The National Institute of Standards and Technology (NIST) Definition of Cloud Computing
(Cloud Computing Essential Characteristics) On-Demand Self-Service
A consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with each service provider.
(Cloud Computing Essential Characteristics) Broad Network Access
Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g.,mobile phones, tablets, laptops, and workstations).
(Cloud Computing Essential Characteristics) Rapid Elasticity
Capabilities can be elastically provisioned and released, in some cases automatically, to scale rapidly outward and inward commensurate with demand. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be appropriated in any quantity at any time.
(Cloud Computing Essential Characteristics) Measured Service
Cloud Systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled and reported, providing transparency for both provider and consumer of utilized service.
NIST definition of Cloud Computing
Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. This cloud model is composed of five essential characteristics, three service models, and four deployment models
(Cloud Computing Deployment Models) Public Cloud
The Cloud Infrastructure is provisioned Open use by General public. It may be owned, managed, and operated by a business, academic, or government organization, or some combination of them. It exists on the premises of the Cloud Provider.
(Cloud Computing Service Models) Platform as a Service (PaaS)
The capability provided to the Costumer is to deploy onto the Cloud Infrastructure consumer - created or acquired applications created using programming languages, libraries, services, and tools supported by provider. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly configuration settings for the application-hosting environment.
(Cloud Computing Service Models) Software as a Service (SaaS)
The capability provided to the consumer is to use the provider's applications running on a cloud infrastructure . The applications are accessible from various client devices through either a thin client interface, such as a web browser (e.g., web-based email), or a program interface. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited User-specific application configuration settings.
(Cloud Computing Service Models) Infrastructure as a Service (IaaS)
The capability provided to the customer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include Operating Systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over Operating Systems, storage, and deployed applications; and possibly limited control of select network components (e.g., host firewalls).
(Cloud Computing Deployment Models) Hybrid Cloud
The cloud infrastructure is a composition of two more distinct cloud infrastructures (private, community or public) that remain unique entities, but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load balancing between clouds).
(Cloud Computing Deployment Models) Private Cloud
The cloud infrastructure is provisioned for exclusive use by a single organization comprising multiple consumers (e.g. business units). It may be owned, managed and operated by the organization, a third party, or some combination of them, and it may exist on or off premises.
(Cloud Computing Deployment Models) Community Cloud
The cloud infrastructure is provisioned for exclusive use by a specific community of consumers from organizations that have shared concerns (e.g., mission, security requirements, policy, and compliance considerations). It may be owned, managed, and operated by one or more of the organizations in the community, a third party, or some combination of them, and it may exist on or off premises.
(Cloud Computing Essential Characteristics) Resource Pooling
The provider's computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand. There is a sense of location independence in that the customer generally has no control or knowledge over the exact location of the provided resources but may be able to specify location at a higher level of abstraction (e.g., country, state, or datacenter). Examples of resources include storage, processing, memory, and network bandwidth.
