The principle of program control means that the processor core turns to the main memory of the computer for operands or instructions. According to architectural features, operands are stored in data segments, and instructions are stored in code segments of the main memory. The operating system uses both page memory organization and segment memory organization. The page memory organization is always mapped to the segment organization. Due to the cached packet cycles of the processor core, copies of the main memory pages are stored in the internal associative cache memory. The associative cache memory consists of three units: a data unit, a tag unit, and an LRU unit. The data unit stores operands or instructions, the tag unit contains fragments of address information, and the LRU unit contains the logic of policy for replacement of string. The missing event attracts LRU logic to decide for substitution of reliable string in the data unit of associative cache memory. The pseudo-LRU algorithm is a simple and better substitution policy among known substitution policies. Two options for the minimization of the hardware for replacement policy by the pseudo-LRU algorithm in q - directed associative cache memory is implemented. The transition from the trigger structure of the synchronous D-trigger to the trigger structure of the synchronous JK-trigger is carried out reasonably in both options. The first option of minimization is based on the sequence for updating of the by the algorithm pseudo LRU, which allows deleting of the combinational logic for updating bits of LRU unit. The second option of minimization is based on the sequence for changing of the q - index of direction, as the consequence for updating the bits of LRU unit by the algorithm pseudo LRU. It allows additionally reducing the number of memory elements. Both options of the minimization allow improving such characteristics as productivity and reliability of the LRU unit.
The article considers the methodology of ensuring the dependability of information and control systems using multi-purpose maintenance strategies. The relevance of research is due to the need to ensure the functioning of dependable information and control systems in the face of changes in requirements, environmental parameters, and the manifestation of unspecified failures of their components. The methodology is presented at the system level as a combination of the concept of multi-purpose maintenance, as well as the principles of taking into account changes in the information and control system and environment during the life cycle; comprehensive consideration of different types of failures, and the effects of change; multi-purpose maintenance and combines a set of new models and methods for determining the parameters of dependability information and control systems and the choice of parameters for their maintenance procedures. The proposed concept of multi-purpose maintenance is obtained by developing the Fon-Neumann paradigm and is formulated as a concept of building reliable and secure systems from insufficiently dependable components and multi-purpose maintenance on combined strategies in changing conditions and environment. The scope of the proposed concept is applicable in cases where the principles of von-Neumann do not allow building a viable system due to economic, temporal, or other reasons. In this case, the use of principles, methods, and models that are conceptual, extends to information and control systems built using maintained components and system multi-purpose service strategies. The proposed principle of taking into account changes involves the expansion of the classical control circuit of the fault-tolerant system, which response to the fault occurrence as errors and failures. The principle of comprehensive consideration of different types of failures and the effects of change is a continuation of the principles of unity and connection during the procedures of system analysis. It is also a logical continuation of the facet arrangement of fault types and chains of causal relationships from faults and defects to faults, failures, and errors. Within the framework of the proposed methodology, multi-purpose maintenance strategies, a set of options for goals, types, processes, properties, and parameters of information and control systems have been developed, which reduces model uncertainty and justifies practical measures to ensure dependability at different stages of the life cycle.
The article is devoted to the analysis of a variant of two-version multi-module web application using cloud services. As the design and development of web applications are increasingly active, there is a need to increase their reliability in the face of the increasing complexity of the applications themselves and the infrastructure on which they are based. One of the key solutions to this problem is the use of cloud services, which can greatly simplify the task of ensuring the reliability and security of various applications. At the same time, cloud providers cannot fully guarantee the fault tolerance of applications that run in their environment. Therefore, users should worry about this themselves. One of the most promising approaches is the use of diversity to increase the security and reliability of web applications hosted in the clouds. The object of research and analysis of this work is a multi-module web application designed using cloud services. The study of this work aims to compare modern solutions and technologies that allow implementing sabotage for a web application. Since many companies are moving their infrastructure to the clouds, it becomes necessary to consider the possibility of using diversity by cloud services. They allow you to create and deploy web applications developed in various programming languages on the servers of cloud providers. Thus, part of the responsibility for ensuring reliability is transferred to them. However, it is still necessary to ensure the resiliency of your programs, which may fail due to defects in the program code. One of the main solutions to this problem is N-version programming, which allows you to create an application from several independent versions. Each version can be written in different programming languages and using various technologies by separate development teams, thereby increasing the reliability of the final software product. As a result, in this paper, we conclude that leading cloud providers provide the opportunity to implement diversity using services of various presentation models, such as IaaS and PaaS. Using the principle of diversity, you can design a reliable web application that will avoid its failure in case of an error in the program code.
The world trends in increasing of threats of natural and man-made nature, a level of terrorist threats, the number and complexity of cyberattacks have caused the actualization of needs for critical information infrastructure protection and improvement it's informational security and functional safety. A critical information infrastructure is considered as a set of information and telecommunication systems, improper operation of which may lead to the occurrence of an accident of critical infrastructure (energy, transport, etc.), as well as to decrease in quality of its services. The subject of paper’s study is the mechanisms for ensuring the safety (protection) of critical information infrastructures. The purpose of the paper is to substantiate the approach to the development of methodological foundations and technologies for assessing and ensuring the safety (protection) of critical information infrastructures taking into account the state and capabilities of modern information technologies. The methods used are: systems analysis methods, mathematical optimization methods, safety, and risk theory methods. The following results were obtained. The main tasks of the critical infrastructure protection system are formulated. The necessity of using the system of protection of critical information infrastructure as part of the system of protection of critical infrastructure is substantiated. The concept and principles of the methodology for assessing and ensuring the safety (protection) of critical information infrastructures are developed, working hypotheses, methods and models necessary for their implementation are suggested. The way of interaction of the elements of the proposed methodology, tasks and elements of the critical infrastructure protection system is shown. The results obtained are aimed at solving of one fundamental problem such as the existence of a contradiction between the intensive development of critical information infrastructures, negative influences and threats of various nature and the lack of methodological foundations, models, methods and information technologies for assessment and assurance of critical information infrastructure security and safety. The results obtained should be used to create elements of informational and analytical support for the decision maker in solving tasks related to the assessment and security (protection) of critical infrastructure
The rapid development of information technology has expanded the capabilities of cyberthreads regarding computer systems. Cybercriminals are developing new ways to avoid attack detection, so existing approaches are not able to withstand the growing threat of attacks. Meanwhile, the consequences of cyberattacks are becoming more dangerous and destructive. One of the approaches to solve the problem is the construction of resilient systems that are able to quickly recover and continue to function under attack conditions. The subject of research is the construction process of the resilient computer systems in the face of cyber threats. The goal is to develop a taxonomy and ontology of resilient computer systems under cyberthreats. Results. The article presents the definitions of the resilience from the point of view of cybersecurity, presents the gap between the concepts of resilience and dependability. The paper presents the main elements of the taxonomic scheme of computer system resilience, which include threats (changes in the environment and requirements, network attacks, attacks on software, software and hardware vulnerabilities, errors, failures), information and technical conditions that computer system passes during its operating cycle, the principles on which resilience is based (proactivity, adaptability, resistance, diversity, elasticity, controlled degradation, defense in depth, ability to evolvability), as well as primary and secondary properties. Based on the above elements, a generalized taxonomic scheme of resilience related to information security has been developed. The work presents the operational cycle of a resilient CS as a set of information and technical states that the system goes through (preparation, system protection, threat detection, threat absorption, response to a threat, system recovery after a cyberattack, adaptation.) An ontology scheme of the resilience from the point of view of information security of computer systems in the presence of cyberthreats is developed. Conclusions A taxonomy and ontology of resilient computer systems in the presence of cyberthreats has been developed.
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