An Algorithm for Computing Serial Correlations of Times in GI/G/1 Queues with Rational Arrival Processes

An algorithm is given for computing the serial correlations of the waiting time, and of the time in system, for successive customers in a GI/G/1 queue. The method depends on representing the inter-arrival time distribution in terms of a process in class K r (i.e., distributions with a rational Laplace transform). Thus Erlang, hyperexponential and weighted sum-of-Erlang arrivals are treated exactly, and approximate results can be found for other distributions. Computed correlation functions for some Erlang/Erlang systems are presented as examples.autocorrelation function, general queue, waiting times, computation

Distributed fault location in networks using mobile agents

This paper describes how multiple interacting swarms of adaptive mobile agents can be used to locate faults in networks. The paper proposes the use of distributed problem solving using mobile agents for fault finding in order to address the issues of client/server approaches to network management and control, such as scalability and the difficulties associated with maintaining an accurate view of the network. The paper uses a recently described architectural description for an agent that is biologically inspired and proposes chemical interaction as the principal mechanism for inter-swarm communication. Agents have behavior that is inspired by the foraging activities of ants, with each agent capable of simple actions; global knowledge is not assumed. The creation of chemical trails is proposed as the primary mechanism used in distributed problem solving arising from the self-organization of swarms of agents. Fault location is achieved as a consequence of agents moving through the network, sensing, acting upon sensed information, and subsequently modifying the chemical environment that they inhabit. Elements of a mobile code framework that is being used to support this research, and the mechanisms used for agent mobility within the network environment, are described

Management of compositions of E- and M-business web services with multiple classes of service

The concept of a Web Service, as defined by W3C, represents a distributed component using XML messaging. Compositions of Web Services are increasingly used to create new IT capabilities fast and flexibly, in an ad hoc manner. The presented work extends the W3C concept of a Web Service in two ways. First, we enable a Web Service to offer several variations of service and QoS. In other words, we add the concept of classes of service for Web Services. This widens usability of a particular Web Service. Second, we explore dynamic (i.e., run-time) adaptation and management based on the manipulation of classes of service. Our dynamic adaptation mechanisms include switching, deactivation/reactivation, and creation of classes of service. Management and dynamic adaptation of Web Service compositions further improve the overall flexibility and adaptability of IT systems using Web Services

Analytical comparisons of switching of web services and switching of service offerings

Dynamic (run-time) adaptation of web service compositions (choreographies and orchestrations) is needed to accommodate various changes and disturbances like poor performance of composed web services. We explain in detail a novel analytical methodology for comparing various approaches to dynamic adaptation of web service compositions. This methodology is based on comparing the number of exchanged SOAP messages. Furthermore, we present formulae generated by this methodology for switching of web services and switching of service offerings (classes of service). These formulae quantify the extent to which switching of service offerings is faster and simpler. The presented results complement previous publications that discussed the corresponding experimental comparisons of dynamic adaptation approaches