Queueing networks are a powerful abstraction for modeling systems involving contention for resources, e.g., manufacturing lines and computer systems. Queueing networks are especially effective in modeling computer communication systems. Most papers concerning queueing models of communication describe analytic solution of queueing models. This paper describes simulation models based on "extended" queueing networks. The primary advantage of using a queueing network representation for simulation of a computer communication system is the high level of description, in comparison with conventional simulation programming languages. For queueing network models to be used effectively for simulation of contention systems, appropriate software is needed. The research queueing package (RESQ) is a general purpose tool for modeling contention for resources and associated system characteristics. RESQ facilitates i) appropriate abstraction of system characteristics through its definitions of extended queueing networks, ii) efficient and convenient definition and revision of models through its integrated interactive and batch model definition interface, and iii) effective experimentation with simulation models through facilities for parameterized sets of experiments, interactive running of simulations and statistical analysis of simulation results. With a tool such as RESQ, an analyst can produce results in days instead of weeks, and so an analyst can answer questions which otherwise would be left unanswered.

Queueing networks are important as performance models of computer and communication systems.Exact numerical solution of a queueing network is usually only feasible if the network has a product form solution in the sense of Jackson.Product form networks allow a rich variety of forms of statedependent behavior.However, efficient computational algorithms have not been developed for several of the allowed forms of state-dependent behavior.This paper develops the two most important computational algorithms.Convolution and Mean Value Analysis, to apply to forms of state-dependent behavior allowed in product form networks.It is demonstrated that these two algorithms are of equal generality, contrary to common belief.

Abstract Several requirements are placed on queueing models of computer systems. These include credibility, accuracy, timeliness and cost. Modelling software can have critical impact on all of these requirements. We survey the characteristics of major pieces of queueing software. Based on this survey we synthesize a set of design objectives for queueing software. Finally, we discuss our own queueing network software, the Research Queueing Package (RESQ), in light of these objectives.

This paper considers the selection of capacities, in two classes of open queueing network models of computer communication systems: 1) local-balanced queueing networks with multiple classes of customers and 2) the Reiser-Kobayashi diffusion approximation model. The problem of selecting optimal bandwidths for communication lines and switches and computing machinery is difficult due to 1) the economy of scale exhibited by components (i.e., the bandwidth per dollar increases with the total cost of the component) and 2) the discrete nature of computer/communication components (for instance it is possible to lease communication lines with 2400-Bd or 4800-Bd band-widths but not one with a 2401.3-Bd bandwidth). This paper develops aun algorithm to select servers taking both of these characteristics of server costs into account. The contribution of this paper is to discuss 1) the optimization of more general network models with 2) the consideration of more realistic tariffs and 3) more constraints on network behavior than were previously analyzed.