Higher availability and better performance of data-centric applications can be achieved by replication of objects or data items. If data integrity, a correctness criterion for such systems, needs to be maintained even during degraded situations (node or link failures) the system soon becomes (partially) unavailable. However, some applications exist (e.g., in control engineering) where data integrity can be relaxed for higher availability during degraded situations. Traditional replication models do not support the balancing of these two properties. In this paper, we present a novel replication model that (i) allows replicas to diverge if data integrity can be temporarily relaxed and (ii) re-establishes both replica consistency and data integrity during repair time
{"title":"A Replication Model for Trading Data Integrity against Availability","authors":"Johannes Osrael, Lorenz Froihofer, K. M. Göschka","doi":"10.1109/PRDC.2006.12","DOIUrl":"https://doi.org/10.1109/PRDC.2006.12","url":null,"abstract":"Higher availability and better performance of data-centric applications can be achieved by replication of objects or data items. If data integrity, a correctness criterion for such systems, needs to be maintained even during degraded situations (node or link failures) the system soon becomes (partially) unavailable. However, some applications exist (e.g., in control engineering) where data integrity can be relaxed for higher availability during degraded situations. Traditional replication models do not support the balancing of these two properties. In this paper, we present a novel replication model that (i) allows replicas to diverge if data integrity can be temporarily relaxed and (ii) re-establishes both replica consistency and data integrity during repair time","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116654786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Database management systems (DBMS) represent the ultimate layer in preventing malicious data access or corruption and implement several security mechanisms to protect data. However these mechanisms cannot always stop malicious users from accessing data by exploiting system vulnerabilities. The aim of this paper is to propose an intrusion detection mechanism for DBMS to fill this gap. Our approach consists of a comprehensive representation of user database utilization profiles to perform concurrent intrusion detection. Prior to the detection it is necessary to define and learn these utilization profiles. Profiles are defined using a three level abstraction and learned directly from monitoring the database utilization in real conditions. The proposed mechanism is generic and can be easily implemented in commercial and open-source DBMS
{"title":"Monitoring Database Application Behavior for Intrusion Detection","authors":"J. Fonseca, M. Vieira, H. Madeira","doi":"10.1109/PRDC.2006.46","DOIUrl":"https://doi.org/10.1109/PRDC.2006.46","url":null,"abstract":"Database management systems (DBMS) represent the ultimate layer in preventing malicious data access or corruption and implement several security mechanisms to protect data. However these mechanisms cannot always stop malicious users from accessing data by exploiting system vulnerabilities. The aim of this paper is to propose an intrusion detection mechanism for DBMS to fill this gap. Our approach consists of a comprehensive representation of user database utilization profiles to perform concurrent intrusion detection. Prior to the detection it is necessary to define and learn these utilization profiles. Profiles are defined using a three level abstraction and learned directly from monitoring the database utilization in real conditions. The proposed mechanism is generic and can be easily implemented in commercial and open-source DBMS","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"43 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120989201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Total order broadcast protocols have been successfully applied as the basis for the construction of many fault-tolerant distributed systems. Unfortunately, the implementation of such a primitive can be expensive both in terms of communication steps and of number of messages exchanged. To alleviate this problem, optimistic total order protocols have been proposed. This paper addresses the problem of offering optimistic total order in geographically wide-area systems. We present a protocol that outperforms previous work, by minimizing the average latency of the optimistic notification
{"title":"On Statistically Estimated Optimistic Delivery in Wide-Area Total Order Protocols","authors":"J. Mocito, A. Respício, L. Rodrigues","doi":"10.1109/PRDC.2006.47","DOIUrl":"https://doi.org/10.1109/PRDC.2006.47","url":null,"abstract":"Total order broadcast protocols have been successfully applied as the basis for the construction of many fault-tolerant distributed systems. Unfortunately, the implementation of such a primitive can be expensive both in terms of communication steps and of number of messages exchanged. To alleviate this problem, optimistic total order protocols have been proposed. This paper addresses the problem of offering optimistic total order in geographically wide-area systems. We present a protocol that outperforms previous work, by minimizing the average latency of the optimistic notification","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126740340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The logical ring topology is a simple protection scheme in WDM networks. The failure of a single physical fiber link may cause the failure of multiple lightpaths. The service becomes unprotected if the failure propagates to the logical ring topology. In this paper, we focus on the elimination of failure propagation from the physical WDM network to the logical topology. We propose a method to make the augmented logical ring topology survivable. The augmented survivable edges (ASE) is based on the connectivity problem of the logical topology. Our method makes the modification of logical ring topology cost-effective, i.e., with the minimal number of the additional edges to the original logical ring topology. Finally, we show the results on various network cases
{"title":"The Survivability of the Augmented Logical Ring Topology in WDM Networks","authors":"Yung-Chiao Chen, C. Sue, S. Kuo","doi":"10.1109/PRDC.2006.61","DOIUrl":"https://doi.org/10.1109/PRDC.2006.61","url":null,"abstract":"The logical ring topology is a simple protection scheme in WDM networks. The failure of a single physical fiber link may cause the failure of multiple lightpaths. The service becomes unprotected if the failure propagates to the logical ring topology. In this paper, we focus on the elimination of failure propagation from the physical WDM network to the logical topology. We propose a method to make the augmented logical ring topology survivable. The augmented survivable edges (ASE) is based on the connectivity problem of the logical topology. Our method makes the modification of logical ring topology cost-effective, i.e., with the minimal number of the additional edges to the original logical ring topology. Finally, we show the results on various network cases","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122616993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since the very concept of simultaneous multi-threading (SMT) entails inherent redundancy, some proposals have been made to run two copies of the same thread on top of SMT platforms in order to detect and correct soft errors. This allows, upon detection of an error, for the rolling back of the processor state to a known safe point, and then a retry of the instructions, thereby resulting in a completely error-free execution. This paper focuses on two crucial implementation issues introduced by this concept: (i) the design trade-off between the fault detection coverage versus the design costs; (ii) the possible occurrence of deadlock situations. To achieve the largest possible fault detection coverage, we replicate the instructions fetched in order to generate the redundant thread copies. Further, we apply the SMT thread scheduling at the instruction dispatch stage so as to lower the performance overhead. As a result, when compared to the baseline processor, our simulation results show that by using our two new schemes, the performance overhead can be reduced down to as little as 34% on the average, down from 42%. Finally, in the fault-tolerant execution mode, since the two copied threads are cooperating with one another, deadlock situations could be quite common. We thus present a detailed deadlock analysis and then conclude that allocating some entries of ROB, LQ, and SQ for the trailing thread is sufficient to prevent such deadlocks
{"title":"Design Trade-Offs and Deadlock Prevention in Transient Fault-Tolerant SMT Processors","authors":"Xiaobin Li, J. Gaudiot","doi":"10.1109/PRDC.2006.25","DOIUrl":"https://doi.org/10.1109/PRDC.2006.25","url":null,"abstract":"Since the very concept of simultaneous multi-threading (SMT) entails inherent redundancy, some proposals have been made to run two copies of the same thread on top of SMT platforms in order to detect and correct soft errors. This allows, upon detection of an error, for the rolling back of the processor state to a known safe point, and then a retry of the instructions, thereby resulting in a completely error-free execution. This paper focuses on two crucial implementation issues introduced by this concept: (i) the design trade-off between the fault detection coverage versus the design costs; (ii) the possible occurrence of deadlock situations. To achieve the largest possible fault detection coverage, we replicate the instructions fetched in order to generate the redundant thread copies. Further, we apply the SMT thread scheduling at the instruction dispatch stage so as to lower the performance overhead. As a result, when compared to the baseline processor, our simulation results show that by using our two new schemes, the performance overhead can be reduced down to as little as 34% on the average, down from 42%. Finally, in the fault-tolerant execution mode, since the two copied threads are cooperating with one another, deadlock situations could be quite common. We thus present a detailed deadlock analysis and then conclude that allocating some entries of ROB, LQ, and SQ for the trailing thread is sufficient to prevent such deadlocks","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114708014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sebastian Gutierrez-Nolasco, N. Venkatasubramanian, Mark-Oliver Stehr, C. Talcott
We extend an executable specification of a state-of-the-art secure group communication subsystem to explore two dimensions of adaptability, namely security and synchrony under crash-recovery and intermittent connectivity scenarios. In particular, we relax the traditional requirement of virtual synchrony and propose various generic optimizations, while preserving essential security guarantees. In order to evaluate how practical and effective our generic optimizations are, we integrate the specification into ns2, bridging the gap between formal specification and classical network simulation
{"title":"Towards Adaptive Secure Group Communication: Bridging the Gap between Formal Specification and Network Simulation","authors":"Sebastian Gutierrez-Nolasco, N. Venkatasubramanian, Mark-Oliver Stehr, C. Talcott","doi":"10.1109/PRDC.2006.62","DOIUrl":"https://doi.org/10.1109/PRDC.2006.62","url":null,"abstract":"We extend an executable specification of a state-of-the-art secure group communication subsystem to explore two dimensions of adaptability, namely security and synchrony under crash-recovery and intermittent connectivity scenarios. In particular, we relax the traditional requirement of virtual synchrony and propose various generic optimizations, while preserving essential security guarantees. In order to evaluate how practical and effective our generic optimizations are, we integrate the specification into ns2, bridging the gap between formal specification and classical network simulation","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124334064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The benefits offered by the use of formal methods are not limited to avoidance of specification errors and elimination of ambiguities only - a formal specification also provides a sound basis for generating test suites. Inheritance is a powerful mechanism in object-oriented paradigm by which a subclass inherits data and functionality of a super class. Testing of inheritance relationships is crucial in object-oriented testing, as an inheritance error may lead to subtle bugs such as due to overridden functionality. In this paper, we introduce a technique to generate test cases for inheritance testing, using a VDM++ formal specification. The proposed technique is based on the flattening of a VDM++ specification class, and then generating operation sequences from the trace structure specified in the VDM++ specification. The input space for each operation is partitioned, and a test model is constructed from the operation sequences and the input partitions. Test paths are generated from the test model, which cover the different operation sequences as well as the partitions. We also define various coverage criteria for test path generation
{"title":"A Framework for Inheritance Testing from VDM++ Specifications","authors":"A. Nadeem, Michael R. Lyu","doi":"10.1109/PRDC.2006.7","DOIUrl":"https://doi.org/10.1109/PRDC.2006.7","url":null,"abstract":"The benefits offered by the use of formal methods are not limited to avoidance of specification errors and elimination of ambiguities only - a formal specification also provides a sound basis for generating test suites. Inheritance is a powerful mechanism in object-oriented paradigm by which a subclass inherits data and functionality of a super class. Testing of inheritance relationships is crucial in object-oriented testing, as an inheritance error may lead to subtle bugs such as due to overridden functionality. In this paper, we introduce a technique to generate test cases for inheritance testing, using a VDM++ formal specification. The proposed technique is based on the flattening of a VDM++ specification class, and then generating operation sequences from the trace structure specified in the VDM++ specification. The input space for each operation is partitioned, and a test model is constructed from the operation sequences and the input partitions. Test paths are generated from the test model, which cover the different operation sequences as well as the partitions. We also define various coverage criteria for test path generation","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"36 12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130796144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The k-set agreement problem is a paradigm of coordination problems encountered in distributed computing. The parameter k defines the coordination degree we are interested in. (The case k=1 corresponds to the well-known uniform consensus problem.) More precisely, the k-set agreement problem considers a system made up of n processes where each process proposes a value. It requires that each non-faulty process decides a value such that a decided value is a proposed value, and no more than k different values are decided. This paper visits the k-set agreement problem in synchronous systems where up to t processes can experience failures. Three failure models are explored: the crash failure model, the send omission failure model, and the general omission failure model. Lower bounds and protocols are presented for each model. Open problems for the general omission failure model are stated. This paper can be seen as a short tutorial whose aim is to make the reader familiar with the k-set agreement problem in synchrony models with increasing fault severity. An important concern of the paper is simplicity. In addition to its survey flavor, several results and protocols that are presented are new
{"title":"Synchronous Set Agreement: a Concise Guided Tour (including a new algorithm and a list of open problems)","authors":"M. Raynal, Corentin Travers","doi":"10.1109/PRDC.2006.59","DOIUrl":"https://doi.org/10.1109/PRDC.2006.59","url":null,"abstract":"The k-set agreement problem is a paradigm of coordination problems encountered in distributed computing. The parameter k defines the coordination degree we are interested in. (The case k=1 corresponds to the well-known uniform consensus problem.) More precisely, the k-set agreement problem considers a system made up of n processes where each process proposes a value. It requires that each non-faulty process decides a value such that a decided value is a proposed value, and no more than k different values are decided. This paper visits the k-set agreement problem in synchronous systems where up to t processes can experience failures. Three failure models are explored: the crash failure model, the send omission failure model, and the general omission failure model. Lower bounds and protocols are presented for each model. Open problems for the general omission failure model are stated. This paper can be seen as a short tutorial whose aim is to make the reader familiar with the k-set agreement problem in synchrony models with increasing fault severity. An important concern of the paper is simplicity. In addition to its survey flavor, several results and protocols that are presented are new","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130825013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents the performance analysis of several well-known partitioning scheduling algorithms in real-time and fault-tolerant multiprocessor systems. Both static and dynamic scheduling algorithms are analyzed. Partitioning scheduling algorithms, which are studied, are heuristic algorithms that are formed by combining any of the bin-packing algorithms with any of the schedulability conditions for the rate-monotonic (RM) and earliest-deadline-first (EDF) policies. A tool is developed which enables to experimentally evaluate the performance of the algorithms from the graph of tasks. The results show that among several partitioning algorithms evaluated, the RM-small-task (RMST) algorithm is the best static algorithm and the EDF-best-fit (EDF-BF) is the best dynamic algorithm, for non fault-tolerant systems. For fault-tolerant systems which require about 49% more processors, the results show that the RM-first-fit decreasing utilization (RM-FFDU) is the best static algorithm and the EDF-BF is the best dynamic algorithm. To decrease the number of processors in fault-tolerant systems, the RMST is modified. The results show that the modified RMST decreases the number of required processors between 7% and 78% in comparison with the original RMST, the RM-FFDU and other well-known static partitioning scheduling algorithms
{"title":"Fault-Tolerant Partitioning Scheduling Algorithms in Real-Time Multiprocessor Systems","authors":"H. Beitollahi, Geert Deconinck","doi":"10.1109/PRDC.2006.34","DOIUrl":"https://doi.org/10.1109/PRDC.2006.34","url":null,"abstract":"This paper presents the performance analysis of several well-known partitioning scheduling algorithms in real-time and fault-tolerant multiprocessor systems. Both static and dynamic scheduling algorithms are analyzed. Partitioning scheduling algorithms, which are studied, are heuristic algorithms that are formed by combining any of the bin-packing algorithms with any of the schedulability conditions for the rate-monotonic (RM) and earliest-deadline-first (EDF) policies. A tool is developed which enables to experimentally evaluate the performance of the algorithms from the graph of tasks. The results show that among several partitioning algorithms evaluated, the RM-small-task (RMST) algorithm is the best static algorithm and the EDF-best-fit (EDF-BF) is the best dynamic algorithm, for non fault-tolerant systems. For fault-tolerant systems which require about 49% more processors, the results show that the RM-first-fit decreasing utilization (RM-FFDU) is the best static algorithm and the EDF-BF is the best dynamic algorithm. To decrease the number of processors in fault-tolerant systems, the RMST is modified. The results show that the modified RMST decreases the number of required processors between 7% and 78% in comparison with the original RMST, the RM-FFDU and other well-known static partitioning scheduling algorithms","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116980040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
End-to-end consensus ensures delivery of the same value to the application layer running in distributed processes. Deliveries that have not been acknowledged by the application before a failure are delivered again. End-to-end primitives are important for applications that need to enforce persistency. We present an algorithm that solves the end-to-end consensus problem. Our approach is to build end-to-end consensus using a new type of communication channels, end-to-end channels
{"title":"End-to-end consensus using end-to-end channels","authors":"M. Wiesmann, X. Défago","doi":"10.1109/PRDC.2006.32","DOIUrl":"https://doi.org/10.1109/PRDC.2006.32","url":null,"abstract":"End-to-end consensus ensures delivery of the same value to the application layer running in distributed processes. Deliveries that have not been acknowledged by the application before a failure are delivered again. End-to-end primitives are important for applications that need to enforce persistency. We present an algorithm that solves the end-to-end consensus problem. Our approach is to build end-to-end consensus using a new type of communication channels, end-to-end channels","PeriodicalId":314915,"journal":{"name":"2006 12th Pacific Rim International Symposium on Dependable Computing (PRDC'06)","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123460286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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