QoS Auditing for Evaluation of SLA in Cloud-based Distributed Services

Given cloud-based realization of a distributed system S, QoS auditing enables risk analysis and accounting of SLA violations under various security threats and resource depletions faced by S. The problem of QoS failures and security infringements arises due to the third-party control of cloud resources and components that are used in realizing the application-oriented service exported by S. The less-than-100% trust between the various sub-systems of S is a major issue that necessitates a probabilistic analysis of the application behavior relative to the SLA negotiated with S. In this light, QoS auditing allows reasoning about how good the SLA is complied by S in the face of hostile environment conditions. The paper describes case studies of CDN and replicated web service realized on a cloud.