In this paper we present a class of nested automata for the modelling of performance, availability, and reliability of software systems with hierarchical structure, which we call systems of systems. Quantitative modelling provides valuable insight into the dynamic behaviour of software systems, allowing non-functional properties such as performance, dependability and availability to be assessed...

Performability is a composite measure for the performance and reliability, which may be interpreted as the cumulative performance over a nite mission time. The computation of its distribution allows the user to ensure that the system will achieve a given performance level. The system is assumed to be modeled as a Markov process with nite state space and a reward rate (performance measure) is as...

ÐPoint availability and expected interval availability are dependability measures respectively defined by the probability that a system is in operation at a given instant and by the mean percentage of time during which a system is in operation over a finite observation period. We consider a repairable computer system and we assume, as usual, that the system is modeled by a finite Markov process...

In this paper, we investigate an efficient off-line scheduling algorithm in which real-time tasks with precedence constraints are executed in a heterogeneous environment. It provides more features and capabilities than existing algorithms that schedule only independent tasks in real-time homogeneous systems. In addition, the proposed algorithm takes the heterogeneities of computation, communica...

Degradable performance of fault-tolerant computer systems has given rise to considerable interest in mathematical models for combined evaluation of performance and reliability. Most of these models are based upon Markov processes. Several methods have been proposed for the computation of the probability distribution of performability upon an interval of time 0; t]. In this paper, two closed for...

The widespread integration of virtualization technologies in data centers has enabled in the last few years several benefits in terms of operating costs and flexibility. These benefits maybe boosted through join optimization of power management (PM) and dependability for virtualized systems. This indeed involves developing appropriate models to better understand their performability behavior wh...

Abstmct~uorum attainment protocols are an important part of many mutual exclusion algorithms. Assessing the performance of such protocols in terms of number of messages, as is usually done, may be less significant than being able to compute the delay in attaining the quorum. Some protocols achieve higher reliability at the expense of increased message cost or delay. A unified analytical model w...

Markov chains (and their extensions with rewards) have been widely used to determine performance, dependability and performability characteristics of computer communication systems, such as throughput, delay, mean time to failure, or the probability to accumulate at least a certain amount of reward in a given time. Due to the rapidly increasing size and complexity of systems, Markov chains and ...

Dynamic Host Configuration Protocol (DHCP) is designed to provide an automatic mechanism for the allocation, configuration and management of IP addresses and TCP/IP protocol stack parameters of computers and devices in IP networks. The important feature of DHCP is a “dynamic allocation” mechanism, which assigns an IP address to a client for a limited period of time (called a lease time). Theref...