this paper, Gnutella is no exception to this finding, and an experimental study of its user patterns shows indeed that free riding is the norm rather than the exception. If distributed systems such as Gnutella rely on voluntary cooperation, rampant free riding may eventually render them useless, as few individuals will contribute anything that is new and high quality. Thus, the current debate over copyright might become a non-issue when compared to the possible collapse of such systems. This collapse can happen because of two factors, the tragedy of the digital commons, and increased system vulnerability, which we now discuss

This paper presents lottery scheduling, a novel randomized resource allocation mechanism. Lottery scheduling provides efficient, responsive control over the relative execution rates of computations. Such control is beyond the capabilities of conventional schedulers, and is desirable in systems that service requests of varying importance, such as databases, media-based applications, and networks. Lottery scheduling also supports modular resource management by enabling concurrent modules to insulate their resource allocation policies from one another. A currency abstraction is introduced to flexibly name, share, and protect resource rights. We also show that lottery scheduling can be generalized to manage many diverse resources, such as I/O bandwidth, memory, and access to locks. We have implemented a prototype lottery scheduler for the Mach 3.0 microkernel, and found that it provides flexible and responsive control over the relative execution rates of a wide range of applications. The overhead imposed by our unoptimized prototype is comparable to that of the standard Mach timesharing policy.

This paper presents stride scheduling, a deterministic scheduling technique that efficiently supports the same flexible resource management abstractions introduced by lottery scheduling. Compared to lottery scheduling, stride scheduling achieves significantly improved accuracy over relative throughput rates, with significantly lower response time variability. Stride scheduling implements proportional-share control over processor time and other resources by cross-applying elements of rate-based flow control algorithms designed for networks. We introduce new techniques to support dynamic changes and higher-level resource management abstractions. We also introduce a novel hierarchical stride scheduling algorithm that achieves better throughput accuracy and lower response time variability than prior schemes. Stride scheduling is evaluated using both simulations and prototypes implemented for the Linux kernel.

Mobile agents are programs that can migrate from machine to machine in a heterogeneous, partially disconnected network. As mobile agents move across a network, they consume resources. We discuss a system for controlling the activities of mobile agents that uses electronic cash, a banking system, and a set of resource managers. We describe protocols for transactions between agents. We present xed-pricing and dynamic-pricing policies for resources. We focus on and analyze the sealed-bid second-price auction as a mechanism for dynamic pricing. 1

. Mobile codetechnology leads to a new type of "open systems": instead of applying openness to a standardization process we now require the running systems to become open for foreign code. The question then is how far this technical openness can go for mobile code. The less constraints we impose on hosts running mobile code, the more can the benefits of mobile code be exploited. However, there must necessarily be basic constraints regarding the utilization of resources which are always finite and most of the time will be operated near the saturation point. In this paper we argue in favor of openness even at the level of resource allocation. We link this topic to (open) market models, describe the mechanisms we developed so far for communication messengers and show how they are used to allocate resourcesin anopenway. Finally we present experimental results of validation runs which help us testing these mechanisms. Keywords: Mobile code, communication messengers, open resourc...

In the economic-based computational grids we need effective schedulers not only to minimize the makespan but also to minimize the costs that are spent for the execution of the jobs. In this work, a novel economy driven job scheduling heuristic is proposed and a simulation application is developed by using GridSim toolkit to investigate the performance of the heuristic. The simulation-based experiments demonstrate the effectiveness of the proposed heuristic both in terms of parameter sweep and sequential workflow type of applications.