It's a hot issue to improve the accuracy of network coordinate systems(NCS). By analyzing the error source of NCSes, it's emphasized that guaranteeing the low dimensionality of embedding datasets is the princi...It's a hot issue to improve the accuracy of network coordinate systems(NCS). By analyzing the error source of NCSes, it's emphasized that guaranteeing the low dimensionality of embedding datasets is the principle on the designing of NCSes. Based on this observation, a PCA based Internet delay space dividing algorithm(IDSD-PCA) is proposed. Beginning at choosing an optimized sub dataset randomly, IDSD-PCA partitions the Internet delay dataset into several sub datasets with low dimensionality by iterations. After the partition, the whole delay dataset and sub datasets are embedded into a hierarchical NCS. The experimental results show that with this framework both the metric space based models and the non-metric space based models can predict the end-to-end delays more accurately.展开更多
Denial of Service (DoS) attack,especially Distributed Denial of Service (DDoS) attack,is one of the greatest threats to Internet.Much research has been done for it by now,however,it is always concentrated in the behav...Denial of Service (DoS) attack,especially Distributed Denial of Service (DDoS) attack,is one of the greatest threats to Internet.Much research has been done for it by now,however,it is always concentrated in the behaviors of the network and can not deal with the problem exactly.In this paper,we start from the security of the protocol,then we propose a novel theory for security protocol analysis of Denial of Service in order to deal with the DoS attack.We first introduce the conception of weighted graph to extend the strand space model,then we extend the penetrator model and define the goal of anti-DoS attack through the conception of the DoS-stop protocol,finally we propose two kinds of DoS test model and erect the novel formal theory for security protocol analysis of Denial of Service.Our new formal theory is applied in two example protocols.It is proved that the Internet key exchange (IKE) easily suffers from the DoS attacks,and the efficient DoS-resistant secure key exchange protocol (JFK) is resistant against DoS attack for the server,respectively.展开更多
With the deepening of the globalization,citizens have realized the mega-cities space elements largely through media,instead of all-over contact with real physical environment,and dominance hierarchy of urban functions...With the deepening of the globalization,citizens have realized the mega-cities space elements largely through media,instead of all-over contact with real physical environment,and dominance hierarchy of urban functions constructed by all media has represented certain groups’selective transmission of space images.Taking downtown areas of Shanghai City for example,this study explored space images embodied in internet media on the basis of statistical analysis of place name frequency in the media texts.First,by reviewing relevant theories of media languages and city space image,media-based methods for collecting and analyzing space image were reviewed and sorted out,and theoretical bases for the space images embodied by different media were established and compared.Second,in empirical researches,word frequency of place names in economic news texts was calculated in terms of landmark constructions/buildings,roads,rivers,and sections,spatial accumulative calculation was adopted to describe space images of downtown areas in Shanghai.Third,differences and similarities of space images of these downtown areas in economic news reports and citizens’internet posts were further compared.展开更多
基金supported by the National Key Research and Development Program of China under Grant No. 2017YFB0801703the National Natural Science Foundation of China under Grant No. 61602114+1 种基金CERNET Innovation Project No. NGII20170406Jiangsu Provincial Key Laboratory of Computer Network Technology
文摘It's a hot issue to improve the accuracy of network coordinate systems(NCS). By analyzing the error source of NCSes, it's emphasized that guaranteeing the low dimensionality of embedding datasets is the principle on the designing of NCSes. Based on this observation, a PCA based Internet delay space dividing algorithm(IDSD-PCA) is proposed. Beginning at choosing an optimized sub dataset randomly, IDSD-PCA partitions the Internet delay dataset into several sub datasets with low dimensionality by iterations. After the partition, the whole delay dataset and sub datasets are embedded into a hierarchical NCS. The experimental results show that with this framework both the metric space based models and the non-metric space based models can predict the end-to-end delays more accurately.
基金This work is supported by National Natural Science Foundation of China under contract 60902008.
文摘Denial of Service (DoS) attack,especially Distributed Denial of Service (DDoS) attack,is one of the greatest threats to Internet.Much research has been done for it by now,however,it is always concentrated in the behaviors of the network and can not deal with the problem exactly.In this paper,we start from the security of the protocol,then we propose a novel theory for security protocol analysis of Denial of Service in order to deal with the DoS attack.We first introduce the conception of weighted graph to extend the strand space model,then we extend the penetrator model and define the goal of anti-DoS attack through the conception of the DoS-stop protocol,finally we propose two kinds of DoS test model and erect the novel formal theory for security protocol analysis of Denial of Service.Our new formal theory is applied in two example protocols.It is proved that the Internet key exchange (IKE) easily suffers from the DoS attacks,and the efficient DoS-resistant secure key exchange protocol (JFK) is resistant against DoS attack for the server,respectively.
基金Sponsored by State Key Social Science Program(11&ZD154)National Natural Science Fund(51108184)ndependent Project of State Key Laboratory of Subtropical Building Science(2011ZC16)
文摘With the deepening of the globalization,citizens have realized the mega-cities space elements largely through media,instead of all-over contact with real physical environment,and dominance hierarchy of urban functions constructed by all media has represented certain groups’selective transmission of space images.Taking downtown areas of Shanghai City for example,this study explored space images embodied in internet media on the basis of statistical analysis of place name frequency in the media texts.First,by reviewing relevant theories of media languages and city space image,media-based methods for collecting and analyzing space image were reviewed and sorted out,and theoretical bases for the space images embodied by different media were established and compared.Second,in empirical researches,word frequency of place names in economic news texts was calculated in terms of landmark constructions/buildings,roads,rivers,and sections,spatial accumulative calculation was adopted to describe space images of downtown areas in Shanghai.Third,differences and similarities of space images of these downtown areas in economic news reports and citizens’internet posts were further compared.
