Inhomogeneous continuous-time Markov chains play an important role in different application areas. In contrast to homogeneous continuous-time Markov chains, where a large number of numerical analysis techniques are available and have been compared, few results about the performance of numerical techniques in the inhomogeneous case are known. This paper presents a new variant of the uniformization technique, the most efficient approach for homogeneous Markov chains. The new uniformization technique allows for the stable computation of strict bounds for the transient distribution of inhomogeneous continuous-time Markov chains, which is not possible with other numerical techniques that provide only an approximation of the distribution and asymptotic bounds. Furthermore, another variant of uniformization is presented that computes an approximation of the transient distribution and is shown to outperform standard differential equation solvers if transition rates change slowly.

In contemporary control nets random access schemes like CSMA are often used and are enhanced by fixed priorities for some messages to guarantee an upper bound for the transmission time of high priority messages. However, if used blindly, priorities can result in a substantial discrimination of non-priority messages such that the overall system does not meet the required quality of service. To analyze the effects of introducing priorities, this paper presents an analytical approach for the analysis of control nets working with a specific variant of the CSMA medium access as used in the LonTalk protocol. This approach allows the efficient and sufficiently accurate analysis of network segments under various parameter settings and can be integrated in a general approach for the automated performance analysis of large LON-based automation systems.

In this paper we present an algorithm of the EM-type that performs fitting of PH-distributions with a given number of states to empirical distribution. In contrast to known approaches, the algorithm first generates a discretized representation of the observed data and then performs the fitting. In this way the algorithm is more efficient than other known EM-type methods. By an appropriate discretization, the main part as well as the tail of the distribution can be approximated sufficiently accurate.

CANDY, Computer-Aided Network Design utility is a concept of an efficient XML-based integrated network. design environment. Its integrating component is NDML (Network Design Markup Language), an XML-based problem-oriented language developed for representation of information components related to network projecting within documents. Its design supports interoperability with the XML family of tools and protocols. It provides a set of components to meet the needs of network design.

This paper introduces an approach for modelling QoS providing mechanisms for computer networks. The presented model of a class based queuing (CBQ) mechanism was built by means of generalized stochastic Petri nets and was analysed with numerical techniques.The developed model of CBQ is applied as basic model in the optimisation procedure for the minimisation of the sum of delays of through-passing data flows with constrains on the maximal affordable delay for each flow. The presented optimisation approach can be applied to other goal functions (e.g. minimization of the sum of loss probabilities) to investigate performance of QoS providing mechanisms.