Edward A. MacNair

Performance study of a collaborative method for hierarchical caching in proxy servers

With the increasing popularity of the World Wide Web, it is desirable to store copies of popular documents in client and proxy caches and thus reduce the network delay times for URL requests. In this paper we study the caching problem for Web documents in a hierarchy of collaborating proxy servers. Specifically, the focus of our work is to reduce duplicate caching between a proxy and its parent or higher level proxies in the hierarchy when making a caching decision. A collaboration protocol passes caching decision information along with the object to the next lower level proxy to facilitate its caching decision. We analyze the performance of the collaborative method and the conventional method by means of event driven simulation. The collaborative approach is found to provide a much more effective use of the caching resource. Various sensitivity analyses have been conducted. This result is found to be relatively insensitive to the nature of the workloads.

Queueing network software for systems modelling

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.

The research queueing package: past, present, and future

Queueing networks are important as performance models of systems where performance is principally affected by contention for resources. Such systems include computer systems, communication networks, office systems and manufacturing lines. In order to effectively use queueing networks as performance models, appropriate software is necessary for definition of the networks to be solved, for solution of the networks (by numerical, approximate and/or simulation methods) and for examination of the performance measures obtained. One of the most widely known and influential pieces of queueing network software is the Research Queueing Package (RESQ). This paper discusses the evolution of RESQ and plans for further RESQ development.

Analysis of manufacturing systems by the Research Queueing Package

Many aspects of manufacturing systems can be analyzed using simulation to model the systems behavior. The Research Queueing Package (RESQ) is a tool developed to construct and solve models of systems with jobs contending for service from many resources. The capabilities of RESQ are described in order to understand the model elements which are available for representing manufacturing systems. Then an analysis of several work-in-process (WIP) policies is presented using RESQ models solved by simulation. Four WIP management policies are analyzed and compared for a future assembly manufacturing line: (1) a push system, (2) a pull system, (3) a transfer line, and (4) a closed loop system.

300 mm wafer fabrication line simulation model

The importance of semiconductor wafer fabrication has been increasing steadily over the past decade. Wafer fabrication is the most technologically complex and capital intensive phase in semiconductor manufacturing. It involves the processing of wafers of silicon in order to build up layers and patterns of metal and wafer material. Many operations have to be performed in a clean room environment to prevent particulate contamination of wafers. Also, since the machines on which the wafers are processed are expensive, service contention is an important concern. All these factors underline the importance of seeking policies to design and operate them efficiently. We describe a simulation model of a planned 300 mm wafer fabrication line that we are using to make strategic decisions related to the factory.

RESQ: a package for solution of generalized queueing networks

RESQ (RESearch Queueing) is a tool for solution of queueing networks. The class of networks treated includes general multi-server queues, passive queues and complex routing decisions. Multiple solution techniques are provided, including numerical solution of separable balance equations and regenerative simulation. User access is provided through both interactive dialogue and a subroutine level interface.

A general methodology for characterizing access patterns and analyzing Web server performance

We develop a general methodology for characterizing Web server access patterns based on a spectral analysis of finite collections of observed data from real systems. Our approach is used together with the access logs from the IBM Web site for the 1996 Olympic Games to demonstrate some of its advantages over previous methods and to analyze certain aspects of large-scale Web server performance.

IBM journey management library: an arena system for airport simulations

Airline passenger terminal congestion caused by increasing passenger traffic results in unsatisfactory levels of customer service. We discuss a simulation modelling tool to help airlines and airports to use advanced technology to improve service to passengers. The tool consists of custom designed, reusable modules that represent the most common airline and airport system data, logic and processes. A model of an actual airline operation based on this approach is described.

An introduction to the Research Queueing Package

The Research Queueing Package (RESQ) is a general purpose modeling tool for constructing and solving extended queueing network models of computer systems, communication networks, automated manufacturing systems and other types of contention systems. This paper is an introduction to RESQ which describes the basic model elements, submodels, statistical output analysis and graphical results.

A model of a 300mm wafer fabrication line

Semiconductor factories are very expensive to build and operate. It is critical to understand how to design and operate them efficiently. We describe a simulation model of a planned 300mm wafer fabrication line that we are using to make strategic decisions related to the factory.