Conciliando satisfação e paridade para promover reciprocidade em federações de provedores de computação na nuvem.

Abstract

Private cloud providers could obtain considerable benefits from operating their infrastructures within a federation. Such operation allows a provider’s exceeding demand to be met by other providers experimenting a resource underutilization on the same moment. From a market perspective, federations with decentralized architecture have as main challenge the promotion of cooperation among rational selfish individuals in a context with no central trusted authorities. This work focuses in decentralized market architectures, based on reciprocity mechanisms, to support P2P (Peer-to-Peer) federations of cloud providers. In reciprocity mechanisms, an individual uses the history of behaviors of other individuals, reflecting their cooperation levels, in order to prioritize the provision of resource to those shown to be the most reciprocative. Most of these strategies are restricted to the prioritization of participants (to whom should I donate?) according to metrics such as reputation or degree of reciprocity. This strategy is sufficient to promote cooperation and assure cooperative participants the best possible levels of satisfaction (percentage of requests met). However, in low resource contention scenarios, prioritization alone is not sufficient to avoid resource provision to non-cooperative individuals and thus to guarantee fairness (percentage of resources reciprocated). In this sense, this work proposes that mechanisms of reciprocity, especially those based on direct reciprocity, be extended with a feedback control loop that regulates the amount of resources that each cloud should offer to the federation. When each cooperative participant controls individually the amount of resources offered to the federation, there is an indirect control of resource contention, which in turn is kept at a level that ensures cooperative participants adequate levels of satisfaction and fairness. Finally, an investigation on the use of a more limited form of indirect reciprocity is presented, the transitive reciprocity, which can be used in conjunction with direct reciprocity mechanisms to avoid deadlocks generated by time/interest asymmetry, moving the federation’s economy and consequently assuring higher levels of fairness and satisfaction to cooperative nodes.