Istituto di Scienza e Tecnologie dell'Informazione     
Dazzi P., Mori P., Aliaksandr L., et al. .. CONTRAIL - SLA requirements. OPEN COMPUTING INFRASTRUCTURES FOR ELASTIC SERVICES. Deliverable D3.1, 2011.
A Service Level Agreement (SLA) is the part of a contract between two parties (the provider and the consumer) about the usage of some service. The service itself is defined in the SLA along with the guarantees offered by the provider. Current cloud providers are not yet focused in taking care of quality and security excellence. Cloud computing is still in a pioneering phase: cloud providers continuously experiment new ideas, new cloud providers face the market introducing different offers and, most of all, feedbacks from customers are not fully acknowledged. Anyhow, the market will be mature soon and, for that time, providing challenging requirements for security and service quality will not be an option anymore. SLAs can be a differentiator for customers when selecting a cloud provider. The reputation of providers can be measured through the rate of respected SLAs over the total number of SLAs agreed. This reputation can then be tracked at Federation level and used to select providers that are more likely to satisfy their customers. The implementation of SLAs for Cloud Computing introduces some challenges. . SLA definition is diverse. Depending on the area where the term is used, a SLA ranges from a document - written in natural language - where technical details are informally listed, to a formal XML document describing all the services and the "promised" quality in terms of objectives stated through some measurable quantity. In addition, depending on the kind of service, the quality can be expressed using very diverse dimensions (e.g. the quality of a network services can be measured using the bandwidth while the quality of a storage service can be measured through its fault tolerance level). . SLA management is expensive. On top of the cost of the supplied service(s), there are costs for negotiating SLAs, for monitoring the services that are supplied for fulfilling a SLA, for enforcing conditions that ensure that established SLAs are fulfilled and for taking corrective actions when a SLA is violated. . Cloud computing needs security requirements. Storing important private information imposes serious security risks but in SLAs this aspect is still an academic problem which is not widely studied and addressed. For this reason, WP3 is aimed on defining what a SLA is, and how a SLA can be automatically managed. WP3 is focused on providing support for SLAs, including creation, instantiation and enactment of agreements at all levels of the Cloud services stack: IaaS, PaaS and Cloud federations. This work will result in the implementation of a software framework, part of Contrail, for supporting SLAs during their whole lifecycle. This document is aimed to define a basic terminology used in SLAs, gather requirements for SLAs and investigate existing standards, procedures and tools that could be used for the framework implementation. Following the Contrail project philosophy, research, studies and standards are investigated for leveraging existing and emerging technology.This document is a new version of the D3.1 deliverable, with improvements in requirements' traceability. Improved sections are section 2 and section 6. Section 2 is common to several requirements deliverables and describes the methodology used by the related work packages to identify requirements, describe them and provide the basis for traceability. Section 2 also describes the incremental process and tools proposed in Contrail to consistently collect, improve and trace requirements. Section 6 has been improved with a better indication of the source of each requirement, most of which are traced back to the four Contrail Business Cases. In this revised version of D3,1, like in the new versions of other requirements deliverables, the new section 3 has also been added which summarizes how the four Contrail Business Cases map to the WP3 requirements and low level use cases.
Subject SLA
Cloud Computing
C.1.1 Single Data Stream Architectures
C.5.1 Large and Medium (``Mainframe'') Computers

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