For better protection of distributedsystems, two well-known techniques are: checkpointing and rollback recovery. While failure protection is often considered a separate issue, it is crucial for establishing better se...
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Bloom filter is a simple space-efficient randomized data structure for representing a set in order to support membership queries, which uses an m-bit array to represent a data set. Dynamic bloom filter (DBF) can suppo...
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Bloom filter is a simple space-efficient randomized data structure for representing a set in order to support membership queries, which uses an m-bit array to represent a data set. Dynamic bloom filter (DBF) can support concisely representation and approximate membership queries of dynamic set instead of static set. It has been proved that DBF not only possess the advantage of standard bloom filter, but also has better features when dealing with dynamic set. But DBF also has a disadvantage: the addition operation which mapped element x into bloom filter s will become no sense, if some of the first s-1 bloom filters have already responded that element x is in set A with some false positive probability. We point out this shortcoming and improve the addition operation with a new algorithm. We call this improved dynamic bloom filter i-DBF. Finally, we prove that this i-DBF has better performance both in the storage space and in the false positive probability
In distributedsystems, checkpointing method can be used to ensure fault-tolerance, which in turn could help the system’s security and stability. In simple terms, checkpointing means saving status information of a sy...
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In disaster situations communication and power infrastructure could be damaged, disrupting their associated services. This could delay relief efforts and cost more lives. In situations where connections are damaged an...
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ISBN:
(纸本)9781509007257
In disaster situations communication and power infrastructure could be damaged, disrupting their associated services. This could delay relief efforts and cost more lives. In situations where connections are damaged and unreliable, peer-to-peer (P2P) and delay-tolerant networking (DTN) technologies can help provide alternative communication modes particularly in support of rescue and relief operations. Combining the benefits of the store-and-forward capability of DTN and the data propagation techniques of Wi-Fi Direct, we have created a flexible framework called ARC which allows users to create applications that could meet their specific requirements, particularly those in support of emergency communications. To demonstrate our framework, we created a simple application using ARC, and used this application to evaluate its DTN and Wi-Fi Direct group recovery capabilities.
In distributed multimedia storage systems where client requests for different multimedia objects may have different demands, placement and replication of the objects is an important factor, as it may result in an imba...
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In distributed multimedia storage systems where client requests for different multimedia objects may have different demands, placement and replication of the objects is an important factor, as it may result in an imbalance in server loading across the system. Replica management and load balancing is all the more a crucial issue for large-scale multimedia systems. We design and analyze a heuristic static strategy to determine the placement, number of replicas of the objects, and balance the client requests among the servers, to minimize the average waiting time (AWT) of the requests. Our strategy exploits clever virtual routing technique to strike a balance among the servers for load balancing. We validate the performance via rigorous simulations with respect to several influencing factors and compare with a system that uses hashing function only for load balancing.
This book constitutes the refereed proceedings of the 4th International Workshop on Self-Organizing systems, IWSOS 2009, held in Zurich, Switzerland, in December 2009. The 14 revised full papers and 13 revised short p...
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ISBN:
(数字)9783642108655
ISBN:
(纸本)9783642108648
This book constitutes the refereed proceedings of the 4th International Workshop on Self-Organizing systems, IWSOS 2009, held in Zurich, Switzerland, in December 2009. The 14 revised full papers and 13 revised short papers presented were carefully selected from the 34 full and 27 short paper submissions. The papers are organized in topical sections on ad hoc and sensor networks; services, storage, and internet routing; peer-to-peer systems; theory and general approaches; overlay networks; peer-to-peer systems and internet routing; wireless networks; and network topics.
A web crawling system employing a parallel and distributed architecture needs to have a mechanism to bring the whole system in a coordinated state when the nodes are added to or removed from the system. This paper pre...
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A web crawling system employing a parallel and distributed architecture needs to have a mechanism to bring the whole system in a coordinated state when the nodes are added to or removed from the system. This paper presents an efficient dynamic reconfiguration model that can be used in such a system. The study shows that this model leads to some nice properties, such as load balance and low traffic in the system, which contribute to high performance. Currently this model is being implemented in WebGather, a well-known Chinese and English web search engine.
It is important for an incremental crawler to know how web pages evolve and the relation between their changing frequencies and the link-attributes such as indegrees. This paper proposes a model for incremental crawli...
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ISBN:
(纸本)9780769521008
It is important for an incremental crawler to know how web pages evolve and the relation between their changing frequencies and the link-attributes such as indegrees. This paper proposes a model for incremental crawling and performs an experiment to verify the correlation between them, by monitoring the evolution of all the link-attributes of the web pages within one website. Particularly, we look deeply into one special kind of page named Index-pages. From the experiment, we can make four conclusions: (1) Pages which have bigger indegrees, outdegrees or PageRank values change more often, and these link-attributes all approximately obey a power-law distribution. (2) The link-attributes of pages seldom change though the pages change themselves. (3) A small proportion of the pages link to most of the vertexes in the web graph. (4) The Index-pages link to sizeable new pages in a website. These conclusions can be used to greatly enhance the performance of an incremental crawler, which is the foremost component for general search engines and web information stores.
In this paper, we propose a static scheduling algorithm forassigning tasks with precedence constraints onto a cluster of heterogeneoussensor nodes connected by a single-hop wireless network so as tomaximize the lifeti...
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ISBN:
(纸本)9783540898931
In this paper, we propose a static scheduling algorithm forassigning tasks with precedence constraints onto a cluster of heterogeneoussensor nodes connected by a single-hop wireless network so as tomaximize the lifetime of the sensor network. The processing element oneach sensor node is equipped with dynamic voltage scaling capability. Inour algorithm, we assign the tasks to the sensor nodes so as to minimizethe energy consumption of the tasks on each sensor node while keepingthe energy consumption as balanced as possible. We also propose an algorithmto generate a second schedule that can improve the lifetime ofthe network further when it is used together with the original *** observe up to 311% lifetime improvement in our simulations whenour algorithms are compared to the baseline case where dynamic voltagescaling is not used.
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