The derivation of performance expressions for communication protocols from timed Petri net models

Petri Net models have been extended in a variety of ways and have been used to prove the correctness and evaluate the performance of communication protocols. Several extensions have been proposed to model time. This work uses a form of Timed Petri Nets and presents a technique for symbolically deriving expressions which describe system performance. Unlike past work on performance evaluation of Petri Nets which assumes a priori knowledge of specific time delays, the technique presented here applies to a wide range of time delays so long as the delays satisfy a set of timing constraints. The technique is demonstrated using a simple communication protocol

Performance analysis using timed Petri Nets

Petri Nets have been successfully used to model and evaluate the performance of distributed systems. Several researchers have extended the basic Petri Net model to include time, and have demonstrated that restricted classes of Petri Nets can be analyzed efficiently. Unfortunately, the restrictions prohibit the techniques from being applied to many interesting systems, e.g. communication protocols. This paper proposes a version of timed Petri Nets which accurately models communication protocols, and which can be analyzed using Timed Reachability Graphs. Procedures for constructing and analyzing these graphs are presented. The analysis is shown to be applicable to a larger class of Timed Petri Nets than previously thought. The model and the analysis technique are demonstrated using a simple communication protocol

Preemptive D-timed Petri nets, timeouts, modeling and analysis of communication protocols

Preemptive D-timed Petri nets are Petri nets with deterministic firing times and with generalized inhibitor arcs to interrupt firing transitions. A formalism is presented which represents the behavior of free-choice D-timed Petri nets by discrete-space discrete-time semi-Markov processes. Stationary probabilities of states can thus be determined by standard techniques used for analysis of Markov chains. A straightforward application of timed Petri nets is modelling and analysis of systems of asynchronous communicating processes, and in particular communication protocols. Places of Petri nets model queues of messages, transitions represent delays in communication networks, interrupt arcs conveniently model timeout mechanisms, and probabilities associated with free-choice classes correspond to relative frequencies of random events. Simple protocols are used as an illustration of modelling and analysis

Modified D-timed Petri nets, timeouts, and modelling of communication protocols

Modified D-timed Petri nets are Petri nets with ”spe- cial” arcs to interrupt firing transitions, and with deter- ministic firing times; these special arcs are called ”in- terrupt” arcs. It is shown that the behaviour of simple modified bounded free-choice D-timed Petri nets can be represented by finite probabilistic state graphs, stationary probabilities of states can thus be obtained by standard techniques used for analysis of Markov chains. An imme- diate application of such a model is performance analysis of systems of interacting asynchronous processes, and in particular communication protocols. Places of Petri nets model queues of messages, transitions represent events in communication networks, interrupt arcs conveniently model timeouts, and probabilities associated with free- choice classes correspond to relative frequencies of random events. A simple protocol based on unnumbered messages and acknowledgements is used as an illustration of analy- sis

Modeling and analysis of concurrent systems

A survey of modeling and analysis techniques in common use for modeling and analyzing concurrent systems. The models surveyed are CSP (Communicating Sequential Processes), Path Expressions, CCS (Calculus of Communicating Systems), CIRCAL, Petri Nets, Coloured Petri Nets, Predicate-Action Nets, Numerical Petri Nets, Contour-Transition Nets, and several varieties of Timed Petri Nets. The analysis techniques are state-space analysis, temporal logic, structural analysis, and inductive analysis

Transformations of timed Petri nets and performance analysis

There are two basic approaches to analysis of timed Petri net models, the so called reachability analysis and structural analysis. Reachability analysis is based of the space of reachable states while structural analysis derives properties of models from properties of model components and component interconnections. This paper discusses several simple transformations of timed nets that significantly simplify performance analysis preserving all important performance properties of the original model. In particular, they can convert a model that can be analyzed by the reachability approach only into an equivalent one (with respect to performance) that can be analyzed by structural methods

The Impact of Petri Nets on System-of-Systems Engineering

The successful engineering of a large-scale system-of-systems project towards deterministic behaviour depends on integrating autonomous components using international communications standards in accordance with dynamic requirements. To-date, their engineering has been unsuccessful: no combination of top-down and bottom-up engineering perspectives is adopted, and information exchange protocol and interfaces between components are not being precisely specified. Various approaches such as modelling, and architecture frameworks make positive contributions to system-of-systems specification but their successful implementation is still a problem. One of the most popular modelling notations available for specifying systems, UML, is intuitive and graphical but also ambiguous and imprecise. Supplying a range of diagrams to represent a system under development, UML lacks simulation and exhaustive verification capability. This shortfall in UML has received little attention in the context of system-of-systems and there are two major research issues: 1. Where the dynamic, behavioural diagrams of UML can and cannot be used to model and analyse system-of-systems 2. Determining how Petri nets can be used to improve the specification and analysis of the dynamic model of a system-of-systems specified using UML This thesis presents the strengths and weaknesses of Petri nets in relation to the specification of system-of-systems and shows how Petri net models can be used instead of conventional UML Activity Diagrams. The model of the system-of-systems can then be analysed and verified using Petri net theory. The Petri net formalism of behaviour is demonstrated using two case studies from the military domain. The first case study uses Petri nets to specify and analyse a close air support mission. This case study concludes by indicating the strengths, weaknesses, and shortfalls of the proposed formalism in system-of-systems specification. The second case study considers specification of a military exchange network parameters problem and the results are compared with the strengths and weaknesses identified in the first case study. Finally, the results of the research are formulated in the form of a Petri net enhancement to UML (mapping existing activity diagram elements to Petri net elements) to meet the needs of system-of-systems specification, verification and validation