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This paper introduces an extension of the Generalized Stochastic Petri Net (GSPN) formalism in order to enable the computation of first passage time distributions of tokens. A “tagged token” technique is used which relies on net’s structural properties to guide the correct specification of this extension. The extended model is suited for an automatic translation into an ordinary GSPN that can be used...
RAID systems are ubiquitously deployed in storage environments, both as standalone storage solutions and as fundamental components of virtualised storage platforms. Accurate models of their performance are crucial to delivering storage infrastructures that meet given quality of service requirements. To this end, this paper presents a flexible fork-join queueing simulation model of RAID systems that...
We develop models of automated E-commerce techniques, which predict the economic outcomes of these decision mechanisms, including the price attained by a good and the resulting income per unit time, as a function of the rate at which bidders provide the bids and of the time taken by the seller to decide whether to accept a bid. This paper extends previous work in two main directions. Since automated...
Among the proposed techniques for the analysis of non-Markovian models the state space expansion approach showed great flexibility in terms of modelling capacities. The principal drawback is the explosion of the state space. An attempt to alleviate such problem has been made in [1] but the storing of the reachability graph of the untimed system, augmented with information about active but not enabled...
In this paper a class of closed queueing network is modelled in the Markovian process algebra PEPA and solved using the classical Mean Value Analysis (MVA). This approach is attractive as it negates the need to derive the entire state space, and so certain metrics from large models can be obtained with little computational effort. The class of model considered includes models which are not obviously...
This paper presents a performance model interoperability framework that brings together performance model interchange formats and experiment specifications with the automatic generation of performance analysis results for presentation and publication. We define the Use Cases and requirements and survey output and results used in practice. We present the output specification, the issues in the output-to-results...
The paper presents a new simple analytical method for a determination of the blocking probability in a full-availability group carrying a mixture of different multi-rate traffic classes with the compression property. The proposed model can be directly used for modelling of the Iub interface in the UMTS network servicing the Release 99 and HSDPA traffic classes. The described model can be applied for...
One of the main attractions of the stochastic process algebra PEPA is its clear compositional structure which allows building a model from elements which reflect the composition of the system to model. Dynamic Fault Trees (DFTs) constitute a simple combinatorial formalism which allows capturing the dynamic behaviour of system failure mechanisms. The resulting model is a combination of component failure...
Passage-end calculations are a new style of passage measurement for eXtended Stochastic Probes (XSP) [1] which add the ability to split the analysis into several cases depending on conditions which hold at the end of a passage. This makes it possible to separate successful responses to a request from negative responses, timeouts or other failures. This allows the expression of service level agreements...
Stochastic monotonicity is one of the sufficient conditions for stochastic comparisons of Markov chains. On a partially ordered state space, several stochastic orderings can be defined by means of increasing sets. The most known is the strong stochastic (sample-path) ordering, but weaker orderings (weak and weak*) could be defined by restricting the considered increasing sets. When the strong ordering...
To evaluate peer-to-peer systems through discrete-event simulation, one needs to be able to generate sufficiently large networks of nodes that exhibit the desired properties, such as the scale-free nature of the connectivity graph. In applications such as the web of trust or analysis of hyperlink structures, the direction of the arcs between two nodes is relevant and one therefore generates directed...
In this paper we investigate the behaviour of a peer to peer driven Grid computing network. We present mean field approximation of the simulation model and show that it captures the essence of the model. In contrast to earlier work we limit the budget of the nodes and observe the consequences for the price development. We also show that the proposed peer to peer network scales much better than a central...
The paper studies a technique to improve the utility and performance of an automated auction application where the auctioneer and bidders communicate through the Internet. The lack of quality-of-service guarantees from site to site can severely influence the results of an auction by affecting the seller’s income rate, auction fairness, and overall protocol efficiency. By properly identifying and migrating...
The paper proposes an analytical approach to blocking probability calculation in the UMTS network. In the proposed method, handoff connections are modelled on the basis of the fixed point methodology. The results of analytical calculation of the blocking probability in the group of cells carrying a mixture of different multi-rate traffic streams are compared with the results of simulation experiments,...
An analytical model of the Transmission Control Protocol (TCP) New Reno [7] performance through a Continuous-Time Markov Chain (CTMC) is presented and its theoretical predictions are corroborated by the well known network simulator ns-2 [15]. An existing TCP Reno model [6] is modified in order to characterise the NewReno algorithm. The NewReno version is modelled given its proven better performance...
Lately, the number of Internet users and, correspondingly, the amount of traversing traffic is growing extremely fast. In spite of the fact that transmission links – mostly optical fibres – have high capacity, the internet routers still remain a point of traffic bottleneck. The construction of highly scalable switches for high-speed transmission still remains a real challenge for designers. In this...
Network coding (NC) has been proposed as a way to compress flows of packets by combining different packets, provided that there is sufficient redundancy through multiple transmission paths so that the receiving nodes can then decode the flows to reconstruct all of the individual packets. However NC does introduce additional computational overhead, and also creates different additional delays which...
The necessity of studying sensor networks, rich internet applications, social networks and molecular biology have raised the need of being able to consider systems composed by very large population of similar objects. This lead to the development of new modelling paradigms, such as Fluid Process Algebra, Mean Field analysis and Markovian Agents. These methodologies produces exact results if the number...
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