Cloud Computing

Cloud Computing

Eduardo Correia (Christchurch Polytechnic Institute of Technology (CPIT), New Zealand)
DOI: 10.4018/978-1-5225-2255-3.ch089


Cloud computing makes use of many standard technologies in surprisingly novel ways. It leaves many people bewildered, even confused, especially as it is an area of computing that is undergoing rapid change in terms of a diversification of available services and the growth in underlying contingent technologies. This article shows how the cloud has changed the user experience and goes on to discuss the definition of cloud computing most commonly used. It describes the three service models of Infrastructure as a Service (IaaS), Platform as a Service (PaaS) and Software as a Service (SaaS) and then discusses the four deployment models of private cloud, public cloud, hybrid cloud and community cloud. It concludes with how the cloud impacts security and how most organizations will likely make use of multiple cloud providers. This article introduces key concepts and characteristics of cloud computing, in this way covering in broad terms what it is and how it essentially works.
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Service Models

Cloud providers, through the use of virtualization, essentially abstract the software, whether it be a server, a database or a network from the underlying physical infrastructure, and offer customers logical software-defined computing resources and services that they can customize, secure, provision and manage in a way that meets their needs and requirements (Buyya, Vecchiola, & Thamarai Selvi, 2013). The service models in cloud computing all reflect this principle of abstraction and represent different sets of responsibility depending how much or how little customers wish to outsource. Infrastructure as a Service (IaaS), Platform as a Service (PaaS) and Software as a Service (SaaS) therefore represent progressively lower levels of engagement on the part of customers, as they cede more of their responsibilities to the cloud provider.

Key Terms in this Chapter

Cloud Service Models: The distribution of responsibilities for technological requirements between customer and cloud provider.

Virtualization: The division of a computer into multiple execution environments so that one level (e.g. the physical) can be abstracted from another (e.g. the operating system).

Virtual Machine: A guest machine that is capable of sharing the same physical hardware with another guest machine and runs on a hypervisor.

Service Level Agreement: A contract that defines the level of service the customer can expect from the cloud provider.

Trust Boundary: The boundary between the responsibilities of the customer and the responsibilities of the cloud provider.

Cloud Deployment Models: The way in which cloud services are provision, for instance the private cloud, the public cloud and the hybrid cloud.

National Institute of Standards and Technologies: A federal agency within the U.S. Department of Commerce that is responsible for measurement science, standards and technology.

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