Giovanni Pacifici

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Since many Internet applications employ a multi-tier architecture, in this paper, we focus on the problem of analytically modeling the behavior of such applications. We present a model based on a network of queues, where the queues represent different tiers of the application. Our model is sufficiently general to capture (i) the behavior of tiers with(More)
Given a set of machines and a set of Web applications with dynamically changing demands, an online application placement controller decides how many instances to run for each application and where to put them, while observing all kinds of resource constraints. This NP hard problem has real usage in commercial middleware products. Existing approximation(More)
We introduce and evaluate a middleware clustering technology capable of allocating resources to web applications through dynamic application instance placement. We define application instance placement as the problem of placing application instances on a given set of server machines to adjust the amount of resources available to applications in response to(More)
We present an architecture and prototype implementation of a performance management system for cluster-based web services. The system supports multiple classes of web services traffic and allocates server resources dynamically so to maximize the expected value of a given cluster utility function in the face of fluctuating loads. The cluster utility is a(More)
What is the impact of the autocorrelation of variable-bit-rate (VBR) sources on real-time scheduling algorithms? Our results show that the impact of long term, or interframe, autocorrelation is negligible, while the impact of short term, or intraframe, autocorrelation can be significant. Such results are essentially independent of the video coding scheme(More)
Since many Internet applications employ a multitier architecture, in this article, we focus on the problem of analytically modeling the behavior of such applications. We present a model based on a network of queues where the queues represent different tiers of the application. Our model is sufficiently general to capture (i) the behavior of tiers with(More)
Can the introduction of traac classes improve upon the performance of ATM networks? We investigate this issue within the framework provided by a class of networks that guarantees quality of service. To provide a meaningful comparison we deene the concept of schedulable region, a region in the space of loads for which the quality of service is guaranteed. We(More)
A joint scheduling and admission control algorithm is presented for Asynchronous Time-Sharing (ATS)-based switching nodes carrying real-time traffic. Systems based on ATS guarantee quality of service, at both the levels of cells and calls, for three well-defined traffic classes. A mechanism is outlined by which an admission control strategy can be tailored(More)