infrastructure composed of highly diverse interconnected mobil...
详细信息
ISBN:
(纸本)0769515886
In the near future, there will be increasingly powerful computers in smart cards, telephones, and other information appliances. This will create a massive infrastructure composed of highly diverse interconnected mobile entities. In this paper, we present a data-centric approach to storage and querying in such environments. At a first level, we view each entity as a miniature database;at a second level we maintain databases of metadata and services. We describe how information delivery and querying are performed in such architectures.
This paper indicates that a scalable fault-tolerant name service can be provided utilizing an overlay network and that such a name service can scale along a number of dimensions: it can be sized to support a large num...
详细信息
ISBN:
(纸本)0769515851
This paper indicates that a scalable fault-tolerant name service can be provided utilizing an overlay network and that such a name service can scale along a number of dimensions: it can be sized to support a large number of clients, it can allow large numbers of concurrent lookups on the same name or sets of names, and it can provide name lookup latencies measured in seconds. Furthermore, it can enable updates to be made pervasively visible in times typically measured in seconds for update rates of up to hundreds per second. We explain how many of these scaling properties for the name service are obtained by reusing some of the same mechanisms that allowed the underlying overlay network to scale. Finally, we observe that the overlay network is sensitive to bandwidth and CPU limitations.
暂无评论