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Truncation error calculation based on Richardson extrapolation for variable-step collaborative simulation

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Science china({1. Sciences) 2011年第6期54卷 1238-1250页

作者： ZHANG HeMing 1., LIANG SiLu 2 , SONG ShiJi 1.& WANG HongWei 3 1.Department of Automation, TNList, tsinghua University, {1. 1.0084, china 2 computer and information management center, tsinghua University {1. 1.0084, china 3 Engineering Design Centre, Engineering Department, Cambridge University, Cambridge CB2 1.Z, UK 1. Department of Automation TNList Tsinghua University Beijing 100084 China2. Computer and Information Management Center Tsinghua University Beijing 100084 China3. Engineering Design Centre Engineering Department Cambridge University Cambridge CB2 1PZ UK

Collaborative simulation is an effective approach to performing simulation analysis for complex systems by integrating models developed for different engineering disciplines. Collaborative simulation issues include the modeling of coupled multidisciplinary systems, and the simulation running time integration of these models that are solved parallelly. Estimation of the local truncation error of coupling models is the key to solve multidisciplinary collaborative simulation problem, which is actually used to restrict the simulation step. This paper presents a variable-step method based on Richardson extrapolation for calculating the local truncation error to solve collaborative simulation problem of multidisciplinary coupling models. Formulas for estimating the local truncation error are derived through theoretical analysis by using integration methods and interpolation technologies, respectively. The simulation experiments are illustrated to validate the accuracy and efficiency of proposed collaborative simulation algorithm in comparison with the usual combinative algorithm.

关键词： multidisciplinary systems collaborative simulation variable-step algorithm error estimation

An introduction to tsinghua Cloud

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Science china({1. Sciences) 2010年第7期53卷 1481-1486页

作者： ZHENG WeiMin1.2 1.epartment of computer Science and Technology, {1. University, beijing 1.0084, china 2{1. National Laboratory for information Science and Technology, beijing 1.0084, china 1. Department of computer Science and Technology Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

Cloud computing has become a trend that draws attention from both academia and industry all over the world. This paper unveils details of tsinghua Cloud, a comprehensive solution for cloud computing developed by Tsing... 详细信息

关键词： cloud computing distributed file system virtual computing environment data sharing

RRM:An incentive reputation model for promoting good behaviors in distributed systems

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Science in china(Series F) 2008年第11期51卷 1871-1882页

作者： ZHANG Hong1,2,DUAN HaiXin1,3 & LIU Wu1,3 1 tsinghua National Laboratory for information Science and Technology,tsinghua University,beijing 1.0084,china 2 Department of computer Science and Technology,tsinghua University,beijing 1.0084,china 3 Network Research center,tsinghua University,beijing 1.0084,china 1. tsinghua National Laboratory for {1. Science and Technology Tsinghua University Beijing 100084 China 2. Department of computer Science and Technology Tsinghua University Beijing 100084 China 3. Network Research center Tsinghua University Beijing 100084 China

Reputation systems represent soft security mechanisms that complement traditional information security mechanisms. They are now widely used in online e-commerce markets and communities in order to stimulate good behaviors as well as to restrain adverse behaviors. This paper analyzes the limitations of the conversational reputation models and proposes an incentive reputation model called the resilient reputation model （RRM） for the distributed reputation systems. The objective of this reputation model is not only to encourage the users to provide good services and, therefore, to maximize the probability of good transaction outcomes, but also to punish those adverse users who are trying to manipulate the application systems. The simulation results indicate that the proposed reputation model （RRM） could effectively resist against the common adverse behaviors, while protecting the profits of sincere users from being blemished by those adversaries.

关键词： reputation model distributed system trust soft security

Theoretical research progress in new-generation Internet architecture

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Science in china(Series F) 2008年第11期51卷 1634-1660页

作者： WU JianPing1,2,3,LIU Ying2,3 & WU Qian2,3 1 Department of computer Science,tsinghua University,beijing 1.0084,china 2 Network Research center,tsinghua University,beijing 1.0084,china 3 tsinghua National Laboratory for information Science and Technology(TNList) ,beijing 1.0084,china 1. Department of computer Science Tsinghua University Beijing 100084 China 2. Network Research center Tsinghua University Beijing 100084 China 3. tsinghua National Laboratory for {1. Science and Technology (TNList) Beijing 100084 China

Internet has become the most important information infrastructure supporting modern socio-economic development, social progress and technological Innovation. Invented 30 years ago, today Internet is facing increasingly severe technical challenges. This paper introduces the progress of the major international newgeneration Internet research plans; analyzes its basic characteristics and the principal contradictions during the development; detsiledly introduces the research carried out by 973 Project ＂Research of Future Internet Architecture＂ on the key scientific issues of new-generation Internet architecture and its latest research results; and looks to the future of the research-focus faced with the new situations of the basic research of new-generation Internet architecture as well as the new demands of innovative applications on Internet architecture.

关键词： new-generation Internet network architecture multi-dimension scalability

Self-healing routing: failure,modeling and analysis

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Science china({1. Sciences) 2011年第3期54卷 609-622页

作者： XU MingWei 1.2 , LI Qi 1.2 , YANG Yuan 1.2 , HOU MeiJia 1.2 & PAN LingTao 1.2 1.Department of computer Science, {1. University, beijing 1.0084, china 2 {1. National Laboratory for information Science and Technology (TNList), beijing 1.0084, china 1. Department of computer Science Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology (TNList) Beijing 100084 China

Network failures occur frequently, and self-healing ability of existing routing protocols cannot guarantee fast route convergence under these failures without impacting packet forwarding. During routing convergence, network routes may be incorrect and even routing black holes and loops occur, which will result in extensive packet loss and thus influence network performance. To solve this problem, several improved routing solutions have been proposed. In this paper, we propose the concept and model of self-healing routing and analyze the key problems in current intra-domain and inter-domain self-healing routing protocols after briefly reviewing the characteristics of network failures. We classify the different self-healing solutions into two categories based on their design principles: routing restoration and routing protection, and systematically analyze these different typical solutions. Finally, we discuss several key issues in self-healing routing and propose a hybrid protection and restoration based routing scheme.

关键词： failure intra-domain routing inter-domain routing self-healing routing

Corslet: A shared storage system keeping your data private

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Science china({1. Sciences) 2011年第6期54卷 1119-1128页

作者： XUE Wei 1.2 , SHU JiWu 1.2 , LIU Yang 1.& XUE Mao 1.1.Department of computer Science and Technology, {1. University, beijing 1.0084, china 2 {1. National Laboratory for information Science and Technology, {1. University, 1. Department of computer Science and Technology Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China

With the exponential growth of digital data, it is becoming more and more popular to store data in shared distributed storage systems inside the same organization. In such shared distributed storage systems, an ordinary user usually does not have the control permission over the whole system, and thus cannot secure data storage or data sharing of his own files. To solve this issue, this paper proposes a new system architecture to secure file storing and sharing efficiently over untrusted shared storage and network environments. Based on this architecture, this paper designs and implements a stackable secure storage system called Corslet. Corslet can run directly on deployed underlying storage systems without modification, while bringing end-to-end confidentiality and integrity as well as efficient access control for user data. For individual users, Corslet is easy to use, and does not require users to maintain or manage any keys on their client machines locally. The Bonnie++ and IOzone benchmark results show that the throughput of Corslet over NFS can achieve more than 90% of native NFS throughput in most tests, proving that Corslet can provide enhanced security for user data while maintaining acceptable performance.

关键词： storage security access control key management shared file system

A formal method to real-time protocol interoperability testing

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Science in china(Series F) 2008年第11期51卷 1723-1744页

作者： WANG ZhiLiang1,3,YIN Xia2,3 & JING ChuanMing2,3 1 Network Research center,tsinghua University,beijing 1.0084,china 2 Department of computer Science and Technology,tsinghua University,beijing 1.0084,china 3 tsinghua National Laboratory for information Science and Technology(TNList) ,beijing 1.0084,china 1. Network Research center Tsinghua University Beijing 100084 China 3. tsinghua National Laboratory for {1. Science and Technology (TNList) Beijing 100084 China 2. Department of computer Science and Technology Tsinghua University Beijing 100084 China

Interoperability testing is an important technique to ensure the quality of implementations of network communication protocol. In the next generation Internet protocol, real-time applications should be supported effectively. However, time constraints were not considered in the related studies of protocol interoperability testing, so existing interoperability testing methods are difficult to be applied in real-time protocol interoperability testing. In this paper, a formal method to real-time protocol interoperability testing is proposed. Firstly, a formal model CMpTIOA （communicating multi-port timed input output automata） is defined to specify the system under test （SUT） in real-time protocol interoperability testing; based on this model, timed interoperability relation is then defined. In order to check this relation, a test generation method is presented to generate a parameterized test behavior tree from SUT model; a mechanism of executability pre-determination is also integrated in the test generation method to alleviate state space explosion problem to some extent. The proposed theory and method are then applied in interoperability testing of IPv6 neighbor discovery protocol to show the feasibility of this method.

关键词： protocol testing interoperability testing real-time testing test generation timed input output automata(TIOA)

The structural analysis of fuzzy measures

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Science china({1. Sciences) 2011年第1期54卷 38-50页

作者： ZHANG Ling1.ZHANG Bo2 & ZHANG YanPing1.1.computer Science College,Anhui University,Hefei 230039,{1. 2State Key Lab of Intelligent Technology & Systems tsinghua National Lab for information Science & Technology information Science & Technology College,computer Science & Technology,tsinghua University,beijing 1.0084,{1. 1. computer Science College Anhui University Hefei 230039 China2. State Key Lab of Intelligent Technology & Systems tsinghua National Lab for {1. Science & Technology information Science & Technology College Computer Science & Technology Tsinghua University Beijing 100084 China

From quotient space based granular computing theory we explore the fuzzy measures of fuzzy sets. Based on the structural analysis of fuzzy sets,we present an"isotropism"*** this assumption we achieved the following insights:(1.the uniqueness of a fuzzy measure being isotropic on a finite complete semi-ordered set;(2)the necessary and suffcient condition of the isomorphism for fuzzy measure functions in fuzzy mathematics;(3)the necessary and suffcient condition that fuzzy measures have fuzzy and granular monotonicity;(4)under a certain assumption,the analytic expression for fuzzy *** results clarify the relationship between fuzzy measures and granular computing,reveal the essence of fuzzy measures,and provide a simple way of constructing fuzzy measures.

关键词： quotient space fuzzy set fuzzy measure rough set structural analysis

A TTCN-3-based protocol testing system and its extension

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Science in china(Series F) 2008年第11期51卷 1703-1722页

作者： YIN Xia1,3,WANG ZhiLiang2,3,JING ChuanMing1,3 & SHI XinGang2,3 1 Department of computer Science and Technology,tsinghua University,beijing 1.0084,china 2 Network Research center,tsinghua University,beijing 1.0084,china 3 tsinghua National Laboratory for information Science and Technology(TNList) ,beijing 1.0084,china 1. Department of computer Science and Technology Tsinghua University Beijing 100084 China 3. ]tsinghua National Laboratory for {1. Science and Technology (TNList) Beijing 100084 China 2. Network Research center Tsinghua University Beijing 100084 China

The protocol testing technology used in the next generation Internet should satisfy some new challenges and requirements. This paper focuses on the test suite description and test implementation techniques. TTCN-3 is chosen as the test suite description language and extended in both syntax and semantics to satisfy the requirements of protocol robustness testing. PITSv3, a protocol integrated testing system based on TTCN-3, is developed, and the extensions for robustness testing are implemented. Finally, two practical test applications are presented.

关键词： protocol testing TTCN-3 PITSv3 robustness testing