网络系统可生存性评估与增强技术研究概述

网络系统可生存性是网络安全研究的新方向,它突破了传统的网络安全的概念,从新的角度对网络安全问题进行研究.本文首先对网络系统可生存性研究领域进行了总结,回顾了可生存性概念以及可生存系统的关键属性,论述了可生存性评估和增强技术之间的关系.然后,阐述了国内外可生存性评估模型以及可生存性增强技术的研究现状和技术方法,分析了不足之处,并提出可生存性评估技术与增强技术的结合,以及生存性进化等方面是未来发展方向.     

系统可生存性研究综述

系统可生存性是信息安全的新研究方向，是对传统安全观念的突破和创新。本文首先给出了开展系统可生存性研究的必要性以及系统可生存性若干定义；基于此，结合可生存性的评测和增强技术研究，从计算系统可生存性、网络可生存性、服务可生存性以及软件可生存性4个角度，综述了可生存性的研究现状，并进行了国内外对比分析；随后探讨了可生存系统的设计与实现问题，最后描述了系统可生存性的发展趋势。     

网络可生存性研究概述

网络可生存性是网络安全研究的新方向,它突破了传统的网络安全的概念,从新的角度对网络安全问题进行研究。该文首先分析了可生存性与传统网络安全技术的差别,并给出了生存性的基本定义,然后介绍了可生存系统设计的两种设计方法,并对两种设计方法进行了对比分析。     

基于Tabu算法的分布式系统可生存性增强

分布式系统的可生存性研究已经成为当前安全领域关注的热点,如何提高系统的可生存性就成为了一个重要的研究内容,该文就从系统结构优化的角度研究了提高系统可生存性的方法。在文章中,以一个分布式系统作为案例,首先建立系统的仿真模型,然后通过3个实验证明了系统结构的变化能够影响系统的可生存性;最后提出利用Tabu搜索算法来优化系统的体系结构,以得到一个在限定条件下可生存性指标最好的系统结构。该文提出的方法是一种全新的思路,并具有一定的实用价值。     

信息系统可生存性定量评估的指标体系

从内容、攻击阶段、测定标准等不同角度综合分析可生存性指标,提出一种能系统地反映可生存性的指标体系,给出其形式化描述和数学模型。分析与验证结果表明,该指标体系具有规范性、完备性,对信息系统可生存性的定量评估具有指导意义。     

网络可生存性研究进展

网络可生存性研究是对传统的安全概念和技术的突破,已经成为网络安全研究的新方向。该文首先分析了可生存性与传统安全概念的差异,通过对网络可生存性研究现状的分析和概括,总结出了可生存性定义要素、测定标准、实现技术及相关研究的一些共识。然后对国外可生存性研究的主要进展——可生存系统分析方法SSA进行了深入探讨,并分析了网络可生存性研究的发展趋势,最后对实现可生存性的两种不同方法进行了对比分析。     

可生存性分析方法研究

系统在受到入侵后依然能够提供必要服务,并在一定时间内恢复受侵害的服务是系统可生存性的本质要求,与传统的将可生存性作为非功能系统属性描述的方法不同,将可生存性作为系统统一系统功能来研究,并用形式化语言来描述,定义和计算是一种全的思路和方法,对可生存性分析阶段可以采用的方法进行了深入的研究,分析,其中重点阐述了工作流回溯,攻击树建立等可生存性需求分析的方法,并给出了可生存性量化分析的算法。     

基于状态转换的信息服务系统可生存性评估方法

可生存性评估是使用各种方法对目标系统进行定性及定量的生存性分析。本文提出了一个基于状态转换的信息服务系统可生存性评估方法,该方法包括一个系统生存性模型和一个生存性函数的定义。最后给出了使用这种评估方法对目标系统进行评估的实例。     

网络系统的可生存性研究综述

本文比较了不同的网络系统可生存性的定义并指出了其中最具本质特征的定义,介绍了网络系统可生存性研究的进展,包括可生存性的分解和可生存系统的特性、定量评估、体系结构以及设计方法,回顾了可生存性研究中存在的问题,探讨了以后的研究方向。     

基于随机Petri网的电信交换系统可生存性分析

网络系统的可生存性问题是系统安全领域的一个重点研究方向。讨论现有的系统可生存性的一般分析方法,确定系统的可生存属性,并采用随机Petri网(SPN)技术,分析电信交换系统生存性问题的特点。重点利用随机Petri网描述系统的失效-修复分析模型和性能分析模型,给出系统可生存性分析中主要指标的定量计算方法。系统仿真结果表明了该方法的有效、合理性。     

复杂网络可靠性评价方法综述

阐述了网络可靠性及相关概念,从抗毁性、生存性、有效性、完成性4个方面对网络可靠性评价指标进行了分类、总结,进一步分析探讨了网络可靠性评估方法,最后对未来的网络可靠性研究工作进行了展望.     

多层服务器集群的可用性能评价

本文对多层服务器机群系统的可用性能评价方法进行了研究，并将可用性能作为系统容量规划评价指标，提出基于边际分析容量规划的MACPA算法，从而有效地降低了规划求 解的计算复杂度。模拟实验显示，在三层服务器条件下，MACPA算法所产生的规划方案可以获得相对最优方案99％以上的可用性能。     

一种卫星网络拓扑抗毁性评价方法的研究

从卫星网络高动态、周期性的特点出发,针对现有基于跳面节点法的网络拓扑结构的抗毁性评估方法对相似拓扑结构区分度不高的问题,提出新的抗毁性评估方法。该方法定义了新的修正因子,在理论上统一了基于跳面节点法及其改进方法的数学解析表达式,并且该方法适用于高动态卫星网络拓扑结构的抗毁性评估。仿真实验验证表明,该方法对不同拓扑结构的区分度更高,更具合理性。     

Quantifying the performability of cluster-based services

In this paper, we propose a two-phase methodology for systematically evaluating the performability (performance and availability) of cluster-based Internet services. In the first phase, evaluators use a fault-injection infrastructure to characterize the service's behavior in the presence of faults. In the second phase, evaluators use an analytical model to combine an expected fault load with measurements from the first phase to assess the service's performability. Using this model, evaluators can study the service's sensitivity to different design decisions, fault rates, and other environmental factors. To demonstrate our methodology, we study the performability of a multitier Internet service. In particular, we evaluate the performance and availability of three soft state maintenance strategies for an online bookstore service in the presence of seven classes of faults. Among other interesting results, we clearly isolate the effect of different faults, showing that the tier of Web servers is responsible for an often dominant fraction of the service unavailability. Our results also demonstrate that storing the soft state in a database achieves better performability than storing it in main memory (even when the state is efficiently replicated) when we weight performance and availability equally. Based on our results, we conclude that service designers may want an unbalanced system in which they heavily load highly available components and leave more spare capacity for components that are likely to fail more often.     

基于可生存性的系统安全评估方法

提出了一种新的计算机系统可生存能力的分析方法，该方法综合考虑系统外部环境和内部组件及其之间的相互关系，描述了系统的可生存能力。阐述了利用该方法对系统进行安全评估的措施及其优势。     

Performability analysis of guarded-operation duration: a translation approach for reward model solutions

Performability measures are often defined for analyzing the worth of fault-tolerant systems whose performance is gracefully degradable. Accordingly, performability evaluation is inherently well suited for application of reward model solution techniques. On the other hand, the complexity of performability evaluation for solving engineering problems may prevent us from utilizing those techniques directly, suggesting the need for approaches that would enable us to exploit reward model solution techniques through problem transformation. In this paper, we present a performability modeling effort that analyzes the guarded-operation duration for onboard software upgrading. More specifically, we define a “performability index” Y that quantifies the extent to which the guarded operation with a duration φ reduces the expected total performance degradation. In order to solve for Y, we progressively translate its formulation until it becomes an aggregate of constituent measures conducive to efficient reward model solutions. Based on the reward-mapping-enabled intermediate model, we specify reward structures in the composite base model which is built on three stochastic activity network reward models. We describe the model-translation approach and show its feasibility for design-oriented performability modeling.     

Performability assessment by model checking of Markov reward models

This paper describes efficient procedures for model checking Markov reward models, that allow us to evaluate, among others, the performability of computer-communication systems. We present the logic CSRL (Continuous Stochastic Reward Logic) to specify performability measures. It provides flexibility in measure specification and paves the way for the numerical evaluation of a wide variety of performability measures. The formal measure specification in CSRL also often helps in reducing the size of the Markov reward models that need to be numerically analysed. The paper presents background on Markov-reward models, as well as on the logic CSRL (syntax and semantics), before presenting an important duality result between reward and time. We discuss CSRL model-checking algorithms, and present five numerical algorithms and their computational complexity for verifying time- and reward-bounded until-properties, one of the key operators in CSRL. The versatility of our approach is illustrated through a performability case study.     

Performability evaluation of emergency call center

Emergency call centers serve people in utmost circumstances; hence they should be highly dependable. Availability and performance are key aspects in call centers. Architectural models, service policies, and redundancies are attributes for defining and evaluating the overall operation of such systems. In this work, we performed the performability evaluation of an important emergency call center located in a large city in Brazil. The results showed that the system’s downtime is considered high, so, we proposed a new architecture to improve the system’s performability. The results obtained in this paper can be used to provide support for decisions on interventions in the emergency call center to improve its performability. It is expected that the models presented in this paper will be useful in a variety of emergency call centers.     

网格监控体系结构的一种可执行性模型

为网格监控体系结构建立可执行性模型有助于网格监控系统的服务质量提升.因为网格环境的动态性和不可靠性,所以对网格监控体系结构建模时要从可用性和性能两方面综合考虑.讨论系统可用性、响应时间分布、事件丢失概率、公平性等问题.用随机Petri网建立网格监控体系结构的可执行性模型并讨论了模型的应用.网格监控体系结构的系统模型有一个关键特性：事件发布信息和监控事件数据由不同通道传递,在模型中重点关注这一特性.     

Reward model solution methods with impulse and rate rewards: an algorithm and numerical results

Reward models have become an important method for specifying performability models for many types of systems. Many methods have been proposed for solving reward models, but no method has proven itself to be applicable over all system classes and sizes. Furthermore, specification of reward models has usually been done at the state level, which can be extremely cumbersome for realistic models. We describe a method to specify reward models as stochastic activity networks (SANs) with impulse and rate rewards, and a method by which to solve these models via uniformization. The method is an extension of one proposed by de Souza e Silva and Gail in which impulse and rate rewards are specified at the SAN level, and solved in a single model. Furthermore, we propose a new technique for discarding paths in the uniformized process whose contribution to the reward variable is minimal, which greatly reduces the time and space required for a solution. A bound is calculated on the error introduced by this discarding, and its effectiveness is illustrated through the study of the performability and availability of a degradable multi-processor system.